User Guide: Keysight (Agilent) N9912A FieldFox RF

User Guide: Keysight (Agilent) N9912A FieldFox RF

70

Zero Span Measurements ..................................... 86

Triggering ................................................................ 87

Single/Continuous/Restart .................................. 87

Points ....................................................................... 89

Trace Display States .............................................. 89

Average Type .......................................................... 90

Average Count ........................................................ 91

Detection Method ................................................... 91

Display Line ............................................................ 92

Noise Marker .......................................................... 92

Band/Interval Power Marker ............................... 94

Frequency Counter at Marker ............................. 95

Audio Beep at Marker Power .............................. 95

Channel Measurements ........................................ 96

o

Channel Power o

Occupied Bandwidth o

Adjacent Channel Power Ratio

See Also

Interference Analyzer (Opt 236)

Spectrogram Display .................................... 105

Waterfall Display........................................... 108

Record / Playback ......................................... 109

Optional settings

Markers .................................................................. 152

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

Save Measurement Settings and Results ......... 168

SA Mode Settings

Select SA Mode before making any setting in this chapter.

Because there is no calibration, these settings can be made in any order.

How to select SA Mode

 Press Mode_.

 Then

SA

.

Frequency Range

The X-axis frequency range determines the frequencies that are measured for each sweep. The default Start frequency is 0 Hz. However, the Start frequency can be set as low as –100 MHz. The internal LO of the FieldFox can be seen at 0

Hz, which will mask signals that may be present.

N9912A FieldFox User’s Guide

NOTE Although the start frequency can be set as low as -100 MHz, amplitude accuracy is specified above 2 MHz. Below 2 MHz, frequency accuracy is maintained, but amplitude accuracy is degraded.

The frequency range of the measurement can be changed using the following methods:

 Set Center and Span frequencies

 Set Start and Stop frequencies

 Toggle between Zero and Last selected span

 Set Full Span of the FieldFox

 Using Channel selection. Learn how on page 73.

 Using Marker -> Center (frequency). Learn how on page 156.

How to set Frequency Range

 Press Freq/Dist.

 Then choose from the following: o

Center

and

Freq Span

frequencies. This is the most common method of entering frequency range. Enter the frequency of interest. The Center frequency is at the exact center of the X-axis. The Frequency Span places half of the frequency range on either side of center. When the Center and

Frequency Span values are entered, then the X-axis annotation on the screen shows the Center and Span frequencies. o

Start

and

Stop

frequencies. Start is the beginning of the X-axis and Stop is the end of the X-axis. When the Start and Stop frequencies are entered, then the X-axis annotation on the screen shows the Start and Stop frequencies.

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

 When using the ▲|▼ arrows, press Enter. The increment setting of the arrows is based on the current span. This can be changed in SA Mode. See How to

change frequency step size below.

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

abbreviations on page 20.

Two more ways to change the frequency range

 Press Freq/Dist.

 Then choose from the following: o

Zero/Last Span

Each key press toggles the frequency span between 0 Hz and the last specified frequency span. o

More

o

Then

Full Span

Selects the entire frequency span of the FieldFox. The

Center frequency is set automatically.

How to change frequency step size

When using the ▲|▼ arrows to change any of the frequency settings, the size of the frequency step can be changed.

SA (Spectrum Analyzer) Mode 71

72

 Press Freq/Dist

 Then

More

 Then

CF Step Auto Man

o

Auto

Each press of the ▲|▼ arrows increments or decrements the value by

1/10 th

(one division) of the current frequency span. Note: To change this setting from Man to Auto, press CF Step twice. o

Man

Type a step size value using the numeric keypad, then select a

multiplier key. Learn about multiplier abbreviations on page 20.

Radio Standard

A Radio Standard is a collection of settings that are applied to the FieldFox for specific RF protocols. When a Radio Standard is applied, the FieldFox frequency and channel settings change to that of the standard.

By default, the FieldFox locates the center frequency of the standard in the middle of the screen and sets the frequency span to cover all of the Uplink and

Downlink frequencies. The selected Radio Standard name appears in the center of the screen below the X-axis.

After a Radio Standard has been selected, the frequency range can be changed by

selecting channel numbers rather than frequency. Learn how on page 73.

When a Channel Measurement is selected such as ACPR, other relevant settings will be changed such as Integration BW. Learn more about Radio Standards and

Channel Measurements on page 96.

How to select a Radio Standard

 Press Measure 1 OR Freq/Dist then

More

 Then

Radio Standard

 Then select a standard using the ▲|▼ arrows or rotary knob and press Enter.

Custom Radio Standards

Beginning with Rev A.05.50, your own custom Radio Standards can be imported into the FieldFox. Custom standards are created in *.csv (spreadsheet) format.

