User Guide: Keysight (Agilent) N9912A FieldFox RF

User Guide: Keysight (Agilent) N9912A FieldFox RF

NA (Network Analyzer) Mode

Learn more about NA Mode measurements in the FieldFox Supplemental Online

Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

In this Chapter

Measurement Selection ......................................... 40

Parameter Conversion .......................................... 40

Quick Settings ........................................................ 42

Calibration Settings ............................................... 42

Format ..................................................................... 43

Frequency Range ................................................... 44

Scale Settings ......................................................... 44

Electrical Delay ...................................................... 45

Phase Offset ............................................................ 45

Averaging ................................................................ 46

IF Bandwidth .......................................................... 47

Smoothing ............................................................... 47

Single/Continuous ................................................. 47

Resolution (number of points) ............................ 48

Sweep Time ............................................................. 48

Output Power ......................................................... 48

System Impedance ................................................. 49

Port Extensions ...................................................... 49

Velocity Factor ....................................................... 50

S21 Transmission Measurement ......................... 51

Increase Dynamic Range ...................................... 51

See Also

All about Calibration ............................................. 61

Set Markers ........................................................... 152

Use Limit Lines .................................................... 162

Use Trace Math .................................................... 165

Learn how to make 75Ω (ohm) Measurements in the Supplemental Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

NA Mode Settings

Select NA Mode before making any setting in this section.

How to select NA Mode

 Press Mode_.

 Then

NA

.

NA (Network Analyzer) Mode 39

40

NOTE

Measurement Selection

How to select a NA Measurement

 Press Measure 1.

 Then choose from the following: o

S11

1-port reflection measurement. o

S21

2-port transmission measurement. Requires Opt 110. Learn how to

make this measurement on page 49.

o

More

- These measurements are typically used as diagnostic tools for service personnel. o o

A

Measurement of the A receiver.

R1

Measurement of the R1 receiver.

The A and R1 receiver measurements are NOT corrected for absolute power.

They are only useful for making relative measurements. The Y-Axis and markers are labeled in dB - NOT dBm. Specifically, R1 does NOT indicate the actual power levels out of the source port. The actual power level is close to the typical output power of +5 dBm (High power) and -25 dBm (Low power).

Learn more about raw receiver measurements in the FieldFox Supplemental

Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

Parameter Conversion

In NA Mode ONLY, converts the active S-parameter trace to an equivalent impedance (Z), admittance (Y), or reciprocal 1/S-parameter.

How to select parameter conversions

 Press Measure 1

 Then select an S-parameter

 Then

More

 Then

Conversion

 Then choose from the following: o

Off

(default) No conversion is performed. o

Z Conv ( -- ) or Y Conv ( -- )

Perform conversion for impedance (Z) or admittance (Y). Then choose from the following for either: o

Auto

The displayed S-parameter is converted to the appropriate Z or Y parameter. o

Refl

The displayed S-parameter is converted to Z or Y reflection, regardless of whether the S-parameter is reflection (S11 or S22) or transmission (S21 or S12). o

Trans

The displayed S-parameter is converted to Z or Y transmission, regardless of whether the S-parameter is reflection (S11 or S22) or transmission (S21 or S12). o

1/S

The displayed S-parameter is converted to 1/S-parameter.

N9912A FieldFox User’s Guide

Multi-Trace Configurations

In NA Mode you can display multiple traces on the FieldFox screen.

A 3-trace configuration. Tr2 is the ACTIVE trace as indicated by the highlighted

Tr 2

Trace Setting Notes

 The Frequency Range, IF BW, Resolution, Average, and Output Power settings are common for all displayed traces.

 All other trace settings, such as measurement, format, and limit lines, are applied individually to the ACTIVE trace in the same manner as when a single trace is present.

 When creating markers, by default a marker is created on ALL traces as shown in the above image. However, they can be created individually by disabling

Coupled Markers. Learn more on page 155.

How to select a multi-trace configuration

 Press Trace 6

 Then

Num Traces

 Then choose from the following:

The default measurements depend on the options that are installed.

x1

1 trace standard configuration

x2

2 traces overlayed on a single graticule

x2H

2 traces on separate horizontal graticules

x3H

3 traces on separate horizontal graticules

X3

3 traces overlayed on a single graticule

x4

4 traces on separate graticules

 How to activate a trace in order to change a setting

NA (Network Analyzer) Mode 41

42

NOTE

 Use the ▲|▼ arrows OR

 Press Trace 6 then select

Trace 1

,

Trace 2

,

Trace 3

, or

Trace 4

, Only traces that are shown can be activated.

