N8974A User's Guide

N8974A User's Guide
Noise Figure Analyzers
NFA Series
User’s Guide
Manufacturing Part Number: N8972-90080
May 2001
© Copyright 2001 Agilent Technologies
Safety Notices
This product and related documentation must be reviewed for
familiarization with safety markings and instructions before use.
This instrument has been designed and tested in accordance with IEC
Publication 61010-1+A1+A2:1991 Safety Requirements for Electrical
Equipment for Measurement, Control and Laboratory Use and has been
supplied in a safe condition. The instruction documentation contains
information and warnings which must be followed by the user to ensure
safe operation and to maintain the instrument in a safe condition.
The information contained in this document is subject to change without
notice.
Agilent Technologies makes no warranty of any kind with regard to this
material, including but not limited to, the implied warranties of
merchantability and fitness for a particular purpose. Agilent
Technologies shall not be liable for errors contained herein or for
incidental or consequential damages in connection with the furnishing,
performance, or use of this material.
The following safety symbols are used throughout this manual.
Familiarize yourself with the symbols and their meaning before
operating this instrument.
WARNING
Warning denotes a hazard. It calls attention to a procedure
which, if not correctly performed or adhered to, could result in
injury or loss of life. Do not proceed beyond a warning note until
the indicated conditions are fully understood and met.
CAUTION
Caution denotes a hazard. It calls attention to a procedure that, if not
correctly performed or adhered to, could result in damage to or
destruction of the instrument. Do not proceed beyond a caution sign until
the indicated conditions are fully understood and met.
ii
NOTE
Note calls out special information for the user’s attention. It provides
operational information or additional instructions of which the user
should be aware.
WARNING
This is a Safety Class 1 Product (provided with a protective
earthing ground incorporated in the power cord). The mains
plug shall only be inserted in a socket outlet provided with a
protected earth contact. Any interruption of the protective
conductor inside or outside of the product is likely to make the
product dangerous. Intentional interruption is prohibited.
WARNING
If this product is not used as specified, the protection provided
by the equipment could be impaired. This product must be used
in a normal condition (in which all means for protection are
intact) only.
WARNING
No operator serviceable parts inside. Refer servicing to qualified
personnel. To prevent electrical shock do not remove covers.
WARNING
For continued protection against fire hazard, replace line fuses
only with the same type and ratings (115V range; type F 5A 125V;
239V range F 5A 250V). The use of other fuses or materials is
prohibited.
iii
CAUTION
To prevent electrical shock, disconnect the instrument from the mains
(line) before cleaning. Use a dry cloth or one slightly dampened with
water to clean the external case parts. Do not attempt to clean internally.
Environmental requirements: This product is designed for indoor use
only and to meet the following environmental conditions:
• Operating temperature: 0° C to +55° C
• Operating humidity: <95% relative
• Altitude: up to 4500 m
Warranty
This Agilent Technologies instrument product is warranted against
defects in material and workmanship for a period of three years from
date of shipment. During the warranty period, Agilent Technologies
Company will, at its option, either repair or replace products which prove
to be defective.
For warranty service or repair, this product must be returned to a service
facility designated by Agilent Technologies. Buyer shall prepay shipping
charges to Agilent Technologies and Agilent Technologies shall pay
shipping charges to return the product to Buyer. However, Buyer shall
pay all shipping charges, duties, and taxes for products returned to
Agilent Technologies from another country.
Agilent Technologies warrants that its software and firmware designated
by Agilent Technologies for use with an instrument will execute its
programming instructions when properly installed on that instrument.
Agilent Technologies does not warrant that the operation of the
instrument, or software, or firmware will be uninterrupted or error-free.
iv
LIMITATION OF WARRANTY
The foregoing warranty shall not apply to defects resulting from
improper or inadequate maintenance by Buyer, Buyer-supplied software
or interfacing, unauthorized modification or misuse, operation outside of
the environmental specifications for the product, or improper site
preparation or maintenance.
NO OTHER WARRANTY IS EXPRESSED OR IMPLIED. AGILENT
TECHNOLOGIES SPECIFICALLY DISCLAIMS THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE.
EXCLUSIVE REMEDIES
THE REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND
EXCLUSIVE REMEDIES. AGILENT TECHNOLOGIES SHALL NOT
BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES, WHETHER BASED ON
CONTRACT, TORT, OR ANY OTHER LEGAL THEORY.
Where to Find the Latest Information
Documentation is updated periodically. For the latest information about
Agilent NFA Noise Figure Analyzers, including firmware upgrades and
application information, please visit the following Internet URL:
http://www.agilent.com/find/nf/
v
Manufacturer’s Declaration
This statement is provided to comply with the requirements of the
German Sound Emission Directive, from 18 January 1991.
This product has a sound pressure emission (at the operator position)
< 70 dB(A).
• Sound Pressure Lp < 70 dB(A).
• At Operator Position.
• Normal Operation.
• According to ISO 7779:1988/EN 27779:1991 (Type Test).
Herstellerbescheinigung
Diese Information steht im Zusammenhang mit den Anforderungen der
Maschinenlärminformationsverordnung vom 18 Januar 1991.
• Schalldruckpegel Lp < 70 dB(A).
• Am Arbeitsplatz.
• Normaler Betrieb.
• Nach ISO 7779:1988/EN 27779:1991 (Typprüfung).
vi
Contents
1. Getting Started
What You will Find in this Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
The Noise Figure Analyzer Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Product Family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3.0 GHz Mechanical Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Microwave Front Panel Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Product Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Main Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Overview of the Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Overview of the Rear Panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Overview of the Front Panel Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
How the Front Panel Keys are Organized . . . . . . . . . . . . . . . . . . . . . .11
Navigating Through the Menu System. . . . . . . . . . . . . . . . . . . . . . . . .11
Display Annotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Making a Fixed Frequency Measurement . . . . . . . . . . . . . . . . . . . . . . . .18
Performing Common File Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Formatting a Diskette . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Saving a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Loading a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Renaming a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Copying a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Deleting a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Working with Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Using the Alpha Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
2. Making Basic Measurements
What You will Find in this Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
vii
Contents
Entering Excess Noise Ratio (ENR) Data. . . . . . . . . . . . . . . . . . . . . . . .
Selecting a Common ENR Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entering ENR Table Data for Normal Noise Sources. . . . . . . . . . . . .
Saving an ENR Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entering a Spot ENR Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entering a Spot Thot Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using a Smart Noise Source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Setting the Tcold value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
33
34
39
39
40
41
43
Setting the Measurement Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting Sweep Frequency Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting List Frequency Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting Fixed Frequency Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
46
48
51
Setting the Bandwidth and Averaging . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Effect of Bandwidth and Averaging on Speed, Jitter, and Measurement
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Selecting a Bandwidth Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Setting Averaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Calibrating the Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
To perform a calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Selecting the RF Input Attenuation Range . . . . . . . . . . . . . . . . . . . . . 58
Displaying the Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting the Display Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting Result Types to Display . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Graphical Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Setting the Scaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Working with Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
61
61
64
65
70
73
Indicating an Invalid Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
RF Input Over and Under Range Conditions . . . . . . . . . . . . . . . . . . . 83
IF Input Over and Under Range Conditions . . . . . . . . . . . . . . . . . . . . 83
Example of a Basic Amplifier Measurement . . . . . . . . . . . . . . . . . . . . . 84
viii
Contents
Calibrating the Noise Figure Analyzer . . . . . . . . . . . . . . . . . . . . . . . . .85
Making Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
3. Advanced Features
What You will Find in this Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
Setting up Limit Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Creating a Limit Line. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Using Loss Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Examples where Loss Compensation is applied . . . . . . . . . . . . . . . . . .98
Configuring Fixed Loss Compensation . . . . . . . . . . . . . . . . . . . . . . . . .98
Configuring Table Loss Compensation . . . . . . . . . . . . . . . . . . . . . . . .101
Working with S2P, S1, and S2 File Formats . . . . . . . . . . . . . . . . . . . .106
Setting Temperature of Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
Making Manual Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Manual Measurements Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . .112
4. Making Extended Frequency Measurements
What You will Find in this Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
Overview of Configuring Extended Frequency Measurements . . . . . .117
Measurement Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
Basic Measurement — No Frequency Conversion . . . . . . . . . . . . . . .120
Frequency Down-converting DUT . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
Frequency Up-converting DUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
System Downconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
Comparison of the 8970B and the NFA Series Measurement Modes. .131
Choosing and Setting Up the Local Oscillator . . . . . . . . . . . . . . . . . . . .132
Selecting a Local Oscillator for Extended Frequency measurements
with the NFA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
Selecting a Local Oscillator for the NFA. . . . . . . . . . . . . . . . . . . . . . .133
ix
Contents
Setting up the NFA to drive the Local Oscillator . . . . . . . . . . . . . . . 134
Connecting the System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Setting Up the Noise Figure Analyzer. . . . . . . . . . . . . . . . . . . . . . . . 137
Measuring a Frequency-Converting DUT. . . . . . . . . . . . . . . . . . . . . . .
Sidebands and Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signal Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LO Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LO Harmonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other signals from the DUT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Single Sideband Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Double Sideband Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fixed IF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fixed LO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
140
142
143
143
144
144
145
147
151
152
Making Frequency-Converting DUT Measurements . . . . . . . . . . . . . . 153
Making Down-Converting DUT Measurements using a Fixed IF and
Variable LO (8970B Mode 1.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Making Down-converting DUT Measurements using a Variable IF and
Fixed LO (8970B Mode 1.4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Making Up-converting DUT Measurements using a Fixed IF and
Variable LO (8970B Mode1.3 with SUM) . . . . . . . . . . . . . . . . . . . . . 163
Making Up-converting DUT Measurements using a Variable IF and
Fixed LO (8970B Mode1.4 with SUM) . . . . . . . . . . . . . . . . . . . . . . . . 164
Measurements with a System Downconverter . . . . . . . . . . . . . . . . . .
USB, LSB or DSB? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Measurement Modes with a DSB System Downconverter . . . . . . . .
Measurement Modes with an SSB System Downconverter . . . . . . .
FIXED IF, LSB: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIXED IF, USB:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIXED LO, LSB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIXED LO, USB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
x
165
166
167
168
171
172
173
174
Contents
Making System Downconverter Measurements . . . . . . . . . . . . . . . . . .175
Using a Fixed IF and Variable LO (8970B Mode1.1) . . . . . . . . . . . . .176
Using a Variable IF and Fixed LO (8970B Mode1.2) . . . . . . . . . . . . .185
Frequency Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
Glossary of Restricted Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
General Restrictions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189
Frequency-Downconverting DUT . . . . . . . . . . . . . . . . . . . . . . . . . . . .190
Frequency Up-converting DUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
System Downconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194
5. Performing System Operations
What You will Find in this Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . .198
Setting the GPIB Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
To Set the GPIB Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
Configuring the Serial Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201
Configuring the Characteristics of an External LO . . . . . . . . . . . . . . .203
Custom Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
Settling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Minimum and Maximum Frequencies . . . . . . . . . . . . . . . . . . . . . . . .206
Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Configuring the Internal Alignment. . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Turning Alignment Off and On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Changing Alignment Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Alignment of the YIG Tuned Filter (YTF) . . . . . . . . . . . . . . . . . . . . .209
Displaying Error, System and Hardware Information . . . . . . . . . . . . .210
Displaying the Error History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210
Displaying System Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210
Displaying Hardware Information . . . . . . . . . . . . . . . . . . . . . . . . . . .210
Presetting the Noise Figure Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . .211
xi
Contents
Defining the Power-On/Preset Conditions . . . . . . . . . . . . . . . . . . . . . . 212
Setting the Power On Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
Setting the Preset Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
Restoring System Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Setting the Time and Date. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
To turn the time and date on and off . . . . . . . . . . . . . . . . . . . . . . . . . 214
To set the time and date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Configuring a Printer with the NFA . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
To Configure a Printer with the NFA . . . . . . . . . . . . . . . . . . . . . . . . 215
Testing Correct Printer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
6. Front Panel Key Reference
MEASURE Keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Frequency/Points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Averaging/Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Meas Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
220
220
225
227
228
229
231
DISPLAY Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Result. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Marker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
237
237
241
243
245
CONTROL Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss Comp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Limit Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Full Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Corr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
250
250
255
258
259
xii
Contents
Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262
Restart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
SYSTEM Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267
System (Local) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267
File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280
Save Trace. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287
Preset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287
Print Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
Print . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
Data Entry Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Numeric Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Back Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Enter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Up/Down Arrow Keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Display and Menu Control Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
Viewing Angle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
Standby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
Next Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Zoom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Tab Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
‹Prev . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
Esc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
Preset/Power Up Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
Preset/Power Up — “Persistent” Group Items . . . . . . . . . . . . . . . . . .295
Preset/Power Up - “Survive Preset” Group Items. . . . . . . . . . . . . . . .297
Unsaved Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
State Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
Default States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
xiii
Contents
7. Troubleshooting
What You’ll Find in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Before You Call Agilent Technologies . . . . . . . . . . . . . . . . . . . . . . . . . .
Check the Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Read the Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How to Call Agilent Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . .
307
307
308
308
308
How to Return Your Analyzer for Service . . . . . . . . . . . . . . . . . . . . . .
Detailing the Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Original Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
310
310
310
312
NFA Battery Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Error Messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Informational Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Error Queues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Error Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Error Message Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0: No Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
-499 to -400: Query Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
-199 to -100: Command Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
-399 to -300 and 201 to 799: Device-Specific Errors. . . . . . . . . . . . .
-299 to -200: Execution Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xiv
314
315
318
319
320
321
322
324
330
347
1
Getting Started
This chapter introduces you to basic features of the Noise Figure
Analyzer, including front panel and rear panel descriptions, and an
overview of the display annotation. You also learn how to make a basic
fixed frequency measurement.
1
Getting Started
What You will Find in this Chapter
What You will Find in this Chapter
This chapter introduces the basic functions of the Noise Figure
Analyzer (NFA). This chapter covers the following:
• The Noise Figure Analyzer Features
• Overview of the Front Panel
• Overview of the Rear Panel
• Display Annotation
• Overview of the Front Panel Keys
• Making a Fixed Frequency Measurement
• Performing Common File Operations
• Working with Tables
• Using the Alpha Editor
Figure 1-1
NFA with a Normal Noise Source connected
2
Chapter 1
Getting Started
The Noise Figure Analyzer Features
The Noise Figure Analyzer Features
Product Family
The Agilent Series Noise Figure Analyzer (NFA) family comprises the
following models:
• The N8972A (NFA); frequency range 10 MHz to 1.5 GHz.
• The N8973A (NFA); frequency range 10 MHz to 3.0 GHz.
• The N8974A (NFA); frequency range 10 MHz to 6.7 GHz.
• The N8975A (NFA); frequency range 10 MHz to 26.5 GHz.
3.0 GHz Mechanical Switch
The N8974A and N8975A NFA models have a mechanical switch fitted to
allow them to switch between the 10 MHz to 3.0 GHz frequency range
and the 3.0 GHz to 6.7 GHz and the 3.0 GHz to 26.5 GHz frequency
ranges respectively. If the frequency range you are working in crosses the
3.0 GHz point, the mechanical switch operates. The mechanical switch
has a limited number of cycles over which it is reliable.
To maximize the switches reliable life, switching over the 3.0 GHz switch
should be limited where possible.
Microwave Front Panel Connector
The N8974A and N8975A NFA models are fitted with a precision 3.5mm
male input connector. The models are supplied with a Precision 3.5mm
Coaxial Adaptor (83059B) and a 3.5mm Spanner (8710-1933). When
making connection you need to ensure you apply the correct torque and
you use the adaptor where needed. Correct torque value guidance is in
the Agilent NFA Series Performance Verification and Calibration
Guide.
Product Options
The NFA family offers the following product options:
• 1D5 The Hi-Stability 10 MHz option.
Chapter 1
3
Getting Started
The Noise Figure Analyzer Features
Main Features
The NFA includes the following main features:
• A dedicated user interface to allow easy measurement set up and
interpretation of results
• A GPIB port to allow remote operation
• Built-in 17cm color LCD display
• Measurement results can be displayed in graphical, table or meter
mode
• Dual-trace display allows simultaneous display of any two of the
following noise parameters: Noise Figure, Gain, Y-Factor, Phot, Pcold,
Teffective
• Measurement modes equivalent to the Agilent 8970B Noise Figure
Meter
• Single-sideband and double-sideband measurements
• Fully compatible with Agilent’s existing range of Noise Sources, for
example the 346 and 347 series
• A dedicated 2nd GPIB allows control of a local oscillator
• An internal disk drive and a 3.5" floppy disk drive for storing ENR
tables, instrument states, limits, frequency lists, loss compensation
tables, and screen captures
• A Centronics printer port
• An RS232 serial port for serial communication
• Normal noise source ENR table entry from front panel, floppy disk, or
over the GPIB
• Limit lines with pass/fail notification
• Marker functions to display measurement data on a trace or a
recalled trace
• Manual measurements which can be made on a single frequency
point or over a number of points over a frequency range
• A Smart Noise Source (SNS) port, when connected to an SNS allows
the facility to automatically upload it’s ENR values and monitor the
ambient temperature of the SNS
4
Chapter 1
Getting Started
Overview of the Front Panel
Overview of the Front Panel
Figure 1-2
Front Panel Overview
Table 1-1
Front Panel Item Descriptions
Item
Description
1
Viewing Angle keys allow you to adjust the display so that it can
be optimally viewed from different angles.
2
The Esc (escape) key cancels any entry in progress. Esc clears
error messages from the display status line, clears data input
entries, and aborts a print (if one is in progress).
Chapter 1
5
Getting Started
Overview of the Front Panel
Table 1-1
Front Panel Item Descriptions
Item
Description
3
Menu keys are the unlabeled keys next to the screen. The menu
key labels are shown on the display next to these unlabeled keys.
See Chapter 6 , “Front Panel Key Reference” for a more
extensive description of all the keys.
4
The MEASURE functions allow you to configure the NFA
parameters needed for making measurements.
The Frequency/Points and Averaging/Bandwidth keys activate
the primary set up function menu keys.
The Calibrate key removes any second stage noise contribution
from the measurement. The ENR key accesses the ENR menu.
The Meas Mode and Mode Setup keys are used to configure the
NFA to measure mixers and devices at frequencies greater than
the basic frequency of the NFA using a Local Oscillator.
5
The DISPLAY functions allow you to configure the display
results.
The Scale key allows you to set the scale of the graph results.
The Format key allows you to set the format of the result. The
Marker key allows you to control the markers and search the
trace. The Result key allows you set which measurements you
want to display.
6
6
The CONTROL functions allow you to setup the NFA’s
advanced features. These are Loss Comp, Limit Lines,
correction (Corr key) setting including input calibration ranges,
Sweep mode including Manual Meas. Also, measurement
Restart and a Full Screen display. The Full Screen functions in
all display formats.
Chapter 1
Getting Started
Overview of the Front Panel
Table 1-1
Front Panel Item Descriptions
Item
Description
7
SYSTEM functions affect the state of the NFA. Various setup
and alignment routines are accessed with the System key.
The green Preset key resets the NFA to a known state.
The File key menu allows you to save and load the various NFA
file types and access the File Manager. The Save Trace key
executes the Save function defined under File.
The Print Setup menu keys allow you to configure hardcopy
output. The Print key sends hardcopy data to the printer.
8
The Media Door on the right side of the front panel accesses the
3.5 inch disk drive.
9
The Data Entry Keys, which include the Up/Down arrow keys,
RPG (rotatable knob), and numeric keys, allow you to enter or
change the numeric value of an active function.
The Numeric Keys allows entry of exact values for many of the
NFA functions. To terminate a numeric, where no unit labels
have been presented, press the Enter key.
The RPG allows continuous change of functions such as marker
position.
The Up/Down arrow keys allow discrete increases or decreases
of the active function value.
10
EXT KEYBOARD. The EXT KEYBOARD connector is a 6-pin
mini-DIN connector for future use with PC keyboards. Not
currently supported.
11
PROBE POWER provides power for other accessories.
12
The ⇐ Prev key accesses the previously selected menu.
Continuing to press ⇐ Prev key takes you to earlier menus in
the present menu system.
13
NOISE SOURCE DRIVE OUTPUT +28V PULSED this
connector provides a 28 Vdc level to switch the noise source on.
The noise source is off when no voltage is applied.
Chapter 1
7
Getting Started
Overview of the Front Panel
Table 1-1
Front Panel Item Descriptions
Item
Description
14
Tab Keys are used to move between, table input fields, fields on
forms, and to move within the fields of the dialog box accessed
by the File menu keys.
15
INPUT 50Ω This is the input connector for the NFA.
N8972/3A models have a Type-N connector.
N8974/5A models have a precision 3.5 mm connector.
16
The
Next Window key selects which graph or result
parameter is active.
Pressing
Zoom key while in graph mode allows you to
switch between the dual-graph and single-graph display.
17
Press the Help key and then any front panel or menu key to get a
short description of the key function and the associated remote
command. The next key you press removes the help window
from the display.
18
The Smart Noise Source (SNS) connector provides the interface
to upload the ENR data, monitor the ambient temperature, and
switch the SNS off and on.
19
The ❙(On) key turns the NFA on, while the O (Standby) key
switches the NFA to standby.
After turning on the NFA, with the factory default Alignment
running, allow 60 minutes of warm-up time to ensure the NFA
meets its specifications.
8
Chapter 1
Getting Started
Overview of the Rear Panel
Overview of the Rear Panel
Figure 1-3
Rear Panel Overview
Table 1-2
Rear Panel Item Descriptions
Item
Description
1
Power input is the input for the AC line-power source. Make
sure that the line-power source outlet has a protective ground
contact.
Chapter 1
9
Getting Started
Overview of the Rear Panel
Table 1-2
Rear Panel Item Descriptions
Item
Description
2
Line Fuse. The fuse is removed by twisting counterclockwise
1/4 turn. Replace only with a fuse of the same rating. See the
label on the rear panel and information in the Setup Guide.
3
Service Connector. The service connector is for service use only.
4
VGA OUTPUT drives an external VGA compatible monitor with
a signal that has 31.5 kHz horizontal, 60 Hz vertical
synchronizing rate, non-interlaced.
5
PARALLEL interface port is for printing only.
6
RS-232 interface supports remote instrument operation.
7
Presel Tune Connector it is not currently supported.
8
10 MHz REF IN accepts an external frequency source to provide
the 10 MHz, −15 to +10 dBm frequency reference used by the
NFA.
9
10 MHz REF OUT provides a 10 MHz, 0 dBm minimum,
timebase reference signal.
10
LO GPIB port is for the control of an external LO by the NFA.
11
MAIN GPIB interface port supports remote instrument operation.
12
AUX OUT (TTL) it is not currently supported.
13
AUX IN (TTL) it is not currently supported.
14
Power On Selection selects an instrument power preference.
This preference applies after power has been absent for > 20
seconds. The PWR NORM position causes the instrument to
remain off when power is applied. The PWR ALWAYS ON
position causes it to turn on. The PWR ALWAYS ON mode is
useful if an external power switch is used to control a rack of
several instruments.
10
Chapter 1
Getting Started
Overview of the Front Panel Keys
Overview of the Front Panel Keys
How the Front Panel Keys are Organized
The front panel keys are divided into four main groups:
• MEASURE keys, which are used to configure the measurement
parameters, such as frequency range, bandwidth, number of
measurement points and so forth.
• CONTROL keys, which are used to configure advanced measurement
parameters, such as Loss Compensation and Limit Lines
• SYSTEM keys, which perform system-level operations such as
configuring the NFA’s GPIB address, displaying status information
and configuring an external LO.
• DISPLAY keys, which adjust the display characteristics of the
measurement, for example setting which parameters are displayed,
whether the display format is graph, table or meter, adjusting the
scaling etc.
In addition to the four main groupings, the keys are also further grouped
according to key size and closeness to the display. The large keys placed
in column nearest the display (Frequency/Points, Averaging/Bandwidth,
Calibrate, Scale and Format) are typically the keys which you use most
frequently when performing a measurement.
Navigating Through the Menu System
Menu keys
Pressing any of the grey front panel keys in the MEASURE, DISPLAY,
RESULT or SYSTEM key groupings accesses menus of functions that are
displayed along the right-hand side of the display. These keys are called
menu keys. See Figure 1-4.
Chapter 1
11
Getting Started
Overview of the Front Panel Keys
Figure 1-4
Menu Keys
Action keys
Pressing any of the white keys (Calibrate, Full Screen, Restart, Save Trace
and Print) invokes an action and these keys are called action keys.
To activate a menu To activate a menu key function, press the key immediately to the right
key function
of the screen menu key. The menu keys that are displayed depend on
which front panel key is pressed and which menu level or page is
selected.
When a menu key value is selected, it is called an active function. The
function label of the active function is highlighted after that key is
selected. For example, if you press the Frequency/Points key the menu of
related configuration parameters appears. If you now press the menu
key labeled Start Freq key, the Start Freq appears in the active function
area. The Start Frequency can be changed using any of the data entry
controls.
Selecting a
function within a
menu key
Some menu keys have functions contained within them, for example, On
and Off. To turn the function on, press the menu key so that On is
underlined. To turn the function off, press the menu key so that Off is
underlined.
12
Chapter 1
Getting Started
Overview of the Front Panel Keys
In some menus, one key label is always highlighted to show which key is
selected but the menu is immediately exited when a selection is made.
For example, when you press the Orientation key (a Print Setup menu key)
its own menu of keys appears. The Portrait key, which is the Orientation
menu default key, is highlighted. When you press another Orientation
menu key, the highlight moves to that key to show it is selected.
For a summary of all front panel keys and their related menu keys, see
Chapter 6 , “Front Panel Key Reference.”
Chapter 1
13
Getting Started
Display Annotation
Display Annotation
The display annotation, shown in Figure 1-5, is referenced by numbers.
Table 1-3 has a description and, where appropriate, a function key
indicating which key activates the function related to the annotation.
Refer to Chapter 6 , “Front Panel Key Reference” for more information on
a specific key.
Figure 1-5
Display Annotation
2
1
3
4
5
6
7
8
31
9
30
29
28
27
10
26
25
24
23
22
11
21
12
20
19
18
14
17
16
15
14
13
Chapter 1
Getting Started
Display Annotation
Each item is given a description and where applicable a function key
associated with it.
Table 1-3
Display annotation item descriptions
Item
Description
1
The active function area displays the label and value of the
currently active key.
2
The time and date display, controlled by the Time/Date menu
key, under the System key menus.
3
The marker numbers are displayed in this column, each row
displays the markers results. It is controlled by the Marker and
the State menu keys.
4
The markers frequency is displayed in this column. It is
controlled by the Marker and the State menu keys.
5
The upper trace measurement result is displayed in this column.
It is controlled by either the Result, Marker, State menu keys.
6
The lower trace measurement result is displayed in this column.
It is controlled by either the Result, Marker, State menu keys.
7
The GPIB annunciators RLTS.
The following GPIB modes are possible:
•
R — Remote operation
•
L — GPIB Listen
•
T — GPIB Talk
•
S — GPIB SRQ (Service Request)
8
The data invalid indicator appears when a measurement starts. It
disappears after a complete sweep.
9
The key menu title, this is dependent on which key is selected.
10
The key menu, see key label descriptions in Chapter 6 , “Front
Panel Key Reference”.
11
The frequency span or stop frequency, controlled by the
Freq Span or Stop Freq key.
Chapter 1
15
Getting Started
Display Annotation
Table 1-3
Display annotation item descriptions
Item
Description
12
Displays the measurement correction state, uncorrected or
corrected. Controlled by the calibration state and the Corr key.
13
Displays the Loss Compensation status, On or Off. Controlled
by the Loss Comp key.
14
The number of points, controlled by the Points menu key.
15
Displays the value of attenuation being applied. The left item is
the RF attenuator and the right item is the microwave attenuator.
On the N8972/3A only the RF attenuator status is displayed.
16
The bandwidth, controlled by the Bandwidth menu key.
This is fixed at 4 MHz on the N8972A model.
17
The number of averages, controlled by the Averages menu key.
18
The center frequency or start frequency, controlled by the
Center Freq or Start Freq menu keys.
19
The Tcold temperature value, controlled by the Tcold menu key.
20
The display status line, displays instrument status and error
messages.
21
The lower trace lower limit, controlled by the Lower Limit menu
key.
22
The lower trace unit of measurement on the Y-axis, controlled
by the Result key or Scale menu key.
23
The lower trace scale, controlled by the Scale/Div menu key.
24
The lower trace result type, controlled by the Result key.
25
The lower trace upper limit, controlled by the Upper Limit menu
key.
26
The upper trace lower limit, controlled by the Lower Limit menu
key.
27
The upper trace unit of measurement on the Y-axis, controlled
by the Result key or Scale menu key.
16
Chapter 1
Getting Started
Display Annotation
Table 1-3
Figure 1-6
Display annotation item descriptions
Item
Description
28
The upper trace scale, controlled by the Scale/Div menu key.
29
The upper trace result type, controlled by the Result key.
30
The upper trace upper limit, controlled by the Upper Limit menu
key.
31
The limit line failure indicator.
Shown in
Figure 1-6
The measurement mode status, controlled by the Meas Mode
key. This information is displayed by default. The status
disappears when the marker results are switched on.
Measurement Mode Status
Basic Setup Measurement Mode
Using a Converter Measurement Mode
Chapter 1
17
Getting Started
Making a Fixed Frequency Measurement
Making a Fixed Frequency Measurement
The Fixed Frequency Measurement is the simplest type of measurement
to explain, in terms of getting you started making measurements.
NOTE
You can experiment with the keys without damaging the NFA. To return
to a known state at anytime, press the green Preset key.
Noise figure measurements are made by measuring the output power of
the DUT for two different input noise power levels. Typically, the high
power input comes from a calibrated noise source, and the low power
input uses the noise power generated at ambient temperature.
A fixed frequency measurement is made by measuring a device at a
specific frequency. To display the result on the NFA use the meter
display format, as this is ideal for displaying fixed results. To make a
fixed frequency measurement on a device using the method described, its
operating frequency range must be within the frequency range of the
NFA and requires no frequency conversion.
The techniques used in the procedure are explained in greater detail in
Chapter 2 , “Making Basic Measurements”.
You need an appropriate noise source, either an SNS or a normal noise
source. The normal noise source input is connected to the 28V OUTPUT
using a BNC cable and its output is connected to the INPUT 50 Ω. The
SNS input is connected to the SNS port using the 11730A cable and its
output is connected to the INPUT 50 Ω.
The following example measures the corrected noise figure and gain of a
device at a frequency of 900 MHz and verifies it meets the manufacture’s
specification listed in Table 1-4. The averaging is On and set to 10. The
bandwidth is set to the default 4 MHz.
Table 1-4
The Example DUT Specifications
Frequency Range
Typical Gain
Minimum Gain
Typical Noise
Figure
900 MHz
23 dB
17 dB
3.5 dB
18
Chapter 1
Getting Started
Making a Fixed Frequency Measurement
When you are making measurements, follow the procedure and change
the values to meet your needs.
Step 1. Turn the instrument on by pressing On and wait for the power-up
process to complete.
NOTE
To obtain greater accuracy, it is recommended the NFA warm up for at
least one hour with Alignment(On). The default setting is Alignment(On)
Step 2. Press System, More 1 of 3, Power On/Preset, Preset (Factory).
Press the green Preset key.
NOTE
If the noise source ENR measurement table has been entered previously,
you can use this data to calibrate the NFA. The NFA interpolates points
automatically. Hence, you ignore Steps 3 and 4. See “Entering Excess
Noise Ratio (ENR) Data” on page 33.
The normal noise source ENR values are typically found on the body of
the noise source, the certificate of calibration, or on the diskette supplied
with the noise source. The SNS ENR values are uploaded to the NFA.
Step 3. Press the ENR key, and set the ENR Mode menu key to ENR Mode(Spot).
Step 4. Press the Spot ENR menu key and enter an ENR value if different from
the default value.
If the frequency you want to measure is not a listed ENR value, then you
need to interpolate to an appropriate value. The default value is
15.200 dB.
Step 5. Select the frequency you want to measure using the Frequency/Points key.
Press the Frequency/Points key. Press the Freq Mode menu key and select
the Fixed menu key. The Freq Mode menu key has Fixed mode displayed.
Press the Fixed Freq menu key and enter the numeric frequency value
you want to measure using the numeric key pad. On this occasion enter
900. Terminate the value using the unit label keys. On this occasion MHz.
Chapter 1
19
Getting Started
Making a Fixed Frequency Measurement
Step 6. Select the averaging and bandwidth you want using the
Averaging/Bandwidth key.
Press the Averaging/Bandwidth key and set the averaging to On, by
selecting the Averaging(On) menu key.
Press the Averages menu key and enter the value you want, on this
occasion enter 10. Terminate it with the Enter key. The default value is 1.
NOTE
On the N8972A model, the average mode menu key is unavailable. The
average mode is performed at the default Average Mode(Point). On other
models set the averaging mode to Average Mode(Point). See “Selecting the
Averaging Mode” on page 53 for an explanation of these averaging
modes. Essentially in Fixed Frequency mode either averaging mode gives
an identical result.
Press the Bandwidth menu key and select the bandwidth value you want
from the list presented to you. On this occasion, the default 4 MHz value
is used. The N8972A only offers a 4 MHz bandwidth.
Step 7. Connect the normal noise source input to the NFA’s 28V OUTPUT with a
BNC cable or if using an SNS connect it to the SNS port. Connect the
preferred noise source’s output to the INPUT 50 Ω.
NOTE
When using the N8974A and N8975A care must be taken to torque the
precision 3.5mm connector to the correct value. To find the correct value
of torque to apply, see the Performance Verification and Calibration
Guide.
Step 8. Set the display mode to meter mode.
Press the Format key, the Format menu key and select the Meter menu key.
Step 9. Press the Calibrate key twice.
The first time you press the key you will be prompted to press it again.
This two-stroke calibration is a safety feature, it keeps you from
accidentally pressing the Calibrate key and erasing any previous
calibration data.
20
Chapter 1
Getting Started
Making a Fixed Frequency Measurement
The calibration corrects for any second stage noise contribution caused
by the NFA. When the calibration is complete the Uncorr text in the
bottom right hand corner changes to Corr text.
The calibration is performed at the default input attenuator settings. If
you need to change these settings, see “Selecting the RF Input
Attenuation Range” on page 58.
Step 10. Connect the device under test between the noise source output and the
NFA’s input.
The measurement result is displayed in meter format, similar to Figure
1-7.
Figure 1-7
Typical Fixed Frequency Measurement Result in Meter Format.
The result displayed in Figure 1-7 shows the DUT noise figure and gain
at 900 MHz.
Thus the DUT meets the manufacturer’s specification as listed in Table
1-4.
Chapter 1
21
Getting Started
Performing Common File Operations
Performing Common File Operations
This section describes how to use the functions located under the
front-panel File key. This section covers:
•
•
•
•
•
•
Formatting a diskette
Saving a file
Loading a file
Renaming a file
Copying a file
Deleting a file
Formatting a Diskette
You can format a diskette in the NFA. The format is MS-DOS. It is not
necessary to format your diskette with the NFA; pre-formatted disks can
be used with the NFA.
Step 1. Place the diskette you wish to format into the diskette drive (A:) of the
NFA.
Step 2. Access the file manager menu by pressing File key, File Manager. See
Figure 1-8.
22
Chapter 1
Getting Started
Performing Common File Operations
Figure 1-8
File Manager Menu
Step 3. Start the format process by pressing Format, then Enter.
CAUTION
To abort disk format press any key, except Enter.
When a disk is formatted all data on the disk is destroyed. A dialog box
appears on the NFA display to warn you, allowing you the opportunity to
abort formatting.
Step 4. Press Enter, a second time to format the disk.
The format process takes approximately three minutes.
You are now ready to save files to the disk.
Chapter 1
23
Getting Started
Performing Common File Operations
Saving a File
You can save files (ENR tables, states, traces, limits, frequency lists, loss
tables, or screens) to a floppy disk (A:), or the internal drive (C:) of the
NFA.
Step 1. To access the Save menu press File, Save.
Step 2. Select the type of file you want to save.
For example, if you have limit line table data present and want to save it,
press Limits.
Step 3. Select the limit line table file you wish to save (1, 2, 3 or 4).
For example, to save file 2, press 2.
Step 4. Enter a filename using the Alpha Editor menu keys. See “Using the
Alpha Editor” on page 29.
NOTE
You must select a unique filename and no greater than eight characters.
The NFA does not allow you to overwrite an existing file. If you select a
file name that already exists, the NFA displays the error message: File
already exists.
Step 5. Select the drive you wish to save to by pressing Tab →, to move to
directory and file list, press Select.
NOTE
If the correct drive is not listed in the Path: field, highlight “..” at the
top of the directory list. This enables you to move up a directory. Press
Select. To highlight the desired drive,[-A-] or [-C-]) use the arrow keys
or the RPG, press Select when highlighted.
Step 6. Press Enter, to save the file to the drive.
24
Chapter 1
Getting Started
Performing Common File Operations
Loading a File
You can load files (ENR tables, states, limits, frequency lists, or loss
tables) from a floppy disk (A:\), or the internal drive (C:\).
NOTE
Files saved in previous versions of firmware can not be loaded into a NFA
with newer firmware.
NOTE
Not all the file types you save can be loaded back into the NFA. For
example, screen files and trace files. The trace file is in a CSV (comma
separated value) format, designed for use with a PC.
Step 1. To access the Load menu press File, Load.
Step 2. Select the type of file you want to load (ENR tables, states, limits,
frequency lists, or loss tables).
Step 3. Select the drive where your file is located by pressing Tab →. Use the
RPG to highlight [-C-] or [-A-], then press Select.
Step 4. Select the file you want to load into the NFA by changing the highlighted
file with the up or down arrow keys to highlight the file name.
Step 5. Press Enter to load the specified file.
Renaming a File
You can rename a file in the [-C-] or [-A-] drive as follows:
Step 1. Press File, File Manager, Rename to access the Rename menu items.