A template and instructions for creating your custom Radio Standard is at: www.agilent.com/find/fieldsfoxsupportReference/CustomRadioStandard.htm

Once imported, the *.csv file is stored in the FieldFox \User Data\ folder. The custom Radio Standards are read and presented at the top of the list of internal

Radio Standards.

How to Import and Delete a Custom Radio Standard

First, press Save/Recall and select the

Device

from which the Radio Standard will be read. Most likely this will be USB or SD Card.

 Press Measure 1 OR Freq/Dist then

More

 Then

Radio Standard

 Then

Import Radio Standards

N9912A FieldFox User’s Guide

Note:

 Then select the *.csv file using the ▲|▼ arrows or rotary knob and press

Enter.

 Custom Radio Standards can be removed from the FieldFox by selecting

Measure 1

then

Radio Standard

then

Delete Radio Standard.

 Then select the *.csv file to delete using the ▲|▼ arrows or rotary knob and press Enter.

To overwrite a custom standard that is already uploaded to the FieldFox, you must first delete the *.csv file from the FieldFox, then re-upload the file that contains the standard. A predefined internal standard (such as GSM 450) can

NOT be deleted from the FieldFox.

Channel Selection

After a Radio Standard has been selected, the frequency range can be changed by selecting channel numbers rather than frequency. Once enabled, the channel number is appended to the X-axis frequency range.

How to enable Channel selection

 Press Freq/Dist

 Then

More

 Then

Unit Freq Chan

How to change the Channel Number of the measurement

With Unit =

Chan

the FieldFox will NOT allow you to specify channels outside of the selected Radio Standard.

 Press Freq/Dist

 Then choose from the following: o

Center Channel

Places the center frequency of the specified channel in the middle of the X-axis. o

Start Channel

Places the lowest frequency of the specified channel at the beginning of the X-axis. o

Stop Channel

Places the highest frequency of the specified channel at the end of the X-axis. o

Freq Span

Changes the span of frequencies while the center frequency remains unchanged. o

Follow each of the above settings by entering a value using the numeric keypad or the rotary knob. o

Use the ▲|▼ arrows to increment the channel number by an amount specified by the Channel Step value (see below). o

Then press Enter.

Select either Uplink or Downlink Frequencies

Press

Chan Direction

to toggle between

Uplink

and

Downlink

. If either of these selections is not available, then the selected Radio Standard does not contain those frequencies.

SA (Spectrum Analyzer) Mode 73

Channel number X-axis annotation

74

Dn indicates Downlink frequencies.

Up (not shown) indicates Uplink frequencies

 () indicates that the lowest frequency in the channel (128) is at the left edge of the screen.

(+) indicates that the highest frequency in the channel (130) is at the right edge of the screen.

 When Center Channel or Freq Span is specified, the X-axis shows the Center

Freq (Channel) and Frequency Span.

 When Start or Stop Channel is specified, the X-axis shows the Start Freq

(Channel) and Stop Freq (Channel).

Change Channel Step Size (Optional)

This setting allows you to use the ▲|▼ arrows to increment the channel number by the specified value.

 Press

Channel Step

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

Scale and Units

Adjust the Y-axis scale to see the relevant portions of the data trace.

The Y-axis is divided into 10 graticules. A Reference Level is shown on the screen as a solid horizontal bar that can be placed at any graticule.

When RF Attenuation set to Auto, the RF Attenuation is coupled to Reference

Level.

How to set Scale

Press Scale / Amptd . Then choose from the following:

Scale Type [current setting]

o

Log

Logarithmic scale (default setting). The Y-axis reference line represents the specified absolute Reference Level in the current Unit selection. Y-axis graticules show dB below or above the reference line. o

Lin

Linear scale. The Y-axis reference line represents the specified absolute

Reference Level in the current Unit selection. Y-axis graticules show percent of Reference Level (%) below or above the reference line.

 Manually set Scale, Reference Level, and Reference Position.

N9912A FieldFox User’s Guide

o

Scale

Manually adjust the scale per division to view specific areas of the current trace. Enter a value using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Then press Enter. 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. This can also change the RF Attenuation setting. See Attenuation Control –

Auto. o

Ref Position

Manually set the position of the reference line. Values must be between 0 (TOP line) and 10 (BOTTOM line). Default position is zero (top). o

Press

More

, then

Autoscale

Automatically adjusts the Y-axis to comfortably fit the Min and Max amplitude of the trace on the screen.

How to set Y-axis Units

The Unit setting appears for the reference line, marker readouts, and trigger level. All Unit choices are available in both Log and Linear Scale Types.

The UNIT setting survives Mode Preset, but NOT Preset.

 Press Scale / Amptd, then

More

, then

Unit

 Then choose from the following: o

dBm (default setting), dBmV (dB milli Volts), dBuV (dB microVolts), W

(watts), V (volts), A (amps), dBmA (dB milliAmps), dBuA (dB microAmps).