How to maximize the viewing of the active trace

 Press System 7

 Then

Full Screen

.

 Press any key to return to the standard display.

Quick Settings

Both CAT and NA Modes allow you to view and change most relevant settings from a single location. All of these settings are discussed in this chapter and, unless otherwise noted, ALL of these settings can also be made using the standard softkey menus.

How to view and change Quick Settings

 Press Meas Setup 4.

 Then

Settings

.

 Press

Next Page

and

Previous Page

to view all settings. If these softkeys are

NOT available, then all available settings fit on one page.

 To change a setting: o

Use the ▲|▼ arrows to highlight a setting. o

Then press

Edit

. The current setting changes to

yellow

. o

Some settings require you to press a softkey to change the value. Otherwise, use the numeric keypad, ▲|▼ arrows, or rotary knob to change the value. o

When finished changing a value, press

Done Edit

.

 Press

Dock Window

to relocate the Settings table to a position relative to the trace window. The Dock Window setting persists through a Preset. Choose from the following: o

Full (Default setting) Only the Settings table is shown on the screen. The trace window is temporarily not shown. o

Left The Settings table is shown to the left of the trace window. o

Bottom The Settings table is shown below the trace window.

 When finished changing ALL settings, press

Done

to save your settings.

Calibration Settings

NA Mode has a page specifically for making settings that pertain to Port

Extensions, including Velocity Factor and Media Type.

Learn more about Port Extensions on page 49.

The N9912A does NOT support Media Type: Waveguide.

N9912A FieldFox User’s Guide

How to view and change Calibration Settings

 Press Meas Setup 4.

 Then

Calibration Settings

 Make these settings in the same manner as Quick Settings in the previous section.

NOTE

Format

Select the display format in which to present measurement results. This setting can be changed at any time without affecting calibration accuracy.

Learn more about Display Formats in the FieldFox Supplemental Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

The marker onscreen readout can be changed to formats other than the display

format. Learn how to set marker format on page 157.

How to select a NA Format

 Press Measure 1.

 Then

Format [current setting]

.

 Then choose from the following: o

Log Magnitude

Displays magnitude in dB o

Linear

Displays positive values only. Y-axis: Unitless (U) for ratioed measurements; Watts (W) for unratioed measurements. o

VSWR

(S11 and Fault Location Only) Displays unitless reflection data. o

Phase

(S11 Only) Displays phase in degrees. The trace ‘wraps’ every 360 degrees, from +180 to –180, for easy scaling. o

Smith

(S11 Only) Displays series resistance and reactance. o

More

then o

Polar

(S11 Only) Displays magnitude and phase of the reflection coefficient. o

Group Delay

(S11 Only). Displays propagation time (in seconds) from the

RF port to the point where it is reflected, and back to the A receiver. The aperture setting is the frequency range/(number of points – 1). Use

Smoothing as the Group Delay aperture. Learn how to set Smoothing on

page 47. Learn more about Group Delay in the FieldFox Supplemental

Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

o

Unwrap Phase

Same as Phase, but without 180 degree wrapping.

NOTE Phase is unwrapped by comparing the phase from one data point to the next. If the phase difference between two data points is greater than 180 degrees, or if the phase of the first data point is greater than 180 degrees from DC, than the phase measurement is probably NOT accurate. To ensure that the phase measurement is accurate, increase the resolution setting. When making a narrowband measurement, reduce the start frequency for the unwrapped phase measurement to ensure the first data point is less than 180 degrees from DC.

NA (Network Analyzer) Mode 43

44

Frequency Range

Set the range of frequencies over which you would like to make measurements.

When the frequency range is changed after a calibration is performed, the cal

becomes interpolated. Learn more on page 65.

How to set Frequency Range

This can be done in two ways:

 Press Freq/Dist

 Then choose from the following:

1.

Start

and

Stop

frequencies – Specify the beginning and end of the sweep.

2.

Center

and

Span

frequencies - Specify the center frequency and span of frequencies (half on either side of center).

 Follow each by entering a value using the numeric keypad, the ▲|▼ arrows, or the rotary knob.

 After using the ▲|▼ arrows or the rotary knob, press Enter. The increment setting of the arrows is based on the current span and can NOT be changed in

NA Mode.

 After using the keypad, select a multiplier key. Learn about multiplier

abbreviations on page 20.

Scale Settings

Adjust the Y-axis scale to see the relevant portions of the data trace. The Y-axis is divided into 10 graticules.

This setting can be changed at any time without affecting calibration accuracy.