Step 2. Select the type of file you want to rename (ENR tables, states, traces,
limits, frequency lists, loss tables, or screens).
For example, if you are renaming a ENR table file, press ENR.
Step 3. Select the drive where your file is located, by pressing the Tab → key,
press Select. To change drive, use the arrow keys to highlight [-C-] or
[-A-], then press Select.
Chapter 1
25
Getting Started
Performing Common File Operations
Step 4. Select the file you want to rename by moving the cursor with the RPG or
arrow keys to highlight the file name.
Step 5. Press Tab → to enter the Alpha Editor menu. File names are limited to
eight (8) characters.
Step 6. Press Enter and your file is now renamed and visible within the directory
displayed on your NFA.
Copying a File
This allows you to copy a file to a different location on both the [-C-]
and [-A-] drive.
Step 1. To access the Copy menu press File, File Manager, Copy.
Step 2. Put a formatted floppy in the A: drive.
Step 3. Select the type of file you want to copy (ENR tables, states, traces, limits,
frequency lists, loss tables or screens).
For example, if you are copying a State file, press State.
Step 4. Select the drive where your file is located, by pressing Tab → to highlight
the From:Path: field. Select the drive, using the RPG or arrow keys to
highlight [-C-] or [-A-], then press Select.
Step 5. Select the file you wish to copy by highlighting the filename using the
front-panel knob or arrow keys.
Step 6. Press Tab → to move to the To:Path: field and select the drive where you
want to copy the file using the RPG or arrow keys then press Select.
NOTE
If the correct drive is not listed in the Path: field, highlight “..” at the
top of the directory list. This enables you to move up a directory. Press
Select, to highlight the desired drive, ([-A-] or [-C-]) then press Select
again.
Step 7. Copy the file by pressing Enter.
26
Chapter 1
Getting Started
Performing Common File Operations
Deleting a File
This allows you to delete a file from the [-C-] or [-A-] drive.
Step 1. To access the Delete menu press File, File Manager, Delete.
Step 2. Select the type of file you want to delete (ENR tables, states, traces,
limits, frequency lists, loss tables, or screens).
Step 3. Select the drive where the file you wish to delete is located, by pressing
Tab → then using the RPG or arrow keys to highlight [-C-] or [-A-],
then press Select.
NOTE
If the correct drive is not listed in the Path: field, highlight “..” at the
top of the directory list. This enables you to move up a directory. Press
Select, to highlight the desired drive, ([-A-] or [-C-]) then press Select
again.
Step 4. Select the file you want to delete by moving the cursor with the RPG or
arrow keys to highlight the file name.
Step 5. Press Enter and your file is now deleted and is no longer visible in the
directory displayed on your NFA.
Chapter 1
27
Getting Started
Working with Tables
Working with Tables
The Frequency List, ENR Table, Limit Line Editor, and Loss
Compensation Tables use table forms. The following is an overview of
how to use the features in these tables.
Table 1-5
Using Tables
To...
Use the...
Move the highlight bar within the table
Tab keys
Bring the highlight bar to the top of the
table
Home key
Clear the table of all entries
Clear Table menu key
Delete a single row entry
Delete Row menu key
Add a new entry
Add menu key
Move the highlight bar up one row
Row Up menu key
Move the highlight bar down one
row
Row Down menu key
Move the table up a page block
Page Up menu key
Move the table down a page block
Page Down menu key
Enter a value
Numerical key pad
Terminate a value
The unit values presented by the
menu keysa
Connect Limit Line points
The arrow keys or the RPG
a. A limit line value is a unitless value and it depends on the result’s
scale unit used.
28
Chapter 1
Getting Started
Using the Alpha Editor
Using the Alpha Editor
The Alpha Editor is a menu driven text entry system. You enter the
character data with the menu keys. If numeric data is needed also use
the numeric keypad. To edit the data use the Back Space key. After
completing the entry terminate it by pressing the Enter key.
The Alpha Editor allows you to:
• name files when saving.
• enter the alphabetical portion of the model ID and the serial number
of the noise source in an ENR table.
• create suffix and prefix commands used to set the External LO
frequency and power levels.
The LO Commands Alpha Editor have more character options available,
see Figure 1-9.
Figure 1-9
Alpha Editor Character Set
Chapter 1
29
Getting Started
Using the Alpha Editor
The Alpha Editor is used as follows. In the example, a three character
file name, NEW, is created.
Step 1. Press the HIJKLMN key.
Step 2. Press the N key.
Step 3. Press the ABCDEFG key.
Step 4. Press the E key.
Step 5. Press the VWXYZ key.
Step 6. Press the W key.
30
Chapter 1
2
Making Basic Measurements
This chapter describes how to make basic noise figure measurements
using your NFA and also covers the most common measurement related
tasks.
31
Making Basic Measurements
What You will Find in this Chapter
What You will Find in this Chapter
This chapter describes the procedures to set up the NFA and uses a basic
example to demonstrate the NFA measuring noise figure and gain of a
device which has no frequency conversion.
• Entering Excess Noise Ratio (ENR) Data
• Setting the Measurement Frequencies
• Setting the Bandwidth and Averaging
• Calibrating the Analyzer
• Displaying the Measurement Results
• Example of a Basic Amplifier Measurement
32
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Entering Excess Noise Ratio (ENR) Data
You can enter ENR data for the noise source you are using as a table of
values or as a single spot value. The table of values are used for
measurements at several frequencies. The single spot value is used for
single frequency measurements or it is applied across the whole
frequency measurement range.
There are two types of noise source. The first type, for example,
Agilent 346B, a normal noise source. These need their ENR data to be
entered manually either using the ENR data stored previously on a
diskette or by using the keypad. The other type, for example,
Agilent N4000A, a Smart Noise Source (SNS), can upload the data
automatically or when requested.
Selecting a Common ENR Table
You can use the same, Common, ENR table for calibration and making
measurements, or you can use separate, Meas and Cal, ENR tables when
a different noise source is used during DUT measurements from that
used for calibration.
NOTE
ENR tables can contain up to 81 frequency points.
To use the same ENR table for calibration and measurement, press the
Common Table menu key to select Common Table(On); see Figure 2-1.
This is the default setting. In this mode the Cal Table is not accessible.
Figure 2-1
Menu Keys showing Common ENR Table On
Chapter 2
33
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
To use different ENR tables for calibration and measurement, press the
Common Table menu key to select Common Table(Off); see Figure 2-2.
In this mode, the Cal Table menu key is accessible. This is the ENR table
of the noise source used to calibrate the NFA. The Meas Table is used to
make measurements. In Common Table(Off) mode the ENR Table is the
Meas Table in the Common Table(On) mode.
Figure 2-2
Menu Keys showing Common ENR Table Off
NOTE
If you are using an SNS when Common Table(Off) is set, you need to set
Auto Load ENR(Off) and use the Fill Table From SNS menu key. See
“Loading the SNS ENR data to the Measurement or Calibration Table.”
on page 42.
Entering ENR Table Data for Normal Noise Sources
You can enter ENR data in the form of an ENR table in four ways:
• manually by inputting the required frequencies and corresponding
ENR values
• loading the ENR data from a diskette, on which the data has been
previously stored
• loading the ENR data from the internal memory, where the data has
been previously stored
• loading the ENR data over GPIB, see the Programmer’s Reference
for more details
34
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
NOTE
Agilent normal noise sources have the ENR values printed on the body of
the device. These ENR values are also provided within separate text in
the form of a calibration report, and on a diskette which is supplied with
every Agilent noise source.
To enter ENR table data manually
NOTE
If the NFA has arrived from the factory, and you are entering ENR data
for the first time, the ENR table is empty. You can create this condition
with an NFA which has been used previously by pressing Clear Table. The
typical display is shown in Figure 2-3.
Enter the ENR data manually as follows:
Step 1. Press the ENR key, and the ENR Table menu key.
An ENR Table appears on the display with the first frequency point in
the table highlighted, see Figure 2-3. For details on working with tables,
see “Working with Tables” on page 28.
Chapter 2
35
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Figure 2-3
An Empty ENR Table
Step 2. Optional Step
Press the Serial Number menu key and enter the noise source serial
number using the numeric keys and the Alpha Editor.
For details on using the Alpha Editor, see “Using the Alpha Editor” on
page 29.
Step 3. Optional Step
Press the ID menu key and enter the noise source model number using
the numeric keys and the Alpha Editor.
Step 4. Press the Edit Table menu key to enter the noise source ENR values.
The table editing and navigation menu items now appear.
Step 5. Enter the frequency value in the table using the numeric keys.
Terminate it using the unit menu keys.
Step 6. Press the Tab —> key to move the highlight to the ENR Value column and
enter the corresponding ENR value of the ENR list.
When terminating the ENR value you can use either dB, K, C, or F menu
keys. The K, C, or F entry is converted to appear in the table as dB.
36
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Step 7. Press the Tab —> key to move the highlight to the Frequency column and
enter the next frequency value on the ENR list.
Step 8. Repeat steps 5 to 7 until all the frequency and ENR values you need are
entered.
Step 9. After completing the ENR table entries, press the Prev key or ENR key to
return to the ENR menu.
Step 10. Optional Step
Once you have completed entering the ENR data, save the ENR table
using the File key.
For details on saving files, see “Saving an ENR Table” on page 39.
NOTE
ENR table data survives a power cycle and preset (except
Restore Sys Defaults). You only need to save the ENR data to save you
from entering the data again.
Figure 2-4
A Typical ENR Table after data entry
Chapter 2
37
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
NOTE
You can insert the frequencies into the ENR Table entry in any order, as
the NFA automatically sorts the frequency list into ascending order.
NOTE
When results are needed at non-cardinal ENR data points, a linearly
interpolated value is automatically used at these points.
To load ENR data from memory
If the noise source you are using has its ENR data supplied or previously
stored on a diskette or internal memory, you can load this ENR data into
the NFA as follows.
Step 1. If the ENR file is on diskette, insert the diskette into the floppy drive of
the NFA.
For more details on loading files, see “Loading a File” on page 25.
Step 2. Press the File key.
Step 3. Press the Load menu key to access the file system.
Step 4. Press the ENR menu key.
Step 5. Press either the Meas Table or Cal Table menu key.
A list of available files on the [-A-] or [-C-] drive is displayed. Use the
arrow keys to access the appropriate file.
Step 6. Press the Enter key.
A Loading File Warning: this may take some time prompt appears
on the display and disappears when complete. On completion a message,
for example, C: xxx.ENR file loaded appears in display status line.
38
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Saving an ENR Table
You can save an ENR table to the NFA’s internal memory or to floppy
disk as follows:
Step 1. Press the File key.
Step 2. Press the Save menu key.
Step 3. Press the ENR menu key.
Step 4. Press either the Meas Table or Cal Table menu key. Also, if you are using
an SNS, an SNS menu key is available to select.
The Alpha Editor now appears, allowing you to create a name for the file.
Step 5. Input the name of the ENR table.
See “Using the Alpha Editor” on page 29 for details on using editor.
Step 6. Select using the arrow keys whether you want to save the files to the
[-A-] or [-C-] drive.
Step 7. Press Enter to save the file.
Entering a Spot ENR Value
When making a measurement in fixed frequency mode you can enter a
specific spot ENR value corresponding to the fixed frequency. The spot
ENR value can also be applied across the whole measurement frequency
range.
To enter a Spot ENR value:
Step 1. Press the ENR key, then the Spot menu key.
Step 2. Press the Spot ENR menu key.
Step 3. Enter an ENR value using the numeric keys and terminate it using the
unit termination menu keys. The default value is 15.20 dB.
NOTE
If you are using a noise source with a calibrated ENR list and the
frequency you want to measure is not a listed ENR value, then you need
to interpolate the ENR list to an appropriate value.
Chapter 2
39
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
To Enable Spot ENR Mode
Step 1. Press the ENR key, and select the ENR Mode(Spot) menu key.
Step 2. Press the Spot menu key, and select the Spot Mode(ENR) menu key.
Entering a Spot Thot Value
When making a manual measurement you can enter a specific spot Thot
value. The spot Thot value is applied across the whole measurement
frequency range
To enter a Spot Thot value:
Step 1. Press the ENR key, then the Spot menu key.
Step 2. Press the Spot Thot menu key.
Step 3. Enter a Thot value using the numeric keys and terminate it using the
unit termination menu keys. The default value is 9892.80 K.
To Enable Spot Thot Mode
Step 1. Press the ENR key, and select the ENR Mode(Spot) menu key.
Step 2. Press the Spot menu key, and select the Spot Mode(Thot) menu key.
40
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Using a Smart Noise Source
NOTE
If there is an SNS connected to the NFA’s Smart Noise Source port, the
NFA, by default, selects the SNS as its noise source. If an SNS is not
connected the NFA uses the normal noise source.
Selecting the Source Preference
If noise sources are connected to both ports you need to select a
preference either Preference(Normal) or Preference(SNS). The default
setting is Preference(SNS).
To select a noise source preference:
Step 1. Press the ENR key.
Step 2. Press the SNS Setup menu key.
Step 3. Press the Preference menu key changing it from the default
Preference(SNS) to Preference(Normal).
Loading the SNS ENR data to the Common Table.
You can enable the NFA to automatically upload the ENR data to the
Common Table. To enable automatic loading on power up or the
connection of the SNS to the NFA’s Smart Noise Source port, set
Auto Load ENR(On). This enables the ENR data to load into the Common
Table automatically. If you do not want to automatically upload the ENR
data into the Common Table, press Auto Load ENR(Off).
If you have selected Auto Load ENR(Off), you can use the
Fill Table From SNS menu key to upload the ENR data from the SNS. The
Fill Table From SNS menu key is found under the ENR Table menu key. It is
only active when an SNS is connected. This allows you to choose when to
upload the ENR data to the ENR Table.
CAUTION
Do not disconnect the noise source from the NFA port while the data is
being transferred.
Chapter 2
41
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Loading the SNS ENR data to the Measurement or Calibration
Table.
NOTE
When an SNS is connected and Auto Load ENR(On) enabled, the
Common Table(On) is set automatically. Hence, the SNS ENR data is
loaded into the common ENR table.
You can use the Fill Table From SNS menu key to upload the ENR data
from the SNS. This allows you to choose between Meas Table or Cal Table,
as the destination for the ENR data.
Step 1. Press the ENR key.
Step 2. Press the SNS Setup menu key.
Step 3. Press the Auto Load ENR menu key setting it to Auto Load ENR(Off).
Step 4. Press the Common Table menu key setting it to Common Table(Off).
Step 5. Press the Meas Table or Cal Table menu key.
Step 6. Press the Fill Table From SNS menu key and wait until all the data is
uploaded.
CAUTION
Do not disconnect the noise source from the NFA port while the data is
being transferred.
42
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Setting the Tcold value
When making measurements in different ambient temperature
conditions you can change the Tcold value.
The default temperature value is set at 296.50K. The Tcold menu key is
set to Tcold(Default) to confirm this default temperature.
There are three methods of changing the Tcold value. These are
dependant on the type of noise source you are using.
• The first method is applicable when using either type of noise source
and allows you to enter a Tcold value manually. This method is
explained in “Changing the User Tcold value manually” on page 43.
• The second method is applicable when using the SNS noise source
and it uploads the value automatically and updates the value after
every sweep. This method is explained in “Setting the SNS Tcold
value to Update Automatically” on page 44.
• The third method is applicable when using the SNS where you can set
the value to be updated as you need. This method is explained in
“Setting the SNS User Tcold value” on page 45.
Changing the User Tcold value manually
To change the User Tcold value:
Step 1. Press the ENR key.
Step 2. Press the Tcold menu key.
NOTE
When using an SNS, the SNS Tcold menu key must set to SNS Tcold(Off)
for this feature to work.
Step 3. Press the User Tcold menu key setting it from the default User Tcold(Off)
to User Tcold(On).
The Tcold menu key, under the ENR menu keys, is now set to Tcold(User)
to confirm you are using this temperature mode.
Chapter 2
43
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Step 4. Press the User Value menu key.
Enter a Tcold value using the numeric keys and terminate it using the
unit termination menu keys.
The unit termination menu keys are in K (Kelvin), C (Celsius) or
F (Fahrenheit).
NOTE
The lower limit is 0K and upper limit is 29,650,000K. The default value
is 296.5K. The K value is always displayed. The K values are converted
from the entered oC and oF.
Setting the SNS Tcold value to Update Automatically
This feature is only available when an SNS is connected to the NFA.
To set the SNS Tcold value:
Step 1. Press the ENR key.
Step 2. Press the Tcold menu key.
Step 3. Press the SNS Tcold menu key, if required, setting it to SNS Tcold(On).
The Tcold menu key, under the ENR menu keys, is now set to Tcold(Auto)
to confirm you are using this temperature mode.
44
Chapter 2
Making Basic Measurements
Entering Excess Noise Ratio (ENR) Data
Setting the SNS User Tcold value
This feature only works when an SNS is connected to the NFA.
To change the User Tcold value:
Step 1. Press the ENR key.
Step 2. Press the Tcold menu key.
NOTE
When using an SNS, SNS Tcold must set to SNS Tcold(Off) for this feature
to work.
Step 3. Press the User Tcold menu key changing it from the default
User Tcold(Off) to User Tcold(On).
Step 4. Press the User Tcold From SNS menu key.
The NFA uploads the Tcold value from the SNS and displays the value in
the User Value menu key.
The Tcold menu key, under the ENR menu keys, is now set to Tcold(User)
to confirm you are using this temperature mode.
Chapter 2
45
Making Basic Measurements
Setting the Measurement Frequencies
Setting the Measurement Frequencies
Before you set the frequencies you want to measure, you need to select a
frequency mode. Three frequency modes are available:
• Sweep — the measurement frequencies are obtained from the start
and stop (or equivalent center and span) frequencies and the number
of measurement points.
• List — the measurement frequencies are obtained from the frequency
list entries.
• Fixed — where the measurement frequency is taken at a single fixed
frequency. An example of using this mode is explained in “Making a
Fixed Frequency Measurement” on page 18.
Selecting Sweep Frequency Mode
In sweep frequency mode you set the start and stop frequencies (or
equivalent center and span frequencies) over which the sweep is made.
You also need to set the number of measurement points. These
measurement points are equally spaced over the frequency span. The
maximum number of points is 401and the default number of points is 11.
CAUTION
The N8974A and N8975A NFA models have a mechanical switch fitted to
allow them to switch between the RF frequency range and the microwave
frequency range. If the frequency range you are working in crosses the
3.0 GHz point, the mechanical switch operates. The mechanical switch
has a limited number of cycles over which it is reliable.
Switching over the 3.0 GHz switch should be limited where possible.
NOTE
You can press Full Span at anytime to return the frequency range to the
specific NFA model’s full range setting. If you do this after a calibration
and the calibration has been made over a narrower frequency range, the
calibration is invalid.
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Setting the Measurement Frequencies
To make a measurement over a specific frequency range:
Step 1. Press the Frequency/Points key.
Step 2. Press the Freq Mode menu key to select frequency mode to
Freq Mode(Sweep).
Step 3. Set the frequency range by either entering the Start Freq and Stop Freq
frequencies, or the Center Freq and the Freq Span.
Use the numeric key pad to enter the value you want. Use the unit menu
keys to terminate the number.
Step 4. Press the More 1 of 2, Points menu keys.
Step 5. Enter the number of measurement points using the numeric keys. Press
the Enter key to terminate.
NOTE
The greater number of frequency points selected, the greater the time
required by the measurement.
Chapter 2
47
Making Basic Measurements
Setting the Measurement Frequencies
Selecting List Frequency Mode
List frequency mode allows you to enter the frequency points where
measurements are made. This allows you to specify measurement points,
for example, in areas of interest that would have less coverage than in
the sweep mode to allow unevenly spaced measurement points.
Frequency lists are limited to 401 entries.
To set the NFA to use the data in the frequency list table:
Step 1. Press the Frequency/Points, Freq Mode menu keys.
Step 2. Press the Fixed menu key to set the frequency mode to Freq Mode(List).
You can create a frequency list in the following ways:
• Manually, by specifying each individual point.
• From the swept points, by specifying the measurement frequency
range and setting the NFA to generate equally spaced points within
that range, using the Fill menu key.
• Loading a list from the internal memory or diskette, where the data
has been previously stored.
• Loading a list over GPIB; see the Programmer’s Reference if you
want to use this method.
To Create a Frequency List Manually
Step 1. Press the Frequency/Points key and press the More 1 of 2 menu key.
Step 2. Press the Freq List menu key.
A Frequency List table appears on the display.
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Setting the Measurement Frequencies
Figure 2-5
An Empty Frequency List
NOTE
You do not need to enter the frequency values in ascending order, as the
NFA continually sorts the values into ascending order.
Step 3. Press the More 1 of 2, Clear Table menu keys.
You are prompted to press this key again, this feature ensures you do not
accidently clear a valid Frequency list table. Press the Clear Table menu
key again. Clearing the table allows you to start entering points knowing
there are no previous entries remaining.
The first frequency point in the table is highlighted.
Step 4. Enter the frequency value you want using the numeric keys. Terminate
it using the unit menu keys which are presented to you.
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Making Basic Measurements
Setting the Measurement Frequencies
Step 5. Press the Tab —> key or Row Down menu key.
The next frequency point on the table is highlighted.
Enter the next frequency value by using the numeric key pad and the
unit termination keys.
Step 6. Repeat step 5 until your list is complete.
Step 7. Save the Frequency List to the NFA internal memory or to a diskette if
required using the File key. See “Saving a File” on page 24 for an
explanation of this.
NOTE
If you do not save the frequency list, you may lose the data. This depends
on your Power On/Preset condition. See “Defining the Power-On/Preset
Conditions” on page 212 for an explanation of these.
Creating a Frequency List from Swept Points
You can create a frequency list from the swept mode frequency and
points data.
To set the NFA to use the swept mode data:
Step 1. Press the Frequency/Points, More 1 of 2 menu keys.
Step 2. Press the Freq List, More 1 of 2 menu keys.
Step 3. Pressing the Fill menu key.
This clears the current frequency list and fills the list with the
frequencies generated by the sweep frequency mode.
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Chapter 2
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Setting the Measurement Frequencies
Selecting Fixed Frequency Mode
The fixed frequency mode is used when you want to make a
measurement at a single frequency. See “Making a Fixed Frequency
Measurement” on page 18 for more details of this mode.
NOTE
If you have not entered the noise source ENR data which you intend
using for the fixed frequency mode measurement, you need to specify a
spot ENR value and set the ENR mode to spot.
To set a fixed frequency:
Step 1. Press the Frequency/Points, Freq Mode menu keys.
Step 2. Press the Fixed menu key to set the frequency mode to Freq Mode(Fixed).
The Fixed Freq menu key is now available.
Step 3. Press the Fixed Freq menu key and enter the frequency value using the
numeric keys and the unit termination menu keys.
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Making Basic Measurements
Setting the Bandwidth and Averaging
Setting the Bandwidth and Averaging
Effect of Bandwidth and Averaging on Speed, Jitter,
and Measurement Accuracy
Jitter is a natural occurrence when measuring noise. To reduce jitter you
must increase the number of averages or increase the measurement
bandwidth.
If the bandwidth is reduced, you need to increase the number of averages
to maintain the same uncertainty.
The greater the number of averages chosen, the more accurate the
measurement, as this reduces jitter on the measurement. However, this
has to be considered against how long it takes to complete the
measurement.
Therefore, there is a trade off between speed and the
accuracy/uncertainty of a measurement.
NOTE
On the N8972A model, the average mode menu key is unavailable. Point
mode averaging is used on this model.
Selecting a Bandwidth Value
The default bandwidth is 4MHz. To change the bandwidth value:
Step 1. Press the Averaging/Bandwidth key.
The current bandwidth is shown on the Bandwidth menu key.
Step 2. Press the Bandwidth menu key and select the bandwidth you want from
the list of available options.
NOTE
On the N8972A model, the bandwidth menu key is unavailable. The
bandwidth is fixed at 4MHz.
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Setting the Bandwidth and Averaging
Setting Averaging
Increased averaging reduces jitter and provides more accurate
measurement results. However, the measurement speed is sacrificed.
The maximum number of averages allowed is 999. The default value is 1
and this equivalent to setting averaging to off.
Enabling
averaging
Averaging can be enabled by setting the Averaging(On). To disable
averaging set Averaging(Off)
Setting the Number of Averages
To set the number of averages you want:
Step 1. Press the Averaging/Bandwidth key, and then the Averages menu key.
Step 2. Enter the numeric value you want using the numeric key pad. Terminate
it with the Enter key.
Selecting the Averaging Mode
Averaging Mode can be set to Average Mode(Point) or
Average Mode(Sweep).
The difference between the averaging modes is:
• In Point mode, the selected number of averages are measured at each
point before moving to the next measurement point in the sweep. The
measurement is complete after one sweep. The measurement restarts
if Sweep(Cont) mode is selected.
• In Sweep mode, a single value is measured at each point in the sweep.
The result at each point is built up by averaging the results from
multiple sweeps until the selected number of averages have been
measured at each point. The average counter is incremented at the
end of each sweep. If Sweep(Sing) mode is selected the measurement
is complete. If Sweep(Cont) mode is selected the measurement
continues, using exponential averaging at each point.
Point averaging provides the fastest overall measurement time, as only
one sweep is required to obtain the averages at each measurement point.
Sweep averaging takes longer overall, as multiple sweeps are required to
obtain the averages at all frequencies. However, initial results are
obtained quickly at all frequencies.
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Making Basic Measurements
Calibrating the Analyzer
Calibrating the Analyzer
To compensate for the noise contribution of the NFA, the associated
cabling, and so forth in the measurement path, a calibration is necessary.
The calibration measures the NFA’s noise contribution with no DUT
(device under test) in place. This correction is often referred to as the
second stage calibration. The correction is then applied to the
measurement with the DUT in place.
To perform calibration you need to enter the ENR values and set up the
frequency range, number of measurement points, the bandwidth, the
averaging, and measurement mode to be used during the measurement.
If you alter the frequency range after you have calibrated the NFA, it
changes NFA’s status to uncorrected or interpolated corrected states. You
need to recalibrate before you make another measurement to obtain as
accurate a measurement result as possible.
Corrected
measurements
You can make corrected measurements only at frequencies which are
covered by the current calibration. Attempting to make corrected
measurements at frequencies less than the lowest calibration frequency
or greater than the highest calibration frequency generates an error and
invalidates the calibration.
To proceed you must either:
• perform a calibration over the desired measurement frequency range,
• perform uncorrected measurements,
• change the measurement frequency to that covered by the existing
calibration.
When to perform
calibration
You must calibrate the NFA whenever:
• you power cycle the NFA
• you Preset the NFA
• you select a measurement frequency or frequency range outside the
currently calibrated range
• you change the fixed IF frequency in certain modes
• you change frequency mode
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Calibrating the Analyzer
• you change measurement mode
• there is a large temperature variation since the last calibration
• the input signal level can no longer be measured using one of the
calibrated input attenuator ranges
• when an invalid result is detected and the condition is indicated by a
“xx”. See “Indicating an Invalid Result” on page 82 for an explanation
of these condition.
Interpolated
results
You obtain interpolated results from the NFA whenever you change
certain measurement parameters, for example, the number of points.
Calibration
indicator
Whenever anything within the NFA changes to invalidate the current
calibration, the Corr field at the bottom right-hand corner of the display
switches to Uncorr. Figure 2-6 shows this indicator.
Figure 2-6
Corrected/Uncorrected indicator
Corrected/Uncorrected indicator
Interpolated
calibration
Whenever anything within the NFA changes to force the current
calibration to interpolate the measurement results, the white Corr field
at the bottom right-hand corner of the display switches to a yellow Corr.
For Agilent 8970B
users
All the NFA models have more RF ranges than the Agilent 8970B and
unlike the Agilent 8970B, all of these ranges can be calibrated using a
15dB ENR noise source without the need for external amplification.
Chapter 2
55
Making Basic Measurements
Calibrating the Analyzer
To perform a calibration
Step 1. Verify that the correct ENR table is loaded in the NFA, or input the ENR
values of the noise source into the NFA.
See “Entering Excess Noise Ratio (ENR) Data” on page 33 for more
details.
Step 2. Configure the measurement parameters (frequency range, number of
points, bandwidth, averages, and measurement mode) you want to use
for the measurement.
Step 3. Connect the noise source output directly to the NFA input.
NOTE
If you are following this procedure using an N8974A or an N8975A
models care needs to be taken when connecting the precision 3.5 mm
connector by applying the correct torque. For an explanation of the
connectors and guidance on the correct torque values, see the
Performance Verification and Calibration Guide.
Figure 2-7
NFA Calibration with Normal Noise Source
Noise Source
NOTE
You may need to use connector adaptors to connect the noise source
output to the NFA input during calibration. The connectors you use need
to be included in the measurement. If you remove the connectors from
the measurement you need to apply Loss Compensation to compensate
for any loss caused by the connectors removal. See “Using Loss
Compensation” on page 98 for an explanation of this.
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Step 4. If required select an input attenuator range by pressing the Corr key and
the Input Cal menu key to set the minimum and maximum input
attenuation.
See “Selecting the RF Input Attenuation Range” on page 58 for more
details on input attenuation.
Step 5. Press the Calibrate key twice to initiate the calibration.
The first time you press the key you are prompted to press it again. This
two-stroke key press feature prevents you from accidentally pressing
Calibrate and erasing the calibration data.
The NFA performs the calibration, displaying a percentage counter while
this is happening.
When the calibration is finished the calibration indicator changes from a
white Uncorr display to a white Corr display. Also the Corrected menu
key is now available to you. This allows you to make corrected or
uncorrected measurements by switch between Corrected(On) and
Corrected(Off) respectively.
NOTE
When performing a calibration only noise figure and effective
temperature result types are calculated by the NFA. If you wish to see
the results during a calibration you need to select either of these two
result types to display them.
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Calibrating the Analyzer
Selecting the RF Input Attenuation Range
When working in the RF frequency range of 10 MHz to 3.0 GHz, the NFA
has a default input attenuation range for calibration of 0dB to 20dB. In
the default mode the calibration takes 5 sweeps as 5 attenuator ranges
need to be calibrated. The greater the attenuator range selected, the
greater the number of calibration sweeps there are, hence, the longer the
calibration routine.
When measuring a high-gain device you may need to increase the input
attenuation. If you do not know the gain of the DUT, you can perform
calibration using the default range, note what error codes are presented
and then calibrate again using increased attenuation value. The
attenuation value is indicated on the display as shown in Figure 2-8 and
Figure 2-9. If the NFA continues to display error codes, there is a need to
add external attenuator pads and correct for this attenuation using the
Loss Compensation feature. For an explanation of how to use the feature,
see “Using Loss Compensation” on page 98.
If an error message occurs while calibrating, you need to recalibrate. For
a complete list of error codes see Chapter 7 “Troubleshooting”.
To select the RF input attenuation:
Step 1. Press the Corr (Corrected) key.
Step 2. Press the Input Cal menu key and select the attenuation range you want
Step 3. Set the attenuator range using the Min RF Atten and Max RF Atten menu
keys, and select the attenuation values you want from the list.
Figure 2-8
N8972A and N8973A Attenuator Indicators
Invalid Indicator
58
Valid Indicator
Chapter 2
Making Basic Measurements
Calibrating the Analyzer
Figure 2-9
N8974A and N8975A Attenuator Indicators
Invalid Indicators
Valid Indicators
Invalid RF Indicator and Valid Microwave Indicator
Selecting Microwave Input Attenuation Range
The N8974A and N8975A models have a microwave frequency range.
When working in the microwave frequency range of 3.0 GHz to 26.5 GHz,
the NFA has a default input attenuation for calibration of 0dB. Unlike
the RF attenuators, the microwave attenuators cannot autorange.
Therefore there is a risk of overdriving the instrument. In most cases
0dB attenuation is adequate. A guide to the input powers that each
range can handle can be seen in Table 2-1.
Table 2-1
Power Detection and Ranging
Attenuation
Maximum Input
Power
Approximate DUT Characteristics
0dB
-30dBm
Combined NF and Gain of DUT
<25dB over full bandwidth
15dB
-20dBm
Combined NF and Gain of DUT
<35dB over full bandwidth
30dB
-10dBm
Combined NF and Gain of DUT
<45dB over full bandwidth
To select the microwave input attenuation:
Step 1. Press the Corr (Corrected) key.
Step 2. Press the Input Cal menu key and select the attenuation range you want
Step 3. Set the attenuator range using the Min µW Atten and Max µW Atten menu
keys, and select the attenuation values you want from the list.
Chapter 2
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Making Basic Measurements
Calibrating the Analyzer
Setting the Microwave Input Attenuation after a Calibration
The microwave attenuators cannot autorange. Hence, when making a
microwave measurement you must manually set the microwave input
attenuation to avoid overdriving the NFA. To set the microwave input
attenuation:
Step 1. Press the Sweep key.
Step 2. Press the Manual Meas, More 1 of 2 menu key.
Step 3. Press the Fixed µW Att menu key and select the attenuation range you
want.
Step 4. Press the More 2 of 2 menu key.
Step 5. Press the RF/µW Atten menu key to enable RF/µW Atten(Fixed).
NOTE
If you want to set the RF input attenuation, “Setting the Microwave
Input Attenuation after a Calibration” procedure can be applied to RF
input attenuation. The procedure is similar except you need to substitute
Fixed RF Att in Step 3.
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Displaying the Measurement Results
Displaying the Measurement Results
The NFA features a 17 cm color display and a comprehensive set of
display features to allow you to analyze the measurement results in
detail, or quickly obtain pass/fail indication.
The following display format features are available:
• Graph, Table or Meter mode display
• Single or dual-graph display allowing any two available result types
to be displayed simultaneously
• Zoom to display only one result graph on the display
• Combine option to display two result types on the same graph
• Markers for searching the trace
• Display an active trace, a memory trace, or both
• Save the current active trace data to memory
• Switch the graticule on or off
• Switch display annotation on or off
NOTE
If the NFA’s display has been previously disabled in Remote mode, you
need to press the System (LOCAL) key to activate the display.
Selecting the Display Format
You can display the measurement results in either:
• Graph format
• Table format
• Meter format
The default display provides a display of noise figure and gain on the
dual-graph display. The upper graph is noise figure and the lower graph
is gain.
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Displaying the Measurement Results
In all formats you can choose two result parameters you want to display.
To set the display format:
Step 1. Press the Format key.
Step 2. Press the Format menu key and select the Graph, Table or Meter menu key
to select the display mode you want. See Figure 2-10.
Figure 2-10
Format modes
Navigating Around the Display
Active Graph
The active graph is highlighted by a green border. Noise Figure is the
active graph by default.
NOTE
When in table or meter format the active measurement parameter title
has a green border around it.
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Displaying the Measurement Results
Figure 2-11
Dual-graph display
Changing the
Active Graph
To change the active graph, press the
key below the display. This
key allows you to set the upper or lower graph as the active graph.
NOTE
When in table or meter format the
parameter.
Viewing the Full
Screen
You can fill the entire display and remove the menu keys, the active
function area annotation, and the display status line annotation from the
display. Press the Full Screen key to view the full screen. Pressing the
Full Screen key again returns it to the previous display. All other key
presses are ignored except: Zoom, Next Window, Save Trace, Help, Preset,
Print, Power Standby, and the Viewing Angle keys.
NOTE
The Full Screen key also functions in table or meter format.
Chapter 2
key changes the active
63
Making Basic Measurements
Displaying the Measurement Results
Selecting Result Types to Display
You can choose to display any pair of measurement results in all of the
display format modes.
NOTE
You cannot display the same result type in both graphs. If you attempt
this, an error message Each result type selected must differ
from all others is displayed in the status line.
The measurement result types are as follows, with their units in
parenthesis:
• Noise Figure (dB or linear)
• Gain (dB or linear)
• Y Factor (dB or linear)
• Teffective (Kelvin, K; Celsius, C; Fahrenheit, F)
• Phot (dB or linear)
• Pcold (dB or linear)
To specify which measurement results are displayed
Step 1. Select which measurement result is active using the
key.
The active measurement is highlighted by a green border.
Step 2. Press the Result key and select the result type that you want to display.
Step 3. Press the
key to make the other measurement result active.
Step 4. Press the Result key and select the result type you want to display.
NOTE
When you press the Scale key, the active measurement result’s scale
menu keys are shown.
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Graphical Features
Viewing a single graph
While in graph format mode, you can press the
key located below
the display and the active graph fills the display as a single graph, as
shown in Figure 2-12. Pressing the key again returns the display to
dual-graph.
Figure 2-12
Displaying a single graph
NOTE
When in single graph mode, pressing the
single graph.
Chapter 2
key displays the other
65
Making Basic Measurements
Displaying the Measurement Results
Combining two graphs on the same graph
You can combine the upper and lower graphs from a dual-graph display
into a single combined display. The default setting is Combined(Off) and
the graphs are not combined.
When combining two graphs the Y-scale result limits are not re-scaled
and both graphs have their own Y-scale result limits.
NOTE
To combine the two graphs:
Step 1. Press the Format key and ensure Format(Graph) is selected.
Step 2. Press the Combined(On) menu key to combine the two currently displayed
graphs on the same graph.
Figure 2-13
Typical display with two traces combined on the same graph
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Displaying the Measurement Results
Displaying the Current Data Trace and the Recalled Memory
Trace
When a trace finishes its first complete sweep, the Data -> Memory menu
key becomes active.
To save a trace to memory, press the Data -> Memory menu key. After
pressing the Data -> Memory menu key, the Trace menu key becomes
active.
To view the saved trace, press the Trace menu key, followed by the
Memory menu key. The memory trace is presented in the display.
To view both the saved trace and the current active trace, press the Trace
menu key, followed by the Data & Memory menu key.
To view the current data trace only, press the Trace menu key, followed by
the Data menu key. This is the default setting.
NOTE
Pressing Autoscale does not re-scale a memory trace.