Antenna correction units are available ONLY by loading or editing an Antenna

file that contains the desired units setting. Learn more on page 78.

External Gain

When using an external amplifier or attenuator, the SA Mode trace amplitude values can be offset to compensate for the effect of the external device. This effectively moves the reference plane of the SA measurement port out to just beyond the external device. For example, when using an external preamp with gain of +10 dB, enter this value for External Gain, and the data trace across the displayed frequency span will be adjusted down by 10 dB.

When RF Atten is set to Auto, you may see a change in the RF Attenuation value.

This is an attempt to measure the signal at top of screen (the Reference Level) without overloading the SA first mixer.

How to set External Gain

 Press Scale/Amptd.

 Then

More

 Then

External Gain

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

(positive for gain; negative for loss). Values less than 5 dB must be typed using the numeric keypad. Then press Enter

ExtGain xx dB is shown at the top of the screen.

SA (Spectrum Analyzer) Mode 75

WARNING

Attenuation Control

Both the RF Attenuation and Pre Amp functions control the power level into the

SA.

When too much power is present at the RF IN port,

ADC Over Range

appears on the FieldFox screen. This does not necessarily mean that damage has occurred, but that the measurement is probably compressed.

When high power levels are present at the RF IN connector, internal attenuation can be switched in to keep the FieldFox receiver from compressing. At extremely high power levels, use external attenuation to protect the internal circuitry from being damaged.

The FieldFox can be damaged with too much power.

RF Damage Level: +27 dBm

DC Damage Level: ±50 VDC

The displayed power level is automatically adjusted for RF Attenuation. As the attenuation value changes, the displayed power level should NOT change.

How to set Attenuation

The default Attenuation setting is 10 dB. This value can be changed from 0 to 31 dB in 1 dB steps.

 Press Scale/Amptd.

 Then

RF Atten Auto Man

.

Auto

RF Attenuation is set by adjusting the Reference Level. As the Reference

Level is lowered, for example from –10 dBm to –30m dB, the FieldFox assumes that you are looking at low-level signals. The RF Attenuation value is automatically lowered in 5 dB steps to allow low-level signals to be viewed.

The RF Attenuation value is never automatically lowered below 5 dB.

Man

RF Attenuation is set manually. Enter a value using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Values less than 5 dB must be typed using the numeric keypad. Then press Enter

#Atten xx dB is shown at the top of the screen. (#) means manual setting.

Preamplifier Control (Opt 235)

When very low-level signals are analyzed, an internal preamplifier can be used to boost the signal level by approximately 22 dB. The gain of the preamp is NOT adjustable. The displayed signal level is automatically adjusted for the increase in system gain.

How to control the Preamp

By default, the preamp is OFF.

 Press Scale/Amptd.

 Then

Preamp ON OFF

The underlined setting is the current setting. When ON,

PA

is shown to the left of the graticules on the display.

76 N9912A FieldFox User’s Guide

Check for Compressed Measurements

Compression occurs when too much power into an amplifier causes it to no longer amplify in a linear manner. When too much power goes into the FieldFox

RF IN connector, the amplifiers in the SA receiver compress and signal power will not be displayed accurately. This can occur even if

ADC Over Range

is not displayed. Increase the RF Attenuation value to prevent the SA receiver from being compressed.

How to Check for a Compressed Measurement

 Using a marker at the signal peak, make note of the signal power level.

 Increase the RF Attenuation level by 5 dB. o

If the signal level does NOT change, then NO compression exists. This indicates that the signal is in the linear region of the FieldFox receiver. o

If the signal level DOES increase, then the receiver was compressed. Set the

RF Attenuation value at the setting when further increases no longer result in an increase in the displayed power level.

Field Strength Measurements

To measure the strength of any signal transmitted through the air, an antenna must be connected to the FieldFox. The Field Strength feature allows you to enter the frequency response of the receiving antenna (the Antenna Factor) and associated cabling, and then have amplitude corrections automatically compensate the displayed trace for that response.

Field Strength Measurements

Trace 1 - Corrected trace with antenna factor. (Antenna = ON, Apply Corr = ON)

Trace 2

- (View) Uncorrected trace (Apply Corr = OFF)

Red Trace

- Current correction factor. See below.

 Learn how to set Y-Axis Units on page 74.

 Use a Band Power marker to measure total power over a range of frequencies.

Learn how on page 162.

SA (Spectrum Analyzer) Mode 77

NOTE

How to select correction for Field Strength measurements

The Antenna and Cable correction data survives a Mode Preset and Preset.

All Correction ON/OFF states survive a Mode Preset, but NOT a Preset.

 Press Scale/Amptd.