How to set Scale

 Press Scale / Amptd.

 Then choose from the following methods:

1.

Autoscale

Automatically adjusts the Y-axis to comfortably fit the Min and

Max amplitude of the trace on the screen.

2.

Autoscale All

Autoscales all of the traces on the screen, useful only for multi-trace configurations.

3. Set Scale, Reference Level, and Reference Position o

Scale

Manually enter a scale per division to view specific areas of the trace. o

Ref Level

Manually set the value of the reference line. Enter a negative value by pressing Run/Hold (+/-) either before or after typing a value. o

Ref Position

Manually set the position of the reference line. Values must be between 0 (TOP line) and 10 (BOTTOM line)

N9912A FieldFox User’s Guide

Scale annotation on the

FieldFox screen

· Reference Line = red arrow

· Ref Level = –40 dB

· Ref Position = 1

· Scale = 2 dB per division

Electrical Delay

Electrical delay is a mathematical function that simulates a variable length of lossless transmission line. Use the electrical delay feature to compensate for the linear phase shift through a device and view only the deviation from linear phase of the device.

You can set the electrical delay independently for each measurement trace. To apply an electrical delay to all measurement traces, use Port Extensions. Learn

how on page 49.

Phase is available only with S11 measurements – NOT S21.

Learn how to set Phase formats on page 42.

How to set Electrical Delay

 Press Scale / Amptd

 Then

More

 Then

Electrical Delay

 Enter a time value using the numeric keypad, the ▲|▼ arrows, or the rotary knob.

 Press a multiplier key. Learn about multiplier abbreviations on page 20.

Electrical Delay can also be set using the Mkr->Delay feature. Learn how on page

161.

Phase Offset

Phase format is available only with S11 measurements. Learn more on page 42.

Phase offset mathematically adjusts the phase measurement by a specified amount, up to 360°. Use this feature in the following ways:

Improve the display of a phase measurement. This is similar to the way you would change the reference level in an amplitude measurement. Change the phase response to center or align the response on the screen.

Emulate a projected phase shift in your measurement. For example, if you know that you need to add a cable and that the length of that cable will add a certain phase shift to your measurement, you can use phase offset to add that amount and simulate the complete device measurement.

You can set the phase offset independently for each measurement trace.

NA (Network Analyzer) Mode 45

46

How to set Phase Offset

 Press Scale / Amptd

 Then

More

 Then

Phase Offset

 Enter a value in degrees using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Press Enter

Averaging

Averaging helps to reduce the effects of random noise on a measurement. You specify the number of measurements to be averaged. The more measurements averaged, the greater the amount of noise reduction. An average counter is shown in the left edge of the screen as Avg <n> where <n> is the number of measurements that are averaged.

Averaging can be set before or after calibration. When set before calibration, each calibration standard is measured <n> times and averaged. More time is needed to perform the calibration, but there will be less noise in the resulting error terms which means that subsequent measurements will also have less noise. In addition, noise is further reduced by continuing to average after calibration.

How to set Averaging

 Press BW 2.

 Then

Average <n>

where <n> is the number of measurements to average.

 Enter a value using the numeric keypad. Enter 1 for NO averaging.

 Press Enter.

 Then

Average Mode

Choose from the following: o

Sweep - Each data point is based on the average of the same data point being measured over <n> consecutive sweeps. The average counter shows the number of previous sweeps that have been averaged together to form the current trace. When the counter reaches the specified count, then a ‘running average’ of the last <n> sweeps is displayed. o

Point - Each data point is measured <n> times and averaged before going to the next data point. On subsequent sweeps, averaging restarts by measuring each data point again <n> times. The average counter is not updated because data is not displayed until all the averages have been applied. o

Point averaging is usually faster than sweep averaging. However, you may need to increase the Point Average count to obtain the same level of noise reduction as with sweep averaging.

 While averaging is in process, press Sweep 3, then

Restart

to restart the averaging at 1.

N9912A FieldFox User’s Guide

IF Bandwidth

The FieldFox converts the received signal from its source to a lower intermediate frequency (IF). The bandwidth of the IF bandpass filter is adjustable. Reducing the IF receiver bandwidth reduces the effect of random noise on a measurement.

However, narrower IF bandwidths cause longer sweep times.

How to set IF BW

 Press BW 2.

 Then

IF BW

 Then choose from the following:

300 Hz | 1 kHz | 3 kHz | 10 kHz | 30 kHz

Smoothing

Trace smoothing averages a number of adjacent data points to smooth the peakto-peak noise values on a displayed trace. The number of adjacent data points that are averaged is known as the smoothing aperture . Aperture is set by specifying a percentage of the X-axis span.