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Displaying the Measurement Results
Turning the Graticule On and Off
When Graticule(On) is set, the graticules are displayed on the screen. This
is the default setting. When Graticule(Off) is set the graticules are not
displayed on the screen.
To turn the graticule on or off:
Step 1. Press the Format key.
Step 2. Press the Graticule menu key to select the Graticule(Off) or Graticule(On) as
required.
Figure 2-14
Typical Graph with Graticule Switched Off
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Displaying the Measurement Results
Turning the Display Annotation On or Off
When Annotation(On) is set, the annotation is displayed on the screen.
This is the default setting. When Annotation(Off) is set the annotation is
not displayed on the screen.
To turn the annotation on or off:
Step 1. Press the Format key.
Step 2. Press the Annotation menu key to select Annotation(Off) or Annotation(On)
as required.
Figure 2-15
Typical Graph with Annotation Switched Off
NOTE
When Annotation(Off) is selected and limit lines are set to Test(On) the
limit line failure indicator is disabled.
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Displaying the Measurement Results
Setting the Scaling
You can set the result’s scale parameters in the active graph. To set the
scale, press the Scale key.
NOTE
To change the active graph, press the Result key and select another
measurement parameter’s menu key. Press the Scale key to set the scale
of the measurement parameter.
Figure 2-16
Typical Noise Figure Displayed on a Graph
You can set the scale for the measurement parameter or press the
Autoscale menu key. Pressing Autoscale selects the optimum values for
Upper Limit, Lower Limit, and Scale/Div.
NOTE
If limit lines are set to Display(On), and Autoscale is pressed or the scale is
changed, the limit lines may no longer appear in the display.
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NOTE
If a memory trace is set to display, and Autoscale is pressed or the scale is
changed, the memory trace may no longer appear in the display.
Setting Noise Figure Scale
NOTE
The following procedure can also be applied to other result types
To make Noise Figure the active screen and set up the noise figure
parameters use the following procedure.
Step 1. Press the Result key.
Step 2. Press the Noise Figure menu key.
Step 3. Press the Scale key.
Step 4. Press the Units menu key and select, either logarithmic ratio Units(dB) or
linear ratio Units(Linear).
Step 5. Press the Upper Limit menu key. Change the upper limit value using the
RPG or the numeric keys. Values are entered using the numeric keys,
and terminated using the Enter key if the units are dB. If your units are
linear, terminate them using the engineering multiplier menu keys
presented.
Step 6. Press the Lower Limit menu key. Change the lower limit value using the
RPG or the numeric keys. Values are entered using the numeric keys,
and terminated using the Enter key if the units are dB. If your units are
linear terminate them using the engineering multiplier menu keys
presented.
NOTE
The upper limit, lower limit, and scale per division values are coupled,
therefore changing one of these may affect the others.
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Making Basic Measurements
Displaying the Measurement Results
Step 7. Press the Scale/Div menu key. Change the scale per division value using
the RPG or the numeric keys. Values are entered using the numeric keys,
and terminated using the Enter key if the units are dB. If your units are
linear terminate them using the engineering multiplier menu keys
presented.
Setting the Reference Level
NOTE
The reference level minimum and maximum limits are restricted to the
values of the upper and lower scale settings.
NOTE
The reference level is only visible when the Display Ref(On) is enabled.
Step 1. Press the Display Ref menu key if you want the reference level displayed
in the active graph. The default setting is Display Ref(Off). Set the
Display Ref(On) to switch the reference level on.
Step 2. Press the Ref Level menu key. Change the reference level value using the
RPG or the numeric keys. Values that are entered using the numeric
keys are terminated using the Enter key.
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Working with Markers
The marker functions only apply when you are working in graph format.
NOTE
Marker functions measure the frequency and measurement result by
placing a diamond-shaped marker at a point on the trace. The
measurement result displayed depends on the result type selected.
You can compare results by placing markers on a previously saved
(memory) trace and the current (data) trace and measuring the
difference.
The NFA has four markers, Marker(1), Marker(2), Marker(3), and Marker(4).
The markers are coupled to both the lower graph trace and upper graph
trace.
Each marker can be enabled as a normal, delta, or band pair marker. The
active marker’s frequency is displayed in the active function area. The
enabled marker’s results are displayed in the annotation above the upper
graph where the measurement mode status is displayed when all the
markers are off.
Selecting Markers
To select a marker:
Step 1. Press the Marker key.
Step 2. Press the Marker menu key to select the marker of interest.
The active marker is identified by being underlined in the Marker menu
key label. See Figure 2-17.
Figure 2-17
The Active Marker is Underlined
Step 3. Press the State menu key and press the Normal menu key to highlight it.
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Displaying the Measurement Results
Figure 2-18
A Normal State Marker
A single coupled pair of markers are now placed on both traces. Turn the
RPG to place the markers at the point on the trace you want to measure
or use the numeric keys to enter the frequency of interest. The marker
frequency and measurement parameter are annotated above the graph.
Its frequency value is displayed in the active function area.
To turn an active
marker off
To turn an active marker off, press the State menu key and press the Off
menu key. This also removes the marker annotation above the graph and
the marker frequency from active function area.
To change the
active marker
The default active marker setting is Marker(1). To change the active
marker, press the Marker menu key. This moves the active marker from
Marker(1) to Marker(2). Press it again and it moves the active marker from
Marker(2) to Marker(3). This process is repeated until it returns to the
Marker(1).
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Figure 2-19
Four Normal State Markers
To Switch all the
Markers Off
To switch all the markers off press Markers All Off. This turns off all the
markers and associated annotation.
Changing the Marker States
To use Delta
Markers
The State(Delta) menu key places a reference marker at the current
position of the active marker. The delta markers enable you to measure
the difference between the reference marker and the delta marker
position on the trace. Turn the RPG to place the delta marker to the
point on the trace you want to measure. The position of the reference
marker remains fixed. The delta marker has its frequency and
measurement result value differences annotated relative to the reference
marker above the upper graph. Its actual frequency value is displayed in
the active function area. See Figure 2-20.
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Figure 2-20
The Delta Marker State enabled
To activate a Delta marker:
Step 1. Press the Marker key.
Step 2. Press the Marker menu key to select the marker of interest.
Step 3. Press the State menu key and press the Delta menu key to highlight it.
Use the RPG to move the Delta marker from the reference. The
annotation displays the difference.
To use Band Pair
Markers
The State(Band Pair) menu key places two markers allowing you to choose
to move either the normal marker or the reference marker. This feature
is similar to the State(Delta) except you can choose to move either marker.
The position of the reference marker remains fixed until
Band Pair(Normal) menu key is pressed and the active marker becomes
the fixed marker. This can be altered by pressing the Band Pair(Ref) menu
key to enable the reference marker as the active marker. The active
marker has its frequency and measurement result value differences
annotated above the graph. Its actual frequency value is displayed in the
active function area. See Figure 2-21.
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Figure 2-21
Band Pair with Reference Marker Enabled
To activate the Band Pair markers:
Step 1. Press the Marker key.
Step 2. Press the Marker menu key to select the marker of interest.
Step 3. Press the State menu key and press the State(Band Pair) menu key to
highlight it.
The Band Pair(Ref) and Band Pair(Normal) menu keys in the Band Pair
menu key is no longer disabled.
Step 4. Use the RPG to move the active marker from the reference. The
annotation displays the difference between the reference and the normal
markers position.
Step 5. Pressing the Band Pair menu key sets the Band Pair(Normal) as the fixed
marker allowing you to move the reference marker. Pressing the
Band Pair menu key again sets the Band Pair(Ref) as the fixed marker
allowing you to move the normal marker.
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Displaying the Measurement Results
Figure 2-22
Band Pair with Normal Marker Enabled
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Displaying the Measurement Results
Marking Memory Traces
Markers can be placed on a memory trace. See “Displaying the Current
Data Trace and the Recalled Memory Trace” on page 67 to obtain an
explanation on memory traces. The default setting is Trace(Data) where
the marker is placed on the active trace.
To place a marker on the recalled memory trace:
Step 1. Enable the Trace(Memory) menu key.
Step 2. Set the marker you want to use to Normal, Delta, or Band Pair.
The marker is placed on the memory trace. If Trace(Data&Memory) on the
format menu is enabled, switching between Trace(Data) and
Trace(Memory) switches the marker between the traces.
NOTE
If a marker is set to Trace(Memory) and the Memory trace is not
displayed, the marker and its annotation are not displayed.
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Searching with Markers
The Search menu key accesses a further menu which allows you to place
an active marker on the minimum and maximum points of a trace, while
in Normal or Delta state. When in Band Pair state you can search for the
Minimum Peak to Maximum Peak on the trace. You can set these to
repeat continuously, or by manually pressing the Find menu key as
required.
NOTE
If you are searching continuously the markers have additional
annotation which identifies which marker is the minimum and the
maximum. The annotation is “∨” a minimum, “∧” a maximum. If you
change the active graph the annotation remains on the original graph.
Searching for Min
or Max point
You need to have activated a Normal or Delta marker state to perform a
minimum or maximum search.
Figure 2-23
Typical Trace showing Maximum Point Found
To search for the maximum point:
Step 1. Press the Search menu key.
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Step 2. Press the Search Type menu key to select the Search Type(Max).
Step 3. Press the Find menu key.
The marker is now placed at the maximum point of the trace.
If you want to continuously find the maximum point on the trace, select
Continuous(On).
Searching for Peak You need to have activated a marker state to Band Pair to perform a
to Peak points
Peak to Peak search.
Figure 2-24
Peak to Peak Found
Step 1. Press the Search menu key.
Step 2. Press the Search Type menu key to select Pk-Pk.
Step 3. Press the Find menu key.
The markers are now on the maximum and minimum points of the trace.
If you want to continuously find the maximum and minimum points on
the trace, select Continuous(On).
The annotation displays the difference between the two points.
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Indicating an Invalid Result
Indicating an Invalid Result
When an invalid result is detected while in graph display format, the
graph is drawn at the top of the screen for the current measurement
point and a special marker indicator is displayed. Also in table and meter
formats the same special indicators are used to display an invalid result.
Several invalid result conditions may exist simultaneously. These
conditions are ranked in order of severity and only the most severe
condition present is displayed.
The ranking order is:
Table 2-2
Ranking Order of Invalid Result Conditions
Ranking Order
Invalid Result Condition
Marker Indicator
1
Hot power ≤ cold power
“==”
2
Corrected calculation not possible
“xx”
3
Measurement result calculation
invalid
“--”
The ranked order 2 only occurs if a corrected measurement is requested
and either:
• The input range used at this measurement point is not calibrated.
• The input range is calibrated, but the calibration data is invalid at
this point.
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Indicating an Invalid Result
RF Input Over and Under Range Conditions
The NFA can detect when the RF input power is either too large for the
current input attenuation or too small for the current input attenuation.
This causes the RF input to over range or under range respectively.
These conditions are indicated beside a marker readout or table/meter
entry as RFO or RFU, for RF input over or under range respectively.
The over range condition could occur when the RF input power is so large
that even with the maximum input attenuation, the output power from
the input stage is still sufficiently large to create a non-linear response at
subsequent stages. This problem could be solved by using external
attenuation.
The under range condition could occur when, for example, the RF input
attenuation has been fixed at such a value that the level of input power,
less attenuation would not lead to compression of the subsequent stages.
This problem could be solved by either allowing the RF input attenuators
to autorange or choosing a lower value of fixed attenuation.
IF Input Over and Under Range Conditions
The NFA can detect when the power presented to the IF input section
detector is either too large for the current IF input attenuation or too
small for the current IF input attenuation. This causes the IF input
section to over range or IF input section to under range respectively.
These conditions are indicated beside a marker readout or table/meter
entry as IFO or IFU, for IF input section over or under range respectively.
The over range condition could occur when the RF attenuation is fixed at
a too small a value for the level of input power and subsequently the IF
section’s input power is so large that even with the maximum IF
attenuation, the power level at the IF detector is too large to obtain
linear measurements. This problem could be solved by using more RF
input attenuation or allowing the RF input attenuators to autorange.
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Example of a Basic Amplifier Measurement
Example of a Basic Amplifier Measurement
Noise figure measurements are made by measuring the output power of
the DUT for two different input noise power levels. Typically, the high
power input comes from a calibrated noise source, and the low power
input uses the noise power generated at ambient temperature.
This section uses a DUT to show how a basic noise figure measurement
and various basic operations are performed. The DUT used is a low noise
amplifier with a usable frequency range of 20 MHz to 3.0 GHz. The
specifications of interest to the example are listed in Table 2-3.
Table 2-3
The Example DUT Specifications
Frequency Range
Typical Gain
Minimum Gain
Typical Noise
Figure
20 MHz to 3 GHz.
19 dB
14 dB
3.8 dB
The example sets a frequency range of interest of 1.0 GHz to 2.0 GHz.
The purpose of the measurement is to verify the specified table results
are as stated over the frequency range of interest.
When you are making measurements, follow the procedure and change
the values to meet your needs.
NOTE
For these basic measurements confirm the NFA Meas Mode is in the
default setting. This status is displayed above the graphs as follows:.
• DUT: Amplifier
• System Downconverter: Off
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Example of a Basic Amplifier Measurement
Calibrating the Noise Figure Analyzer
The first step is to calibrate the NFA to obtain the corrected
measurement you wish to make.
Step 1. Turn the instrument on by pressing On and wait for the power-up
process to complete.
NOTE
To obtain greater accuracy, it is recommended the NFA warm up for at
least one hour with Alignment(On). The default setting is Alignment(On)
Step 2. Press System, Power On/Preset, Preset (Factory) and press the green Preset
key to return the NFA to its factory-default state.
Step 3. Press ENR, ENR Mode(Table), Common Table(On), ENR Table to enter the
ENR values of the noise source.
In this example, a 346B noise source is used which has the following
Frequency/ENR pairs up to 2 GHz (covering the required frequency
range of 1.0 GHz to 2.0 GHz):
Table 2-4
Example Noise Source ENR/Frequency values
Frequency
GHz
ENR
dB
.01
15.29
.10
15.39
1.0
15.17
2.0
15.10
Step 4. Press the Frequency/Points key to set the frequency parameters of the
measurement:
• Freq Mode — Sweep
• Start Freq — 1.0 GHz
• Stop Freq — 2.0 GHz
• Points — 15
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Example of a Basic Amplifier Measurement
Step 5. Press the Averaging/Bandwidth key to set the bandwidth and averaging
you want.
This example uses the following settings:
• Averaging — On
• Averages — 5
• Average Mode — Point
• Bandwidth — 4 MHz
Step 6. Press Corr, Input Cal to set the minimum and maximum input
attenuation, if required.
This example uses the default minimum and maximum input
attenuation of Min RF Atten(0 dB) and Max RF Atten(20 dB), respectively.
Step 7. Connect the noise source input to the 28V OUTPUT port using a BNC
cable, and connect the output to the INPUT 50 Ω port as shown in Figure
2-25.
NOTE
When using the N8974A and N8975A models care must be taken to
torque the precision 3.5mm connector to the correct value. To find the
correct value of torque to apply, see the Performance Verification and
Calibration Guide.
Figure 2-25
Calibration Setup with Normal Noise Source
Noise Source
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Step 8. Press the Calibrate key twice to calibrate the NFA.
Once you have set the frequency span, averaging, bandwidth, and
calibrated; a graph similar to Figure 2-26 is now displayed.
With calibration completed and no device under test inserted, both gain
and noise figure with Corrected(On) are near zero dB. This shows that the
NFA has removed the noise contribution from the measurement system.
Since the input is noise, there is some variation above and below zero.
Figure 2-26
Typical Graph after calibration is complete
Press the Format key to select Format menu key to Table. A result similar
to Figure 2-27 is now displayed. The expectation is 0 dB of noise figure
and gain. It may be better to view these results using table format mode.
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Figure 2-27
Typical Tabulated Results after Calibration
Making Measurements
To make noise figure measurements once calibration is complete:
Step 1. Disconnect the noise source from the 50Ω input of the NFA
Step 2. Connect the DUT to the 50Ω input of the NFA.
Step 3. Connect the noise source to the DUT as shown in Figure 2-28.
Figure 2-28
Connecting the DUT to make a measurement
Noise Source
DUT
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After the DUT and noise source are connected, the measurement result
appears on the NFA’s display. If it does not, press Restart. If you want to
get a continuous update ensure Sweep(Cont) is enabled. This is the
default setting.
A result similar to Figure 2-30 is now displayed.
Figure 2-29
Typical Tabulated Results after Measurement
Step 4. Press the Format key to select Format menu key to Graph. A graphical
result similar to Figure 2-29 is now displayed.
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Figure 2-30
Typical Graphical Results after Measurement
The results shown in Figure 2-29 and Figure 2-30 shows the DUT has an
average noise figure of 3.35 dB and a gain of 18.50 dB. The device under
test therefore meets its manufacturer’s specification over the frequency
range of interest.
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Advanced Features
This chapter describes how to use the Limit Lines and Loss
Compensation features on your Noise Figure Analyzer. It also covers how
to make manual measurements.
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Advanced Features
What You will Find in this Chapter
What You will Find in this Chapter
This chapter covers:
• Setting up Limit Lines and using them for pass/fail testing of the
measurements.
• Using Loss Compensation and using this to correct for system losses
in cabling, switches, or connectors and so forth. Also, the use of S2P
file formats to create Loss Compensation Tables.
• Making Manual Measurements.
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Setting up Limit Lines
Setting up Limit Lines
Limit lines can be set to mark lower or upper boundaries of the active
traces and they can also be set to notify you of a failure when a trace
passes over a limit line. Two limit lines can be applied to a single trace,
for example, allowing an upper and lower boundary limit to be specified.
The NFA features four independent Limit Lines. The Limit Line(1⇑) and
Limit Line(2⇑) are applied to the upper graph, and Limit Line(3⇓) and
Limit Line(4⇓) are associated with the lower graph.
To change the
Limit Line
The default limit line setting is Limit(1⇑). To change the active indicator,
press the Limit Line menu key. This moves the active indicator from
Limit Line(1⇑) to Limit Line(2⇑), press it again and it moves the active
indicator from Limit Line(2⇑) to Limit Line(3⇓). This process is repeated
until it returns to the Limit Line(1⇑).
Setting the Type of You can set the Limit Line to be an upper limit or lower limit and test the
Limit Line
trace against this limit line setting.
To set the limit line type, choose Type(Upper) if you want it to be above the
trace or Type(Lower) if you want it to be below the trace. Each of the four
limit line needs to be set up separately.
NOTE
There can be instances when you want to have two limit lines on a screen
configured as Upper or Lower type, where one limit line could be a
tolerance limit fail and the other an absolute limit fail.
Enabling Testing
against a Limit
Line
You can set the Limit Line to test against the trace. If a result fails
testing it is reported in the upper left hand corner of the display as
shown in Figure 3-1. In table mode you also see the reported result
failure.
To set the testing of the trace against the limit line, choose Test(On) if you
want the result reported or Test(Off) if you do not want the result
reported. Each of the four limit lines need to be set up separately.
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Setting up Limit Lines
NOTE
After a failure the LIMITS FAIL: indicator remains displayed until you
either switch Test(Off), change the limit line type, or press Restart.
Figure 3-1
Limit Fail Indicator
Limit Fail Indicator
To Display a Limit
Line
You can choose to display a Limit Line.
To Switch all the
Limit Lines Off
To switch all the Limit Lines off, press Limit Lines All Off. This
simultaneously switches off all Limit Lines, regardless of what graph or
trace they are associated with and setting both Test(Off) and Display(Off).
NOTE
When a limit line is switched off the limit line data is not affected.
To display the limit line on the graph, choose Display(On). To not display
the limit line on the graph, choose Display(Off). Each of the four limit line
needs to be set up separately.
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Setting up Limit Lines
Creating a Limit Line
To set up limit lines, you need to specify the frequencies, the Y-axis value
and whether it is to be connected to the previous limit line point or not.
The limit line consists of a table of entries each of which is a
frequency-limit-connected group.
The Limit or Y-axis value is a dimensionless unit, hence you need to know
what Y-axis scale you are working in before you set this.
NOTE
When you change the result parameter, the Limit or Y-axis value is not
converted. This is due to the value being dimensionless.
To create a limit line:
Step 1. Press the Limit Lines key and select the limit line you want to create.
Step 2. Press the Editor menu key.
You are presented with a Limit Line table.
Figure 3-2
Limit Line Table
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Setting up Limit Lines
Step 3. Enter the first Frequency value. Press the Tab key.
Step 4. Enter the first Limit or Y-axis unit value. Press the Tab key.
For a limit line value to be useful, it should be derived from the scale
values you are using to display the trace.
Step 5. Press the arrow key to change Connected to either Yes or No.
When Connected is set to Yes it connects the point to the previous point
to form a continuous line. To disconnect a point, set Connected to No, this
disconnects it from the previous point. Figure 3-3 shows the connections
and Figure 3-4 shows the graphical result with limit line Display(On).
NOTE
When the Limit Line is set to Test(On), and a trace crosses over the limit
line, the test is only performed between connected points. Also, if you are
making a fixed frequency measurement you only need to specify that
frequency value and the limit line can be tested on the single point.
Step 6. Repeat this process until the limit line is defined. Limit line tables can
have a maximum of 201 entries.
The limit line is now defined. Press the Prev key or Limit Line key to
return to the limit line menu. When saving a limit line table you need to
specify which limit line number. See “Saving a File” on page 24.
For a greater explanation of table use, See “Working with Tables” on
page 28.
NOTE
You can load a previously saved Limit Line table. However, you need to
specify which limit line number you want loaded. See “Loading a File” on
page 25.
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Figure 3-3
Typical Limit Line Connections in Table
Figure 3-4
Limit Line Connections Displayed
Limit Line Not Connected to Previous point
Connected Limit Line
Connected Limit Line
Trace
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Using Loss Compensation
Using Loss Compensation
You can configure the NFA to compensate for losses due to cabling,
connectors and temperature effects that occur in the measurement
setup. These can be between the Noise Source and the DUT, Before DUT,
and/or between the DUT and the NFA input, After DUT. Loss
compensation can be set either by specifying a single, fixed loss value
which gets applied at all frequencies, or using various loss values,
specified in a table, applied across the frequency span. In the table mode,
linearly interpolated values are used between each table entry. You can
also specify a temperature value which is applied at all frequencies.
You can also use S2P data file formats output from a Network Analyzer
to create Loss Compensation tables. The NFA converts the S2P file
format to a Loss Compensation table.
Examples where Loss Compensation is applied
This is important in cases such as:
1. Amplifiers with waveguide input, where a lossy waveguide-to-coax
adapter is needed.
2. Transistors, where input and output tuners are required.
3. Non-50Ω converters (such as TV tuners and amplifiers) where
matching pads or transformers are required.
4. Compensation for fixed attenuators used to improve SWR.
5. Double sideband measurement modification (of receivers and mixers)
to approximate single sideband results.
Configuring Fixed Loss Compensation
To configure fixed loss compensation follow the example below:
Step 1. Press the Loss Comp key
Step 2. Press the Setup menu key to access the Loss Compensation Setup form,
see Figure 3-5
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Figure 3-5
Loss Compensation Setup Form
Step 3. When configuring loss compensation before the DUT, use the Tab key to
navigate to the Before DUT field and set before DUT to fixed by selecting
the Fixed menu key to highlight it.
NOTE
A fixed loss compensation value cannot be entered or changed if the
Before DUT field or the After DUT field is not set to fixed. It is selected by
highlighting the Fixed menu key.
Step 4. To set the loss compensation value before the DUT, use the Tab key to
navigate to the Before DUT Fixed Value field and input the required value
for the loss occurring before the DUT, see Figure 3-6.
Enter a value using the numerical keypad and terminate it using the
unit keys presented to you, linear or dB.
The lower limit is -100.000 dB, the upper limit is 100.000 dB, and the
default is 0.000 dB.
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Step 5. When configuring loss compensation after the DUT, use the Tab key to
navigate to the After DUT field and set after DUT to fixed by selecting the
Fixed menu key to highlight it, see Figure 3-6.
Step 6. To set the loss compensation value after the DUT, use the Tab key to
navigate to the After DUT Fixed Value field and input the required value
for the loss occurring after the DUT.
Enter a value using the numerical keypad and terminate it using the
unit keys presented to you, linear or dB.
The lower limit is -100.000 dB, the upper limit is 100.000 dB and the
default is 0.000 dB.
Figure 3-6
Loss Compensation Setup Form with Fixed Selected
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Configuring Table Loss Compensation
To configure table loss compensation proceed as follows.
Step 1. Press the Loss Comp key
Step 2. Press the Setup menu key to access the Loss Compensation Setup form,
see Figure 3-7.
Figure 3-7
Loss Compensation Setup Form
Step 3. When configuring table loss compensation before the DUT, use the Tab
key to navigate to the Before DUT field and select the Table menu key to
highlight it, see Figure 3-8.
The table loss compensation used is as specified in the Loss
Compensation Before DUT Table. See “Creating a Loss Compensation
Table” on page 103.
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Using Loss Compensation
Step 4. When configuring table loss compensation after the DUT, use the Tab key
to navigate to the After DUT field and select the Table menu key to
highlight it, see Figure 3-8.
The table loss compensation used is as specified in the Loss
Compensation After DUT Table. See “Creating a Loss Compensation
Table” on page 103
Figure 3-8
Loss Compensation Setup Form with Table Selected
NOTE
You can load a previously saved Loss Compensation table. However, you
need to specify whether the Loss Compensation table is an After Table or
a Before Table. See “Loading a File” on page 25.
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Creating a Loss Compensation Table
Loss Compensation tables can have a maximum of 201 entries. To create
a loss compensation table proceed as follows.
NOTE
The example shows how to enter a Before DUT Table. If you want to
enter an After DUT Table follow the procedure, changing the Before Table
key presses to After Table key presses.
NOTE
If you want to enter new loss compensation data and there is previous
loss compensation data in the NFA, you can delete the previous data by
pressing Clear Table. An empty table is shown in Figure 3-9.
NOTE
The Loss Compensation table frequency limits in the Before DUT Table
are specified in terms of the DUT’s input frequencies and the
After DUT Table are specified in terms of the DUT’s output frequencies.
This is important when making frequency-converting DUT
measurements or using a system downconverter.
Step 1. Press the Loss Comp key, and the Before Table menu key.
A Loss Compensation Before DUT Table appears on the display with
the first loss frequency point in the table highlighted, see Figure 3-9. The
table editing and navigation menu items now appear. For details on
working with tables, see “Working with Tables” on page 28.
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Using Loss Compensation
Figure 3-9
An Empty Loss Compensation Table
Step 2. Enter the Loss Frequency value in the table using the numeric keys.
Terminate it using the unit menu keys.
Step 3. Press the Tab key to move the highlight to the Loss Value column and
enter the corresponding Loss Value.
When terminating the Loss Value you can use either dB or linear menu
keys. However, the result appears in the table in dB.
Step 4. Press the Tab key to move the highlight to the Loss Frequency column
and enter the next Loss Frequency Value.
Step 5. Repeat steps 2 to 4 until all the Loss Frequency and Loss Values you
need are entered.
Step 6. After completing the Loss Compensation table entries, press the Prev key
or Loss Comp key to return to the Loss Compensation menu.
Step 7. Once you have completed entering the Loss Compensation data, save the
Loss Compensation table using the File key.
For details on saving files, See “Saving a File” on page 24.
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NOTE
If you do not save the Loss Compensation table, you may lose the data.
This depends on your Power On/Preset condition. See “Defining the
Power-On/Preset Conditions” on page 212 for an explanation of these.
NOTE
You can insert the Loss Frequency/Loss Values in the Loss Compensation
Table entry in any order, as the NFA automatically sorts the table list
into ascending frequency order.
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Using Loss Compensation
Working with S2P, S1, and S2 File Formats
The S2P data file formats are described as frequency dependent linear
network parameters for 2 port components. The S2P file is output from a
Network Analyzer in the standard ASCII Touchstone S2P format. The
output format includes frequency values, S11, S21, S12, and S22
network parameters. Not all these parameters are used by the NFA. The
NFA uses the frequency parameter which it reads as a loss frequency
and the S21 parameter which it converts to a loss value.
NOTE
When saving S2P data format from a Network Analyzer you need to
ensure the data is saved in an ascending frequency order.
The S2P file format is loaded as a Loss Compensation table in the NFA,
either as a Before DUT or an After DUT Table. The NFA accepts any files
with the following extensions: S2P, S1, and S2.
The NFA can only load S2P file formats, it cannot save them. However,
they can be copied, deleted and renamed using the NFA’s file manager
functions.
NOTE
If saving a previously loaded S2P file in the NFA, it is saved as a LOS file.
Loading an S2P, S1, or S2 File
To load a S2P format file into the NFA, the process is identical to loading
a loss compensation (LOS) file which has been stored previously on a
diskette. The choice needs to be made using the file manager’s list of
available file formats of LOS, S2P, S1, and S2.
Step 1. Insert the diskette into the floppy drive of the NFA.
For more details on loading files, see “Loading a File” on page 25.
Step 2. Press the File key.
Step 3. Press the Load menu key to access the file system.
Step 4. Press the Loss menu key.
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Step 5. Press either the Before Table or After Table menu key.
A list of available files on the [-A-] drive is displayed. Use the arrow
keys to access the appropriate file. The options have the following file
extensions S2P, S1, and S2
Step 6. Press the Enter key.
A Loading file prompt appears on the display and when this
disappears the file has been successfully loaded.
NOTE
To verify a successful loading of the S2P file as loss compensation table
data, view the Loss Compensation Before or After DUT Table form.
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Using Loss Compensation
Setting Temperature of Loss
To set temperature of loss proceed as follows.
Step 1. Press the Loss Comp key
Step 2. Press the Setup menu key to access the Loss Compensation Setup form,
see Figure 3-10.
Figure 3-10
Loss Compensation Setup Form with Temperature Selected
Step 3. To set the temperature value before the DUT, use the Tab key to navigate
to the Before Temperature field and input the required temperature of loss
value occurring before the DUT.
Enter a value using the numerical keypad and terminate it using the
unit keys presented to you, either in degrees K, C or F. Entries
terminated using the C or F menu keys are converted to K.
The lower limit is 0.0 K, the upper limit is 29,650,000.0 K and the
default is 0.0 K.
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Step 4. To set the temperature value after the DUT, use the Tab key to navigate
to the After Temperature field and input the required temperature of loss
value occurring after the DUT.
Enter a value using the numerical keypad and terminate it using the
unit keys presented to you, either in degrees K, C or F. Entries
terminated using the C or F menu keys are converted to K.
The lower limit is 0.0 K, the upper limit is 29,650,000.0 K and the
default is 0.0 K.
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Making Manual Measurements
Making Manual Measurements
This feature is for making manual measurements with a hot/cold noise
source. It is primarily for users who do not use SNS or 346 Series noise
sources. These measurements are more difficult and slower than those
made automatically using a Noise Source with the NFA. The technique
can be applied using either a normal or SNS noise source to make Phot
and Pcold measurements by turning the noise source on and off.
The measurement is similar to one made using a Noise Source, except
that a hot source and a cold source must be physically connected for each
noise power reading. The difficulty in working with a cold source, for
example, liquid nitrogen, is in correcting for temperature gradients,
condensation, and so forth. This can introduce errors unless the
measurement is very carefully performed. If a normal noise source is
used it can act as the hot/cold source. The Noise Source is turned on or off
by the appropriate Noise Source(On) and Noise Source(Off), for example,
Noise Source(On) provides Phot.
The following paragraphs give a step-by-step procedure for making the
measurement. Several steps are required for measurements at each
frequency point.
NOTE
The N8972A and the N8973A models do not have microwave hardware
installed and the menu keys are also different. Hence, in the following
procedures the RF/µW Att menu key should be referred to as the RF Att
menu key. Also the Fixed µW Att menu key is unavailable.
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Four important details you need to note when making manual
measurements:
1. A stable reading must be stored in the NFA memory before any
change is made to the physical connections.
A reading is stored by pressing the Accept menu key in the sequence
before changing connections.
2. The DUT must first be connected to the measurement system and
then the NFA’s input attenuators set. The input attenuators must be
fixed for the entire manual measurement by selecting either
RF/µW Att(Hold) or RF/µW Att(Fixed). When using the fixed mode the
fixed attenuator values are specified using the
Fixed RF Att/Fixed µW Att menu keys.
3. The IF attenuators must be allowed to autorange between calibration
and measurement.
4. The IF attenuators must be held fixed for both calibration readings
(noise source on and off) and also for both measurement readings
(noise source on and off) by selecting either IF Att(Hold) or IF Att(Fixed).
When using the fixed IF mode the fixed IF attenuator value is
specified using the Fixed IF Att menu key.
NOTE
When calibrating a series of frequency points and an error is made on
one of the points, you need to start calibrating the series of frequency
points again. Press the Calibrate key to reset the calibration.
NOTE
When measuring a series of frequency points and an error is made on one
of the points, you need to start measuring the series of frequency points
again. Press the Restart key to reset the measurement.
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Making Manual Measurements
Figure 3-11
Manual Measurement Display in Meter Format
Manual Measurements Procedure
NOTE
Between each stage of this procedure, ensure you wait until the data
invalid indicator has disappeared before you proceed.
The steps of a typical measurement are as follows:
Step 1. Find and hold RF/µW attenuators.
1. Connect the hot source, Th, to the DUT input, and the DUT output to
the NFA.
2. Press Noise Source(On) to measure noise power with the source at T h.
3. Press RF/µW Att(Hold) to hold RF attenuators for the entire
measurement.
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Making Manual Measurements
Step 2. Calibrate.
1. Remove the DUT and connect the noise source to the NFA
2. Press Calibration (On) to calibrate with noise source at Phot.
3. Press IF Att(Hold) to hold the IF attenuators fixed at the new value or
use the previously defined IF Att(Fixed) value.
4. Press Accept to store the Phot calibration reading.
5. Press Noise Source(Off) to select the Pcold calibration reading.
6. Press Accept to store the Pcold calibration reading.
Step 3. Measure.
1. Press Calibration (Off).
2. Connect Noise Source to the DUT and the DUT to the NFA.
3. Press Noise Source(On) to select the Phot reading.
4. Press IF Att(Auto) to allow the IF attenuators to autorange.
5. Press IF Att(Hold) to hold the IF attenuators fixed at the new value or
use the previously defined IF Att(Fixed) value.
6. Press Accept to store Phot measurement result.
7. Press Noise Source(Off) and press Accept to store Pcold measurement.
NOTE
If you have set up to measure a number of points over a frequency range.
You need to change the point number by pressing the Point menu key and
entering the point number and repeat the procedure from the next
measurement point. Repeat this until all the points have been measured.
The points need not be measured sequentially.
Chapter 3
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Advanced Features
Making Manual Measurements
114
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4
Making Extended Frequency
Measurements
This chapter describes how to make measurements outside the baseband
frequency range of your Noise Figure Analyzer.
115
Making Extended Frequency Measurements
What You will Find in this Chapter
What You will Find in this Chapter
This chapter covers:
• Overview of Configuring Extended Frequency Measurements
• An overview of the Measurement Modes
• Comparison of the 8970B and the NFA Series Measurement Modes
• Choosing and Setting Up the Local Oscillator
• Connecting the System
• A description of Measuring a Frequency-Converting DUT
• Making Frequency-Converting DUT Measurements using examples
• A description of Measurements with a System Downconverter
• Making System Downconverter Measurements using examples
• Frequency Restrictions
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Overview of Configuring Extended Frequency Measurements
Overview of Configuring Extended Frequency
Measurements
Configuring extended frequency measurements involves four steps.
Step 1. Press the System key and configure the measurement system parameters
as required using the GPIB and External LO menu items.
Table 4-1
System Parameters
Parameter
Description
NFA Address
This sets the NFA’s GPIB address.
Valid addresses are from 0 to 30.
The default address is 8.
External LO Address
This sets the GPIB address of the
External LO attached to the LO GPIB
port.
Valid addresses are from 0 to 30.
The default address is 19.
LO GPIB Address
This sets the address through which
other devices, attached to the LO GPIB,
communicate with the NFA.
Valid addresses are from 0 to 30.
The default address is 8.
Command Set
This sets the External LO command
language. The default setting is
Command Set(SCPI) to operate a SCPI
compliant LO. Command Set(Custom)
is used when the External LO is not
SCPI compliant and operated using the
custom command strings.
LO Commands
This accesses the External LO
Commands Form. The form is used to
enter the commands used to control a
non-SCPI-compliant External LO.
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Making Extended Frequency Measurements
Overview of Configuring Extended Frequency Measurements
Table 4-1
System Parameters
Parameter
Description
Settling Time
This sets the settling time of the
External LO. This is used as a settling
period after the External LO frequency
is changed.
Min and Max Frequency
This sets the minimum and maximum
frequencies of the External LO.
Multiplier
This sets the multiplier value of the
External LO frequency.
Step 2. Press the Meas Mode key to configure the measurement mode of the
Noise Figure Analyzer.
For more details on the available measurement modes, see
“Measurement Modes” on page 119.
Step 3. Press the Mode Setup key to configure the measurement mode
parameters for the specific measurement mode you have selected.
Step 4. Configure the measurement (measurement frequency range, number of
measurement points and averages and so forth) using the
Frequency/Points and Averaging/Bandwidth keys.
For more details on configuring measurements, including calibration, see
Chapter 2 , “Making Basic Measurements,” on page 31.
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Measurement Modes
Measurement Modes
Available modes
The Noise Figure Analyzer offers the following measurement modes
through the Meas Mode key on the front panel:
• The DUT is an amplifier-type device with no frequency conversion.
This is the basic measurement mode where the measurement
frequency is within the NFA’s frequency range. It is described in
“Example of a Basic Amplifier Measurement” on page 84.
• The DUT is an amplifier-type device with frequency downconversion
occurring in the measurement test setup (system downconversion).