 Then

More

 Then

Corrections

 Then choose from the following: o

Apply Corrections ON OFF

Turn ON and OFF correction for all settings o

Antenna ON OFF

Turn ON and OFF Antenna correction. o

Edit/Save/Recall Antennas

Recall or edit an Antenna Correction table. See below. o

Cable ON OFF

Turn ON and OFF Cable correction. o

Edit/Save/Recall Cables

Recall or edit a Cable Correction table. See below. o

View Corrections ON OFF

Turn ON and OFF

Red Trace

- Antenna/Cable corrections.

Using the Antenna/Cable Editor

The Antenna Editor and the Cable Editor menus are identical. Both tables include header information, and a Frequency/Value table.

The FieldFox limits Antenna and Cable correction to a maximum of 90 values.

78

FieldFox Antenna Editor

How to use the Antenna/Cable Editor

 Press

New

then

Yes

to clear all data from the existing Antenna or Cable table and reset header information to default settings.

 Then

Edit Antenna

or

Edit Cable

to open the Antenna / Cable Editor.

 Then use the ▲|▼ arrows to select a field, o

When editing Header information, press

Edit

then modify the selected field using the FieldFox labeler.

N9912A FieldFox User’s Guide

o

When editing Frequency/Value pairs, enter numbers using the numeric keypad, and a frequency suffix when necessary. Then

Enter

. Positive Values are interpreted as LOSS for both Cable Loss and Antenna Gain Factor.

Learn more about “How the Freq/Value pairs are applied” below.

 Optionally choose from the following: o

Previous / Next Page

Quickly scrolls through pages of Freq/Value data. o

Add Data

Add a blank Freq/Value pair to the table, o

Delete/Clear

then: o

Delete Line

Remove the selected Freq/Value pair from the table. o

Clear All

then

Yes

Remove all Freq/Value pairs from the table and resets header information to default settings.

When the table edits are complete

 Press

Done

to closes the Antenna/Cable Editor.

 Press

Save Antenna

or

Save Cable

to saves your changes to the specified

Storage Device. Enter a filename using the FieldFox labeler (learn how on page

168). Learn more about Antenna and Cable files below.

 Press

Recall Antenna

or

Recall Cable

to load an Antenna or Cable file from the specified Storage Device.

Storage Device

Changes the device used to save or recall files. Choose from

Internal (default setting), USB (must be connected) or SD card. This is a different setting from the Save/Recall Storage Device setting.

About the Antenna/Cable header fields

Description: Enter a description for the antenna or cable correction table. This is NOT the filename used to save the file.

Antenna Unit: Units in which the measurement will be displayed. Select

NONE (default setting) to select from standard SA Units on the Scale menu.

Learn how on page 74.

Choose from: dB μV/m - (dB micro Volts per meter), dB μA/m - (dB micro

Amps per meter), dBG (gauss), dBpT (tesla).

Freq Interpolation: Set to LINear and can NOT be edited.

About the Freq/Value pairs

 Positive Values are interpreted as LOSS for both Cable Loss and Antenna Gain

Factor.

 When one Freq/Value pair is entered, that correction value is applied to the entire displayed frequency span.

 When two or more Freq/Value pairs are entered, the data points between the lowest and highest frequencies are corrected. Linear interpolation is applied between frequencies when necessary.

About Antenna and Cable files

 Cable files are saved and recalled from the Cables folder.

SA (Spectrum Analyzer) Mode 79

 Antenna files are saved and recalled from the Antenna folder.

 If the folder does not already exist on a USB or SD card, it is created automatically before storing the file.

 All SA Mode Antenna and Cable files are saved and recalled as *.csv files, which allows them to also be read by spreadsheet programs.

 The FieldFox can also read *.ANT (Antenna) files that were created from older

Agilent Spectrum Analyzers.

 Data Link does NOT support the SA Mode cable or antenna (*.csv or *.ANT) files. Learn more about Data Link software at: www.agilent.com/find/fieldfoxsupport

How to create a Cable file from an S21 (NA mode) measurement

1. Measure the S21 of a cable. Learn how in NA Mode on page 51.

2. Use Manage Folders to change the active folder to CABLES. Learn how to

manage folders on page 173.

3. Save the measurement as a *.csv file. Learn how on page 170.

4. Recall the *.csv file for correction.

Tune & Listen (AM/FM)

The Tune & Listen feature can be used to identify an interfering AM or FM signal.

The demodulated AM or FM signal can be heard through the internal speaker or through headphones using the 3.5 mm jack located on the FieldFox side panel.

The Tune & Listen tuner is separate from the SA display. This allows you to listen to one frequency while displaying a different range of frequencies. The

Tune & Listen measurement alternates between normal SA sweeps for the display and performing audio demodulation at the Tune Frequency. See the

Listen Time setting for more information.

80

Tune & Listen ON with Tune Frequency indicated by a vertical bar (highlighted).