Trace smoothing does NOT significantly increase measurement time.

Smoothing is used in Group Delay measurements, although it can be used with any NA format EXCEPT Polar or Smith Chart. Learn more about NA Mode

formats, including Group Delay, on page 42.

When enabled,

Smo

appears on the FieldFox screen.

How to set Smoothing

 Press BW 2.

 Then

Smoothing ON OFF

 Then

Sm. Aperture

and enter a value between 0 and 25 (percent) using the numeric keypad.

 Press Enter

Single or Continuous Measure

This setting determines whether the FieldFox measures continuously or only once each time the

Single

button is pressed. Use Single to conserve battery power or to allow you to save or analyze a specific measurement.

This setting can be changed at any time without affecting calibration accuracy.

How to set Single or Continuous

 Press Sweep 3.

 Then choose one of the following: o

Single

Automatically sets Continuous OFF and causes FieldFox to make

ONE measurement, then hold for the next Single key press. When a data trace is displayed, the entire trace is measured, then holds. The

Hold

annotation changes to an arrow

-->

while the measurement occurs. o

Continuous

Makes continuous measurements. This is the typical setting when battery power is not critical.

NA (Network Analyzer) Mode 47

48

NOTE

You can also use Run / Hold +/- to toggle between Single and Continuous.

Resolution (Number of Data Points)

Data points are individual measurements that are made and plotted across the Xaxis to form a trace. Select more data points to increase measurement resolution.

However, more data points also takes more time to complete an entire measurement sweep.

When the Resolution is changed after a calibration is performed, the cal becomes

interpolated. Learn more on page 65.

How to set Resolution

 Press Sweep 3.

 Then

Resolution

.

 Then choose from the following:

101 |201 | 401 | 601 | 801 | 1001 | 1601 | 4001 | 10001

.

 Using SCPI, Resolution can be set to ANY number of points between 3 and

10001. See the Programming Guide at www.agilent.com/find/fieldsfoxsupport

Sweep Time

The fastest possible sweep time is always used as the default setting. Use the Min

Swp Time setting to slow the sweep time when measuring long lengths of cable.

Learn more at the FieldFox Supplemental Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

The actual sweep time is shown on the FieldFox screen. See the Screen Tour on

page 19. To increase the sweep time, enter a value that is higher than the actual

sweep time. The increase will not be exactly the amount that you enter, as the actual sweep time is the composite of many factors.

Measurement speed specifications do NOT apply in Temperature Control Mode.

Learn more on page 14.

How to set Sweep Time

 Press Sweep 3.

 Then

Min Swp Time

.

 Enter a value using the numeric keypad.

 Press a multiplier key. Learn about multiplier abbreviations on page 20.

Output Power

Set the power level out of the FieldFox to High, Low, or manually set power level to a value between High and Low.

Generally, the high power setting is used when measuring passive, high-loss devices to place the signal farther from the noise floor. However, for devices that are sensitive to high power levels such as amplifiers, use the Low power setting.

For best measurement accuracy, use the Manual power setting at -15 dBm. After calibration, the power level can be decreased for amplifiers, or increased for higher dynamic range.

N9912A FieldFox User’s Guide

Caution Power Level settings in this mode will NOT change Power Level settings in other modes. To help prevent damage to your DUT, use caution when changing modes with your DUT connected to the FieldFox test ports.

How to set Output Power

Output power is NOT leveled with any of the power settings:

 Press Meas Setup 4.

 Then

Output Power

o

High (Default setting) Sets output power to the maximum achievable power

at all displayed frequencies. Please see the FieldFox Specifications (page 209)

for expected power levels. o

Low Sets output power to approximately –27 dBm, o

Man Set output power to an arbitrary value, o o o

Then press

Nominal Power

Then enter a value using the numeric keypad, the ▲|▼ arrows, or the rotary knob.

Press

Enter

.

System Impedance (Z0)

To accurately view data presented in Smith Chart format, first set the System

Impedance.

Learn how to select Smith Chart format on page 42.

Learn how to make 75 measurements at the FieldFox Supplemental Online

Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

How to set System Impedance

 Press Meas Setup 4.

 Then

Settings

.

 Then scroll to System Z0 and press

Edit

 Then type either 50 or 75 and press

Enter

Port Extensions

Port extensions allow you to electrically move the calibration reference plane on port 1 after you have performed a calibration.

Phase measurements, and therefore Port Extensions, are NOT available on port

2.