The LO can be either fixed or variable in this case.
• The DUT is a frequency downconverter (that is, frequency
downconversion occurs in the DUT itself and not in the measurement
test setup). The LO can be fixed or variable.
• The DUT is a frequency upconverter (that is, frequency up conversion
occurs in the DUT itself and not in the measurement test setup). The
LO can be fixed or variable.
NOTE
The Amplifier measurement mode is for any DUT that does not perform
frequency conversion and includes amplifiers, filters, attenuators and so
forth.
Noise figure measurements involving mixers are necessary when:
• The frequency conversion is part of the DUT. For example, the DUT is
a mixer or a receiver.
• The frequency conversion is part of the measurement test set-up. The
DUT is to be measured at a higher frequency than the NFA’s
frequency range covers, hence an external mixer and local oscillator
are added to the measurement test set-up to convert this frequency to
a frequency within the NFA's range.
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Making Extended Frequency Measurements
Measurement Modes
The NFA can make a single frequency conversion, either in the DUT, or
as an added System Downconverter, which configures the NFA as a
frequency range extender. The NFA can also control an LO source
remotely using the SCPI commands or the custom commands. Under this
control the LO can be swept.
Basic Measurement — No Frequency Conversion
The basic measurement setup is shown in Figure 4-1, allowing you to
compare more complex setups with it.
Figure 4-1
Basic Noise Figure Measurement — No Frequency Conversion
Calibration Setup
Noise Source
Measurement Setup
Noise Source
DUT
When an uncorrected measurement is performed, the result is the
measured Noise Figure of all of the components after the noise source.
When the calibration setup is connected and the calibration performed,
the NFA measures its own noise figure and the connection set up. When
a corrected measurement is performed, the contribution of the
calibration setup is removed from the uncorrected result, giving a
corrected measurement of the DUT only.
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Measurement Modes
For these measurements the NFA mode is set to
DUT
Amplifier
System Downconverter
Off
NOTE
The RF input section on all NFA models has a built-in 3.0 GHz Low Pass
Filter. This filter needs to accounted for when planning your filter
requirements during calibration and measurement.
NOTE
On the N8974A and the N8975A models the microwave input section has
no filtering. This needs to accounted for when planning your filter
requirements for calibration and measurement. This is also important
when making measurements which cross over the 3.0 GHz switch.
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Making Extended Frequency Measurements
Measurement Modes
Frequency Down-converting DUT
In this mode, the DUT contains a frequency down-converting device, for
example, a mixer or receiver.
There are two modes to choose from:
1. A variable frequency LO and fixed IF.
Making this measurement, the NFA remains locked at one frequency
and the LO sweeps.
2. A fixed frequency LO and variable IF.
Making this measurement, the LO remains locked at one frequency
and the NFA sweeps.
NOTE
Filtering is needed to remove the unwanted sideband when making
single-sideband measurements in both modes. Ideally these filters
should be included in the calibration path and measurement path.
However, if it is not in the path, you can enter loss compensation to
account for any additional error.
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Measurement Modes
Fixed IF Variable LO (8970B Mode 1.3)
This is an overview of the key presses needed to set up the mode. See
“Frequency Restrictions” on page 188, for the restrictions applicable to
this mode. See “Making Frequency-Converting DUT Measurements” on
page 153 for an example of this mode. This shows a procedure for making
an LSB, Fixed IF and Variable LO measurement. However, you need to
change the settings and apply the appropriate filtering. For greater
detail on this see “Measuring a Frequency-Converting DUT” on page
140.
In the Measurement Mode Form set the following:
DUT
Downconv
System Downconverter
No Access
LO Mode
Variable
In the Mode Setup Form set the following:
NOTE
IF Frequency
Enter a value
Sideband
LSB, USB or DSB
LO Control
On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as RF (input to DUT)
frequencies.
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Making Extended Frequency Measurements
Measurement Modes
Variable IF Fixed LO (8970B Mode 1.4)
These are an overview of the key presses needed to set up the mode. See
“Frequency Restrictions” on page 188, for the restrictions applicable to
this mode. See “Making Frequency-Converting DUT Measurements” on
page 153 for an example of this mode. This shows how to make an LSB,
Fixed IF and Variable LO measurement. However, you need to change
the settings and apply the appropriate filtering. For greater detail on this
see “Measuring a Frequency-Converting DUT” on page 140.
In the Measurement Mode Form set the following:
DUT
Downconv
System Downconverter
No Access
LO Mode
Fixed
In the Mode Setup Form set the following:
NOTE
LO Frequency
Enter a value
Sideband
LSB, USB or DSB
LO Control
Off or On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as IF (output from
DUT) frequencies.
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Measurement Modes
Frequency Up-converting DUT
In this mode, the DUT contains a frequency up-converting device, for
example, a transmitter.
There are two modes to choose from:
1. A variable frequency LO and fixed IF.
Making this measurement, the NFA remains locked at one frequency
and the LO sweeps.
2. A fixed frequency LO and variable IF.
Making this measurement, the LO remains locked at one frequency
and the NFA sweeps.
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Making Extended Frequency Measurements
Measurement Modes
Fixed IF Variable LO (8970B Mode 1.3 with SUM Sideband)
These are an overview of the key presses needed to setup using this
mode. See “Frequency Restrictions” on page 188, for the restrictions
applicable to this mode. See “Making Frequency-Converting DUT
Measurements” on page 153 for an example of this mode. This shows a
procedure how to make an LSB, Fixed IF and Variable LO measurement.
However, you need to change the settings and apply the appropriate
filtering. For greater detail on this see “Measuring a
Frequency-Converting DUT” on page 140. In this mode, the DSB
measurement is not allowed.
In the Measurement Mode Form set the following:
DUT
Upconv
System Downconverter
No Access
LO Mode
Variable
In the Mode Setup Form set the following:
NOTE
IF Frequency
Enter a value
Sideband
LSB or USB
LO Control
On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as RF (input to DUT)
frequencies.
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Making Extended Frequency Measurements
Measurement Modes
Variable IF Fixed LO (8970B Mode 1.4 with SUM Sideband)
These are an overview of the key presses needed to set up using this
mode. See “Frequency Restrictions” on page 188, for the restrictions
applicable to this mode. See “Making Frequency-Converting DUT
Measurements” on page 153 for an example of this mode. This shows a
procedure how to make an LSB, Fixed IF and Variable LO measurement.
However, you need to change the settings and apply the appropriate
filtering. For greater detail on this see “Measuring a
Frequency-Converting DUT” on page 140. In this mode, the DSB
measurement is not allowed.
In the Measurement Mode Form set the following:
DUT
Upconverter
System Downconverter
No Access
LO Mode
Fixed
In the Mode Setup Form set the following:
NOTE
LO Frequency
Enter a value
Sideband
LSB or USB
LO Control
Off or On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as IF (output from
DUT) frequencies.
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Making Extended Frequency Measurements
Measurement Modes
System Downconverter
The DUT is a non-frequency converting device, for example an amplifier
or filter, and its frequency is higher than the NFA’s measurement range.
Frequency down-conversion is required within the measurement system,
using a mixer, external to the DUT, to convert the signal of interest to the
frequency range of the NFA.
There are two modes to choose from:
1. A variable frequency LO and fixed IF.
Making this measurement, the NFA remains locked at one frequency
and the LO sweeps.
2. A fixed frequency LO and variable IF.
Making this measurement, the LO remains locked at one frequency
and the NFA sweeps.
NOTE
Filtering is needed to remove the unwanted sideband when making
single-sideband measurements in both modes. Ideally any filtering is
included in the calibration path and measurement path. However, if it is
not in the path, you can enter loss compensation to account for any
additional error.
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Measurement Modes
Fixed IF Variable LO (8970B Mode 1.1)
These are an overview of the key presses needed to set up using this
mode. See “Frequency Restrictions” on page 188, for the restrictions
applicable to this mode. See “Making System Downconverter
Measurements” on page 175 for an example of this mode. This shows a
procedure how to make a DSB, Fixed IF and Variable LO measurement.
However, you need to change the settings and apply the appropriate
filtering. For greater detail on this see “Measurements with a System
Downconverter” on page 165.
In the Measurement Mode Form set the following:
DUT
Amplifier
System Downconverter
On
LO Mode
Variable
In the Mode Setup Form set the following:
NOTE
IF Frequency
Enter a value
Sideband
LSB, USB or DSB
LO Control
On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as RF (input to DUT)
frequencies.
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Making Extended Frequency Measurements
Measurement Modes
Variable IF Fixed LO (8970B Mode 1.2)
These are an overview of the key presses needed to set up using this
mode. See “Frequency Restrictions” on page 188, for the restrictions
applicable to this mode. See “Making System Downconverter
Measurements” on page 175 for an example of this mode. In this mode, a
DSB measurement is not allowed. This shows a procedure how to make a
DSB, Fixed IF and Variable LO measurement. However, you need to
change the settings and apply the appropriate filtering. For greater
detail on this see “Measurements with a System Downconverter” on
page 165.
In the Measurement Mode Form set the following:
DUT
Amplifier
System Downconverter
On
LO Mode
Fixed
In the Mode Setup Form set the following:
NOTE
LO Frequency
Enter a value
Sideband
LSB or USB
LO Control
Off or On
External LO Power Level
Enter value and terminate
using either dBm or W
The External LO Power Level is displayed on the NFA as dBm.
In the Frequency menu, frequencies are specified as RF (input to DUT)
frequencies.
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Comparison of the 8970B and the NFA Series Measurement Modes
Comparison of the 8970B and the NFA Series
Measurement Modes
Table 4-2 is to assist 8970B users map the 8970B measurement modes to
the NFA Series measurement modes.
Table 4-2
8970B Mode Comparison
8970B
NFA Series
Mode 1.1: Swept LO
System Downconverter
Fixed IF Variable LO
Mode 1.2: Fixed LO
System Downconverter
Variable IF Fixed LO
Mode 1.3: Swept LO
Downconverting
Fixed IF Variable LO
Mode 1.4: Fixed LO
Downconverting
Variable IF Fixed LO
Mode 1.3 with SUM Sideband: Swept LO
Upconverting
Fixed IF Variable LO, USB
Mode 1.4 with SUM Sideband: Fixed LO
Upconverting
Variable IF Fixed LO, USB
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Making Extended Frequency Measurements
Choosing and Setting Up the Local Oscillator
Choosing and Setting Up the Local Oscillator
Selecting a Local Oscillator for Extended Frequency
measurements with the NFA
Because of reciprocal mixing, noise components in the LO are converted
into the IF band applied to the NFA. This converted LO noise causes the
measured noise figure to be higher than the actual noise figure of the
mixer.
If the mixer is to be used with a particular LO in its final application, its
noise figure should be measured with that LO. The measurement then
gives the actual noise figure of the extended frequency device - LO
combination in the final system.
For testing of extended frequency measurements, the LO must have a
low noise floor over frequencies equal to the LO ± IF.
Effect of high LO spurious signals and noise on mixer
measurements with low L-to-I rejection.
The LO’s spurious level also has to be low. At frequencies where there is
a high spurious signal the noise figure measured will have a peak at that
IF. For example, ideally the LO’s noise, including spurious, needs to be
below -90 dBm. If a mixer has higher isolation, then the LO’s noise can
be higher since the mixer will be better able to reject the LO’s noise.
This is especially necessary if the mixer has a poor balance, or L-to-I
isolation. With low isolation, the mixer is more likely to pass the LO
noise through and thus increase the measured noise figure.
NOTE
L-to-I rejection is the mixers ability to reject the LO’s spurious signals
and not allow them to pass through to the IF output.
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Choosing and Setting Up the Local Oscillator
Selecting a Local Oscillator for the NFA
Here are several criteria that must be met when choosing the LO:
1. It should have a frequency range appropriate to the DUT’s frequency
range, IF range, and sideband chosen.
2. It should be controllable over GPIB if variable LO measurements are
to be made.
3. It should have sufficient power to drive mixers (typically, +7 dBm)
4. It should have excellent frequency accuracy and repeatability
(typically, the same as the NFA you are using.)
The last point, frequency accuracy, deserves further comment. There are
three frequency-dependent components in an NFA measurement that
must all be aligned to make an accurate measurement at the IF. The
need for frequency accuracy is the main reason for recommending a
synthesized source for the LO, such as the Agilent 83712B Synthesized
CW Generator.
Other LOs may be used, but should be tested to determine that their
noise is sufficiently low, as LO noise can cause a increase in noise figure
for the mixer/LO combination, and calibration of the system may not be
possible. A broadband, high gain amplifier at the LO output usually
generates unacceptable noise. This is almost always the case when a
heterodyne-type sweep oscillator or signal generator is used.
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Making Extended Frequency Measurements
Choosing and Setting Up the Local Oscillator
Setting up the NFA to drive the Local Oscillator
The following procedures are general to all the measurement mode
settings. These can be done independently of setting up the
measurement.
• Setting the External LO address
• Setting the Minimum and Maximum LO Frequencies
• Setting the Settling Time
Setting the External LO address
Step 1. Press the System key, the GPIB menu key.
The System GPIB Form appears on the display.
Step 2. Using the Tab key, highlight the External LO Address field, Figure 4-2
shows the form and the selected address. Set the External LO Address
using the numeric keypad and terminate it using the Enter key.
Figure 4-2
External LO Address
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Choosing and Setting Up the Local Oscillator
NOTE
If an error message GPIB Error, Write command timeout appears in
the NFA’s display status line, this indicates the external LO cannot be
written to. The problem is most likely one of the following:
• The GPIB cable is either not attached or is not making proper
contact.
• The external LO is not turned on.
• The NFA has the wrong address for the external LO.
If the NFA does not appear to be controlling the LO as described above,
check your setup to make sure all connections are properly made. Also
check for any bad connections or cables and that the LO is working
properly.
Setting the Minimum and Maximum LO Frequencies
Step 1. Press the System key, the External LO menu key.
Step 2. Press the Min Freq menu key and enter the minimum frequency value.
Using the numeric keypad, terminate it using the unit menu keys, or use
the RPG and rotate it to the required value. Set the External LO to have
a minimum frequency equivalent to the LO you are using. The default
value is 10 MHz.
Step 3. Press the Max Freq menu key and enter the maximum frequency value.
Using the numeric keypad, terminate it using the unit menu keys, or use
the RPG and rotate it to the required value. Set the External LO to have
a maximum frequency equivalent to the LO you are using. The default
value is 40.0 GHz.
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Making Extended Frequency Measurements
Choosing and Setting Up the Local Oscillator
Figure 4-3
Setting Maximum and Minimum Frequencies and Settling Time
and Multiplier of the External LO
Setting the Settling Time
Step 1. Press the System key, the External LO menu key.
Step 2. Press the Settling Time menu key and enter the Settling Time value.
Using the numeric keypad, terminate it using the unit menu keys, or use
the front panel knob and rotate it to the required value. The default
value is 100 mS.
Setting the Multiplier
Step 1. Press the System key, the External LO menu key.
Step 2. Press the Multiplier menu key and enter the multiplier value.
Using the numeric keypad, terminate it using the Enter key, or use the
front panel knob and rotate it to the required value. The default value is
1. The maximum value is 1000000000.
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Connecting the System
Connecting the System
Figure 4-4 and Figure 4-5 show the connection diagram options you can
use to calibrate the NFA and after calibration, to measure a DUT,
whether it is a down-converter mixer, up-converter mixer, amplifier, or
filter. It does not show where to place a filter to remove any unwanted
sideband or input noise.
Setting Up the Noise Figure Analyzer
NOTE
You may connect the 10 MHz timebase frequency reference. Hence, the
NFA and the LO are locked at the same frequency reference. This can be
done from the NFA’s 10 MHz Ref Out to the LO’s 10 MHz Ref In or the
LO’s 10 MHz Ref Out to the NFA’s 10 MHz Ref In. It can also be provided
by an external reference. Ideally use the best standard reference
available.
To connect the NFA to make measurements.
Step 1. Connect a GPIB cable between the NFA’s LO GPIB rear panel connector
and the Local Oscillator’s GPIB connector.
Step 2. Turn on both instruments and press the Preset key to return the NFA to
a known state.
The NFA can control the Local Oscillator, over its General Purpose
Interface Bus (LO GPIB) without the need for an external controller. The
NFA does not send LO controlling commands over it’s main GPIB. LO
control is only done over it’s LO GPIB.
Step 3. Enter the ENR values in to the NFA. See “Entering Excess Noise Ratio
(ENR) Data” on page 33 for the procedures to do this.
Step 4. Follow the procedure to calibrate the system, and measure the DUT, in
the mode to suit your needs.
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Making Extended Frequency Measurements
Connecting the System
Figure 4-4
System Downconverter Mode
LO
LO GPIB
Calibration Setup
Noise Source
LO
Measurement Setup
LO GPIB
Noise Source
DUT
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Connecting the System
Figure 4-5
Frequency Converting DUT Measurement Modes
Calibration Setup
Noise Source
LO
LO GPIB Control
Measurement Setup
Noise Source
DUT
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Making Extended Frequency Measurements
Measuring a Frequency-Converting DUT
Measuring a Frequency-Converting DUT
Figure 4-6
Frequency Converting DUT Measurement Modes
Calibration Setup
Noise Source
LO
LO GPIB Control
Measurement Setup
Noise Source
DUT
In this mode, the DUT has frequency conversion in the measurement
setup. However, there is no frequency conversion in the calibration setup,
this is shown in Figure 4-6. The purpose of the calibration setup is to
allow the NFA to measure its own noise figure and sensitivity with the
noise source. This must be performed across the frequency range the
NFA will tune over in the measurement setup. When the measurement
is made, the NFA calculates the input frequency to the DUT, and using
the appropriate values from the noise source ENR table, interpolating as
necessary, measures the DUT.
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Measuring a Frequency-Converting DUT
To allow the frequencies in the measurement setup to be calculated, the
frequency parameters for the measurement are entered into the NFA.
There are two possible sweep options:
1. The DUT LO is swept and the NFA is set to a fixed IF for the DUT.
2. The DUT LO is fixed and the NFA tuned frequency is swept.
If the DUT includes a fixed LO, then only option two is possible. If the
DUT uses an external LO, then either option is possible. The frequency
parameters for the measurement are entered into the NFA, hence it is
convenient to allow the NFA to perform all the frequency calculations
and control the LO.
For these measurements the NFA mode is set to
• DUT: Upconv or Downconv
NOTE
The Upconverter and Downconverter modes include any DUT
performing frequency conversion, whether a simple single mixer or a
complex receiver structure.
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Making Extended Frequency Measurements
Measuring a Frequency-Converting DUT
Sidebands and Images
For any measurement involving frequency conversion, you need to
consider the exact frequency ranges involved, and make decisions about
the filtering requirements for the specific measurement. For example,
there may be several different methods of measuring a mixer, and the
method chosen may be set by the choice of available filters.
Figure 4-7
Sidebands and Images
Amplitude
Fusb-Flo
mixing
FLO
Flo-Flsb
mixing
Broadband Noise
NFA Input
Band
Frequency
LSB Input
USB Input
Simple, ideal, mixers output signals on both the sum and difference of
their RF and LO frequencies. Hence, for a fixed output frequency and a
fixed LO frequency, there are two different input frequencies that are
converted to the output frequency. This is shown in Figure 4-7.
The noise sources used in noise figure measurements are broad-band,
hence, there is a probability that noise will be presented to a simple
mixer in both the upper and lower input frequency bands that are
converted into the same IF output band that the NFA is tuned to. The
NFA receives mixer-created noise from the two frequency bands
superimposed. The noise is random, hence the two power levels combine
by simple addition. Similarly, the NFA receives noise-source-created
noise from the two frequency bands combined as added power. Any
measurement where two mixing products are combined like this is
usually termed Double-Sideband, DSB.
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Measuring a Frequency-Converting DUT
It is conventional to call the higher frequency band of an image pair the
Upper-Sideband, USB, and the lower frequency band of an image pair
the Lower-Sideband, LSB.
Non-ideal mixers exhibit some unwanted behaviors:
1. Some of the input signal leaks directly to the output.
2. Some of the LO signal, and its harmonics, leak directly to the output.
3. Mixing products are created between the input signal and the
harmonics of the LO.
There are other unwanted products involving input signal harmonics,
but these tend to be less troublesome than those above, provided the
mixer is operated at a level within its linear range.
Signal Leakage
Direct signal leakage of input signal through to a mixer’s output can
occur, because the noise sources cover a broad frequency range. Signal
leakage is not normally a problem unless the noise source has a large
variation in ENR, or the mixer’s RF-to-IF leakage is high.
LO Leakage
The LO power is normally greater than the largest input signal that a
mixer is intended to operate with. The LO power leaking from the
mixer’s output is at a high level compared to the signal levels involved in
the noise figure measurement. Hence, LO leakage needs to considered
when measuring noise figure of a frequency converting DUT.
If the LO frequency is low enough to be passed by the NFA’s RF section’s
input filter (a 3.0 GHz Low Pass Filter), the LO leakage will force the
NFA's RF input attenuator to autorange onto a very insensitive range.
This will prevent successful measurement of the DUT noise figure.
Desensitization by LO leakage can be avoided by adding a filter between
the DUT and the NFA to remove the LO frequency component.
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LO Harmonics
Many mixers are operated by sinusoidal LO signals, LO harmonics can
be formed in the mixer at significantly high levels. It is common for the
specified LO input level for a diode mixer to be chosen to operate the
diodes between saturation and off conditions, hence making the mixer
act as a switch. LO harmonic derived products from industry standard
double-balanced mixers may be similar in level to what they would have
been with a square-wave LO signal. Instead of just being sensitive at one
pair of frequencies [ F LO ± F IF ] , the mixer input is sensitive at a series of
pairs:
Equation 4-1
[ F LO ± F IF ] + [ 2FLO ± F IF ] + [ 3FLO ±F IF ] + [ 4FLO ± FIF ] + [ 5FLO ± FIF ] + …
Filtering is needed to eliminate the noise input to the DUT at these
higher order frequencies. However, their frequencies may be great
enough that the mixer attenuates them, making them insignificant.
Other signals from the DUT
NFA RF input attenuator auto-ranging has already been covered in “LO
Leakage” on page 143. However, signals close to the tuned frequency can
de-sensitize the NFA measurements by forcing auto-ranging of the NFA's
IF gain control. The NFA has a similar, internal, limitation set by the LO
leakage of its own first mixer, and the requirement for the NFA to tune
down to 10 MHz. The NFA's analogue IF filter is designed for high
rejection for signals more than 10 MHz away from the tuned frequency.
This is not changed when narrow bandwidths are selected. An unwanted
signal within 10 MHz of the tuned frequency could corrupt a noise figure
measurement.
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Single Sideband Measurements
Most mixer applications involve single sideband (SSB) mixing - either
LSB or USB, hence it is ideal to make noise figure measurements on a
mixer in the circumstances in which it is used. Making an SSB
measurement requires suitable filters to remove the unwanted image,
any LO leakage, and other unwanted mixer products. This may require
filters that are not available, or expensive, and a DSB measurement may
be chosen as a compromise. There is no general guidance on what
filtering is needed. Each case needs individual consideration.
Items to be considered are:
1. Decide the frequency ranges that must be covered; Input, LO, and
Output.
2. Calculate the frequency range that the unwanted image will cover.
3. Calculate the frequency range that the LO harmonic modes will cover.
4. Choose a filter to go between the noise source and the DUT, that will
pass the wanted input band and stop the unwanted input bands.
5. Consider the LO frequency range (and harmonics), is a filter needed
to protect the NFA input being desensitized by LO leakage in the
0 - 3.5 GHz range?
6. Choose a filter, if necessary to go between the DUT and the NFA
If any of these ranges conflict, making the filter requirements
impossible, the measurement could be split into a group of smaller
ranges, with different filters for each.
If the DUT is a complicated mixer, it may already contain filters to
operate the mixer in single sideband mode over the frequency range of
interest. A mixer in its final application exhibits the same problems that
make noise figure measurement difficult, hence the application will need
similar filtering to that needed during noise figure measurement.
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Figure 4-8
Single Sideband Mixer Measurements
Amplitude
FLO
Flo-Flsb
mixing
Depending on Flo, a DUT
output filter may be needed
to reject LO leakage
Noise reaching mixer from
the DUT Input filter
Frequency
NFA Input
Band
LSB Input
USB Input
Figure 4-8 shows an SSB mixer measurement (Downconverter, LSB)
where a filter makes it single sideband. If the IF frequency is lowered the NFA is tuned to a lower frequency, the USB and LSB bands will
move closer to the LO frequency. This makes filtering more difficult, and
if the IF is lowered further, a point is reached where filtering is not
possible and SSB measurements cannot be made. The width of the filter
limits where the LO or IF frequencies sweep to make a measurement.
The NFA performs frequency calculations, controls the NFA frequency,
and the LO frequency, for a variety of mixer modes. However, you have to
determine the filter requirements, and provide those filters in the
measurement setup.
Downconverter means that the output frequency, (IF) is lower than the
input, (RF).
Upconverter means that the output frequency, (IF) is higher than the
input (RF).
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The NFA can handle SSB mixer measurements in modes defined by the
following combinational choices:
• DUT: Upconverter or Downconverter
• LO Mode: Fixed or Variable.
• Sideband: LSB or USB.
Double Sideband Measurements
DSB techniques can make useful noise figure measurements. Consider
the following:
• What if adequate filters for image-free SSB measurements are not
available?
• What if frequency ranges have to be covered that make SSB filters
impractical or impossible?
DSB measurements do not eliminate the need for filtering, however, it
can greatly simplify the filtering needed. This benefit is achieved at the
loss of frequency resolution.
Figure 4-9
Double Sideband Measurements
Amplitude
Fusb-Flo
mixing
FLO
Flo-Flsb
mixing
Frequency
NFA Input
Band
Chapter 4
LSB Input
USB Input
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Figure 4-9 shows a double sideband, downconversion, mixing. Noise from
two separated RF bands are mixed into the IF band, where the power
addition takes place.
DSB measurements are made with the noise from a pair of separate
bands, symmetrically arranged about the LO frequency. The selection of
the IF frequency value should be a low frequency. Hence this technique
maintains the two bands close together. The reason is to justify making
the assumption that the variations in noise source ENR, gain and noise
figure are linear between the two bands. This means that the averaging
of results for the two bands, due to the power summation, gives a result
which can be assigned to the centre frequency - the LO frequency.
Figure 4-9 shows that noise from two bands are combined during the
measurement, while during calibration, when the DUT was not
connected, only one band (at the IF frequency) was used.
If the assumptions about the parameters being flat over frequency
between the two sidebands are valid, this causes a doubling in power
(3 dB increase) in noise level during the measurement. This does not
happen during calibration. This can be corrected for, using the
Loss Compensation facility, and entering Before DUT Value of -3 dB and
selecting Fixed in the Before DUT field. The DSB power addition occurs
for both the Hot and Cold noise from the noise source, and the noise
created in the input of the DUT. A temperature value can be assigned to
this loss using the Before Temperature. Using the Cold temperature of the
noise source (often assumed to be 290 Kelvin) corrects for this, and the
NFA will give corrected results comparable to those that would have
been given by an SSB measurement.
If you must use a high IF frequency, or if it has variations in performance
over frequency, then the assumption is invalid.
DSB measurements are not appropriate for making measurements
where DUT performance, or noise source ENR, have significant variation
over the frequency range [ F LO ± F IF ]
DSB measurements need care to determine their filtering needs.
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LO Leakage (with specific DSB information)
LO leakage is a problem and is avoided by tuning the LO at frequencies
greater than 3.5 GHz. Below 3.0 GHz, the LO leakage drives the NFA to
add input attenuation to prevent overload, making the NFA
insufficiently sensitive to measure the noise component at the input.
Above 3.0 GHz, the NFA’s input filter progressively attenuates the LO
signal. For a DSB downconverter measurement with the LO going below
about 3.5 GHz, a lowpass filter will be needed. The cutoff frequency must
be chosen to pass the IF frequency of the measurement. The amount of
attenuation over the LO frequency range has to be sufficient to reduce
the LO leakage down to the broadband (10.0 MHz - 3 GHz) noise level
presented to the NFA input.
With most DSB Downconverter measurements, the IF is made low, with
respect to, the RF and LO frequencies, so filter needs are not complex.
NOTE
Low pass filters with cutoffs at low frequencies, may exhibit spurious
resonances and leakage at low microwave frequencies. It may be
necessary to use a pair of lowpass filters, one microwave, one RF, in order
to assure a stopband attenuation over a wide frequency range.
LO Harmonics (with specific DSB information)
Many mixers have product pairs associated with harmonics of the LO.
Depending on the mixer, these could be at a sufficient level to distort the
measured noise figure results. To avoid this insert an input filter
between the noise source and the DUT. A Highpass filter may also be
needed in this location if signal leakage is a problem.
There is no general guidance on what filtering is needed. Each case
needs individual consideration:
1. Decide the frequency ranges that have to be covered; Input, LO, and
Output.
2. Calculate the frequency range that the LO harmonic modes will cover.
3. If LO harmonic related products are a problem, choose a filter to go
between the noise source and the DUT, that will pass the wanted
input band and stop the LO harmonic modes. If the frequency ranges
are wide, the measurement may have to be split into frequency
ranges with different filters for each.
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4. Consider the LO frequency range (and harmonics), is a filter needed
to protect the NFA input being desensitized by LO leakage in the
0-3.5GHz range?
5. Choose a filter, if necessary to go between the DUT and the NFA
The NFA can handle DSB mixer measurements in modes defined by the
following combinational choices:
• DUT: Upconverter or Downconverter
• LO Mode: Fixed or Variable.
• Sideband: DSB.
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Fixed IF
In the fixed IF mode, the IF frequency at the NFA’s input is constant, and
the LO frequency is swept to perform the measurement.
Figure 4-10
Fixed IF Measurements
Sweep Point
Stop
Fusb-Flo
mixing
LSB Input
FLO
Flo-Flsb
mixing
USB Input
Frequency
Start
FIF
Figure 4-10 shows how the different frequencies in a DSB,
downconverter, fixed IF, measurement vary as the measurement sweep
proceeds. This mode measures the DUT's noise figure across a range of
DUT input frequencies. This is the main use of the DSB mode.
A similar diagram could be drawn, if needed, showing the LO harmonic
mixing modes at higher frequencies, with flatter slopes due to frequency
multiplication.
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Fixed LO
The fixed LO mode produces no sweep at the DUT input, as the two
sideband input pairs diverge their average remains fixed. This mode
could be useful for measuring a complex DUT where the effect of
variation of performance of the post-mixer stage over IF frequency is of
interest.
Because the LO frequency is held constant it is the IF frequency at the
NFA input that is swept. Figure 4-11 illustrates this mode.
Figure 4-11
Fixed LO Measurements
Sweep Point
Fixed LO
Stop
Fusb-Flo
mixing
Flo-Flsb
mixing
LSB Input
USB Input
Start
FIF
152
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Making Frequency-Converting DUT Measurements
Making Frequency-Converting DUT
Measurements
An example is provided where the NFA remains locked at one frequency
and the LO sweeps. A lower sideband measurement of a mixer is made.
The example can be modified to make measurements using a fixed LO
where the IF is swept. Also, from the example, upper and double side
band measurements can be made. The changes in the example’s
procedure are explained in each case.
Calibration of the measurement system is similar to a basic calibration,
the noise source is connected directly to the RF input of the NFA and a
calibration is made. The DUT is then placed between the noise source
and the NFA, and a corrected measurement is made.
NOTE
The RF input section on all NFA models has a built-in 3.0 GHz Low Pass
Filter. This filter needs to accounted for when planning your filter
requirements during calibration and measurement.
NOTE
On the N8974A and the N8975A models the microwave input section has
no filtering. This needs to accounted for when planning your filter
requirements for calibration and measurement. This is also important
when making swept IF measurements which cross over the 3.0 GHz
switch.
Making Down-Converting DUT Measurements using a
Fixed IF and Variable LO (8970B Mode 1.3)
Lower Sideband Measurement (Fixed IF and Variable LO)
The example lower sideband measurement is made using a N8973A
model. The result is obtained by using a fixed IF of 1.0 GHz. Setting the
RF frequency of interest to be 3.7 GHz to 4.2 GHz, giving an LO sweep
from 4.7 to 5.2 GHz. This also meets with the need to maintain the LO
frequency out of the NFA’s passband.
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Making Extended Frequency Measurements
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The example uses a Signal Generator as a local oscillator. The system is
used to measure a mixer over a 3.7 to 4.2 GHz frequency range. The
noise figure for this mixer typically varies from 7 to 15 dB and the gain
(conversion loss) from -5 to -15 dB over this frequency band.
See Figure 4-12.
NOTE
In the example, a 4.4 GHz Low Pass Filter with an out of band rejection
by 4.6 GHz is used to remove the upper sideband. (see Figure 4-12).
Figure 4-12
Fixed IF and Variable LO, LSB Spectrum
LPF
IF
3.7
1
2
3
RF 4.2
4
4.7 LO 5.2
5
Rejected
5.7 USB 6.2
6 (GHz)
Initial Setup Procedure Follow the overview procedure of the initial
set up.
Step 1. Power Up the NFA and the LO. You need to wait for the recommended
warm up time to get accurate measurement results
Step 2. Connect the GPIB cables and the 10 MHz reference, if required. See
“Connecting the System” on page 137 for more detail.
Step 3. Load the ENR values. See “Entering Excess Noise Ratio (ENR) Data” on
page 33 for more detail.
Step 4. Set up the LO and the NFA’s LO settings. See “Choosing and Setting Up
the Local Oscillator” on page 132 for more detail.
Step 5. Set the LO address
Step 6. Connect the system and add filtering where required. Figure 4-5 on page
139 shows the connections
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Selecting Measurement Mode
Figure 4-13
Measurement Mode Form
Step 1. Press the Meas Mode key. A Meas Mode Form is displayed (Figure 4-13).
Confirm that the Device Under Test field is set to Downconv (select the
Downconv menu key to highlight it).
The default Device Under Test setting is Amplifier.
NOTE
The System Downconverter field is no longer accessible to you in this
measurement mode.
Step 2. Press the Tab key to navigate to the LO Mode field and press the Variable
menu key for a variable LO setup.
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Selecting Mode Setup
Figure 4-14
Mode Setup Form
Step 1. Press the Mode Setup key. A Mode Setup Form is displayed (Figure 4-14).
This form allows you to enter values for the IF frequency, setup the LO
parameters and choose the sideband required.
Step 2. Press the Tab key to navigate to the IF Frequency field. Set the IF
Frequency.
In the example, enter 1.0 GHz using the numeric keypad and terminate
it using the unit keys which are presented to you.
Step 3. Press the Tab key to navigate to the Sideband field. Set the Sideband.
In the example, enter LSB using the menu keys which are presented to
you.
Step 4. Press the Tab key to navigate to the LO Control field. Set the LO Control.
In the example, enter on by pressing the On menu key which is presented
to you.
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Step 5. Press the Tab key to navigate to the External LO Power Level field. Set the
External LO Power Level.
In this example, enter 10 dBm using the numeric keypad and terminate
it using the unit keys which are presented to you.
Setting Frequency, Point, Bandwidth, Averaging
Step 1. Configure the measurement with the Frequency/Points and
Averaging/Bandwidth keys. For a description of these keys “Setting the
Measurement Frequencies” on page 46 and “Setting the Bandwidth and
Averaging” on page 52.
Set start and stop frequencies and number of points for the amplifier to
be tested. For the example microwave amplifier, the appropriate figures
are:
• Start: 3700 MHz
• Stop: 4200 MHz
• Points: 15
• Averaging: On
• Averages: 5
• Average Mode: Point
NOTE
The N8972A Average Mode is set to point by default, as sweep mode is
only available on the other NFA models.
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Calibration of the Microwave Setup Calibration of the microwave
measurement system is similar to a basic RF calibration. If not done
already, connect the Noise Source output to the NFA input, see Figure
4-15.
Figure 4-15
Frequency Converting DUT Measurement Modes
Calibration Setup
Noise Source
LO
LO GPIB Control
Measurement Setup
Noise Source
DUT
Step 1. Press the Calibrate key twice
The first time you press the key you are prompted to press it again. This
two-stroke calibration is a safety feature to prevent you from
accidentally pressing Calibrate and erasing the calibration data.
When calibration is complete the measurement system is calibrated at
the mixer input. The white Uncorr text changes to Corr text in the lower
right hand side of the display.
NOTE
The calibration is only made at the fixed IF frequency.
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Calibration of the Microwave Setup
Step 1. Figure 4-16 shows typical results in table format after calibration.
Figure 4-16
Typical Calibration Results after a Restart is Pressed
NOTE
After calibration the instrument will not show 0 dB + jitter with no DUT
inserted. This is because the instrument is now using the microwave
frequency ENR, while the input is tuned to the IF. When DUT is added,
the NFA measures the noise figure of the DUT. If the configuration is
arranged to reject one sideband, the SSB result is displayed. If both
sidebands are converted by the mixer the DSB result is displayed.
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Making the Corrected Noise Figure and Gain Measurement A
measurement corrected for the second stage contribution may now be
made. Insert the DUT into the system as shown in Figure 4-15. The
results are displayed on the display using the same steps as those
described in “Displaying the Measurement Results” on page 61. A
typical display of noise figure and gain (conversion loss) is shown in
Figure 4-17.
Figure 4-17
Typical Microwave Results
NOTE
Once you have successfully made your measurement you may want to
save the set up for future measurements. This can be done by saving the
state. See “Saving a File” on page 24 for more details.
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Upper Sideband Measurement (Fixed IF and Variable LO)
The upper single sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering to remove the LSB image. Follow the LSB procedure, and in the
Mode Setup Form select the USB in the sideband option.
NOTE
During measurement with the DUT inserted, it is important that the
filter is placed on the mixer input. Otherwise some added noise from the
device under test will likely be in the unwanted sideband and create a
measurement error. The filter must be in place for both calibration and
measurement.