N9912A FieldFox User’s Guide

Tip

How to select Tune & Listen

 Press Measure 1

 Then

Tune & Listen

 Then choose a demodulation type. Select a setting based on the type of interfering signal you suspect is being broadcast. o

None

Turns Tune & Listen OFF o

AM

Amplitude Modulation o

FM Narrow

Frequency Modulation; Narrow bandwidth. Choose when interfering transmission consist of voice or data. o

FM Wide

Frequency Modulation; Wide bandwidth. Choose for high quality music transmissions of FM broadcast radio.

Tune Frequency

The Tune & Listen tuner is separate from the SA display. This allows you to listen to one frequency while displaying a different range of frequencies.

Set the Tune Frequency using one of three methods:

1. Selecting Preset, Mode Preset, or Meas Preset sets Tune Frequency to 3.0 GHz.

2. Specify Tune Frequency:

 Press Meas Setup 4

 Then

Tune Freq

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

Then select a multiplier key. Learn about multiplier abbreviations on page 20.

3. Using Mkr->Tune Freq

 Create a normal marker at the frequency of interest. Learn how on page 152.

 Press Mkr->/Tools

 Then

Mkr->Tune Freq

to change the Tune Frequency to that of the marker.

To improve sound quality, try increasing power by reducing the Attenuation

setting and, if available, turn ON the Preamplifier. Learn how on page 75.

Listen Time

While Tune & Listen is actively demodulating a signal, the SA does not sweep and update the display. Listen Time sets the amount of time that the FieldFox demodulates, then stops to perform a single sweep and update the display, then again demodulates.

To select Listen Time:

 Press Meas Setup 4

 Then

Listen Time

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

Then select a multiplier key. Learn about multiplier abbreviations on page 20.

Volume Control

To increase or decrease the Volume of the demodulated signal:

SA (Spectrum Analyzer) Mode 81

 Press Meas Setup 4

 Then

Volume

 Enter a value in percent between 0 and 100 (loudest) using the numeric keypad, ▲|▼ arrows, or the rotary knob.

 Volume can also be changed and easily muted from the System menu. Learn

more on page 177.

Demod ON and OFF

To quickly stop the audio demodulation and perform only the normal SA sweeps, select the following:

 Press Meas Setup 4

 Then

Demod ON OFF

Independent Source/Tracking Generator

A tracking generator, a popular option with Spectrum Analyzers, is a source which always tracks the SA receiver.

Like a traditional tracking generator, the Independent Source feature can set the internal FieldFox source to track the SA receiver frequency range. It can also set the internal source to a CW frequency that is independent of the SA frequency.

Independent Source can be enabled ONLY when the FieldFox is in SA mode.

To view the internal source, you must connect a cable or device between the RF

OUT connector and the RF IN connector.

NOTES The FieldFox output power is approximate and NOT flat across the frequency range.

How to make Independent Source Settings

 Press Measure 1.

 Then

Source

Source Enable ON OFF

o

ON

Turns ON the internal source. o

OFF

Turns OFF the internal source.

Source Mode

Choose from the following: o

Tracking

The internal source sweeps simultaneously (tracks) with the SA receiver over the displayed frequency range, emulating NA mode measurements.

Src

is annotated on the screen. o

CW

The source is set to a CW frequency independent from the SA setting.

Srcw

is annotated on the screen. o

Coupled CW

The source is set to a CW frequency, but that frequency

“tracks” the SA receiver Center Frequency setting. Therefore, the signal always appears at center of the display.

Srcp

is annotated on the screen.

82 N9912A FieldFox User’s Guide

NOTE

NOTE

Normalize ON OFF

With Source Enable ON and Source Mode = Tracking,

Normalize ON stores the current measurement trace into Trace 4 in View state as a reference trace. All subsequent trace measurements subtract out this

Trace 4 reference trace, and therefore become relative to it. This causes measurements to appear near the ZERO absolute level on the y-axis (0 dBm if

UNIT is set to dBm).

SrcN

is annotated on the screen. Normalize is automatically turned OFF when the frequency range or Resolution is changed.

Learn more about Trace Display States on page 89.

Source Atten

Sets the source attenuation from 0 to 31 dB in 1 dB steps. This effectively sets the source output power. While changing the source attenuation, the approximate Nominal Output power is annotated to the right of the active entry setting.

Source CW Freq

Sets the CW frequency that is used when Source Mode is set to CW.

By default, the source output will turn off momentarily at the end of each SA sweep. To cause the source to stay ON at the end of each sweep, turn battery

saver OFF. (Learn about Battery Saver on page 182.)