Why use Port Extensions

Use port extensions if you are unable to perform a calibration directly at your device because the location is not accessible. Perform a calibration at a convenient place, then use port extensions to compensate for the time delay

(phase shift) to the desired reference plane. On the FieldFox, port extensions does not compensate for the loss of the additional electrical length, nor any mismatch errors beyond the calibration reference plane.

NA (Network Analyzer) Mode 49

50

Also use port extensions if you have already performed a calibration, and then decide that you need to add a length of transmission line in the measurement configuration. Use port extensions to "tell" the FieldFox that you have added the length to a specific port.

With S11, the FieldFox doubles the port extension valued that you enter to account for the additional delay in the forward and reverse directions.

Port extensions and Electrical Delay differ in the following ways:

 Electrical delay is applied to a specific trace.

 Port extensions are applied to specific ports.

Port Extensions and Electrical Delay can be set independently. When both are

set, the delay adds together. Learn more about Electrical Delay on page 45.

How to apply Port Extensions

 Press Meas Setup 4.

 Then

Port Extensions

 Then

Port Extensions ON

 Then

Port1 Extension

 Then enter time value using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Press

Enter

or select a seconds (time) multiplier.

You can also set Port Extensions by pressing Meas Setup 4 then

Calibration

(settings).

While setting Port Extension, the physical length of the extension, at the current

Velocity Factor setting, is visible to the right (red box in above image).

Velocity Factor

The electrical delay or port extension value is entered as delay, or electrical

length, in units of time.

Entering the velocity factor causes the FieldFox to accurately display the equivalent physical length in meters (NOT available in feet) that corresponds to the entered electrical delay.

Velocity factor is the ratio of the velocity of wave propagation in a coaxial cable to the velocity of wave propagation in free space. This velocity depends on the relative permittivity of the cable dielectric (

 r

).

Velocity factor = 1/sqrt(εr)

VF = 0.66 corresponds to wave propagation through a polyethylene dielectric.

VF = 1.0 (default setting) corresponds to wave propagation through free space (a vacuum).

How to set Velocity Factor

 Press Meas Setup 4.

N9912A FieldFox User’s Guide

 Then

Port Extensions

 Then

Velocity Factor

 Then enter a value between 0.1 and 1 using the numeric keypad, then press

Enter

.

You can also set Velocity Factor by pressing Meas Setup 4 then

Calibration

(settings).

S21 Transmission Measurements

An S21 Transmission measurement, available with option 110, is used to measure the loss through a DUT – or cable – over a specified frequency range.

The FieldFox signal source is transmitted out the RF OUT connector, through the

DUT, and into the RF IN connector. Both ends of the DUT must be connected to the FieldFox.

An S21 measurement is exactly the same measurement as “2-Port Insertion Loss” in CAT Mode.

NOTE A Normalization Cal is REQUIRED when making 2-port CAT or NA measurements.

For highest accuracy, when measuring the DUT also attach any cable or adapter that was used in the normalization cal.

How to make an S21 Transmission Measurement

1. Press Mode then

NA

then

S21 Transmission

.

2. Press Freq/Dist and enter

Start

and

Stop

frequency values of the measurement.

3. Press Sweep 3 then select a

Resolution

setting.

4. Press Cal 5 then press

Normalization

. Perform normalization as explained

on page 64.

5. Connect the DUT and view the transmission measurement results.

When measuring very long lengths of cable, it may be necessary to increase the

sweep time. Learn how on page 26. Learn why at the FieldFox Supplemental

Online Help: http://na.tm.agilent.com/fieldfox/help/FieldFox.htm

Increase Dynamic Range

Dynamic range is the difference between maximum input power to the FieldFox receiver (without compressing the receiver), and the minimum measurable power

(noise floor). Measurement accuracy is increased when the DUT response is at least 10 dB above the noise floor. For a measurement to be valid, input signals must be within these boundaries.

NA (Network Analyzer) Mode 51

The following settings will increase the dynamic range of your NA mode measurement.

 Increase Power Level: Press Meas 4 then

Output Power High

 Lower the IFBW: Press BW 2 then

IF BW

 Increase Averaging: Press BW 2 then

Average

The following procedure MAY increase the dynamic range of your NA mode measurement. The results you see will depend on the performance of your DUT.

With an S21 trace active:

1. With RF OUT (port-2) open, press Trace 6 then

Math and Memory

then

Data->Mem

2. Re-connect the DUT.

3. Press

Data Math

then

Data-Mem

52 N9912A FieldFox User’s Guide

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