Double Sideband Measurement (Fixed IF and Variable LO)
The double sideband measurement set up is similar to the LSB
measurement described in “Lower Sideband Measurement (Fixed IF and
Variable LO)” on page 153. However, you need to provide filtering.
Follow the LSB procedure, and in the Mode Setup Form select the DSB in
the sideband option.
NOTE
During measurement with the DUT inserted, it is important that the
filter is placed on the mixer input. Otherwise some added noise from the
device under test will likely be in the unwanted sideband and create a
measurement error. The filter must be in place for both calibration and
measurement.
NOTE
The calibration is only made at the IF frequency
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Making Down-converting DUT Measurements using a
Variable IF and Fixed LO (8970B Mode 1.4)
Both double and single sideband measurements may be made in this
mode. This measurement may be useful to choose the optimum IF for a
mixer or receiver, or to measure how a mixer’s or a receiver’s noise figure
and gain vary with IF.
Double Sideband Measurement (Variable IF and Fixed LO)
The double sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. Follow the LSB procedure, and
in the Mode Setup Form select the DSB in the sideband option. On the
Meas Mode Form set the LO Mode to Fixed.
Lower Sideband Measurement (Variable IF and Fixed LO)
The lower sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form select
the LSB in the sideband option. On the Meas Mode Form set the LO Mode
to Fixed.
Upper Sideband Measurement (Variable IF and Fixed LO)
The upper sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form select
the USB in the sideband option. On the Meas Mode Form set the LO Mode
to Fixed.
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Making Frequency-Converting DUT Measurements
Making Up-converting DUT Measurements using a
Fixed IF and Variable LO (8970B Mode1.3 with SUM)
Making an up-converter measurement is similar to measuring down
converters. The terminology is the same as the downconverter mode, the
input to the NFA is called the IF and the noise source output is called the
RF.
In the Meas Mode Form set the Device Under Test to Upconv.
Lower Sideband Measurement (Fixed IF and Variable LO)
The lower sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form ensure
the LSB in the sideband option is selected. On the Meas Mode Form set
the LO Mode to Variable.
Upper Sideband Measurement (Fixed IF and Variable LO)
The upper sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form select
the USB in the sideband option. On the Meas Mode Form set the LO Mode
to Variable.
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Making Extended Frequency Measurements
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Making Up-converting DUT Measurements using a
Variable IF and Fixed LO (8970B Mode1.4 with SUM)
Lower Sideband Measurement (Variable IF and Fixed LO)
The lower sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form ensure
the LSB in the sideband option is selected. On the Meas Mode Form set
the LO Mode to Fixed.
Upper Sideband Measurement (Variable IF and Fixed LO)
The upper sideband measurement set up is similar to the LSB
measurement procedure described in “Lower Sideband Measurement
(Fixed IF and Variable LO)” on page 153. However, you need to provide
filtering. Follow the LSB procedure, and in the Mode Setup Form select
the USB in the sideband option. On the Meas Mode Form set the LO Mode
to Fixed.
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Measurements with a System Downconverter
Measurements with a System Downconverter
A system downconverter can be thought of as a frequency extender for
the NFA, to allow measurements to be made on DUTs at frequencies the
NFA does not cover with it’s frequency range.
Figure 4-18
System Downconverter Mode
LO
l LO GPIB
Calibration Setup
Noise Source
LO
Measurement Setup
LO GPIB
Noise Source
DUT
A system downconverter is part of the measuring system, and is present
in both the calibration setup and the measurement setup, see Figure
4-18. During calibration the noise performance of both the NFA and the
system downconverter are measured. Because of this, when corrected
measurements are performed, the results apply to the DUT only. ENR
data for the same frequency range is used for both calibration and
measurements
The NFA has the capability to control a single frequency conversion, so
system downconverter measurements under the NFA's control are
limited to non-frequency converting DUTs.
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Making Extended Frequency Measurements
Measurements with a System Downconverter
The NFA can be used in much more complex systems, with multiple
frequency conversions between the DUT and measurement system.
However, the control of such systems is application-specific. You need to
perform frequency calculations to suit that particular system, account for
the effects of any DSB conversions, determine filter requirements, and
calculate the appropriate ENR values for calibration and measurement.
USB, LSB or DSB?
If the DUT is broadband, a system downconverter could operate in USB,
LSB, or DSB mode, and the same circumstances occur in both calibration
and measurements, hence DSB sideband power addition corrections are
not needed. Corrected measurements cancel any sideband summation
effects.
If the DUT is narrowband and a DSB system downconverter is used, the
calibration setup will operate in true DSB mode. However, the
measurement setup mode will be influenced by the DUT’s selectivity.
The possibilities fit into two groups and a third situation which should be
avoided:
1. The DUT bandwidth is much greater than the LSB-USB separation,
so a normal DSB measurement results.
2. The DUT bandwidth is much less than the LSB-USB separation, and
the sweep width is less than the USB-LSB separation, so an SSB
measurement results. This needs a gain correction factor due to the
DSB calibration
NOTE
There is a third situation and this must be avoided. Where the DUT
selectivity can resolve the individual sidebands of the DSB measurement
and the sweep is wide enough to scan the DUT across them. Different
parts of the measurement plot are in different modes. USB, LSB and
DSB could occur in different places on the same plot, with gradual
changes between them, set by the shape of the DUT's frequency
response. Variable gain correction would be needed across the plot and
the corrections needed would change if adjustments to the DUT changed
its shape.
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Measurements with a System Downconverter
Measurement Modes with a DSB System
Downconverter
The NFA supports only one DSB System Downconverter mode; where
the IF is fixed and the system downconverter LO is swept. The benefits
of a DSB measurement are, minimal filter requirements, and wide
frequency coverage. DSB measurements are appropriate for wideband
DUTs. Their disadvantages, covered in the “USB, LSB or DSB?” section,
make them inappropriate for narrowband DUTs. The usual aim is to
choose as low a frequency IF as possible, in order to minimize the
separation between the sidebands, thus get the optimum resolution
possible. Figure 4-19 shows this.
Figure 4-19
DSB System Downconverter Measurements
Amplitude
Fusb-Flo
Flo-Flsb
LSB Input
USB Input
FLO
Broadband Noise
Frequency
NFA Input
Band
DSB system downconverter measurements have implicit linear
averaging of DUT characteristics and ENR values between the USB and
LSB frequencies. Results are made against the average frequency of the
two bands - the LO frequency.
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Figure 4-20
DSB System Downconverter Measurements
Sweep Point
Stop
Fusb-Flo
mixing
LSB Input
FLO
USB Input
Flo-Flsb
mixing
Frequency
Start
FIF
For microwave measurements, above 3.5 GHz, the NFA’s input filter will
reject LO leakage from the downconverter, otherwise a filter is needed
between the system downconverter and the NFA. Also, considerations
about mixer LO harmonic modes apply.
Measurement Modes with an SSB System
Downconverter
The NFA can perform frequency calculations and LO control for either
USB or LSB system downconverter conversions. It is the provision of
filtering that makes a mode USB or LSB.
The filtering requirements will be measurement-specific.
Figure 4-21 shows how filtering makes an LSB measurement, and
Figure 4-22 shows a USB downconversion measurement.
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Figure 4-21
LSB System Downconverter Measurements
Amplitude
Depending on Flo, a
downconverter output filter
may be needed to reject
LO leakage
FLO
Flo-Flsb
mixing
Noise reaching mixer from
the DUT Input filter
Frequency
NFA Input
Band
Figure 4-22
LSB Input
USB Input
USB System Downconverter Measurements
Amplitude
Fusb-Flo
mixing
FLO
Noise reaching System
Downconverter is band
limited by filtering
Depending on Flo, a
downconverter output filter
may be needed to reject
LO leakage
Frequency
NFA Input
Band
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LSB Input
USB Input
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Ideally choose a high IF frequency for the conversion to separate the
USB and LSB bands, thus reducing the filter requirements.
The filter needed to make an SSB measurement could be part of the
DUT, or a measurement-specific filter must be obtained and applied at
the input to the system downconverter.
The bandwidth of the SSB filter limits the maximum frequency range
that a measurement can be swept over. Therefore SSB measurements
are not suited to very wideband DUTs. However, variable LO (Fixed IF)
SSB measurements can be made over wider sweep widths than variable
IF (Fixed LO) measurements can be.
The NFA can perform frequency calculations and LO control for both
USB and LSB. It can perform both variable LO (NFA frequency fixed)
and fixed LO (NFA frequency swept). The fixed LO mode is useful where
the downconverter, has a fixed LO system. The sweep of the NFA’s tuned
frequency causes the frequencies at which the system downconverter is
sensitive to sweep. Filtering is needed to select the wanted sideband. A
swept noise figure measurement is then possible even if the system LO
cannot be swept.
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FIXED IF, LSB:
Figure 4-23
LSB Measurements
Sweep Point
Filter Passband
Stop
LSB
FIF
FLO
USB
Flo-Flsb
mixing
Frequency
Start
Figure 4-23 shows a fixed-IF, LSB, system downconverter where the NFA
steps the LO through the sweep.
A filter is used to pass the LSB and reject the USB. Manufactured filters
cannot have infinite transition-band slopes, hence some margin is
needed between the maximum frequency of the LSB component (at the
end of the sweep) and the minimum frequency of the USB component (at
the start of the sweep). Choosing a high IF separates the USB and LSB
frequencies more, and allows a wider sweep, or a simpler filter. The filter
could be a lowpass or a bandpass, it must pass the range that the LSB
frequency sweeps over, while rejecting the range that the USB frequency
sweeps over. Figure 4-23 shows that the sweep width cannot exceed twice
the IF frequency.
You need to make an allowance for the filter’s transition band.
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FIXED IF, USB:
Figure 4-24
USB Measurements
Sweep Point
Filter Passband
FIF
Stop
LSB
FLO
USB
Fusb-Flo
mixing
Frequency
Start
The fixed IF, USB mode is similar to the fixed IF, LSB mode. It allows the
measurement to extend up to 3.0 GHz higher than the maximum LO
frequency (1.5GHz with N8972A). The filter needs to be a bandpass or
highpass. A bandpass filter has an advantage in rejecting LO harmonic
mixing modes. This mode is shown in Figure 4-24, again, the sweep
width is limited to less than twice the IF frequency, less an allowance for
the filter transition band.
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Measurements with a System Downconverter
FIXED LO, LSB
The main benefit of the fixed LO system downconverter modes is that a
programmable synthesized LO is not needed. The disadvantage is the
limited sweep width available, and the increased demands placed on the
sideband selection filters. These modes are suited to the measurement of
DUTs with narrow frequency bands of less than 4 MHz.
Figure 4-25
LSB Measurements
Sweep Point
Filter Passband
Stop
FIF
LSB
FLO
USB
Flo-Flsb
mixing
Start
Frequency
Figure 4-25 shows how the NFA sweeps its own input frequency
backwards from high to low frequency so that as the LSB tunes, the
frequency increases across the sweep. The filter required is either; a
lowpass or a bandpass. The maximum sweep width is now limited to the
maximum IF frequency, less an allowance for the filter transition band.
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FIXED LO, USB
Figure 4-26
USB Measurements
Sweep Point
Filter passband
FIF
LSB
FLO
USB
Stop
Fusb-Flo
mixing
Start
Frequency
Figure 4-26 shows as the NFA tunes in the normal direction for the fixed
LO USB mode. The filter can be a bandpass or highpass, and the sweep
width is again limited to the maximum IF frequency, less an allowance
for the filter transition band.
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Making System Downconverter
Measurements
To make a System Downconverter measurement requires an external
mixer and local oscillator. In this mode the frequency conversion is in the
measurement system, not in device under test.
An example is provided where the NFA remains locked at one frequency
and the LO sweeps with the noise source input frequency. A double
sideband measurement of an amplifier is made. The example can be
modified to make measurements using a fixed LO where the IF is swept.
Also, from the example, upper and lower side band measurements can be
made. The changes in the example’s procedure are explained in each
method.
NOTE
The RF input section on all NFA models has a built-in 3.0 GHz Low Pass
Filter. This filter needs to accounted for when planning your filter
requirements during calibration and measurement.
NOTE
On the N8974A and the N8975A models the microwave input section has
no filtering. This needs to accounted for when planning you filter
requirements for calibration and measurement. This is also important
when making measurements which cross over the 3.0 GHz switch.
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Using a Fixed IF and Variable LO (8970B Mode1.1)
In this mode the LO sweeps with the input frequency and the NFA is set
at a fixed IF frequency. The IF frequency and the measurement input
frequency range values are entered into the analyzer. The NFA
calculates the set of frequencies that the LO will be swept over.
Double Sideband Measurement (Fixed IF and Variable LO)
The example double sideband measurement is made using a N8973A
model. The result is obtained, by using a fixed IF of 1.0 GHz. Setting the
frequency of interest to be 3.6 GHz to 4.0 GHz, giving an LO sweep from
3.6 GHz to 4.0 GHz. This also meets with the need to maintain the LO
frequency out of the NFA’s passband.
NOTE
Typically select an low IF, as there may be differences in ENR values.
Also, differences in gain performance at the two sidebands.
The example uses the a Signal Generator as a local oscillator, and a
mixer to downconvert to the frequency range of the NFA. The system is
used to measure a 2000 to 4300 MHz amplifier over a 3.6 to 4.0 GHz
frequency range. The noise figure for this amplifier typically varies from
6 to 10 dB and the gain from 15 to 5 dB over this reduced frequency
band. Figure 4-27 shows the frequencies involved.
NOTE
Filtering is not needed in the DSB mode. Ensure the LO frequencies are
out of the passband range of the NFA, Hence, LO sweep is always greater
than 3.5 GHz over its swept range.
Figure 4-27
Variable LO, Fixed IF, DSB Spectrum
LO
RF
IF
1
176
3.6
2
3
4.0
4
5
6(GHz)
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Making Extended Frequency Measurements
Making System Downconverter Measurements
Initial Setup Procedure Follow the overview procedure of the initial
set up.
Step 1. Power Up the NFA and the LO. You need to wait for the recommended
warm up time to get accurate measurement results
Step 2. Connect the GPIB cables and the 10 MHz reference, if required. See
“Connecting the System” on page 137 for more detail.
Step 3. Load the ENR values. See “Entering Excess Noise Ratio (ENR) Data” on
page 33 for more detail.
Step 4. Set up the LO and the NFA’s LO settings. See “Choosing and Setting Up
the Local Oscillator” on page 132 for more detail.
Step 5. Set the LO address
Step 6. Connect the system and add filtering where required. Figure 4-4 on page
138 shows the connections
NOTE
The LO GPIB menu key accesses the System LO GPIB Form. This feature
is currently not supported, as currently only the NFA can act as GPIB
controller. Hence, if the LO Control is set to On in the Mode Set Up Form,
the NFA controls the LO.
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Selecting Measurement Mode
Figure 4-28
Measurement Mode Form
Step 1. Press the Meas Mode key. A Meas Mode Form is displayed (Figure 4-28).
Confirm that the Device Under Test field is set to Amplifier.
Use the Tab key to move round the form and in the Device Under Test field
select the Amplifier menu key to highlight it. The default
Device Under Test setting is Amplifier.
Step 2. Press the Tab key to navigate to the System Downconverter field and press
the On menu key to turn on system down conversion.
Step 3. Press the Tab key to navigate to the LO Mode field and press the Variable
menu key for a variable LO setup.
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Selecting Mode Setup
Figure 4-29
Mode Setup Form
Step 1. Press the Mode Setup key. A Mode Setup Form is displayed (Figure 4-29).
This form allows you to enter values for the IF frequency, setup the LO
parameters and choose the sideband required.
Step 2. Press the Tab key to navigate to the IF Frequency field. Set the IF
Frequency.
In the example, enter 1.0 GHz using the numeric keypad and terminate
it using the unit keys which are presented to you.
Step 3. Press the Tab key to navigate to the Sideband field. Set the Sideband.
In the example, enter DSB using the menu keys which are presented to
you.
Step 4. Press the Tab key to navigate to the LO Control field. Set the LO Control.
In the example, enter on by pressing the On menu key which is presented
to you.
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Step 5. Press the Tab key to navigate to the External LO Power Level field. Set the
External LO Power Level.
In this example, enter 10 dBm using the numeric keypad and terminate
it using the unit keys which are presented to you.
Setting Frequency, Point, Bandwidth, Averaging
Step 1. Configure the measurement with the Frequency/Points and
Averaging/Bandwidth keys. For a greater description of these keys, see
“Setting the Measurement Frequencies” on page 46 and “Setting the
Bandwidth and Averaging” on page 52.
Set start and stop frequencies and number of points for the amplifier to
be tested. For the example amplifier, the appropriate figures are:
• Start: 3600 MHz
• Stop: 4000 MHz
• Points: 15
• Averaging: On
• Averages: 5
• Average Mode: Point
• Bandwidth: 4 MHz
NOTE
The N8972A Average Mode is set to point by default, as sweep mode is
only available on the other NFA models.
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Calibration of the DSB Setup Calibration of the DSB measurement
setup requires, if not done already, you to attach the mixer LO port to the
output of the LO, connect the Noise Source output to the mixer RF input,
and connect the mixer IF output to the NFA input, see Figure 4-30.
Figure 4-30
System Downconverter Mode
LO
LO GPIB
Calibration Setup
Noise Source
LO
Measurement Setup
LO GPIB
Noise Source
DUT
Step 1. Press the Calibrate key twice
The first time you press the key you are prompted to press it again. This
two-stroke calibration is a safety feature to prevent you from
accidentally pressing Calibrate and erasing the calibration data.
When the calibration is complete the measurement set up is calibrated at
the mixer input. The white Uncorr text changes to yellow Corr text in
the lower right hand side of the display. The second stage calibration now
includes the mixer, the LO, the cables, adapters, and the NFA.
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Figure 4-31 shows typical results in table format after calibration. It is
good practice to measure the gain and noise figure of the direct
connection before the DUT is inserted.
Figure 4-31
Typical Calibration Results after a Restart is Pressed
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Making the Corrected Noise Figure and Gain Measurement A
measurement corrected for the second stage contribution may now be
made. Insert the DUT into the system as shown in Figure 4-30. The
results are displayed on the display using the same steps as those
described in “Displaying the Measurement Results” on page 61. A
typical display of noise figure and gain is shown in Figure 4-32.
Figure 4-32
Typical DUT Results
NOTE
Once you have successfully made your measurement you may want to
save the set up for future measurements. This can be done by saving the
state. See “Saving a File” on page 24 for more details.
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Lower Single Sideband Measurement (Fixed IF and Variable LO)
The lower single sideband measurement set up is similar to the DSB
measurement. However, you need to provide filtering to remove the USB
image. Follow the DSB procedure, however in the Mode Setup Form
select the LSB in the sideband option.
NOTE
During measurement with the DUT inserted, it is important that the
filter be on the mixer input rather than the noise source output.
Otherwise some added noise from the device under test will likely be in
the unwanted sideband and create a measurement error. The filter must
be in place for both calibration and measurement.
Upper Single Sideband Measurement (Fixed IF and Variable LO)
The upper single sideband measurement set up is similar to the DSB
measurement. However, you need to provide filtering to remove the LSB
image. Follow the DSB procedure, however in the Mode Setup Form
select the USB in the sideband option.
NOTE
During measurement with the DUT inserted, it is important that the
filter be on the mixer input rather than the noise source output.
Otherwise some added noise from the device under test will likely be in
the unwanted sideband and create a measurement error. The filter must
be in place for both calibration and measurement.
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Using a Variable IF and Fixed LO (8970B Mode1.2)
In this mode the NFA sweeps with the input frequency and the LO is set
to a fixed frequency. The LO frequency and the measurement input
frequency range values are entered into the analyzer. The NFA
calculates the set of frequencies that the IF is swept over.
NOTE
Even if the LO is not controlled by the NFA the LO’s frequency value
must be entered in the Mode Setup Form.
A measurement with a variable IF, always requires a single-sideband
measurement. Hence the need to filter the unwanted sideband in the
measurement setup.
Calibration in this mode is the same as for the variable LO
single-sideband modes, and you need to ensure that the filter is in place
for both the calibration and the measurement.
Connecting the System
To connect the calibration and measurement set up for this mode see
Figure 4-33. If the NFA is the controller as in the previous section, and
the LO is one that can respond over GPIB, this automatically sets the LO
frequency.
If the LO cannot respond over GPIB or using the custom commands, you
can set the frequency and amplitude manually to a fixed value. However,
the frequency value must be entered in the Mode Setup Form in the
NFA.
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Figure 4-33
System Downconverter Mode
LO
LO GPIB
Calibration Setup
Noise Source
LO
Measurement Setup
LO GPIB
Noise Source
DUT
Lower Sideband Measurement (Variable IF and Fixed LO)
The lower single sideband measurement set up is similar to the DSB
measurement example, see “Double Sideband Measurement (Fixed IF
and Variable LO)” on page 176. However, you need to provide filtering to
remove the USB image. Follow the DSB procedure, and the Mode Setup
Form select the LSB in the sideband option. On the Meas Mode Form
select the LO Mode to Fixed.
NOTE
During measurement with the DUT inserted, it is important that the
filter be on the mixer input rather than the noise source output.
Otherwise some added noise from the device under test will likely be in
the unwanted sideband and create a measurement error. The filter must
be in place for both calibration and measurement.
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Upper Sideband Measurement (Variable IF and Fixed LO)
The upper single sideband measurement set up is similar to the DSB
measurement example, see “Double Sideband Measurement (Fixed IF
and Variable LO)” on page 176. However, you need to provide filtering to
remove the LSB image. Follow the DSB procedure, and the Mode Setup
Form select the USB in the sideband option. On the Meas Mode Form
select the LO Mode to Fixed.
NOTE
During measurement with the DUT inserted, it is important that the
filter be on the mixer input rather than the noise source output.
Otherwise some added noise from the device under test will likely be in
the unwanted sideband and create a measurement error. The filter must
be in place for both calibration and measurement.
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Frequency Restrictions
Frequency Restrictions
To assist you troubleshoot problems encountered when setting up these
measurement modes, there are restrictions that apply to the mode of
operation.
Glossary of Restricted Terms
Table 4-3 is a description of the terms used in the restrictions
Table 4-3
188
Restricted Terms
Term
Description
fFIF
Fixed IF
fFLO
Fixed LO frequency
fLO
External LO frequency
fSIF
System input frequency
fSTART
Start frequency
fSTOP
Stop frequency
IF
The output from DUT frequency or
the tuned frequency of the NFA
RF
The input to DUT frequencies
Chapter 4
Making Extended Frequency Measurements
Frequency Restrictions
General Restrictions
In the measurement modes the following general restrictions apply:
• The Fixed IF frequency, fFIF, limits are defined by the NFA's
minimum and maximum system input frequencies, fSIF(MIN) and
fSIF(MAX) respectively. For example, the N8973A has fSIF(MIN) = 10
MHz and fSIF(MAX) = 3 GHz.
• Fixed LO frequency, fFLO, limits are defined by the external LO's
minimum and maximum frequencies, fLO(MIN) and fLO(MAX)
respectively, as entered in the System⇒External LO menu.
NOTE
Whether the input frequencies are RF or IF frequencies, the Frequency
menu is used to enter these frequency values.
• For modes with a fixed IF, the frequency span, fSPAN, is limited to
fSTOP - fSTART.
• For modes with a variable IF, the frequency span, fSPAN, is limited to
fSIF(MAX) - fSIF(MIN).
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Frequency Restrictions
Frequency-Downconverting DUT
In this mode, the DUT contains a frequency down-converting device. For
example, a mixer or receiver.
Fixed IF Variable LO
These are the restrictions applicable to this mode.
LSB Restrictions In the LSB, Fixed IF Variable LO mode the following
restrictions apply:
• fRF(START) > fFIF
If this restriction is broken, Mode setup error;Start freq must
be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
USB Restrictions In the USB, Fixed IF Variable LO mode the
following restrictions apply:
• fLO(START) > fFIF
If this restriction is broken, Mode setup error;Start LO freq
must be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
DSB Restrictions In the DSB, Fixed IF Variable LO mode the
following restrictions apply:
• fRF(START) > fFIF
If this restriction is broken, Mode setup error;Start freq must
be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
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Frequency Restrictions
Variable IF Fixed LO
These are the restrictions applicable to this mode.
LSB Restrictions In the LSB, Variable IF Fixed LO mode the following
restrictions apply:
• fIF(STOP) < fRF(STOP)
If this restriction is broken, Mode setup error;Stop freq must be
less than stop RF freq is generated.
To resolve this error condition, increase fFLO or decrease fIF(STOP).
USB Restrictions In the USB, Variable IF Fixed LO mode the
following restrictions apply:
• fIF(STOP) < fFLO
If this restriction is broken, Mode setup error;Stop freq must be
less than fixed LO freq is generated.
To resolve this error condition, increase fFLO or decrease fIF(STOP).
DSB Restrictions In the DSB, Variable IF Fixed LO mode the
following restrictions apply:
• fIF(STOP) < fRF(STOP)
If this restriction is broken, Mode setup error;Stop freq must be
less than stop RF freq is generated.
To resolve this error condition, increase fFLO or decrease fIF(STOP).
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Frequency Restrictions
Frequency Up-converting DUT
In this mode, the DUT contains a frequency up-converting device. For
example, a transmitter.
Fixed IF Variable LO
These are the restrictions applicable to this mode.
LSB Restrictions In the LSB, Fixed IF Variable LO mode the following
restrictions apply:
• fRF(STOP) < fFIF
If this restriction is broken, Mode setup error;Stop freq must be
less than fixed IF freq is generated.
To resolve this error condition, increase fFIF or decrease fRF(STOP).
USB Restrictions In the USB, Fixed IF Variable LO mode the
following restrictions apply:
• fRF(STOP) < fLO(STOP)
If this restriction is broken, Mode setup error;Stop freq must be
less than stop LO freq is generated.
To resolve this error condition, increase fFIF or decrease fRF(STOP).
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Frequency Restrictions
Variable IF Fixed LO
These are the restrictions applicable to this mode.
LSB Restrictions In the LSB, Variable IF Fixed LO mode the following
restrictions apply:
• fIF(STOP) < fFLO
If this restriction is broken, Mode setup error;Stop freq must be
less than fixed LO freq is generated.
To resolve this error condition, increase fFLO or decrease fIF(STOP).
• fIF(START) > fRF(START)
If this restriction is broken, Mode setup error;Start freq must
be greater than start RF freq is generated.
To resolve this error condition, decrease fFLO or increase fIF(START).
USB Restrictions In the USB, Variable IF Fixed LO mode the
following restrictions apply:
• fIF(START) > fFLO
If this restriction is broken, Mode setup error;Start freq must
be greater than fixed LO freq is generated.
To resolve this error condition, decrease fFLO or increase fIF(START).
• fRF(STOP) < fFLO
If this restriction is broken, Mode setup error;Stop RF freq must
be less than fixed LO freq is generated.
To resolve this error condition, increase fFLO or decrease fIF(STOP).
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Frequency Restrictions
System Downconverter
The DUT is a non-frequency converting device, for example an amplifier
or filter measurement, and its frequency is outside the NFA’s
measurement range (frequencies less than 10 MHz or greater than
3.0 GHz). Frequency down-conversion is required within the
measurement system, in other words, using a mixer, external to the DUT,
to convert the signal of interest to the frequency range of the NFA.
Fixed IF Variable LO
These are the restrictions that apply to this mode.
DSB Restrictions
In the DSB, Fixed IF Variable LO mode the following restrictions apply:
• fRF(START) > fFIF
If this restriction is broken, Mode setup error;Start freq must
be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
LSB Restrictions
In the LSB, Fixed IF Variable LO mode the following restrictions apply
to the set up:
• fRF(START) > fFIF
If this restriction is broken, Mode setup error;Start freq must
be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
USB Restrictions
In the USB, Fixed IF Variable LO mode the following restrictions apply
to the set up:
• fRF(START) > fFIF
If this restriction is broken, Mode setup error; Start freq must
be greater than fixed IF freq is generated.
To resolve this error condition, decrease fFIF or increase fRF(START).
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Frequency Restrictions
Variable IF Fixed LO
These are the restrictions applicable to this mode.
LSB Restrictions
In the LSB, Variable IF Fixed LO mode the following restrictions apply:
• fRF(STOP) < fFLO
If this restriction is broken, Mode setup error;Stop freq must be
less than fixed LO freq is generated.
To resolve this error condition, increase fFLO or decrease fRF(STOP).
• fRF(START) > fIF(START)
If this restriction is broken, Mode setup error;Start freq must
be greater than start IF freq is generated.
To resolve this error condition, decrease fFLO or increase fRF(START)
• fFLO - fRF(STOP) > fSIF(MIN)
If this restriction is broken, Mode setup error;LO - Stop freq
must be >= min system input freq is generated.
To resolve this error condition, increase fFLO or decrease fRF(STOP)
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Frequency Restrictions
USB Restrictions
In the LSB, Variable IF Fixed LO mode the following restrictions apply:
• fRF(START) > fFLO
If this restriction is broken, Mode setup error; Start freq must
be greater than fixed LO freq is generated.
To resolve this error condition, decrease fFLO or increase fRF(START).
• fIF(STOP) < fFLO
If this restriction is broken, Mode setup error; Stop IF freq must
be less than fixed LO freq is generated.
To resolve this error condition, increase fFLO or decrease fRF(STOP).
• fRF(START) - fFLO > fSIF(MIN)
If this restriction is broken, Mode setup error; Start - LO freq
must be >= min system input freq is generated.
To resolve this error condition, decrease fFLO or increase fRF(START).
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5
Performing System Operations
This chapter describes how to perform the system-level tasks, such as
configuring the Noise Figure Analyzer’s GPIB address, defining the
preset conditions and so forth.
197
Performing System Operations
What You will Find in this Chapter
What You will Find in this Chapter
This chapter covers:
• Setting the GPIB Addresses
• Configuring the Serial Port
• Configuring the Characteristics of an External LO
• Configuring the Internal Alignment
• Displaying Error, System and Hardware Information
• Presetting the Noise Figure Analyzer
• Defining the Power-On/Preset Conditions
• Restoring System Defaults
• Setting the Time and Date
• Configuring a Printer with the NFA
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Setting the GPIB Addresses
Setting the GPIB Addresses
Purpose of the
The NFA has two GPIB connectors on its rear panel. One connector is
GPIB and LO GPIB used for communicating with a computer using the remote command set
and the other connector, the LO GPIB, is used by the NFA to control an
external local oscillator. The NFA acts as the controller over the
LO GPIB.
To Set the GPIB Addresses
Step 1. Press the System key
Step 2. Press the GPIB menu key.
The System GPIB Form now appears in the display. See Figure 5-1.
Figure 5-1
System GPIB Form
Step 3. Using the Tab key to navigate through the form configure the GPIB
parameters as required.
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Performing System Operations
Setting the GPIB Addresses
The System GPIB parameters are described in Table 5-1.
Table 5-1
System GPIB parameters
Parameter
Description
Noise Figure Analyzer
Address
The instrument’s GPIB address.
Valid addresses are from 0 to 30.
Default is 8.
External LO Address
The GPIB address of the External LO attached to
the LO GPIB.
Valid addresses are from 0 to 30.
Default is 19.
LO GPIB Address
The address through which devices, attached to the
LO GPIB, communicate with the instrument.
Valid addresses are from 0 to 30.
Default is 8
NOTE
Ensure the Remote Port menu key is set Remote Port(GPIB).
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Configuring the Serial Port
Configuring the Serial Port
The NFA has a serial port on the rear panel to allow the it to
communicate using the remote command set.
To configure the serial port:
Step 1. Press the System key
Step 2. Press the Serial menu key.
The System Serial Form now appears. See Figure 5-2
Figure 5-2
System Serial Form
Step 3. Use the Tab keys to navigate through the form and the menu keys to
configure the serial parameters as required.
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Performing System Operations
Configuring the Serial Port
The System serial port parameters are described in Table 5-2.
Table 5-2
Serial port parameters
Parameter
Description
Data Terminal Ready
Sets the DTR line control.
Request To Send
Baud
•
OFF de-asserts DTR, hence disabling the serial
port
•
ON asserts DTR, hence enabling the serial port
•
IBF tells the driver to use DTR for data pacing
Sets the RTS line control.
•
OFF de-asserts RTS, hence disabling the serial
port
•
ON asserts RTS, hence enabling the serial port
•
IBF tells the driver to use RTS for data pacing
Sets the Baud rate of the NFA’s serial port.
Note: The value you set here must match the Baud
rate of the connected device.
Receive Pacing
Transmit Pacing
NOTE
Sets the receive pacing handshake characters.
•
NONE
•
XON/XOFF
Sets the transmit pacing handshake characters.
•
NONE
•
XON/XOFF
Ensure the Remote Port menu key is set Remote Port(Serial). The NFA
needs a power cycle to take effect if you changed it from
Remote Port(GPIB),
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Configuring the Characteristics of an External LO
Configuring the Characteristics of an
External LO
The NFA can control an external LO using its LO GPIB port. The
External LO menu allows you to configure the following characteristics of
the external LO:
• Type of command set used: the default is SCPI, however, the NFA
also allows you to create and use custom command sequences for LOs
that do not use SCPI commands.
• The minimum and maximum input frequencies of the LO: See
“Minimum and Maximum Frequencies” on page 206.
• The settling time of the LO: See “Settling Time” on page 206.
• The frequency multiplier of the LO: See “Multiplier” on page 207.
• Auxiliary command, if any used, for example, Continuous Wave (CW)
or Modulation type.
NOTE
The custom command sequence is stored as part of the “persistent”
instrument state.
Custom Command Set
The custom command set allow you to customize a command set to define
the operation of a non-SCPI compliant LO.
The custom command set supports an LO that could use a maximum of
seventy-nine characters in the prefix and suffix. These characters
include the prefix characters and the suffix characters.
The purpose of the frequency prefix and suffix is to correctly format the
commands from the NFA to the LO. The format is different for different
LOs. The frequency information is determined by the frequency
parameters entered into the NFA during the measurement setup and by
the measurement mode in which the NFA is operating.
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Configuring the Characteristics of an External LO
The purpose of the Power prefix and suffix is to set the output signal
power level of the LO. The allowable range is from -100 to +100 dBm.
The actual output signal power level is limited by the output signal
power level capability of the LO.
The purpose of the auxiliary command is to set other features in the LO,
for example, enable RF output (OUTP:STAT ON).
To access the menu to configure the command characteristics of an
external LO follow the procedure:
Step 1. Press the System key.
Step 2. Select the External LO menu key.
Step 3. Select the LO Commands menu key.
You are presented with an External LO Commands Form.
Figure 5-3
External LO Commands Form
NOTE
The default suffix commands have an intentional space inserted.
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Step 4. Press the Tab key to move the highlight to the required position in the
form.
You can choose to enter the Prefix and Suffix of the power commands and
frequency commands. Also you can enter an auxiliary command. This
procedure explains this process using the auxiliary commands.
Figure 5-4
External LO Auxiliary Menu Keys
• Selecting the Clear Command menu key, clears the current command.
See Figure 5-4 showing the Auxiliary menu keys.
• Selecting the Change Command menu key, you are presented with an
Alpha Editor. This and the numeric keys allows you to enter a
command string, see Figure 5-5. Press the Prev key to enter the
command. The command string can have up to a maximum of
seventy-nine characters.
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Configuring the Characteristics of an External LO
Figure 5-5
External LO Auxiliary Command Changes
Settling Time
The purpose of the settling time is to ensure that the NFA waits a
sufficient amount of time after issuing a frequency or power command to
allow the LO’s output to stabilize.
Pressing the Settling Time menu key allows you to set the settling time of
NFA. Valid settling times are between 0 ms and 100 s. The default value
is 100 ms.
Minimum and Maximum Frequencies
The minimum and maximum frequencies represent the frequency
capability of the LO. They are only used by the NFA to determine if the
frequencies needed by the measurement are acceptable.
Pressing the Min Freq menu key allows you to set the minimum frequency
the NFA expects the External LO to have. The default value is 10 MHz.
Pressing the Max Freq menu key allows you to set the maximum
frequency the NFA expects the External LO to have. The default value is
40.0 GHz.
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Configuring the Characteristics of an External LO
Multiplier
The external LO frequency multiplier value sets the frequency
multiplying factor of the external LO.
Pressing the Multiplier menu key allows you to set the multiplier
frequency of the External LO. The default value is 1.
NOTE
When using the multiplier feature and setting the minimum and
maximum frequencies capabilities of the external LO, note that these
limits refer to the multiplied frequency input to the DUT. For example,
with a multiplier of 4, and an external LO which can operate from
10 MHz to 20 GHz, the limits should be set to 40 MHz and 80 GHz.
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Configuring the Internal Alignment
Configuring the Internal Alignment
Data from the internal alignment routine is necessary for accurate NFA
operation. When enabled, the internal alignment routine runs
continuously to ensure that the NFA is using current alignment data
which improves the NFA’s accuracy.
Alignment is the process of routing a known internally generated signal
through a selected signal path and measuring the signal. This measured
value is then compared with the expected value in order to derive the
correction needed to convert the measured value to the expected value.
No external connections are needed.
Turning Alignment Off and On
Step 1. Press the System key.
Step 2. Press the Alignment menu key to access the Alignment menu.
Step 3. Press the Alignment menu key selecting Alignment(On) or Alignment(Off) as
required.
The default setting is Alignment(On).
Changing Alignment Mode
Step 1. Press the System key.
Step 2. Press the Alignment menu key to access the Alignment menu.
Step 3. Press the Alignmnt Mode menu key selecting Alignmnt Mode(Point) or
Alignmnt Mode(Sweep) as required.
The default mode setting is Alignmnt(Sweep).
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Configuring the Internal Alignment
Alignment of the YIG Tuned Filter (YTF)
NOTE
The YTF alignment feature only applies to the N8974A and the N8975A
models.
Step 1. Press the System key.