 Press System 7

 Then

Preferences

 Then

Battery Saver OFF

Resolution Bandwidth (Res BW)

In SA Mode, the Res BW provides the ability to resolve, or see closely spaced signals. The narrower (lower) the Res BW, the better the spectrum analyzer can resolve signals. In addition, as the Res BW is narrowed, less noise is measured by the spectrum analyzer ADC and the noise floor on the display lowers as a result.

This allows low level signals to be seen and measured. However, as the Res BW is narrowed, the sweep speed becomes slower.

How to set Res BW

Press BW 2.

 Then

Res BW Auto | Man

. o

Auto

Res BW is coupled to the frequency span. As the frequency span is narrowed, the Res BW is also narrowed providing increased ability to resolve signals.

To change this setting from Man to Auto, press Res BW twice. o

Man

Enter a Res BW value using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Then press a multiplier if necessary or press Enter .

The current Res BW setting is shown at the bottom of the screen.

#Res BW x.xx XHz ( # ) means manual setting.

This setting could impact the accuracy of the measurement. See Specifications on

page 209.

The Res BW setting also affects the Sweep Type setting. Learn how on page 84

SA (Spectrum Analyzer) Mode 83

84

NOTE

Video Bandwidth (Video BW)

Video BW is a smoothing operation that is performed after measurement data is acquired. The trace data is effectively smoothed so that the average power level of the displayed noise is the same, but the peaks and valleys of adjacent data points are smoothed together. More smoothing occurs as the Video BW is set lower. However, as the Video BW is narrowed, the sweep speed becomes slower.

How to set VBW

Press BW 2.

 Then

Video BW Auto Man

. o

Auto

Couples Video BW to the ResBW in a 1-to-1 ratio. o

Man

Enter a Video BW value using the numeric keypad, the ▲|▼ arrows, or the rotary knob. Then press a multiplier if necessary or press Enter.

To change this setting from Man to Auto, press Video BW twice.

The current Video BW setting is shown at the bottom of the screen.

# VBW x.xx XHz ( # ) means manual setting.

When the Res BW/Video BW ratio exceeds 10,000, a

Meas UNCAL

warning may appear to indicate that the Video BW filter has reached the maximum capacity for averaging.

In Zero Span, the maximum Res BW/ Video BW ratio is 100.

Sweep Type

In SA mode, the FieldFox uses two sweep types to process inputs signals. The sweep type that is currently being used (FFT or Step) is displayed in the lowerleft corner of the FieldFox screen.

For a more comprehensive tutorial, see Spectrum Analysis Basics (App Note 150) at http://cp.literature.agilent.com/litweb/pdf/5952-0292.pdf

How to set Sweep Type

Press BW 2.

Then

Advanced

 Then

Sweep Type Auto FFT Step

o

Auto

The FieldFox selects the most efficient sweep type based on the Res

BW. When Res BW is set to 200 kHz and below, FFT sweep type is selected.

Above 200 kHz, and Step sweep type is being performed. o

FFT

The FieldFox uses FFT sweep type regardless of the Res BW. o

Step

The FieldFox uses Step sweep type regardless of the Res BW. This is useful for capturing impulsive noise that may be generated from nearby electrical equipment.

Sweep Acquisition

When set to Auto, Sweep Acquisition is set to the minimum value required with the current settings in order to achieve amplitude accuracy when measuring CW signals yielding the fastest sweep update rate.

N9912A FieldFox User’s Guide

However, you can adjust this setting in order to increase the probability of intercepting and viewing pulsed RF signals.

For example, with SwpAcquisition set to Auto a pulsed GSM signal is NOT visible on the FieldFox screen, as shown in a blue trace in the following image.

However, while watching the trace, increase the SwpAcquisition value until the pulse spectrum rises out of the noise and reaches its maximum level. Increasing the SwpAcquisition value beyond this point only slows the update rate (increases the actual Sweep time readout) but does not improve measurement quality.

NOTE

A GSM signal in a framed data format; timeslot zero ON; all others OFF;

PRF = 218Hz, Duty Cycle = 12.5%. The pulsed signal becomes visible on every sweep update with SwpAcquisition = 50.

How to set Sweep Acquisition Parameter

 Press Sweep 3.

 Then

SwpAcquistion Auto Man

.

 Then choose from the following: o

Auto

Sweep is set to the fastest sweep possible with the current settings. o

Man

Enter a relative acquisition value between 1 and 5000, where: o 1 = Fastest sweep possible o 5,000 = Slowest sweep possible o # is shown in front of the actual sweep time to indicate a manual setting.

Some Detector and Video Bandwidth settings will raise the Auto Sweep

Acquisition value greater than 1. In these cases, manually setting Sweep

Acquisition lower than the Auto value may have NO effect.

Measurement speed specifications do NOT apply in Temperature Control Mode.

Learn more on page 14.

Learn more about SA mode SwpAcquisition time in the Supplemental Online

Help:

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

SA (Spectrum Analyzer) Mode 85

Very Long Sweep Times

Two primary settings are responsible for the sweep time: Res BW and

SwAcquisition.

 When the sweep time exceeds 1200 seconds (20 minutes), an informational message:

Alert:

Very long sweep in progress…

is annotated on the screen for the duration of the sweep.

 When the sweep time exceeds 4000 seconds (about 1 hour),

Meas UNCAL

is annotated on the screen. Accuracy cannot be guaranteed.

Zero Span Measurements

When setting the frequency span to Zero, there is NO spectrum of frequencies to display, so the X-axis units becomes Time. The SA becomes like a tunable oscilloscope, with the center frequency being the frequency of interest. This capability is useful for analyzing modulation characteristics, such as pulsed measurements.

86

GSM signal, framed data format, timeslot 0 and 3 on. Sweep Time is set to approximately the frame interval. Press Single several times until the waveform section of interest is viewable and stable. Then markers can be used to measure the timeslot width and interval as shown.

How to set Zero Span

 Set

Center

to the frequency of interest o then set

Span

to 0 Hz o or select

Zero/Last Span

. Each key press toggles the frequency span between 0 Hz and the last specified frequency span.

How to change Sweep Time in Zero Span.

 Press Sweep 3

N9912A FieldFox User’s Guide

NOTE

 Then

SweepTime

 Enter a value using the numeric keypad.

 Then select a multiplier key. Learn about multiplier abbreviations on page 20.

When the sweep time is longer than can be acquired with the current available memory,

Meas UNCAL

is displayed on the screen. Learn more on page 94.

Four times the amount of memory is available with the FieldFox A.04.00 release, allowing longer sweep times in Zero Span.

Triggering

External and Video triggering allows you to start a FieldFox sweep which is initiated by an external event such as a signal burst.

External and Video triggering can be used in either Zero Span (time domain) or frequency span measurements. However, Video triggering in frequency domain sweeps is limited to cases where Res BW is less than or equal to 200 kHz.

FFT Gating is available for non-zero span measurements. Learn more about FFT

Gating at: www.agilent.com/find/fieldsfoxsupportFieldFox.htm

The following Trigger Settings are available ONLY when performing an FFT

sweep or when in Zero Span. Learn more about FFT on page 84 . Learn more

about Zero Span on page 86.

Trigger Type

 Press Sweep 3

 Then

Trigger Settings

 Then

Trig Type

 Then choose from the following: o

Free Run

Triggering is provided by the FieldFox internal circuitry. A new sweep begins when the previous sweep ends. o

External

A sweep is triggered on an external TTL signal at the EXT

TRIG/EXT REF BNC connector on the FieldFox top panel. Choose to trigger on the rising slope at about 1.7 V or on the falling slope at about 1.0 V using the Trigger Slope setting (below). o

Video

A sweep is triggered on a signal at the RF IN connector when the amplitude of the incoming signal exceeds the settable Trigger Level. In frequency domain sweeps, Res BW must be set to 200 kHz or less. This setting is called Video trigger because the signal that initiates the trigger appears on the display.

Trigger Slope

Trigger Slope determines which edge of an External or Video trigger signal initiates a sweep.

 Press Sweep 3

 Then

Trigger Settings

 Then

Trig Slope

 Then choose from the following:

SA (Spectrum Analyzer) Mode 87

88

o

Pos

Sweep is triggered by the rising (positive) edge of signal. o

Neg

Sweep is triggered by the falling (negative) edge of signal.

Trigger Delay

After a valid External or Video trigger signal is received, the sweep begins after the specified Trigger Delay time. Only positive values are allowed.

To see the rising edge of a repetitive signal which is triggered on that edge, use trigger delay to clearly view the subsequent signal one period later.

 Press Sweep 3

 Then

Trigger Settings

 Then

Trig Delay

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

 Then select a multiplier key or press Enter. Learn about multiplier

abbreviations on page 20.

Trigger Level

Used with Video triggering, an incoming signal with this amplitude or higher (for positive slope) will initiate a sweep. The Units depend on the Scale Type setting:

(Log or Linear). Learn more on page 74.

The Video Trigger Level is a time domain (Zero Span) signal level comparison.

Therefore, the sweep will trigger close to the displayed level in Zero Span measurements. In frequency span measurements, processing can cause broadband signal energy to display at lower power levels than the originating time domain signal. Therefore, you may need to set the trigger level higher than the displayed level.

 Press Sweep 3

 Then

Trigger Settings

 Then

Trig Level

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

 Then select a multiplier key or press Enter. Learn about multiplier

abbreviations on page 20.

Auto Trigger Time

If an External or Video trigger signal is not received before the specified Auto

Trig Time, a sweep will occur automatically.

Enter 0 to set Auto Trigger OFF. When Auto Trigger is OFF, the FieldFox does

NOT sweep unless a valid External or Video trigger signal is received.