Step 2. Press the Alignment menu key to access the Alignment menu.
Step 3. Press the Align YTF menu key to set the YTF alignment.
You are prompted to press this key again. This feature ensures you do
not accidently erase the current YTF alignment data.
Step 4. Wait until the Alignment routine has completed.
Step 5. Press the Save YTF Alignment menu key to store the Alignment data.
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Displaying Error, System and Hardware Information
Displaying Error, System and Hardware
Information
Displaying the Error History
The 10 most recent errors are stored in an error queue which you can
display as a full size table. The most recent messages appear at the top of
the table. To display the error queue:
Step 1. Press the System key and the More 1 of 3 menu key.
Step 2. Press Show Errors menu key to view the error queue.
To clear the error screen, press Clear Error Queue.
Displaying System Information
You can display the instrument product number, serial number, memory,
loaded firmware details and fitted options.
Step 1. Press the System key and the More 1 of 3 menu key.
Step 2. Press Show System menu key to view system information.
Displaying Hardware Information
Step 1. Press the System key and the More 1 of 3 menu key.
Step 2. Press Show Hdwr menu key to view hardware information.
The name and version numbers of the hardware modules in the
instrument are now displayed.
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Presetting the Noise Figure Analyzer
Presetting the Noise Figure Analyzer
Pressing the Preset key places the NFA in a known state and provides a
convenient starting point for making most measurements. You can
specify the preset state with the Preset menu key located under the
System key.
To preset the analyzer using its factory defaults:
Step 1. Turn the NFA on by pressing the On key and wait for the power on
process to complete.
Step 2. Press System key, More 1 of 3, Power On/Preset, Preset (Factory) menu keys.
Step 3. Press the green Preset key.
The instrument preset function performs a processor test but does not
affect alignment data. Pressing Preset clears both the input and output
buffers. The status byte is set to 0.
NOTE
Turning on the analyzer performs an instrument preset. Turning on the
analyzer also fetches alignment data; clears both the input and output
buffers; and sets the status byte to 0. The last state of the analyzer before
it was turned off is recalled when Power On(Last) is selected (under the
System key).
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Defining the Power-On/Preset Conditions
Defining the Power-On/Preset Conditions
The power up and preset conditions can be different if required. You can
set the NFA to return it to a user-defined state after a power on or preset.
Setting the Power On Conditions
Step 1. Press the System key and the More 1 of 3 menu key.
Step 2. Press the Power On/Preset menu key.
Step 3. Set Power On to Power On(Last) or Power On(Preset) as required.
‘Last’ means that the instrument, upon power on returns to the state it
was in when it was powered off.
‘Preset’ means the instrument returns to its defined preset state.
Setting the Preset Conditions
You can set the NFA to return to its factory default state or a user
defined state upon preset. The configured user defined state is provided
by pressing the Save User Preset menu key to save the current NFA state
To set the preset conditions to factory default
Step 1. Press the System key and the More 1 of 3 menu key.
Step 2. Press the Power On/Preset menu key.
Step 3. Enable the Preset(Factory) menu key.
To set the preset conditions to user defined
Step 1. Configure the NFA to the desired state.
Step 2. Press the System key and the More 1 of 3 menu key.
Step 3. Press the Power On/Preset menu key.
Step 4. Enable the Preset(User) menu key.
Step 5. Press the Save User Preset menu key to save the current NFA state.
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Restoring System Defaults
Restoring System Defaults
This will reset the NFA to the original factory default settings. It will
also clear the non-volatile memory of ENR tables, limit lines, address
setting, and so forth.
To restore the system defaults:
Step 1. Press the System key
Step 2. Press the More 1 of 3 menu key.
Step 3. Press the Restore Sys Defaults menu key.
Press the Restore Sys Defaults menu key again.
NOTE
You are prompted to press this key again. This feature ensures you do
not accidently restore the original factory default settings.
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Setting the Time and Date
Setting the Time and Date
The NFA allows you to set and display the time and date. The date can
be set in US or European format as required.
To turn the time and date on and off
Step 1. Press the System key.
Step 2. Press the More 1 of 3 menu key.
Step 3. Press the Time/Date menu key.
Step 4. Press the Time/Date menu key to select Time/Date(On) or Time/Date(Off) as
required.
The default is Time/Date(On).
To set the time and date
Step 1. Press the System key.
Step 2. Press the More 1 of 3 menu key.
Step 3. Press the Time/Date menu key.
Step 4. Set the Date Mode to either US format MDY (Month/Day/Year) or
European format DMY (Day/Month/Year).
US format is the default setting.
Step 5. Enter the time in hhmmss (hours, minutes, seconds) format.
Step 6. Enter the date in yyyymmdd (year, month, day) format.
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Configuring a Printer with the NFA
Configuring a Printer with the NFA
Printer
requirements
• IEEE 1284 compliant printer cable.
• Supported printer equipped with a parallel interface. A supported
printer is one that accepts Printer Control Language Level 3 or 5.
— PCL3 printers include most HP DeskJet printers.
— PCL5 printers include most HP LaserJet printers and the
HP 1600C DeskJet printer.
Printer connection To connect your printer to the NFA, connect the printer to the parallel
I/O interface connector of the NFA using an IEEE 1284 compliant
parallel printer cable.
If appropriate, configure your printer (see your printer documentation
for more details on configuring your printer).
To Configure a Printer with the NFA
Step 1. Power on the NFA and the printer.
Step 2. Press the Print Setup key and then press the Printer Type menu key.
Step 3. Press Printer Type to access the Printer Type menu keys and press Auto to
make the NFA attempt to identify the connected printer.
When you select Auto as the Printer Type, the NFA responds in one of the
following three ways:
• The Print Setup menu is displayed with the Auto key selected and no
new message is displayed in the display status line. This indicates
that the NFA recognizes the connected printer and no further setup is
required. As long as Auto remains selected in the Printer Type menu,
the NFA attempts to identify the printer when you press the front
panel Print key. The selected printer is displayed by pressing System,
More 1 of 3, Show System.
• The Print Setup menu is displayed with the Custom key selected and
one of the following diagnostic messages is displayed in the display
status line:
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Unknown printer, Define Custom to set up printer
No printer response, Define Custom to set up printer
Invalid printer response, Define Custom to set up printer
This indicates that the NFA is unable to automatically identify the
connected printer, and Custom is selected in the Printer Type menu.
Press Print Setup, Define Custom to select specific printer
characteristics such as the printer language (PCL3 or PCL5) and
color printing capability. Once you have set these characteristics to
match those of your connected printer, the printer setup process is
complete. As long as Custom remains selected in the Printer Type
menu, the NFA does not attempt to automatically identify the
connected printer when you press the front panel Print key.
• The Print Setup menu is displayed with the None key selected and the
following message appears in the display status line:
Unsupported printer, Printer Type set to None
This indicates that the NFA recognizes the connected printer, but the
printer is not supported by the NFA. As long as None is selected in the
Printer Type menu, the NFA responds to any print command by
displaying the message Printer Type is None in the display status
line.
The Printer Type accesses the following keys:
None
None disables the NFA from attempting to print to a
printer. This is the appropriate setting if no printer is
connected to the NFA.
Custom
Custom allows you to access the Define Custom menu
keys. The Define Custom menu keys allow you to specify
printer characteristics such as PCL Level and printer
color capability.
Auto
Auto enables the NFA to automatically attempt to
identify the connected printer when the Print key is
pressed or when Printer Type is set to Auto.
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Testing Correct Printer Operation
When printer setup is complete test correct printer operation by pressing
Print Setup, Print (Screen) and then pressing the Print key to print a test
page.
If the printer is ready and printer setup is successful, a printout of the
NFA display is printed. If the printer is not ready, the message Printer
Timeout appears on the NFA display. Printer Timeout remains on the
display until the printer is ready or until you press ESC to cancel the
printout request.
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Front Panel Key Reference
This chapter describes each key and menu item contained within the
user interface of the NFA. The keys are listed in their key groupings and
are listed with their corresponding menu keys as they appear in the key
menus.
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MEASURE Keys
Figure 6-1
Measure Key Group
Frequency/Points
This accesses the menu keys that control the measurement frequency
range and the number of discrete measurement points in the frequency
range. It also accesses the menus allowing you to set a spot measurement
frequency and create frequency lists.
The center frequency and frequency span, or start and stop frequency
values appear in the lower annotation on the display. This is dependent
on which of these options you have selected.
When entering a frequency value you specify units of Hz, kHz, MHz, or
GHz using the menu keys presented.
NOTE
The frequency range upper limits are model dependent. All models have
a lower limit of 10 MHz and each model’s upper limit is as follows:
• The N8972A upper limit is 1.5 GHz.
• The N8973A upper limit is 3.0 GHz.
• The N8974A upper limit is 6.7 GHz.
• The N8975A upper limit is 26.5 GHz.
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NOTE
Models, N8974A and N8975A have their default frequency ranges set to
avoid crossing the 3.0 GHz switch. See “3.0 GHz Mechanical Switch” on
page 3 for an explanation of this.
NOTE
When varying the External LO, the frequency limits are specified by you.
The limits applied depend on whether the LO or IF is being varied. See
“Making Extended Frequency Measurements” on page 115 for a further
explanation of this.
Figure 6-2
A Typical Frequency/Points Menu Map
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Freq Mode
This selects between swept, list and fixed frequency modes. The
frequency mode which is selected is displayed in the menu key.
The frequency modes available are:
• Sweep where the frequencies are generated from the frequency range
selected and the number of measurement points.
• List where the frequencies are taken from the frequency list.
• Fixed where the measurement is taken at the fixed frequency.
Start Freq
This allows you to set the frequency at which the measurement sweep
starts. In the graphical format, the trace starts at the left side of the
graticule. When Start Freq is selected its value is displayed in the lower
annotation.
Stop Freq
This allows you to set the frequency at which the measurement sweep
stops. In the graphical format, the trace stops at the right side of the
graticule. When Stop Freq is selected its value is displayed in the lower
annotation.
Center Freq
This allows you to set the center frequency at which the measurement
frequency range is centered. When Center Freq is selected its value is
displayed in the left lower annotation.
Freq Span
This allows you to set the frequency range symmetrically about the
centre frequency. When Freq Span is selected its value is displayed in the
right lower annotation.
Fixed Freq
This allows you to set the frequency point used in fixed frequency
measurements. When Fixed Freq is selected its value is displayed in the
left and right lower annotation as start and stop values respectively.
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Points
This allows you to set the number of discrete equidistant measurement
frequency points at which measurements are made during Sweep
frequency mode. The maximum number of points allowed is 401. Default
value is 11. The number of points are shown at the bottom of the display.
NOTE
The maximum number of 401 points are conditional, as they are limited
by the frequency span. This is because the minimum resolution between
any two points is set at 10 KHz. Hence, to achieve 401 points, the
frequencies measurement range must be greater than 4 MHz.
Full Span
This changes the measurement span to the full span of the NFA showing
the full frequency range. The full span of the NFA is model dependant.
See “The Noise Figure Analyzer Features” on page 3 for your model’s
frequency range.
Freq List
This allows you access to a form to enter or edit a frequency list.
The frequency list allows you to enter a list of frequencies at which
measurements are to be made. Frequency lists are limited to 401 entry
points. The number of points are shown at the bottom of the display. The
frequencies are automatically sorted in ascending order.
Row Up
This allows you to select a particular entry in the table
by pressing this menu key to move up to its position in
the table one entry at a time.
Row Down
This allows you to select a particular entry in the table
by pressing this menu key to move down to its position
in the table one entry at a time.
Page Up
This allows you to move up the table entries in page
blocks.
Page Down
This allows you to move down the table entries in page
blocks.
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Add
This allows you to add a new entry. It adds the entry to
the bottom of the table after the last valid entry. It
sequences the entry in the correct ascending order
when the entry is terminated. To terminate an entry
use the frequency unit value keys presented to you.
Delete Row
This removes the highlighted row entry from the table.
Clear Table
This removes all entries from the table. You need to
press this menu key twice.
The first time you press the key you are prompted to
press it again. This two-stroke key press is a safety
feature to prevent you from accidentally pressing
Clear Table and erasing the table data.
Fill
224
This clears then fills the frequency list with current
frequencies generated by swept frequency mode.
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Averaging/Bandwidth
This accesses the menu keys that control the measurement averaging
and bandwidth parameters.
Figure 6-3
Averaging/Bandwidth Menu Map
N8972A Menu
All Other Models Menus
Averaging
This allows you to enable or disable the averaging function. To enable the
averaging set the Averaging(On) function. To disable the averaging set the
Averaging(Off) function.
NOTE
If the averaging number is set to 1 and averaging is enabled, this gives
the same result as averaging disabled.
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Averages
This sets the number of times each data points is to be averaged. This is
a value between 1 and 999. The default value is 1, meaning that no
averaging is performed. You can either scroll using the RPG to the
average value you want, or enter the numerical value you want with the
numerical keypad and press Enter to terminate it. The value is annotated
in the bottom of the display.
Average Mode
This allows you to choose the type of averaging mode. To average at each
point enable the Average Mode(Point) function. To average at each sweep
enable the Average Mode(Sweep) function. See “Selecting the Averaging
Mode” on page 53 for an explanation on the difference between the two
modes.
NOTE
The sweep average function is not available on the N8972A.
Bandwidth
This allows you to set the measurement bandwidth to one of the
following values listed below. See page 52 for an explanation of
measurement bandwidth.
• 100kHz
• 200kHz
• 400kHz
• 1MHz
• 2MHz
• 4MHz
NOTE
The bandwidth menu key is unavailable on the N8972A and its
bandwidth value is set at the default 4MHz.
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Calibrate
This performs the internal calibration routine. The calibration is similar
to a measurement except that the device under test is not in the
measurement path. It is used to correct any noise added by the second
stage test system.
You must press the Calibrate key twice before calibration starts. After the
first press you are presented with a popup dialogue box that prompts you
to press the calibrate key a second time to start the calibration, or to
press Escape to abandon the calibration.
The values generated during a calibration are used to correct subsequent
measurements as long as the calibration remains valid or until the next
calibration.
Figure 6-4
Calibration Warning Pop Up Box
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Meas Mode
This key accesses the Meas Mode Form, which allows you to select the
measurement mode of the NFA. You can choose which type of Device
Under Test and, if applicable, whether the LO is fixed or variable using
this form.
Use the Tab keys to highlight items in the form. When an item is
highlighted you can change its value. Its value is displayed in the
highlighted area and in the active function area.
Device Under Test
This selects which type of DUT you want to measure.
• Amplifier
• Downconv
• Upconv
System
Downconverter
This selects whether or not the downconverter is On or Off. This is only
accessible if the Device Under Test is set to Amplifier.
LO Mode
This selects whether the LO mode is Fixed or Variable.
Figure 6-5
Meas Mode Menu Maps
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Mode Setup
This key accesses the Mode Setup Form, which allow you to setup the
measurement mode of the NFA you selected under the Meas Mode key.
This allows you to choose the fixed frequency value, sideband, the NFA
control of the LO, and the LO power level to be used.
Use the Tab keys to highlight items in the form. When an item is
highlighted you can change it’s value. Its value is displayed in the
highlighted area and in the active function area.
IF Frequency
This allows you to set a fixed IF frequency when the LO Mode is set to
variable.
LO Frequency
This allows you to set a fixed LO frequency when the LO Mode is set to
fixed.
Sideband
This allows you to set the measurement side-band selection, where the
selected measurement mode allows, to either lower side-band (LSB),
upper side-band (USB), double side-band (DSB).
LO Control
This allows you to set whether the external LO is controlled by the NFA,
LO Control(On), or if the LO is set up manually, LO Control(Off). If you are
working with a fixed LO, you can set up the LO manually, however you
are required to enter the LO’s frequency value in the LO Frequency.
External LO Power
Level
This allows you to set the power level of the external LO. It only
functions if the NFA’s LO control is set to LO Control(On). To enter a
value, you can either scroll using the RPG to the value you want, or enter
the numerical value you want with the numerical keypad. Press the
units menu keys presented to you to terminate it.
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Figure 6-6
Mode Setup Form with Sideband Menu Map Displayed
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ENR
This accesses a menu which allows you to select a noise source
preference, enter the ENR tables, specify a Tcold temperature, specify a
spot Thot temperature, and select a spot frequency ENR value.
Figure 6-7
ENR Menu Maps
ENR Mode
This switches between ENR Mode(Table) and ENR Mode(Spot) modes. The
default is ENR Mode(Table).
When ENR Mode(Spot) is enabled the ENR table data is ignored and a
single value specified by Spot ENR or Spot Thot is used.
Common Table
This switches between Common Table(On) and Common Table(Off) modes.
The default is Common Table(On).
When Common Table(On) is enabled, the same noise source ENR data is
used during both the measurement and calibration. When
Common Table(Off) is enabled, separate noise source ENR data is used for
the measurement and calibration.
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ENR Table
This allows you to enter, alter, or check data in the ENR table.
Edit Table
The allows you to enter or edit an ENR table of
frequency/ENR pairs from which ENR values are
interpolated. See “Working with Tables” on page 28.
• Row Up
This allows you to select a particular entry in the
table, by pressing this menu key you move up to its
position in the table one row at a time.
• Row Down
This allows you to select a particular entry in the
table, by pressing this menu key you move down to
its position in the table one row at a time.
• Page Up
This allows you to move up the table entries in page
blocks.
• Page Down
This allows you to move down the table entries in
page blocks.
• Add
This allows you to add a new entry. It adds the entry
to the bottom of the table and sequences it in the
correct ascending frequency order when the row is
complete.
To terminate the ENR Value entry use the unit keys
presented to you. You can also terminate using the
Enter key and it uses the dB unit value by default.
• Delete Row
This removes the single row which is highlighted
from the table.
• Clear Table
This removes all entries from the table. You need to
press this menu key twice.
The first time you press the key you are prompted
to press it again. This two-stroke key press is a
safety feature to prevent you from accidentally
pressing Clear Table and erasing the table data.
Serial Number
232
This allows you to enter the serial number of the noise
source associated with the ENR table. To enter a value,
you use the Alpha Editor which is presented and the
numerical keypad. To complete the entry press the Prev
key. Its value is displayed in the highlighted area and
in the active function area.
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ID
Fill Table
From SNS
This allows you to enter the model number of the noise
source associated with the ENR table. To enter a value,
you use the Alpha Editor which is presented and the
numerical keypad. To complete the entry press the Prev
key. Its value is displayed in the highlighted area and
in the active function area.
This allows you to automatically upload the ENR Table
information from a SNS. This menu key is only active
when an SNS is connected. This information may
already be present, if the Auto Load ENR(On) is set.
Meas Table
This allows you to enter, alter, or check data in the measurement ENR
table.
Cal Table
This allows you to enter, alter, or check data in the calibration ENR
table.
NOTE
An ENR table can have a maximum of 81 entries.
Figure 6-8
Typical ENR Table with Table Entry Menu Map Displayed
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Spot
This allows you to select a specific ENR value or Thot value. The selected
value is applied across the entire frequency range during calibration and
measurement. To operate ENR Mode(Spot) must be enabled. The default
setting is Spot ENR(15.200 dB).
Spot Mode
This switches between the Spot Mode(ENR) and the
Spot Mode(Thot) modes. The default is Spot Mode(ENR).
Spot ENR
This allows you to enter a spot ENR value which is
applied across the entire frequency range during
calibration and measurement. The value is applied
when Spot Mode(ENR) and ENR Mode(Spot) are enabled.
The default value is 15.200 dB.
The ENR value is entered using the numeric key pad
and terminated by selecting unit menu keys.
NOTE
The dB limits have a lower limit of -7.0 dB and an upper limit of 50.0 dB.
The K, C, and F limits are converted to the dB limits.
Spot Thot
This allows you to enter a spot Thot value which is
applied across the entire frequency range during
calibration and measurement. The value is applied
when Spot Mode(Thot) and ENR Mode(Spot) are enabled.
The default value is 9892.80 K.
The Thot value is entered using the numeric key pad
and terminated by selecting unit menu keys.
NOTE
The K limits have a lower limit of 0.00K and an upper limit of
29000290.0 K.
The C and F limits are converted to the K limits.
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Tcold
This menu key give access to the Tcold functions. When no Tcold functions
are enabled the default Tcold value of 296.50 K is used and the menu key
is set to Tcold(Default). When Tcold(User) is enabled, it uses your entered
User Value, or if an SNS is connected, the User Tcold From SNS value is
used. When Tcold(Auto) is enabled, it uses the SNS ambient temperature
value and updates this value after every measurement sweep. These
SNS features use the built-in SNS temperature sensor. The NFA can
upload this value and use it to calculate an accurate Tcold value.
SNS Tcold
This allows you to automatically upload the Tcold value
from the SNS built-in temperature sensor. The value
updates after every sweep. This feature is only enabled
when a SNS is connected.
When SNS Tcold(On) is selected the NFA uploads the
Tcold values from the attached SNS. Also, when
SNS Tcold(On) is selected the other Tcold menu keys are
unavailable. When the default SNS Tcold(Off) is selected
no automatic Tcold upload occurs.
User Tcold
This allows you to change the Tcold value. When
User Tcold(On) is selected it uses the value set in the
User Value. When the User Tcold(Off) is selected, the
NFA uses the default 296.50 K value.
User Value
This allows you to enter either a Tcold value manually,
or if an SNS is connected, by pressing the
User Tcold From SNS the value is automatically
uploaded from the SNS built-in temperature sensor.
The value is only valid when User Tcold(On) is enabled.
When entering a value manually use the numeric key
pad and terminated using one of the menu keys which
are presented to you.
User Tcold
From SNS
Chapter 6
Pressing this menu key allows you to upload the Tcold
value from the SNS built-in temperature sensor. The
value is only valid when User Tcold(On) is enabled. This
feature is only enabled when a SNS is connected.
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SNS Setup
NOTE
This allows you to select which type of noise source you prefer to use.
Also, if you are using an SNS, it allows you to choose to load it’s ENR
values automatically.
Preference
Selecting Preference(Normal) uses the +28V NOISE
SOURCE OUTPUT PORT and selecting
Preference(SNS) uses the SNS PORT, if an SNS is
connected. It is possible to have both an SNS and a
+28V driven normal noise source connected to the NFA
at the same time. However, the NFA’s +28V drive can
only drive one noise source at a time. Hence, you need
to select which noise source should be used. The default
setting is Preference(SNS) as this is typically expected
to be the preferred option. However, if an SNS is not
connected the NFA uses the +28V NOISE SOURCE
OUTPUT PORT even when Preference(SNS) is selected.
Auto Load ENR
Selecting Auto Load ENR(On) enables the SNS to
automatically upload it’s ENR values and associated
data to the Common ENR Table. This happens when
the NFA is powered on or an SNS is connected to the
SNS port. Selecting Auto Load ENR(Off) disables the
automatic loading of the SNS data.
When an SNS is connected and Auto Load ENR(On) enabled, the
Common Table(On) is set automatically. Hence, the SNS ENR data is
loaded into the common ENR table.
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DISPLAY Keys
Figure 6-9
Display Key Group
Scale
This key allows you to specify the units and limits for each active
measurement result type. The units are available in all display formats,
however, the limits only apply to the graph format.
Only the active measurement result graph units and limits are
displayed. The scale menu displayed is dependent on the active
measurement result selected. See Figure 6-10 showing the six
measurement parameter scale menu keys.
The graph limits and levels only affect how the data is displayed and do
not affect the measurement process or results.
Autoscale
Creates the graph limits to provide an optimum view of the result data.
NOTE
Autoscale does not scale a memory trace only the current data trace.
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Figure 6-10
Scale Menu Keys
Units
This sets the units used to display the data. It is dependent on which
result parameter you selected. The options are displayed in Table 6-1
Table 6-1
Result Parameter and Unit, Limit, and Scale/Div Type
Result Parameter
Units, Limits, and Scale/Div
Noise Figure
dB or Linear
Gain
dB or Linear
Y Factor
dB or Linear
Teffective
K, C or F
Phot
dB or Linear
Pcold
dB or Linear
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Upper Limit
This sets the upper graph limit on the y-axis. The linear scale values use
engineering multipliers to terminate the entry, see Figure 6-11. As the
the scale per division values are coupled to the upper limit, setting the
upper limit causes the scale per division value to be adjusted.
Lower Limit
This sets the lower graph limit on the y-axis. The linear scale values use
engineering multipliers to terminate the entry, see Figure 6-11. As the
scale per division values are coupled to the lower limit, setting the lower
limit causes the scale per division value to be adjusted.
Ref Level
This allows you to enter a reference level value. The linear scale values
use engineering multipliers to terminate the entry, see Figure 6-11. It is
displayed as a horizontal line in the graph, if the Display Ref(On) is
enabled. To enter a value, use the numerical keypad.
NOTE
The Ref Level value can only be set within the Upper Limit value and
Lower Limit value.
Display Ref
This allows you to show or hide the reference level on the graph. To show
the reference level set Display Ref(On). To hide the reference level set
Display Ref(Off), this is the default setting.
Scale/Div
This sets the units per division on the y-axis. The linear scale values use
engineering multipliers to terminate the entry, see Figure 6-11. Setting
this causes the upper and lower limits to be adjusted as the items are
coupled.
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Figure 6-11
Scale Linear Termination Menu Keys
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Format
This accesses menu keys to select which display format you want the
measurement data presented. You can choose between graph, table and
meter format.
When Format is set to Graph, you can combine the two graphs, save a
trace to volatile memory and recall it later. Also, the annotation and
graticules can be switched off or on.
Figure 6-12
Format Menu Keys
Format
This selects between Format(Graph) where a graphical display is shown,
Format(Table) where the measurement results are shown in tabular form,
or Format(Meter) where the measurement results are shown in single
frequency point result display format. The default setting is Graph.
Combined
When Combined(On) is enabled it combines the upper and lower graphs
from a dual graph display into a single graphical display. It overlays both
upper and lower graphs simultaneously. When Combined(Off) is enabled
the graphs are not combined, this is the default setting.
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Trace
The Trace menu key only becomes available after you have pressed the
Data->Memory menu key.
When Trace(Data) is enabled, it displays the current measurement trace.
This is the default setting.
When Trace(Memory) is enabled, it displays the measurement trace you
saved to memory when the Data->Memory menu key was pressed.
When Trace(Data&Memory) is enabled, it displays the measurement trace
you saved to memory when the Data->Memory menu key was pressed and
the current measurement trace. This allows you to compare two traces.
Data->Memory
When the Data->Memory menu key is pressed the current trace is stored
in volatile memory and remains there until change the measurement
parameter, you switch the NFA off, preset it, or press the Data->Memory
menu key again saving another trace. After you have pressed the
Data->Memory menu key the Trace menu key becomes available. The
Data->Memory menu key is only available after a complete sweep of data
is made.
Graticule
When Graticule(On) is enabled, it switches the graph graticule on. This is
the default setting. When Graticule(Off) is enabled, it switches the graph
graticule off and the graticule is removed from the graph.
Annotation
When Annotation(On) is enabled it switches the screen annotation
surrounding the graphs on, and the annotations are displayed. This is
the default setting. When Annotation(Off) is enabled it switches the screen
annotation surrounding the graphs off and the annotations are removed
from the display. However, menu key annotation remains on the screen.
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Result
This key allows you to specify which measurement result parameter you
want to display in the active measurement. This is applicable to all
display formats.
NOTE
You cannot make the same two measurement result active, as each
measurement result type selected must differ from the other.
NOTE
The result menu shows the current, active measurement result. To
obtain the other result parameter use the
Figure 6-13
key.
Result Menu Key
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Noise Figure
This selects noise figure as the measurement result.
Gain
This selects gain as the measurement result.
NOTE
This gain measurement result is only valid after a calibration has been
performed and Corrected(On) is selected.
Y Factor
This selects Y-Factor as the measurement result.
Teffective
This selects equivalent temperature as the measurement result.
Phot
This selects hot power density as the measurement result.
Pcold
This selects cold power density as the measurement result.
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Marker
This accesses the marker control keys which select the marker type,
placement, number, and switch them on and off. Markers are
diamond-shaped characters that identify points of traces. Up to four
pairs of markers are available. They can be distributed on the various
traces and may appear on the display simultaneously; only one pair can
be controlled at a time. The marker that is controlled is called the
“active” marker.
Above the graph, all the enabled marker’s results are displayed. When a
marker is activated, its frequency value is displayed in the active
function area.
Figure 6-14
Marker Menu Maps
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Marker
Selects one of the four possible marker pairs, Marker(1), Marker(2),
Marker(3), and Marker(4). Only one of the markers can be active, although
they can, if required, all be enabled. To make a marker active, you need
to underline the marker, for example, Marker(1) is active and while active
it’s frequency value is displayed in the active function area.
State
Off
This switches off an active marker and removes it from
the graph. It also removes the marker annotation from
the display. This is the default state.
Normal
Places a single marker on the graph's trace. If a marker
has been displayed previously and is reactivated, the
marker is enabled at the marker's previously selected
position. The marker number is indicated above the
marker.
Use the RPG to control the position of the marker. Its
frequency value is displayed in the active function area
and frequency and measurement parameter values are
reported above the graph.
Pressing Normal when the Delta or Band Pair function is
enabled, switches off the reference marker.
Delta
Activates a second marker at the position of the first
marker. It is identified as a reference marker and its
position is fixed. (If no marker is present, the marker
appears at the center of the graph, or if the marker has
been previously active it appears in the last marker
position) The marker number is indicated above the
delta marker, and the same number is indicated with
an R (for example, 1R) above the reference marker. Use
the RPG to position the delta marker.
The delta marker’s frequency value is displayed in the
active function area. Also frequency and measurement
parameter values are reported above the graph to
indicate the difference between the two markers. The
reference marker's position remains fixed until delta is
disabled.
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Band Pair
Enters a mode that allows adjustment of the two
markers independently. It is similar to the delta
marker mode, except you can choose to move the
normal marker or the reference marker. Pressing
Band Pair(Ref) and Band Pair(Normal) menu keys,
switches between the reference and normal markers.
The reference marker number is indicated with a
number and an R (for example, 1R) and the normal
marker is indicated with a marker number.
The band pair marker’s frequency value is displayed in
the active function area. Also the frequency and
measurement parameter values are reported above the
graph to indicate the difference between the two
markers.
Band Pair
This menu key is only accessible when State(Band Pair) has been selected.
Band Pair(Ref) and Band Pair(Normal) menu keys, switch between the
reference and normal markers. The reference marker number is
indicated with a number and an R (for example, 1R) and the normal
marker is indicated with a marker number. Use the RPG to position the
currently selected marker.
Trace
This menu key becomes active after Data->Memory has been pressed. It is
used to place a marker on either the data or memory trace. Trace(Data)
places a marker on the active trace. This is the default setting.
Trace(Memory) places a marker on the memory trace.
For example, when the recalled and active traces are both displayed,
pressing this key causes the marker to hop from the data trace to the
memory trace.
NOTE
If you disable the memory trace display with a marker on, the marker
disappears
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Search
This menu key allows you access to a further menu where you can
configure a marker search on the trace. The type of search is dependent
on the setting type.
Marker
The Marker menu key allows you to change the active
marker. See “Marker” on page 246 for an explanation.
Search Type
When the Search Type menu key is pressed a further
optional choice can be made. The options are: • When Search Type(Min) is enabled, the active marker
is placed at the minimum point of the trace.
This key is not accessible when the Marker state is
Band Pair.
• When Search Type(Max) is enabled, the active
marker is placed at the maximum point of the trace.
This key is not accessible when the Marker state is
Band Pair.
• When Search Type(Pk-Pk) is enabled, the active band
pair markers are placed on the highest and lowest
trace points. The reference marker is placed on the
highest peak while the normal marker is placed on
the lowest trough. Its frequency and measurement
parameter values are reported above the graph to
indicate the difference between the two markers.
This key is only accessible when the Marker state is
Band Pair.
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Continuous
NOTE
If you are searching continuously the markers have additional
annotation which identifies which marker is the minimum and the
maximum. The annotation is “∨” a minimum, “∧” a maximum. If you
change the active graph the annotation remains on the original graph.
Find
Markers All Off
When Continuous(On) is enabled, the active marker
continuously finds the maximum, minimum, or
peak-to-peak on the trace as successive sweep results
are reported. This is dependent on which search type is
selected. When Continuous(Off) is enabled, the marker
search is controlled by the Find menu key.
Pressing the Find menu key manually places an active
search marker. This functions when Continuous(Off)
and a Marker is enabled. The annotation displays the
frequency and measurement parameter differences.
Also in the Find mode the marker’s frequency value is
displayed in the active function area.
This switches off all of the markers, including the marker annotation.
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CONTROL Keys
Figure 6-15
Control Key Group
Loss Comp
This key accesses features which allow the NFA to compensate for losses,
for example, due to additional cabling, before and/or after the DUT’s
measurement, by allowing you to specify the compensation loss. This loss
can either be the same fixed value over the whole frequency span or it
can vary across the frequency span using values specified in a table.
Figure 6-16
Loss Compensation Menu Keys
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Setup
This accesses the Loss Compensation Setup form.
Figure 6-17
Loss Compensation Setup Form
You use the Tab keys to highlight items in the form. When an item is
highlighted its value or option is also displayed in the menu key, allowing
you to change its status or value.
Before DUT
This controls the compensation before the device under
test. It is either,
• Off, where there is no compensation before device
under test. The default status is Off.
• Fixed, where the Before DUT Fixed Value
compensation is used.
• Table where the values in the Before DUT Table
are used.
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Before DUT
Fixed Value
Before
Temperature
After DUT
This sets the amount of compensation, before the
device under test, as a fixed value. This is only valid if
the Before DUT(Fixed) is enabled. You can enter the
value as dB or linear. However, the linear value is
converted to dB. The lower limit is -100.000 dB and the
upper limit is 100.000 dB. The default value is
0.000 dB.
This sets the temperature of loss compensation, before
the device under test, as a fixed value. This is only
valid if Before DUT is enabled. You can enter the value
as K, C, or F. However, the C and F values are converted
to K. The lower limit is 0.00K and the upper limit is
29,650,000.0K. The default value is 0.00K.
This controls the compensation after the device under
test. It is either,
• Off, where there is no compensation after device
under test. The default status is Off.
• Fixed, where the After DUT Fixed Value compensation
is used.
• Table where the values in the After DUT Table are
used.
After DUT
Fixed Value
After
Temperature
252
This sets the amount of compensation, after the device
under test, as a fixed value. This is only valid if
After DUT(Fixed) is enabled. You can enter the value as
dB or linear. However, the linear value is converted to
dB. The limit and default values are the same as
Before DUT.
This sets the temperature of loss compensation, after
the device under test, as a fixed value. This is only
valid if After DUT is enabled. You can enter the value as
K, C, or F. However, the C and F values are converted to
K. The limit and default values are the same as
Before DUT.
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Before DUT Table
This accesses the Loss Compensation Before DUT Table form.
This allows you to enter a Loss table of frequency/value pairs from which
loss values are interpolated. See “Working with Tables” on page 28 or
the following description.
Figure 6-18
Loss Compensation Before DUT Table
You use the Tab keys to highlight items in the form. When an item is
highlighted it is also displayed in the menu key, allowing you to change
its status or value.
Row Up
This allows you to select a particular row in the table,
by pressing this menu key you move up to its position
in the table one entry at a time.
Row Down
This allows you to select a particular row in the table,
by pressing this menu key you move down to its
position in the table one entry at a time.
Page Up
This allows you to move up the table entries in page
blocks.
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Page Down
This allows you to move down the table entries in page
blocks.
Add
This allows you to add a new entry. It adds the entry to
the bottom of the table and sequences it in the correct
ascending order of frequency when it is terminated.
To terminate the value entry use the unit keys
presented to you. You can also terminate the loss value
using the Enter key and it uses the dB unit value by
default.
Delete Row
This removes the highlighted single row entry from the
table.
Clear Table
This removes all entries from the table. You need to
press this menu key twice.
The first time you press the key you are prompted to
press it again. This two-stroke key press is a safety
feature to prevent you from accidentally pressing
Clear Table and erasing the table data.
After DUT Table
This accesses the Loss Compensation After DUT Table form.
This allows you to enter an Loss table of frequency/value pairs from
which loss values are interpolated. See “Working with Tables” on page
28 or the descriptions under the “Before DUT Table” on page 253.
NOTE
A Loss Compensation table can have a maximum of 201 entries.
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Limit Lines
The limit lines mark boundary limits of a trace. Limit lines feature four
independent lines numbered from 1 to 4. Limit line 1 and 2 are
associated with the upper graph, and limit line 3 and 4 are associated
with the lower graph. The limit lines can be set to inform you when the
trace of interest crosses one of the limit lines. The limit lines can be set
as an upper or lower limit. They can also be displayed on the their
associated graph.
Figure 6-19
Typical Limit Line Menu Map
Limit Line
Selects one of the four possible limit lines. Limit Line(1⇑) and Limit Line(2⇑)
are associated with the upper graph trace, and Limit Line(3⇓) and
Limit Line(4⇓) are associated with the lower graph trace. The selected
limit line is underlined and the other limit line menu items apply to it.
Type
This menu key sets the selected limit line to, either Type(Upper) or
Type(Lower). The limit line is tested against the trace if Test(On) is
enabled.
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Test
This menu key becomes active after limit line data has been entered. It
sets the selected limit line to test against the trace. To enable the test,
set Test(On). If a limit line failure occurs, the result is reported in the
upper left hand corner of the display annotation. To disable the test, set
Test(Off). This is the default setting.
Editor
This accesses a Limit Line editor which allows you to enter or edit the
selected limit line. Figure 6-20 shows the editor.
Limit lines are limited to 201 frequencies. The limit line entries are
automatically sorted in ascending frequency order, after the point has
been entered. The limit unit is the unit of the selected graph.
Figure 6-20
Limit Line Editor with Table Entry Menu Map
Frequency
This sets the frequency value of the current entry.
Limit
This sets the limit value of the current entry. The limit
line is a unitless value. The values are dependent on
the associated graphical limits.
Connected
This is used to connect the current point to, or
disconnect the current point from the previous point.
Setting it to Yes, connects the point to the previous
point. Setting it to No, the point is not connected to the
previous point.
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See “Working with Tables” on page 28 or the following descriptions on
how to enter values into a table.
• Row Up
This allows you to select a particular entry in the
table, by pressing this menu key you move up to its
position in the table one row at a time.
• Row Down
This allows you to select a particular entry in the
table, by pressing this menu key you move down to
its position in the table one row at a time.
• Page Up
This allows you to move up the table entries in page
blocks.
• Page Down
This allows you to move down the table entries in
page blocks.
• Add
This allows you to add a new entry. It adds the entry
to the bottom of the table and sequences it in the
correct ascending frequency order when the row is
complete.
• Delete Row
This removes the single row which is highlighted
from the table.
• Clear Table
This removes all entries from the table. You need to
press this menu key twice.
The first time you press the key you are prompted
to press it again. This two-stroke key press is a
safety feature to prevent you from accidentally
pressing Clear Table and erasing the table data.
Display
This menu key becomes active after limit line data has been entered. It
displays the selected limit line on the graph. To enable the limit line
display, set Display(On). To disable the limit line display, set Display(Off),
this is the default setting.
Limit Lines All Off
This switches off all of the limit lines, including any limit line test result
and annotation.
NOTE
When a limit line is switched off the limit line data is unchanged and can
be retrieved if the limit line is switched on again.
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Full Screen
This allows the measurement window to expand over the entire display
removing the menu keys, the active window annotation, and the display
status line annotation. This functions in all formats, graph, table and
meter. Press the Full Screen key again to return to the previous display.
All other key presses are ignored except; Zoom, Next Window, Save Trace,
Help, Preset, Print, Power Standby, and the Viewing Angle keys.
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Corr
This key allows you to switch corrected measurements off or on. The
default status is dependent on whether a calibration has been made
previously.
You can change the choice of input attenuation of the NFA used during
calibration, allowing you to make the calibration faster, or measure
higher gain DUTs.
Figure 6-21
N8972A and N8973A Corrected Menu Maps
Corrected
This allows you to select between corrected and uncorrected results.
You have the option of doing the measurement with the Corrected(On) or
the Corrected(Off). The correction uses the calibration data of the second
stage and accounts for errors associated with this.
After you have made a calibration the annotation Corr is displayed at
the bottom right corner of the display.
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NOTE
If you change the frequency range to greater than the current
calibration, the NFA changes to Uncorr. If you want corrected
measurements over a greater range, you need to re-calibrate the NFA
again before making this measurement. If you change the frequency
range to less than the current calibration, the NFA changes to a yellow
Corr. This demonstrates the NFA is using interpolated results and
interpolated errors may be introduced.
Input Cal
The menu key gives you access to menu keys allowing you to set the
maximum and minimum attenuator values.
Figure 6-22
N8974A and N8975A Microwave Attenuator Menu Maps
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NOTE
On the N8972A and N8973A models there are no Min µW Atten and
Max µW Atten menu keys. The microwave attenuator is only available on
the N8974A and N8975A models.
Min Atten
This menu key allows you to change the RF
attenuator’s minimum input attenuation during
calibration. The RF attenuator’s frequency range is less
than or equal to 3.0 GHz. The choice is from 0dB to
40dB in 5 dB steps. The default value is 0dB.
Max Atten
This menu key allows you to change the RF
attenuator’s maximum input attenuation during
calibration. The RF attenuator’s frequency range is less
than or equal to 3.0 GHz. The choice is from 0dB to
40dB in 5 dB steps. The default value is 20dB.
Min µW Atten
Max µW Atten
Chapter 6
This menu key allows you to change the microwave
attenuator’s minimum input attenuation during
calibration. The microwave attenuator’s frequency is
greater than 3.0 GHz. The choice is from 0dB to 30dB in
15 dB steps. The default value is 0dB.
This menu key allows you to change the microwave
attenuator’s maximum input attenuation during
calibration. The microwave attenuator’s frequency is
greater than 3.0 GHz. The choice is from 0dB to 30dB in
15 dB steps. The default value is 0dB.
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Sweep
Sweep Mode
This menu key is used to control the NFA’s measurement repetition, so
that it is performed once or multiple times.
To set the measurement to perform once, enable Sweep Mode(Single). To
set the measurement to repeat continuously, enable Sweep Mode(Cont),
this is the default setting.
Figure 6-23
Sweep Menu Map (N8974/5A Models)
Manual Meas
This allows you access to the Manual Measurement menu keys. This also
allows you to manually set the RF attenuator, the IF attenuator, and the
microwave attenuator on the N8974/5A models. See “Manual
Measurements Procedure” on page 112.
NOTE
The microwave attenuator is only available on the N8974A and N8975A
models.
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NOTE
On the N8972A and N8973A models the RF/µW Att menu key is labelled
RF Att. Also, there is not a Fixed µW Att menu key.
Manual State
This allows you to either enable the Manual State(On) or
disable the Manual State(Off) in the Manual
Measurement Mode. The default status is
Manual State(Off) and the other menu keys in the
Manual Measurement Menu are disabled, except the
RF attenuator, microwave attenuator, and IF
attenuator keys.
Accept
Press this menu key when you are satisfied that the
reading is sufficiently settled to be used in the manual
measurement calculations. When pressed, the NFA will
use the current power reading in the manual
measurement calculations.
This menu key is disabled when Manual Meas(Off) is
selected.
Calibration
This menu key allows you to control whether the NFA
is performing a calibration or measurement. Selecting
Calibration(On) a calibration is performed at a selected
frequency point. Selecting Calibration(Off) a
measurement is performed at a selected frequency
point. The default status is Calibration(Off).
This menu key is disabled when Manual Meas(Off) is
selected.
Noise Source
This allows you to switch the noise source on and off.
Selecting Noise Source(On) a Phot measurement is
performed at a selected frequency point. Selecting
Noise Source(Off) a Pcold measurement is performed at
a selected frequency point. The default status is
Noise Source(Off).
This menu key is disabled when Manual Meas(Off) is
selected.
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RF/µW Att
This is used to control the RF and microwave
attenuator setting. Selecting RF/µW Att(Auto) enables
the RF and/or microwave attenuator auto-ranging.
This is the default value. Selecting RF/µW Att(Hold)
enables the current RF attenuator setting to be held
until the selection is changed. Selecting
RF/µW Att(Fixed) enables the values specified in
Fixed RF Att value or Fixed µW Att value to be used.
IF Att
This is used to control the IF attenuator setting.
Selecting IF Att(Auto) enables the IF attenuator
auto-ranging. This is the default value. Selecting
IF Att(Hold) enables the current IF attenuator setting to
be held until the selection is changed. Selecting
IF Att(Fixed) enables the values specified in Fixed IF Att
value to be used.
Point
This allows you to specify the frequency point at which
you want to make the measurement. The points are the
number of sweep points in the frequency settings.
This menu key is disabled when Fixed Freq or
Manual Meas(Off) is selected.
Fixed RF Att
This allows you to specify a fixed value of the RF
attenuator, where the frequency is less than or equal to
3.0 GHz. It is applied when RF/µW Att(Fixed) is enabled.
The choice is from 0dB to 40dB with a 5 dB step option.
The default value is 0dB.
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NOTE
The Fixed µW Att menu key is only available on the N8974A and N8975A
models.
Fixed µW Att
This allows you to specify a fixed value of the
microwave attenuator, where the frequency is greater
than 3.0 GHz. It is applied when RF/µW Att(Fixed) is
enabled.
The choice is from 0dB to 30dB with a 15 dB step option.
The default value is 0dB.
Fixed IF Att
This allows you to specify a fixed value of the IF
attenuator. It is applied when IF Att(Fixed) is enabled.
The maximum attenuation allowed is 70 dB. The
default value is 59 dB.
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Restart
When a measurement is in progress and the Restart key is pressed, it
stops the measurement and a new one is started. Depending on the
sweep setting, the measurement is either made once or continuously.
When in Manual Measurement Mode pressing Restart causes the
measurement to start again and all the previous data is lost.
NOTE
The Restart key can also be used to stop a calibration routine.
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SYSTEM Keys
Figure 6-24
System Key Group
System (Local)
This key has two functions. When the instrument is in remote mode
pressing this key returns it to local mode.
Pressing System (Local) after the NFA has been placed in the remote
mode, places the NFA in the local mode and enables front panel control.
During remote operation, R appears in the upper-right corner of the
screen. A T, L or S may appear during remote operation, indicating talk,
listen, or service request. Pressing the System (Local) key removes the R
symbol in the upper-right corner.
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Figure 6-25
System(Local) Menu Maps
Remote Port
This allows you to select between Serial and GPIB remote modes.
You have the option of using the Remote Port(Serial) or the
Remote Port(GPIB)
NOTE
The NFA needs to be power cycled before the remote port change takes
effect.
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GPIB
The GPIB menu key accesses the System GPIB Form. This allows access
to the GPIB address of the NFA and the LO GPIB related addresses.
Figure 6-26
System GPIB Form with a Menu Displayed
You use the Tab keys to highlight items in the form. When an item is
highlighted it is also displayed in the menu allowing you to change its
value.
Noise Figure
Analyzer Address This sets the instrument GPIB address. Valid
addresses are from 0 to 29. The default address is 8.
External LO
Address
This sets the GPIB address of the External LO
attached to the LO GPIB. Valid addresses are from 0 to
30. The default address is 19
LO GPIB Address This sets the address through which devices, attached
to the LO GPIB, communicate with the NFA. Valid
addresses are from 0 to 30. The default address is 8.
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Serial
The Serial menu key accesses the System Serial Form. This allows
access to the Serial port configuration of the NFA.
You use the Tab keys to highlight items in the form. When an item is
highlighted it is also displayed in the menu allowing you to change its
value.
Figure 6-27
System Serial Form with Baud Rate Menu Map Displayed
Data Terminal Ready This sets the DTR line control. To disable the serial
port and de-assert the DTR, press OFF, this is the
default setting. To enable the serial port and assert the
DTR, press ON. To enable the driver to use the DTR for
receive data pacing, press IBF.
Request To Send This sets the RTS line control. To disable the serial port
and de-assert the RTS, press OFF, this is the default
setting. To enable the serial port and assert the RTS,
press ON. To enable the driver to use the RTS for
receive data pacing, press IBF.
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Baud
This sets the baud rate. The following list is the Baud
rate values. The default setting is 9600.
• 1200
• 2400
• 4800
• 9600
• 19200
• 38400
Receive Pacing
This sets the receive pacing handshake characters. To
disable the software receive pacing, press NONE, this is
the default setting. To enable the XON/XOFF
characters, press XON/XOFF.
Transmit Pacing
This sets the transmit pacing handshake characters. To
disable the software transmit pacing, press NONE, this
is the default setting. To enable the XON/XOFF
characters, press XON/XOFF.
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External LO
This menu is used to set the External LO limits and commands. The
frequency and power limits that are included in the system LO menu to
stop the External LO from being controlled outside its working range.
The NFA is unable to check the validity of the inputs.
Figure 6-28
External LO Menu Map
Command Set
This sets the External LO command language. Set the
Command Set(SCPI) to use the built in commands to
drive an LO which is SCPI compliant. Set the
Command Set(Custom) when the External LO is not
SCPI compliant and enter the custom command
strings.
LO Commands
This accesses the External LO Commands Form.
This form allows you to enter the commands used to
control a non-SCPI-compliant External LO. To enter a
command use the Alpha Editor and the numeric
keypad.
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NOTE
When entering an External LO Command, spaces after the prefix and
before the suffix may be important.
Figure 6-29 External LO Commands Form with Menu Keys
• Power Prefix, sets the prefix for the command used to
set the External LO's power level.
• Power Suffix, sets the suffix for the command used to
set the External LO's power level.
• Freq Prefix, sets the prefix for the command used to
set the External LO's frequency.
• Freq Suffix, sets the suffix for the command used to
set the External LO's frequency.
• Auxiliary, other commands required to properly
control the External LO (for example, to preset the
LO or to put the LO in a CW operation).
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Settling Time
This sets the settling time of the NFA’s command to the
External LO. This is used as a settling period after
commands are sent to the LO. Valid settling times are
between 0 ms and 100 s. The default value is 100 ms.
Min Freq
This sets the minimum frequency the NFA expects the
External LO to have. The default value is 10 MHz.
Max Freq
This sets the maximum frequency the NFA expects the
External LO to have. The default value is 40.0 GHz.
Multiplier
This sets the value of the External LO frequency
multiplier. The default value is 1.
Alignment
Accesses the Alignment menu keys which align the internal circuitry of
the NFA and allow you to choose the alignment mode.
Figure 6-30
Alignment Menu Map
Alignment
274
Selecting Alignment(On) enables the automatic
alignment of the NFA, this is the default setting.
Selecting Alignment(Off) disables automatic alignment.
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IMPORTANT
In unstable temperature environments or where a lot of averaging is
being applied, it is better to align more often. Hence, point mode should
be more accurate.
Alignmnt Mode
Selecting Alignmnt Mode(Sweep) enables the alignment
of the NFA to align at the beginning of a sweep. This is
the default setting. Selecting Alignmnt Mode(Point)
enables alignment to align at each point of the sweep.
Align YTF
This aligns the tuning current of the YIG Tuned Filter
(YTF) against frequency. To avoid an accidental key
press you need to press Align YTF menu key again.
Save YTF
Alignment
This saves the YTF alignment data to persistent
memory. This is stored in the NFA’s non-volatile RAM
and remains there after a preset or a power cycle. It
also remains in memory after Restore Sys Defaults
menu key is pressed. To avoid an accidental key press
you need to press Save YTF Alignment menu key again.
NOTE
On N8972A and N8973A models the Align YTF and Save YTF Alignment
menu keys are unavailable.
Show Errors
Accesses a display of the last 10 errors reported. The most recent errors
appear at the top of the list.
Clear Error Queue Clears the error queue in the Show Errors display.
Show System
Displays the instrument model name, product number, serial number,
host ID, firmware revision number, bootrom revision, and amount of
RAM and ROM. Also displayed are the hardware modules in each card
slot, options fitted, the printer type, and a time counter.
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Show Hdwr
Displays the instrument model name, product number, serial number,
firmware revision number, bootrom revision, and amount of RAM and
ROM. Also, displayed are the assembly name and where appropriate the
part number, serial number and version numbers of the hardware
modules in your NFA.
Power On/Preset
Accesses menu keys to change the setting of the NFA state which is
recalled at power on. The power on preset system controls the power on
state of the NFA.
Figure 6-31
Power On/Preset Menu Map
Power On
276
Determines the preferred state of the NFA when the
NFA is powered on. If the function is set to
Power On(Preset), the power on state of the NFA is the
same as it is after the Preset is pressed. If the function
is set to Power On(Last), then the state that the NFA
was in when it was powered off is recalled when it is
powered on.
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NOTE
The setting Power On is not changed by pressing Preset.
Preset
This sets the preset state to be used when
Power On(Preset) is the selected state. The NFA is put in
the preset state by pressing the Preset key. Selecting
Preset (Factory) allows the NFA to be in the default
configuration originally set at the factory. Selecting
Preset (User) allows the NFA to be in the settings
defined by the Save User Preset key. See “Preset” on
page 287 in this chapter.
Save User Preset Saves the current instrument active state of the NFA
into your Preset register for recall on Preset if
Preset(User) is selected.
Restore Sys
Defaults
Pressing this menu key restores the NFA to the factory default settings.
This key needs to be pressed twice, as it has this safety feature to stop
you accidently pressing this key.
The restored items are, for example, the GPIB address, that are
unaffected by a power cycle or a preset.
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Time/Date
Accesses menu keys used to set and display the real-time clock in the
Date Window.
Figure 6-32
Time/Date Menu Map
Time/Date
Enable Time/Date(On) to switch the display of the
real-time clock on, or enable Time/Date(Off) to switch the
display of the real-time clock off.
Date Mode
Enable Date Mode(MDY) to display the date in a
month-day-year format, or enable Date Mode(DMY) to
display the date in a day-month-year format.
Set Time
This allows you to set the time of the real-time clock.
Enter the time in 24 hour HHMMSS format, using the
numeric keypad and pressing Enter to terminate it.
Valid hour (HH) values are from 00 to 23. Valid minute
(MM) and second (SS) values are from 00 to 59.
Set Date
This allows you to set the date of the real-time clock.
Enter the date in the YYYYMMDD format using the
numeric keypad and press Enter. Valid year (YYYY)
values are 0000 through 9999. Valid month (MM)
values are from 01 to 12, and valid day values are from
01 to 31.
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Diagnostics
Accesses the Front Panel Test menu key.
Front Panel Test
Service
Allows you to verify the functionality of each front
panel key (except Preset). The number next to each key
name increments once each time the key is pressed.
Rotating the RPG causes the number of pulses to be
counted. Press Esc to exit.
Accesses the Service menu keys which requires a password for further
access. For information, refer to the Noise Figure Analyzers NFA
Series Performance Verification and Calibration Guide..
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File
This accesses the menu keys used to load, save, and manage data on a
floppy disk or the internal NFA drives. The file system consists of two
DOS compatible volumes. The first, volume A, is the floppy disk. The
second, volume C, is the internal flash file system.
The file menu keys also access dialog boxes appropriate for the selected
function. You can store and retrieve information to and from files in the
file systems and perform file system management functions. The Tab
keys allow you to move between the dialog box fields and set up a desired
operation. Press the Enter key to execute an operation.
The file select submenu changes in format depending on where it was
entered from. From the Load File and File Manager menus it has a
single softkey which is used to select a file name from a scrollable list of
files. From the Save File menu it uses the Alpha Editor to enter new file
names. It also numbers the files with default names sequentially.
Load
Accesses menu keys that allow you to load ENR values, states, limits,
frequency lists, loss compensation tables into the NFA from a floppy (A:)
drive or internal flash (C:) drive. To load a file, use the following steps:
1. Select the type of data you wish to load by pressing the appropriate
menu key. For example, if you select Limits, you also have to select
which limit line 1, 2, 3, or 4.
2. The drive letter name is activated in the Path dialog box. Select the
source of the data. Select the desired drive with the Select key. If you
are already in a drive, press Select while “..” is active to select a
different drive. Use the ⇑ and ⇓ keys or the RPG to activate the
desired drive. Press Select.
3. When you are ready to load the data, press Enter.
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ENR
ENR files contain tables of ENR/frequency pairs used
to characterize a noise sources. Files of this type have
the three letter suffix (ENR). You need to decide
whether the ENR file is either, a Meas Table or a
Cal Table by pressing the appropriate menu key.
State
State files contain the instrument settings. Loading a
state file restores the settings to the previously saved
values. Files of this type have the three letter suffix
(STA).
Limits
Limits files contain limit line specifications and
provides data sets to determine whether a trace has
crossed the limit line specifications. You need to decide
whether the limits file is either, a limit line 1, 2, 3, or 4,
by pressing the appropriate menu key. Files of this type
have the three letter suffix (LIM).
Frequency List
Frequency list files contain specified list of frequencies
at which measurements are to be made. Files of this
type have the three letter suffix (LST).
Loss
Loss files contain loss compensation data. You need to
decide whether the loss file is either a Before Table or
After Table by pressing the appropriate menu key. Files
of this type have the three letter suffix (LOS).
The NFA can also load S2P file formats. The NFA
accepts any files with the following extensions: S2P, S1,
and S2.
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Save
Accesses menu keys that allow you to save the NFA’s ENR, states, traces,
limits, frequency lists, loss compensation tables, and screen data to a
floppy (A:) drive or internal flash (C:) drive.
NOTE
The Save Menu is similar to the Load Menu, except that it supports two
additional file types, these are, trace and screen. It also only allows you
to save loss compensation as .LOS files. The S2P formats are only
available to load into the NFA.
To save a file, use the following steps:
1. Select the type of data you wish to save by pressing the appropriate
menu key. For example, if you select ENR, you need to select either
Meas Table or Cal Table.
2. If appropriate, in the Format dialog box, select the desired format.
3. If the auto-selected name is not acceptable, enter a name using the
Alpha Editor menu keys. File names are limited to eight characters.
4. The Path dialog box becomes active, allowing you to change the
destination drive of the data. Select the desired drive with the Select
key. If you are already in a drive, press the Select key while “..” is
activated to select a different drive. Use the ⇑ and ⇓ keys or the RPG
to activate the desired drive. Press Select.
5. When you are ready to save, press Enter.
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ENR
ENR files contain tables of ENR/frequency pairs used
to characterize a noise sources. ENR allows you to save
an ENR table in memory. You need to decide whether
the ENR file is a Meas Table, a Cal Table, or an SNS table
by pressing the appropriate menu key.
State
State files contain the instrument settings. State allows
you to save an NFA state in memory.
Trace
A trace is saved in a Comma Separated Value (CSV)
format, and is readable by a spreadsheet on your PC.
However, it cannot be loaded back into the NFA.
Limits
Provides data sets to determine whether a trace has
exceeded allowed specified limits. You need to decide
whether the limits file is either, a limit line 1, 2, 3, or 4
by pressing the appropriate menu key. Limits can only
be saved individually.
Frequency List
Frequency list files contain your specified list of
frequencies at which measurements are to be made.
Loss
Loss files contain loss compensation data. You need to
decide whether the loss file is either a Before Table or
After Table by pressing the appropriate menu key. Files
of this type have the three letter suffix (LOS).
Screen
Saves the screen image to a file and allows you to
choose between bitmap and metafile formats. The
Bitmap saves the screen image in Graphics Interchange
Format (GIF) and the Metafile saves the screen image in
Windows Metafile (WMF) format. Also, the screen
images can be saved as reverse images where the colors
are reversed. Press Reverse Bitmap or Reverse Metafile
menu key to save a reverse image. Screen images
cannot be loaded back into the NFA.
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File Manager
Accesses menu keys that allow you to perform functions such as copying,
deleting, and renaming files.
The file manager allows you to perform house keeping functions on saved
data.
Copy
Allows you to copy a file to another file with a different
name or to a different drive (in which case the same
name is acceptable).
Copy accesses the following menu keys:
ENR
Allows you to copy ENR files.
State
Allows you to copy state files.
Trace
Allows you to copy trace files.
Limits
Allows you to copy limits files.
Frequency List
Allows you to copy frequency list files.
Loss
Allows you to copy loss compensation files.
Screen
Allows you to copy screen files.
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Delete
Allows you to delete a file from a floppy disk or the
NFA’s internal memory.
ENR
Allows you to delete ENR files.
State
Allows you to delete state files.
Trace
Allows you to delete trace files.
Limits
Allows you to delete limits files.
Frequency List
Allows you to delete frequency list files.
Loss
Allows you to delete loss compensation files.
Screen
Allows you to delete screen files.
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Rename
Allows you to rename a file. File names are limited to
eight (8) characters.
ENR
Allows you to rename ENR files.
State
Allows you to rename state files.
Trace
Allows you to rename trace files.
Limits
Allows you to rename limits files.
Frequency List
Allows you to rename frequency list files.
Loss
Allows you to rename loss compensation files.
Screen
Allows you to rename screen files.
Format
286
Formats a double-density floppy disk to 1.44 MB
format. 760 KB disks are not supported.
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Save Trace
This is an action key which saves what is set-up under File. When you
need to change the parameters to be saved, press File and change them.
See “File” on page 280 for an explanation of setting up of saving files.
Preset
This key provides a convenient starting point for making most
measurements. Pressing the Preset key sets the instrument into a preset
state, the actual state depends on the Power On/Preset menu selections.
See the “Preset/Power Up Groups” on page 295, for the conditions
established by pressing Preset.
The instrument preset function performs a processor test, but does not
affect alignment data. Pressing Preset clears both the input and output
buffers and sets the status byte is set to 0. See “Preset/Power Up Groups”
on page 295 for a description of the preset states.
NOTE
Switching on the NFA performs an instrument preset, and also fetches
alignment data. The last state of the NFA (before it was powered off) is
recalled when Power On (Last) is selected (under the System key).
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Print Setup
Accesses the menu keys which allow you to define a printer and select
the printer options.
This menu allows you choose the information to be printed, the layout of
that information on the printed page, and the type of printer.
Figure 6-33
Print Setup Menu Maps
Print
Pressing Print (Screen) and then the Print action key, prints out what is on
the NFA display. Pressing Print (Report) and then the Print action key,
prints out the NFA information displayed under the Show System menu
key. Show System information includes the NFA’s product number, serial
number, firmware revision, and installed options.
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Printer Type
Define Custom
Orientation
Accesses the Printer Type menu keys. When you connect your printer
and press the Print key, the NFA attempts to identify your printer. If
identification is unsuccessful, None or Custom are automatically set in
the Printer Type menu. You can select one of the following options:
None
The Printer Type is automatically set to None when you
press the Print key and there is no attached printer or
an unsupported printer is connected to your NFA.
Custom
When you press the Print key and the NFA cannot
identify your printer, Custom is automatically set in the
Printer Type menu. Setting the Printer Type menu key
to Custom allows you to define your printer using the
Define Custom menu keys.
Auto
When Auto is selected, and the Print key is pressed, the
NFA attempts to communicate with the printer and
obtain its identification. If the printer is identified, the
print is successful and no message appears on the
display. If the NFA is not able to identify the printer,
the Printer Type is automatically set to Custom and an
error message asking you to press Define Custom to set
up your printer is displayed. If the printer is not
supported, the Printer Type is automatically set to
None and an error message informs you that your
printer is unsupported.
Allows you to define your printer.
Language
Allows you to define your printer as a Language(PCL3),
Deskjet type printer, or Language(PCL5), Laserjet type
printer.
Color Capable
Allows you to define the color capability of your printer.
When Color Capable(Yes) is enabled, the printer is color
capable. When Color Capable(No) is enabled, the printer
is not color capable.
Allows you to select either Portrait or Landscape printing. Landscape is
not available with a PCL3 (Deskjet) printer.
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Color
Allows you to select between color or black and white printing. This key
does not function when pressed unless the connected printer supports
color. When Color(Off) is set color printing is disabled. When Color(On) is
set color printing is enabled.
Prints/Page
Selects the number of prints per page when orientation is set to Portrait.
In Landscape printing, Prints/Page is always set to 1.
When Prints/Page(1) is enabled, the printer ejects the page after making a
single printout. When Prints/Page(2) is enabled, the printer ejects the
page after making a second printout.
Eject Page
This causes the printer to eject the current page.
Print
Pressing the Print key initiates an output of the display data to a
previously specified graphics printer. See “Configuring a Printer with the
NFA” on page 215 of this manual for detailed information about printing.
Press the Print key to immediately print the screen to the
currently-defined printer. The screen remains frozen (no further sweeps
are taken) until the data transfer to the printer is complete. Refer to the
“Print Setup” key description in this chapter for more information about
the structure and definitions of the printer keys.
If you need to abort a print in progress, use the Esc (escape) key.
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Data Entry Keys
Data Entry Keys
Numeric Keys
These keys are used to enter numeric data. After each complete
numerical entry you need to terminate it using the units menu keys
when presented to you or the Enter key.
Back Space
Used to correct front panel numeric input value or an Alpha Editor entry.
Press the Bk Sp ⇐ key and tab back to where you need the correction
over written.
Enter
Terminates and enters into the NFA a numerical value that has been
entered from the front panel using the numeric keypad.
NOTE
For certain applications, you must use the units menu keys to terminate
an entry.
When using the File key menus, the Enter key is also used to save, load,
copy, delete, or rename a file.
Up/Down Arrow Keys
These keys are used to increment and decrement active function values,
and also to move up and down file selection lists.
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Display and Menu Control Keys
Viewing Angle
Controls the optimum viewing angle of the display. The viewing angle
keys are located next to each other at the upper left-hand corner of the
NFA, bordering the display. These two keys allow you to adjust the
intensity of the display so that it can be optimally viewed from different
angles.
The Viewing Angle keys automatically repeat when they are continually
pressed down.
On
This powers up the NFA.
Standby
Removes power from the NFA, except for a small portion of circuitry
inside the power supply. No internal timebase circuitry, or any other
function outside of the power supply is powered when the NFA is in
Standby mode.
To remove power from the small portion of circuitry inside the power
supply which remains powered when the NFA is in Standby mode, you
need to disconnect the power cord from the rear of the NFA.
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Next Window
The Next Window key is used to switch the selection between the upper
and lower windows in dual and single graph display layout. The active
window has a green border.
NOTE
The Next Window key is also used in table and meter formats to change
the active measurement parameter. The active measurement parameter
title has a green border.
Zoom
Allows you to switch between the dual graph split-screen and full-sized
display of the active window.
The graph selected by the next window key is the one that is expanded to
create the single graph display.
NOTE
The Zoom key is only active when in graph format.
Help
This accesses a short description of any front panel key or menu key.
After pressing Help, an explanation of the next key pressed appears on
the display.
The help key provides on-line help for other keys on the front panel. The
help is context sensitive so that the key’s help is specific to its current
function.
NOTE
After the help text is displayed, pressing any key, except Preset, removes
the help window. Pressing ESC allows you to remove the help window
without changing functions.
Chapter 6
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Front Panel Key Reference
Display and Menu Control Keys
Tab Keys
These are three Tab keys that are used to select entries in tables when
editing or viewing them. They are used in the forms to select the entry to
allow you to edit it. Also, these keys move between entry fields in the file
selection menus.
• The up-left arrow moves to the first entry in the table.
• The left arrow moves to the previous table entry.
• The right arrow moves to the next table entry.
⇐Prev
Returns you to the previous menu. Repeated presses of this key move
back through previously selected menus. When a menu requiring a yes or
no key press has been accessed, the Prev key does not respond.
Esc
Deactivates the active function and clears the active function text from
the display. This ensures that no data can be accidentally entered using
the RPG, front panel keys, or numeric keypad.
Pressing Esc also aborts a print, clear input or output overloads, and
clear error messages from the status line along the bottom of the display.
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Preset/Power Up Groups
Preset/Power Up Groups
The NFA has preset and power up settings which are allocated into four
groupings. These occur on Preset/Power Up and recalling a State file.
These are as follows: • A persistent group which remains in memory after a preset or a
power cycle and is not saved as part of a State file.
• A “survive preset” group which remains in memory after a preset or a
power cycle and can be saved as part of a State file.
• A No Save group which does not remain in memory after a preset or a
power cycle. It is not saved or recalled as part of a State file.
• A State group which remains in memory after a preset or a power
cycle. It contains data which is reset by preset or a power cycle and is
stored and recalled as a State file.
Preset/Power Up — “Persistent” Group Items
The “persistent” group is stored in the NFA’s non-volatile RAM and
remains there after a preset or a power cycle. It is not stored as part of a
State file, hence is not affected when a State file is recalled. It is reset
to its initial value by Restore Sys Default, which is under the System key.
The “persistent” group items are listed in the following list: • Automatic Filename Counter
• Viewing Angle
• Remote Port (Serial) or (GPIB)
• GPIB (Noise Figure Analyzer Address)
• GPIB (External LO Address)
• GPIB (LO GPIB Address)
• Serial (Data Terminal Ready)
• Serial (Request To Send)
• Serial (Baud)
• Serial (Receive Pacing)
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Front Panel Key Reference
Preset/Power Up Groups
• Serial (Transmit Pacing)
• Power On (Last) or (Preset)
• Preset (Factory) or (User)
• Time/Date (On) or (Off)
• Date Mode (MDY) or (DMY)
• Printer Type
• Orientation (Portrait) or (Landscape)
• Color (On) or (Off)
• Prints/Page (1) or (2)
• Language (PCL3) or (PCL5)
• Color Capable (No) or (Yes)
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Preset/Power Up Groups
Preset/Power Up - “Survive Preset” Group Items
The “survive preset” group is stored in the NFA’s non-volatile RAM and
remains there after a preset or a power cycle. It typically contains table
data which you do not want to re-enter when the NFA is preset or power
cycled.
The group can also be stored as part of a State file, hence it is refreshed
when a State file is recalled. It is reset to its initial value by Restore Sys
Default, which is under the System key.
These group items are detailed in the following list: • Limit Lines
This also includes Type. However, it does not include Test (On) or (Off)
and Display (On) or (Off)
• Freq List data
• Before DUT Table and After DUT Table Loss Compensation data
• LO Commands
The custom command strings (Power Prefix, Power Suffix, Freq
Prefix, Freq Suffix, Auxiliary)
• External LO, Settling Time
• External LO, Min Freq
• External LO, Max Freq
NOTE
The ENR Table data, both Meas Table and Cal Table, is part of the “survive
preset” group. However, it is not stored as part of this group in a State
file.
Chapter 6
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Front Panel Key Reference
Preset/Power Up Groups
Unsaved Items
This data does not need to remain after a preset or a power cycle. It
contains data which is not saved or recalled from a State file. The data is
reset on power up or preset
These unsaved items are listed in the following list:
• The current menu
• The editing position within a table
• The marker selection number
• The limit line selection number
• The file type
State Items
State saved items are stored in the NFA's non-volatile RAM and remain
there after a power cycle. These contain data which is normally reset by
preset or a power cycle. They are stored as part of a State file. It
contains all menu/remote settings except those listed in the “Unsaved
Items” section.
NOTE
An NFA’s State file also stores the Calibration Data and Marker Memory
Trace Data. Hence, this data is recalled with a State file.
NOTE
Calibration Data is volatile and is lost after a power cycle. However, it is
not lost after a preset.
NOTE
Memory Trace Data is volatile and is lost after a preset or a power cycle.
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Preset/Power Up Groups
Default States
Table 6-2 shows the NFA’s system default states. Where the value is
initially not active, its activated default state is shown in parenthesis
Table 6-2
Default States
Menu Key
Default States
After DUT
Off
After DUT Fixed Value
Inactive (0.000 dB)
After Temperature
0.00 K
Alignment
On
Alignment Mode
Sweep
Annotation
On
Auto Load ENR
On
Average Mode
(Key not available on the N8972A)
Point
Averages
1
Averaging
Off
Band Pair
Inactive (Ref)
Bandwidth
4 MHz
Baud
9600
Before DUT
Off
Before DUT Fixed Value
Inactive (0.000 dB)
Before Temperature
0.00 K
Cal Table
Inactive
Center Freq (N8972A)
755.0 MHz
Center Freq (N8973A)
1.505 GHz
Center Freq (N8974A)
1.505 GHz
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Preset/Power Up Groups
Table 6-2
300
Default States
Menu Key
Default States
Center Freq (N8975A)
14.75 GHz
Color
Off
Combined
Off
Command Set
SCPI
Common Table
On
Continuous
Inactive (Off)
Corrected
Inactive (Off)
Define Custom
Inactive
Data->Memory
Inactive
Date Mode
MDY
Data Terminal Ready
OFF
Device Under Test
Amplifier
Display
Inactive (Off)
Display Ref
Off
ENR Mode
Table
ENR Table
Active
External LO Address
19
External LO Power Level
0.0000 dB
Find
Inactive (Off)
Fixed Freq
Inactive
Format
Graph
Freq Span (N8972A)
1.490 GHz
Freq Span (N8973A)
2.990 GHz
Chapter 6
Front Panel Key Reference
Preset/Power Up Groups
Table 6-2
Default States
Menu Key
Default States
Freq Span (N8974A)
2.990 GHz
Freq Span (N8975A)
23.50 GHz
Freq. Mode
Sweep
Graticule
On
IF Frequency
Inactive (30.0 MHz)
Limit Line
1⇑
LO Control
Off
LO Frequency
30.0 GHz
LO GPIB Address
8
LO Mode
Inactive
Marker
1⇑
Manual State
Off
Meas Table
Inactive
Min RF Atten
0 dB
Max RF Atten
20 dB
Min µW Atten
(Key selection not on the
N8972/3A)
0 dB
Max µW Atten
(Key selection not on the
N8972/3A)
0 dB
Multiplier
1
Noise Figure Analyzer Address
8
Orientation
Inactive (Portrait)
Chapter 6
301
Front Panel Key Reference
Preset/Power Up Groups
Table 6-2
302
Default States
Menu Key
Default States
Points
11
Power On
Preset
Preference
SNS
Preset
Factory
Print
Screen
Printer Type
Auto
Prints/Page
1
Receive Pacing
XON/XOFF
Ref. Level
4.000
Request To Send
OFF
Remote Port
GPIB
Search Type
Inactive (Max)
Sideband
LSB
Spot ENR
15.200 dB
Spot Mode
ENR
Spot Thot
9892.80 K
SNS Tcold
Inactive (On)
Start Freq (not N8975A model)
10.00 MHz
Start Freq (only N8975A model)
3.000000001 GHz
State
Off
Stop Freq (N8972A)
1.50 GHz
Stop Freq (N8973A)
3.00 GHz
Stop Freq (N8974A)
3.00 GHz
Chapter 6
Front Panel Key Reference
Preset/Power Up Groups
Table 6-2
Default States
Menu Key
Default States
Stop Freq (N8975A)
26.50 GHz
Sweep Mode
Cont
System Downconverter
Off
Tcold
SNS (if connected)
Default (if SNS not connected)
Test
Inactive (Off)
Time/Date
On
Trace
Inactive (Data)
Transmit Pacing
XON/XOFF
Type
Upper
Units (Default Noise Figure)
dB
User Tcold
Off
User Tcold from SNS
Inactive
User Value
296.50K
Chapter 6
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Front Panel Key Reference
Preset/Power Up Groups
304
Chapter 6
7
Troubleshooting
This chapter includes information on how to check for a problem with
your Noise Figure Analyzer, and how to return it for service. It also
includes descriptions of all of the analyzer built-in messages.
305
Troubleshooting
What You’ll Find in This Chapter
What You’ll Find in This Chapter
This chapter includes information on how to check for a problem with
your Noise Figure Analyzer, and how to return it for service. It also
includes descriptions of all of the analyzer built-in messages.
Your analyzer is built to provide dependable service. However, if you
experience a problem, or if you desire additional information or wish to
order parts, options, or accessories, Agilent’s worldwide sales and service
organization is ready to provide the support you need.
In general, a problem can be caused by a hardware failure, a software
error, or a user error. Follow these general steps to determine the cause
and to resolve the problem.
1. Perform the quick checks listed in “Check the Basics” in this chapter.
It is possible that a quick check may eliminate your problem
altogether.
2. If the problem is a hardware problem, you have several options:
• Repair it yourself; see the “Service Options” section in this
chapter.
• Return the analyzer to Agilent Technologies for repair; if the
analyzer is still under warranty or is covered by an Agilent
maintenance contract, it is repaired under the terms of the
warranty or plan (the warranty is at the front of this manual).
If the analyzer is no longer under warranty or is not covered by an
Agilent maintenance plan, Agilent Technologies notifies you of the
cost of the repair after examining the instrument. See “How to
Call Agilent Technologies” and “How to Return Your Analyzer for
Service” for more information.
WARNING
No operator serviceable parts inside the analyzer. Refer
servicing to qualified personnel. To prevent electrical shock do
not remove covers.
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Before You Call Agilent Technologies
Before You Call Agilent Technologies
Check the Basics
A problem can often be resolved by repeating the procedure you were
following when the problem occurred. Before calling Agilent Technologies
or returning the analyzer for service, please make the following checks:
❏ Check the line fuse.
❏ Is there power at the receptacle?
❏ Is the analyzer turned on? Make sure the fan is running, which
indicates that the power supply is on.
❏ If the display is dark or dim, press the upper Viewing Angle key in the
upper-left corner of the front panel. If the display is too bright, adjust
the lower Viewing Angle key in the upper-left corner of the front panel.
❏ If other equipment, cables, and connectors are being used with your
Noise Figure Analyzer, make sure they are connected properly and
operating correctly.
❏ Review the procedure for the measurement being performed when the
problem appeared. Are all the settings correct?
❏ If the analyzer is not functioning as expected, return the analyzer to a
known state by pressing the Preset key.
Some analyzer settings are not affected by a Preset. If you wish to
reset the analyzer configuration to the state it was in when it was
originally sent from the factory, press System, Power On/Preset,
Preset (Factory).
❏ Is the measurement being performed, and the results that are
expected, within the specifications and capabilities of the analyzer?
Refer to the “Technical Specifications” chapter in the Agilent NFA
Series Performance Verification and Calibration Guide for the
NFA specifications.
❏ In order to meet specifications, the analyzer must be aligned. Press
System, Alignment and enable Alignment(On). If Alignment(Off) is
enabled the analyzer must be aligned whenever the temperature
changes more than 3° centigrade.
Chapter 7
307
Troubleshooting
Before You Call Agilent Technologies
❏ Is the analyzer displaying an error message? If so, refer to “Error
Messages” in this chapter.
❏ If the necessary test equipment is available, perform the performance
verification tests in the Agilent NFA Series Performance
Verification and Calibration Guide. Record all results on a
Performance Verification Test Record form which follows the tests.
Read the Warranty
The warranty for your analyzer is at the front of this manual. Please
read it and become familiar with its terms.
If your analyzer is covered by a separate maintenance agreement, please
be familiar with its terms.
Service Options
Agilent Technologies offers several optional maintenance plans to service
your analyzer after the warranty has expired. Call your Agilent
Technologies sales and service office for full details.
How to Call Agilent Technologies
Agilent Technologies has sales and service offices around the world to
provide you with complete support for your analyzer. To obtain servicing
information, contact the nearest Agilent Technologies sales and service
office listed in Table 7-1. In any correspondence or telephone
conversations, refer to your analyzer by its product number, full serial
number, and firmware revision. (Press System, More 1 of 3, Show System,
and the product number, serial number, and firmware revision
information is displayed on your analyzer screen.) A serial number label
is also attached to the rear panel of the analyzer.
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Before You Call Agilent Technologies
Table 7-1
Agilent Technologies Sales and Service Offices
UNITED STATES
Agilent Technologies
(tel) 1 800 452 4844
CANADA
Agilent Technologies Canada Inc.
Test & Measurement
(tel) 1 877 894 4414
EUROPE
Agilent Technologies
Test & Measurement
European Marketing Organization
(tel) (31 20) 547 2000
JAPAN
Agilent Technologies Japan Ltd.
(tel) (81) 426 56 7832
(fax) (81) 426 56 7840
LATIN AMERICA
Agilent Technologies
Latin America Region Headquarters, USA
(tel) (305) 267 4245
(fax) (305) 267 4286
AUSTRALIA/NEW ZEALAND
Agilent Technologies Australia Pty Ltd.
(tel) 1-800 629 4852 (Australia)
(fax) (61 3) 9272 0749 (Australia)
(tel) 0-800 738 378 (New Zealand)
(fax) (64 4) 802 6881 (New Zealand)
ASIA PACIFIC
Agilent Technologies, Hong Kong
(tel) (852) 3197 7777
(fax) (852) 2506 9284
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Troubleshooting
How to Return Your Analyzer for Service
How to Return Your Analyzer for Service
Detailing the Problem
If you are returning your analyzer to Agilent Technologies for servicing,
enter details of the problem and send them with the analyzer. Please be
as specific as possible about the nature of the problem. If you have
recorded any error messages that appeared on the display, or have
completed a Performance Test Record, or have any other specific data on
the performance of your analyzer, please send a copy of this information
with your analyzer.
Original Packaging
Before shipping, pack the unit in the original factory packaging
materials if they are available. If the original materials were not
retained, see “Other Packaging”.
NOTE
Ensure that the instrument handle is in the rear-facing position in order
to reduce the possibility of damage during shipping. Refer to Figure 7-1.
NOTE
Install the transportation disk into the floppy drive to reduce the
possibility of damage during shipping. If the original transportation disk
is not available, a blank floppy may be substituted.
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How to Return Your Analyzer for Service
Figure 7-1
Chapter 7
311
Troubleshooting
How to Return Your Analyzer for Service
Other Packaging
CAUTION
Analyzer damage can result from using packaging materials other than
those specified. Never use styrene pellets in any shape as packaging
materials. They do not adequately cushion the equipment or prevent it
from shifting in the carton. They cause equipment damage by generating
static electricity and by lodging in the analyzer louvers, blocking airflow.
You can repackage the instrument with commercially available
materials, as follows:
1. Attach the details of the problem to the instrument.
2. Install the transportation disk or a blank floppy disk into the disk
drive.
3. If you have a front-panel cover, install it on the instrument. If you do
not have a front panel cover, make sure the instrument handle is in
the forward-facing position to protect the control panel.
4. Wrap the instrument in antistatic plastic to reduce the possibility of
damage caused by electrostatic discharge.
5. Use a strong shipping container. The carton must be both large
enough and strong enough to accommodate the analyzer. A
double-walled, corrugated cardboard carton with 159 kg (350 lb)
bursting strength is adequate. Allow at least 3 to 4 inches on all sides
of the analyzer for packing material.
6. Surround the equipment with three to four inches of packing material
and prevent the equipment from moving in the carton. If packing
foam is not available, the best alternative is S.D.-240 Air Cap™ from
Sealed Air Corporation (Hayward, California, 94545). Air Cap looks
like a plastic sheet filled with 1-1/4 inch air bubbles. Use the
pink-colored Air Cap to reduce static electricity. Wrapping the
equipment several times in this material should both protect the
equipment and prevent it from moving in the carton.
7. Seal the shipping container securely with strong nylon adhesive tape.
8. Mark the shipping container “FRAGILE, HANDLE WITH CARE” to
assure careful handling.
9. Retain copies of all shipping papers.
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NFA Battery Information
NFA Battery Information
The NFA uses a lithium battery to enable the internal memory to retain
data. The date when the battery was installed is on a label on the rear
panel of the NFA.
The minimum life expectancy of the battery is 7 years at 25 °C, or 1 year
at 55 °C. If you experience problems with the battery or the
recommended time period for battery replacement has elapsed, contact
Agilent Technologies. See “How to Call Agilent Technologies” on
page 308 for a list of your nearest Agilent Sales and Service office.
If you wish to replace the battery yourself, you can by following the
service documentation that provides all necessary test and maintenance
information.
You can order the service documentation for an Agilent NFA through
your Agilent Sales and Service office.
After replacing the NFA battery, write the date of battery replacement on
the rear panel label.
Chapter 7
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Troubleshooting
Error Messages
Error Messages
The analyzer can generate various messages that appear on the display
during operation. There are three types of messages.
• Informational Messages provide information that requires no
intervention. These messages appear in the status line at the bottom
of the display, in green if you have a color display. The message
remains until you preset the analyzer, press ESC, or another message
is displayed in the status line.
• User Error Messages appear when an attempt has been made to set a
parameter incorrectly or an operation has failed (such as saving a
file). These messages are often generated during remote operation
when an invalid programming command has been entered. These
messages appear in the status line at the bottom of the display, in
yellow if you have a color display. The message remains until you
preset the analyzer, press ESC, or another message is displayed in the
status line. A summary of the last 10 error messages may be viewed
by pressing, System then Show Errors. When generated by activity on
the remote interface, the messages are output to the remote bus.
When output to the remote interface, they are preceded by an error
number. Note that the error number is not displayed under the
System, Show Errors key sequence.
• Pop-up Messages indicate a condition that may require intervention.
They display in the middle of the display in a framed box. The
message remains until the appropriate intervention has taken place
or the condition is corrected.
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Error Messages
Informational Messages
The following messages provide information that requires no
intervention. These type of messages are in green. The information
provided in brackets, for example <filename> or <name> is a variable
that represents a specific input provided previously.
<filename> file loaded
The filename indicated has been successfully loaded.
<filename> file saved
The filename indicated has been successfully saved.
<filename> file copied
The filename indicated has been successfully copied.
<filename> file deleted
The filename indicated has been successfully deleted.
<filename1> file renamed to <filename2>
Filename1 has been successfully renamed to filename2.
Duplicate frequency entered in table, old
entry replaced
A duplicate entry was made in either the ENR table,
frequency list, limit line table or loss table. The
previous entry is replaced with the new entry.
Each result type selected must differ from
all others
An attempt was made to select the same result type for
both of the two displayed result types.
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Troubleshooting
Error Messages
Volume <name> formatted
The indicated disk has been successfully formatted.
Zoom active in graph mode only
The
to Graph.
key is only active when display format is set
Zoom inactive when showing combined graph
The
key is not active if the display format is set
to Combined.
User cal now valid
Previously invalidated user cal is now valid due to
change of instrument parameter(s).
Invalid frequency list for measurement mode
A frequency within the frequency list cannot be used to
make a measurement in the current mode.
ENR table will be extrapolated
The measurement requires ENR values beyond the
limits of the existing ENR table.
User cal will be interpolated
For a corrected measurement, the measurement
frequencies do not coincide with the user cal
frequencies.
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Error Messages
Memory trace invalidated
A change of instrument parameter has caused the
memory trace to be invalidated (removed from screen
and no longer selectable).
Maximum number of entries in table reached
The maximum number of entries in the ENR table,
frequency list or limit line table has been reached.
Chapter 7
317
Troubleshooting
Error Messages
Error Queues
When a user-error condition occurs in the instrument as a result of SCPI
activity, it is reported to both the front-panel display-error queue and the
SCPI (remote interface) error queue. If it is a result of front-panel
activity it reports to the front panel display error queue, and may also
report to the SCPI error queue depending on the error. These two queues
are viewed and managed separately.
Error messages have a signed error number followed by some error text
in double quotes. Negative error numbers are for predefined SCPI errors,
for example error -350, “Queue overflow” which is issued if an error
occurs when the error queue is already full. Positive errors are
instrument specific.
The query used to get the head of the error queue is
SYSTEM:ERROR:NEXT?. It can only retrieve one error at a time.
The special error message +0, “No error” indicates that the error queue is
empty. You can query the error queue as often as you like, when it is
empty you just keep getting +0, “No error”.
A single command or query can generate more than one error message.
For this reason it is best to drain the error queue after each command or
query. If not, you will lose track of what commands caused what errors.
Errors can occur that are not directly related to the last command issued.
You can use status information to find out if your command generated an
error. Status information can also tell you if some other type of error has
occurred. However, if the status information indicates there are different
types of error in the error queue, you cannot know which of the errors
was caused by the last command unless it is obvious from the error itself.
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Error Messages
Table 7-2
Characteristics of the Error Queues
Characteristic
Front Panel Display
Error Queue
SCPI Remote Interface
Error Queue
Capacity (#errors)
10
30
Overflow Handling
Circular (rotating).
Drops oldest error as new error
comes in.
Linear, first-in/first-out.
Replaces newest error with:
-350,Queue overflow
Viewing Entries
Press: System, Show Errors
Use SCPI query
SYSTem:ERRor?
Clearing the Queue
Press: System, Show Errors,
Power up
Send a *CLS command
Read last item in the queue
Clear Error Queue
Error Message Format
The system-defined error numbers are chosen on an enumerated (“1 of
N”) basis. The error messages are listed in alphabetical order within
each error message type section.
In this chapter, an explanation is included with each error to further
clarify its meaning. The last error described in each class (for example,
-400, -300, -200, -100) is a “generic” error.
Error messages appear at the bottom of the display.
Chapter 7
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Troubleshooting
Error Messages
Error Message Types
Events do not generate more than one type of error. For example, an
event that generates a query error will not generate a device-specific,
execution, or command error.
-499 to
-400: Query
Errors
These errors indicate that the instrument output queue control has
detected a problem with the message exchange protocol described in
IEEE 488.2, Chapter 6. Errors in this class set the query error bit (bit 2)
in the event status register (IEEE 488.2, section 11.5.1). These errors
correspond to message exchange protocol errors described in IEEE 488.2,
6.5. In this case:
• Either an attempt is being made to read data from the output queue
when no output is either present or pending, or
• data in the output queue has been lost.
-199 to
-100: Command
Errors
These errors indicate that the instrument parser detected an IEEE 488.2
syntax error. Errors in this class set the command error bit (bit 5) in the
event status register (IEEE 488.2, section 11.5.1). In this case:
• Either an IEEE 488.2 syntax error has been detected by the parser
(a control-to-device message was received that is in violation of the
IEEE 488.2 standard. Possible violations include a data element
which violates device listening formats or whose type is unacceptable
to the device.), or
• an unrecognized header was received. These include incorrect
device-specific headers and incorrect or non-implemented IEEE 488.2
common commands.
-399 to -300 and
201 to
799: Device-Speci
fic Errors
These errors indicate that a device operation did not properly complete,
possibly due to an abnormal hardware or firmware condition. These
codes are also used for self-test response errors. Errors in this class set
the device-specific error bit (bit 3) in the event status register (IEEE
488.2, section 11.5.1).
The <error_message> string for a positive error is not defined by SCPI.
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Chapter 7
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Error Messages
-299 to -200:
Execution Errors
These errors indicate that an error has been detected by the instrument’s
execution control block. The occurrence of any error in this class shall
cause the execution error bit (bit 4) in the event status register (IEEE
488.2, section 11.5.1) to be set. One of the following events has occurred:
• A <PROGRAM DATA> element following a header was evaluated by
the device as outside of its legal input range or is otherwise
inconsistent with the device’s capabilities.
• A valid program message could not be properly executed due to some
device condition.
Execution errors shall be reported by the device after rounding and
expression evaluation operations have taken place. Rounding a numeric
data element shall not be reported as an execution error. Events that
generate execution errors shall not generate Command errors,
device-specific errors, or Query errors.
0: No Error
0
No error
The queue is empty. Every error in the queue has been
read or the queue was purposely cleared by power-on or
*CLS.
Chapter 7
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Troubleshooting
Error Messages
-499 to -400: Query Errors
The instrument output queue control has detected a problem with the
message exchange protocol described in IEEE 488.2, Chapter 6. Errors in
this class set the query error bit (bit 2) in the event status register (IEEE
488.2, section 11.5.1). These errors correspond to message exchange
protocol errors described in IEEE 488.2, 6.5.
In this case, either an attempt is being made to read data from the
output queue when no output is either present or pending, or data in the
output queue has been lost.
-430
Query DEADLOCKED
Indicates that a SCPI output queue has filled,
preventing further SCPI command execution, and
there is no more room left in the corresponding SCPI
input queue to accept a query to read from the output
queue. The system automatically discards output to
correct the deadlock.
-400
Query Error
This is a generic query error for devices that cannot
detect more specific errors. The code indicates only that
a query error as defined in IEEE 488.2, 11.5.1.1.7 and
6.3 has occurred.
-410
Query INTERRUPTED
Indicates that a condition causing an INTERRUPTED
query error occurred (see IEEE 488.2, 6.3.2.7). For
example, a query was followed by DAB or GET before a
response was completely sent.
-420
Query UNTERMINATED
Indicates that a condition causing an
UNTERMINATED query error occurred (see IEEE
488.2, 6.3.2.2). For example, the device was addressed
to talk and an incomplete program message was
received.
322
Chapter 7
Troubleshooting
Error Messages
-440
Query UNTERMINATED after indefinite response
Indicates that a query was received in the same
program message after a query requesting an
indefinite response was executed (see IEEE 488.2,
6.3.7.5).
Chapter 7
323
Troubleshooting
Error Messages
-199 to -100: Command Errors
The instrument parser detected an IEEE 488.2 syntax error. Errors in
this class set the command error bit (bit 5) in the event status register
(IEEE 488.2, section 11.5.1). In this case:
• Either an IEEE 488.2 syntax error has been detected by the parser
(a control-to-device message was received that is in violation of the
IEEE 488.2 standard. Possible violations include a data element
which violates device listening formats or whose type is unacceptable
to the device.), or
• an unrecognized header was received. These include incorrect
device-specific headers and incorrect or non-implemented IEEE 488.2
common commands.
-160
Block data error
This error, and also error -168, is generated when
parsing a block data element. This particular error
message is used if the device cannot detect a more
specific error.
-168
Block data not allowed
A legal block data element was encountered, but not
allowed by the device at this point in the parsing.
-140
Character data error
This error, as well as errors -144 and -148, are
generated when parsing a character data element. This
particular error message is used if the device cannot
detect a more specific error.
-148
Character data not allowed
A legal character data element was encountered where
prohibited by the device.
324
Chapter 7
Troubleshooting
Error Messages
-144
Character data too long
The character data element contains more than twelve
characters (see IEEE 488.2, 7.7.1.4).
-100
Command error
This is a generic syntax error for devices that cannot
detect more specific errors. The code indicates only that
a command error as defined in IEEE 488.2, 11.5.1.1.4
has occurred.
-110
Command header error
An error was detected in the header. This message is
used when the device cannot detect the more specific
errors described for errors -111 through -119.
-104
Data type error
The parser recognized a data element that is not
allowed. For example, numeric or string data was
expected, but block data was encountered.
-123
Exponent too large
The magnitude of an exponent was greater than 32000
(see IEEE 488.2, 7.7.2.4.1).
-170
Expression error
This error, as well as error -178, is generated when
parsing an expression data element. This particular
error message is used if the device cannot detect a more
specific error.
-178
Expression data not allowed
A legal expression data was encountered, but was not
allowed by the device at this point in parsing.
Chapter 7
325
Troubleshooting
Error Messages
-105
GET not allowed
A Group Execute Trigger was received within a
program message (see IEEE 488.2, 7.7). Correct the
GPIB controller program so that the GET does not occur
within a line of GPIB program code.
-111
Header separator error
A character which is not a legal header separator was
encountered while parsing the header.
-114
Header suffix out of range
The value of a header suffix attached to a program
mnemonic makes the header invalid.
-161
Invalid block data
A block data element was expected, but was invalid
(see IEEE 488.2, 7.7.6.2). For example, an END message
was received before the end length was satisfied.
-101
Invalid character
A syntactic command contains a character which is
invalid for that type. For example, a header containing
an ampersand, SETUP&. This error might be used in
place of error numbers -114, -121, -141 and some
others.
-141
Invalid character data
Either the character data element contains an invalid
character or the particular element received is not
valid for the header.
326
Chapter 7
Troubleshooting
Error Messages
-121
Invalid character in number
An invalid character for the data type being parsed was
encountered. For example, an alpha in a decimal
numeric or a “9” in octal data.
-171
Invalid expression
The expression data element was invalid (see IEEE
488.2, 7.7.7.2). For example, unmatched parentheses or
an illegal character.
-103
Invalid separator
The parser was expecting a separator and encountered
an illegal character. For example, the semicolon was
omitted after a program message unit.
-151
Invalid string data
A string data element was expected, but was invalid
(see IEEE 488.2, 7.7.5.2). For example, an END message
was received before the terminal quote character.
-131
Invalid suffix
The suffix does not follow the syntax described in IEEE
488.2, 7.7.3.2, or the suffix is inappropriate for this
device.
-109
Missing parameter
Fewer parameters were received than required for the
header. For example, the *ESE common command
requires one parameter, so receiving *ESE is not
allowed.
Chapter 7
327
Troubleshooting
Error Messages
-120
Numeric data error
This error, as well as error -128, is generated when
parsing a data element which appears to be numeric,
including non-decimal numeric types. This particular
error message is used if the device cannot detect a more
specific error.
-128
Numeric data not allowed
A legal numeric data element was received, but the
device does not accept one in this position for the
header.
-108
Parameter not allowed
More parameters were received than expected for the
header. For example, the *ESE common command only
accepts one parameter, so receiving *ESE 0,1 is not
allowed.
-112
Program mnemonic too long
The header contains more than twelve characters (see
IEEE 488.2, 7.6.1.4.1).
-150
String data error
This error, as well as error -158, is generated when
parsing a string data element. This particular error
message is used if the device cannot detect a more
specific error.
-158
String data not allowed
A string data element was encountered, but not
allowed by the device at this point in the parsing.
328
Chapter 7
Troubleshooting
Error Messages
-130
Suffix error
This error, as well as errors -134 and -138, are
generated when parsing a suffix. This particular error
message is used if the device cannot detect a more
specific error.
-138
Suffix not allowed
A suffix was encountered after a numeric element
which does not allow suffixes.
-134
Suffix too long
The suffix contained more than twelve characters (see
IEEE 488.2, 7.7.3.4).
-102
Syntax error
An unrecognized command or data type was
encountered. For example, a string was received when
the device does not accept strings.
-124
Too many digits
The mantissa of a decimal-numeric data element
contained more than 255 digits excluding leading zeros
(see IEEE 488.2, 7.7.2.4.1).
-113
Undefined header
The header is syntactically correct, but it is undefined
for this specific device. For example, *XYZ is not defined
for any device.
Chapter 7
329
Troubleshooting
Error Messages
-399 to -300 and 201 to 799: Device-Specific Errors
Some device operations did not properly complete, possibly due to an
abnormal hardware or firmware condition. These codes are also used for
self-test response errors. Errors in this class set the device-specific error
bit (bit 3) in the event status register (IEEE 488.2, section 11.5.1).
The <error_message> string for a positive error is not defined by SCPI.
304
Alignment failed
The alignment failed because of one of the following
reasons:
• Gain less than 0
During alignment, the measured value of the IF
section gain was less than 0.
• Microwave noise greater than signal
The alignment failed at the current microwave
frequency because the reading at the IF detector
was greater when only the noise floor of the
instrument was present compared to when the
alignment noise source was on.
NOTE
This error can occur if the YTF alignment has not been performed at the
current operating temperature.
NOTE
This error applies only to the N8974A and N8975A.
• Noise greater than signal
The reading at the IF detector was greater when
only the noise floor of the instrument was present
compared to when the alignment CW signal was
present.
330
Chapter 7
Troubleshooting
Error Messages
614
Bad or missing disk
The floppy is not inserted or the directory could not be
read. Insert a known good disk and try again.
219
Command not valid in this model
Indicates that the command sent from the remote
interface does not apply to this model number.
615
Corrupted file
The file that you were trying to load is corrupt.
768
Failed to load ENR data
A problem occurred when attempting to load an ENR
table.
771
Failed to load Freq list
A problem occurred when attempting to load a
frequency list.
774
Failed to load Limit Line
A problem occurred when attempting to load a limit
line.
779
Failed to load Loss data
A problem occurred when attempting to load loss data.
772
Failed to store Freq list
A problem occurred when attempting to save a
frequency list.
Chapter 7
331
Troubleshooting
Error Messages
769
Failed to store ENR data
A problem occurred when attempting to save an ENR
table.
775
Failed to store Limit Line
A problem occurred when attempting to save a limit
line.
780
Failed to save Loss data
A problem occurred when attempting to save loss data.
778
Failed to store Trace
A problem occurred when attempting to save a trace.
610
File access is denied
The file is protected or hidden and cannot be accessed.
604
File already exists
Attempt to save to a file that already exists. Delete or
rename the old file and try again.
607
File name error
An invalid file name has been specified. Use filenames
with a maximum of 8 characters (letters and digits
only) and use a 3 character extension. Note that
lowercase and uppercase are perceived as the same.
612
File does not exist
The analyzer could not find the specified file.
332
Chapter 7
Troubleshooting
Error Messages
754
File does not exist
The state file you were trying to recall does not exist.
500
Hardware config error
A hardware configuration error occurred due to one of
the following reasons:
• Unknown product number
During start-up, an attempt to match the hardware
found against the NFA's product number could not
be made because the product number was unknown.
This is a fatal hardware configuration error.
• HW ID x in slot y not required
A card with ID x was found in slot y but for this
product number is not required. This is a non-fatal
hardware configuration error.
• HW ID x must be in slot y, not z
A card with ID x was found in slot z but was
expected to be found in slot y for this product
number. This is a fatal hardware configuration
error.
• HW ID x is missing
A card with ID x was expected for this product
number but was not found. This is a fatal hardware
configuration error.
• Measurement not possible
An attempt was made to perform a measurement
but a previous fatal hardware configuration error
has occurred, preventing measurements.
• Option ’x’ not installed
Software option 'x' must be enabled for this product
number, but was not installed. The NFA will
attempt to enable this option, requiring a power
cycle. This is a fatal hardware configuration error.
(until the option is reinstalled).
Chapter 7
333
Troubleshooting
Error Messages
300
IF autorange failed
The IF section could not be autoranged because of one
of the following:
• RF att. is fixed
The RF front-end attenuation is fixed.
• RF att. limit reached
The RF front-end attenuation limit is reached.
313
IF over range req. RF re-range: Meas.
restarted
During a continuous measurement, a IF section over
range condition occurred, requiring a change of RF
front-end attenuation. To do this the measurement
needs to be restarted.
302
IF PLD error;Power detector read timed out
A read of the IF section power detector timed out.
603
Illegal MSDOS name given
An invalid file name has been specified. Use filenames
with a maximum of 8 characters (letters and digits
only) and use a 3 character extension. Note that
lowercase and uppercase are perceived as the same.
770
Incorrect filename, allowable extension ENR
Attempt to save an ENR table to a file with an
incorrect extension.
763
Incorrect filename, allowable extensions are
GIF or WMF
Attempt to save a screen image to a file with an
incorrect extension.
334
Chapter 7
Troubleshooting
Error Messages
776
Incorrect filename, allowable extensions LIM
Attempt to save limit line data to a file with an
incorrect extension.
781
Incorrect filename, allowable extension LOS
An attempt was made to save loss data using an
extension other than LOS.
773
Incorrect filename, allowable extension LST
Attempt to save frequency list data to a file with an
incorrect extension.
777
Incorrect filename, allowable extension STA
Attempt to save the instrument state to a file with an
incorrect extension.
762
Incorrect filename, allowable extension CSV
Attempt to save a trace to a file with an incorrect
extension.
782
Incorrect SNS data format
An attempt to read SNS data failed either because the
device attached was not an SNS or because the data
was corrupt.
307
Input attenuation x dB not calibrated
Corrected measurements have been requested and the
required RF front-end attenuation setting of x dB has
not been calibrated.
Chapter 7
335
Troubleshooting
Error Messages
751
Instrument state may be corrupt, state has
been reset to initial values
An attempt was made to load a possibly corrupt state.
The instrument state is reset to the state prior to the
attempt to load. If the state load was for a user preset,
then the instrument state is reset to the factory state.
216
Invalid baud rate
Attempt to use invalid baud rate. Refer to “Baud” on
page 271 of User’s Guide for valid rates.
308
Invalid frequency list for measurement mode
A frequency within the frequency list cannot be used to
make a measurement in the current mode.
306
Invalid input attenuation
An attempt was made to set an invalid RF front-end
attenuation limit for calibration.
701
Invalid printer response
In attempting to identify the printer an invalid
response was received. Check that you are using a
supported printer. Be sure you are using the proper
cable and that it is securely fastened.
301
LO GPIB error
An LO GPIB error occurred because of one of the
following:
• Did not become system controller
An attempt to become system controller failed,
possibly because another controller is present on
the LO GPIB bus.
336
Chapter 7
Troubleshooting
Error Messages
• Need to be system controller
To perform the required action, the NFA needs to be
the system controller on the LO GPIB bus and is not
because a prior attempt to become the system
controller failed.
• Controller collision
Another controller on the LO GPIB has attempted
to use the bus concurrently with the NFA.
• Address bus timeout
Attempted to address bus and failed — check
cabling connections.
• Write command timeout
Attempt to write command to device failed — check
device address is correct.
• Read response timeout
Attempt to read response from device failed - check
device address is not the same as the LO GPIB
address.
606
Media is not writable
A save was attempted to a read-only device.
605
Media is protected
A save was attempted to a write-protected device.
315
Microwave input attenuation x dB not
calibrated
Corrected measurements have been requested and the
required microwave front-end attenuation setting of x
dB has not been calibrated.
Chapter 7
337
Troubleshooting
Error Messages
305
Mode setup error
A mode setup error occurred because of one of the
following:
• System input frequency out of range
One or more system input frequencies are out of
range. If using a frequency list, check that all
entries are valid for current measurement mode.
• External LO frequency out of range
One or more external LO frequencies are out of
range. Check that the LO frequency limits are set
correctly and check the entered measurement
frequencies and measurement mode.
• Stop freq must be less than fixed LO freq
The current measurement mode requires that the
stop frequency must be less than the fixed LO
frequency.
• Start freq must be greater than start IF
freq
The current measurement mode requires that the
start RF (input to DUT) frequency must be greater
than the start IF (output from DUT) frequency.
• LO - Stop freq must be >= min system input
freq
The current measurement mode requires that the
difference between the fixed LO frequency and the
stop RF (input to DUT) frequency must be more
than the minimum system input frequency.
• Start freq must be greater than fixed LO
freq
The current measurement mode requires that the
start frequency must be greater than the fixed LO
frequency.
338
Chapter 7
Troubleshooting
Error Messages
• Stop IF freq must be less than fixed LO
freq
The current measurement mode requires that the
stop IF (output from DUT) frequency must less than
the fixed LO frequency.
• Start - LO freq must be >= min system input
freq
The current measurement mode requires that the
start RF (input to DUT) frequency must be more
than the minimum system input frequency away
from the fixed LO frequency.
• Stop freq must be less than stop RF freq
The current measurement mode requires that the
stop IF (output from DUT) frequency must be less
than the stop RF (input to DUT) frequency.
• Start freq must be greater than start RF
freq
The current measurement mode requires that the
start IF (output from DUT) frequency must be
greater than the start RF (input to DUT) frequency.
• Stop RF freq must be less than fixed LO
freq
The current measurement mode requires that the
stop RF (input to DUT) frequency must be less than
the fixed LO frequency.
• Start freq must be greater than fixed IF
freq
The current measurement mode requires that the
start RF (input to DUT) frequency must be greater
than the fixed IF frequency.
• Start LO freq must be greater than fixed IF
freq
The current measurement mode requires that the
start LO frequency must be greater than the fixed
IF frequency.
Chapter 7
339
Troubleshooting
Error Messages
• Stop freq must be less than fixed IF freq
The current measurement mode requires that the
stop RF (input to DUT) frequency must be less than
the fixed IF frequency.
• Stop freq must be less than stop LO freq
The current measurement mode requires that the
stop RF (input to DUT) frequency must be less than
the stop LO frequency.
310
No entries in ENR table
A measurement was attempted or a SCPI query of an
ENR table was made and there were no entries in the
relevant ENR table (Common, Meas or Cal).
309
No entries in frequency list
A measurement was attempted with List frequency
mode or a SCPI query of the frequency list table was
made and the frequency list table is empty.
311
No entries in limit line table
A measurement was attempted using a limit line table,
or a SCPI query of an limit line table was made and
there were no entries in the relevant limit line table.
314
No entries in loss table
A measurement was attempted or a SCPI query of a
loss table was made and there were no entries in the
relevant loss table (either Before or After table).
700
No printer response
An attempt to identify the printer failed.
340
Chapter 7
Troubleshooting
Error Messages
704
Printer interface error
An error occurred while trying to print. Make sure the
printer is turned on and properly connected.
705
Printer type is none
The current printer type is set to None, so no print
operations are possible. Change the type in the Print
Setup menu and try again.
-350
Queue Overflow
There is no room in the error queue and an error
occurred but was not recorded.
312
RF re-range required: Meas. restarted
During a continuous measurement, a change of RF
front-end attenuation was required. To do this the
measurement needs to be restarted.
217
RS-232 Interface Error
An error occurred on the serial interface due to one of
the following reasons:
• Input data overrun
An error occurred on the serial interface.
• Input data parity
An error occurred on the serial interface.
• Input data framing
An error occurred on the serial interface.
• Output data timeout
An error occurred on the serial interface
• Command input timeout
An error occurred on the serial interface.
Chapter 7
341
Troubleshooting
Error Messages
-330
Self-Test Failed
A self-test error occurred due to one of the following
reasons:
• IF test [x][y] failure
• RF test [x] failure
• RF gain (x) out of range
• IF gain out of range
• RF cal x out of range amp[y]
• RF amp[x] floor too high
• Tuner EEPROM cal value out of range
• IF filter offset x out of range
501
SNS read failure
An attempt to read from the SNS failed. This could be
due to SNS cable problems such as poor connection or
disconnection while reading.
502
SNS write failure
An attempt to write to the SNS failed. This could be
due to SNS cable problems such as poor connection or
disconnection while writing.
316
Thot must be greater than Tcold
A spot Thot temperature has been specified which is
not greater than Tcold temperature.
766
Unable to format drive
A problem occurred when attempting to format a drive.
342
Chapter 7
Troubleshooting
Error Messages
765
Unable to load file
A problem occurred when attempting to load a file.
759
Unable to load state file into instrument with
older firmware date
A saved state file from a newer firmware revision was
attempted to be loaded into an older instrument.
752
Unable to load state from file
An attempt to load a state from the File Manager or
through MMEM:LOAD:STAT failed. Preceding error
messages may indicate the cause of failure.
755
Unable to load state from register
An attempt to load a state from a register using the
*RCL command failed. Preceding error messages may
indicate the cause of failure.
757
Unable to load user state, factory preset was
done
An attempt to perform a User Preset failed, so the
Factory Preset values were used. Save a valid state into
User Preset and try again.
760
Unable to query state from the remote
A problem occurred while trying to query the
instrument state as part of a *LRN command.
764
Unable to save file
A failure occurred while saving a file; the file was not
saved.
Chapter 7
343
Troubleshooting
Error Messages
753
Unable to save state to file
An attempt to save a state from the File Manager or
through MMEM:STOR:STAT failed. Preceding error
messages may indicate the cause of failure.
756
Unable to save state to register
An attempt to save a state to a register using the *SAV
command failed. Preceding error messages may
indicate the cause of failure.
758
Unable to save user state
An attempt to save the User Preset state failed.
761
Unable to set state from the remote
A problem occurred while trying to set the instrument
state as part of a SYST:SET command.
703
Unknown printer
In attempting to identify the printer, a valid response
was received but the printer is not known to the
analyzer. Use the Custom printer menu under Print
Setup to configure the printer.
702
Unsupported printer
A printer which is recognized, but known to be
unsupported was identified. This printer cannot be
used with the analyzer. For example, a printer only
supported by Microsoft Windows generates this error.
344
Chapter 7
Troubleshooting
Error Messages
303
User cal invalidated
The existing user cal has been invalidated because of
one of the following reasons:
• Meas mode changed
The measurement mode has been changed from
that used for user cal.
• Freq outside cal range
The current measurement frequencies lie partially
or wholly outside the range of frequencies used for
user cal.
• Fixed IF changed
The fixed IF frequency has been changed from that
used for user cal.
• Fixed LO changed
The fixed LO frequency has been changed from that
used for user cal.
• Sideband changed
The sideband has been changed from that used for
user cal.
Chapter 7
345
Troubleshooting
Error Messages
660
YTF align error
The alignment failed because of one of the following
reasons:
• Peak / floor too small
During a YTF alignment the level of a peak above
the noise floor was too small. If this error occurs
then the quality of the YTF alignment is
questionable.
• Image / floor too small
During a YTF alignment the level of an image
response above the noise floor was too small. If this
error occurs then the quality of the YTF alignment
is questionable.
346
Chapter 7
Troubleshooting
Error Messages
-299 to -200:
Execution Errors
-222
Data out of range
A parameter of a command or query was outside the
defined range for that command or query.
-224
Illegal parameter value
An unexpected value was entered. (for example, a value
other then the available options)
-225
Out of memory
The analyzer has insufficient memory to perform the
requested operation.
-221
Settings conflict
A legal program data element was parsed but could not
be executed due to the current device state.
-223
Too much data
A block, expression or string parameter of a command
or query contained more data than the analyzer could
handle due to memory constraints.
-213
Init ignored
Indicates that a request for a measurement initiation
was ignored as another measurement was in progress.
NOTE
The front panel Restart key does not generate this error, only the remote
command INIT:IMM.
Chapter 7
347
Troubleshooting
Error Messages
-230
Data corrupt or stale
Possibly invalid data; new reading started but not
completed since last access.
348
Chapter 7
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