 Press Sweep 3

 Then

Trigger Settings

 Then

AutoTrig Time [current setting]

 Enter a Auto Trig Time using the numeric keypad.

 Then select a multiplier key. Learn about multiplier abbreviations on page 20.

N9912A FieldFox User’s Guide

NOTE

Single / Continuous / Restart

The following behavior is unique to SA Mode.

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

Single

or Run / Hold +/- button is pressed. Use Hold /

Single or to conserve battery power or to allow you to save or analyze a specific trace.

How to set Single, Continuous, or Restart

 Press Sweep 3.

 Then choose one of the following: o

Continuous

o

ON

Causes the SA to make continuous sweeps. This is the typical setting for making measurements. Each Run / Hold +/- press causes the SA to toggle between continuous sweep and Hold. o

OFF

Causes the SA to Hold. Each Run / Hold +/- or

Single

press causes the SA to make ONE sweep, then Hold. The

Hold

annotation changes to an arrow

-->

while the sweep occurs. o

Single

Automatically sets Continuous OFF and causes the SA to make ONE sweep, then Hold. o

Restart

Resets the Average counter to 1. When in Hold, causes the SA to make ONE sweep, then Hold. The Average counter has is used with MaxHold

and MinHold Trace States. Learn more on page 91.

Points

Points is the number of measured frequencies the X-axis. The higher number of data points, the better the ability to resolve closely spaced signals and the slower the sweep speed.

How to set number of points

 Press Sweep 3

 Then

Points [current setting]

 Then choose from:

101 | 201 | 401 | 601 | 801 | 1001

Trace Display States

In SA Mode you can display up to four of the following types of trace states. All

SA settings are applied to all displayed traces.

A color-coded legend for displayed traces is visible in the left pane of the SA

Mode screen:

W = Clear/Write; M = MaxHold; m = MinHold; A = Average; V = View

How to display Trace States

 Press Trace 6.

 Then

Trace 1,2,3,4

repeatedly to select a trace number to display. Traces are displayed in the following colors:

SA (Spectrum Analyzer) Mode 89

90

NOTE o

Trace 1 – Yellow Trace 2 – Blue o

Trace 3 – Orange Trace 4 – Red

 Then

State [current setting]

.

 Then choose from the following Trace States: o

Clr /Wr

(Clear/Write) Displays the actual measured data for each sweep. o

MaxHold

Displays the maximum response of the input signal at each data

point over multiple sweeps. See also Average Count on page 91.

o

MinHold

Displays the minimum response of the input signal at each data

point over multiple sweeps. See also Average Count on page 91.

o

Average

Each data point is averaged over multiple sweeps as set by the

Average Count setting. Learn more in following Average Type section. o

View

Displays and then holds the last complete measurement trace on the screen. o

Blank

Displays no trace.

 Press

Default All

to return all traces to their default settings: Trace 1

(Clear/Write); all other traces (Blank).

Trace 4 data WILL be overwritten by the FieldFox when using the Independent

Source Normalize feature (page 80) or using Field Strength antenna or cable

corrections (page 77).

Average Type

In SA Mode, there are four different processes in which Averaging is performed:

 Average Traces – Learn more on page 89.

 Detection Method Averaging – Learn more on page 91.

 Noise Marker Averaging - Learn more on page 93.

 Video BW filtering (for non-Zero Span measurements) - Learn more on page

84.

There are two types of mathematical averaging that can be performed. Select

ONE of these types and it is used for all of the above averaging processes.

How to set Average Type

 Press Meas Setup 4

 Then choose from the following: o

Auto

- The FieldFox chooses the most appropriate type of averaging for the current settings. When Detection Method is set to Average, a Noise Marker is present, or a Channel measurement is active, then Power Average is

ALWAYS selected. Otherwise, Log Average is selected. o

Log

Averaging – Best for displaying Trace Averaging. LgAv is shown on the left side of the FieldFox screen when selected.

N9912A FieldFox User’s Guide

o

Power

(Linear) Averaging – Best for measuring true power levels. Used in

Detection Average and Noise Marker Average. Mathematically, trace noise is

2.5 dB higher than when using Log Average. PAvg is shown on the left side of the FieldFox screen when selected.

Average Count

The Average Count setting is used mainly with the Average Trace State described above. In this Trace State, the Average Count setting determines the number of sweeps to average. The higher the average count, the greater the amount of noise reduction.

When Trace (display) State is set to Average, MaxHold, or MinHold, the average counter is shown in the left edge of the screen below the Average Type.

For all three of these Trace States, when Sweep 3

Continuous

is set to OFF, press

Restart

to reset the sweep count to 1, perform <n> sweeps, then return to

Hold

.

How to set Average Count

 Press Meas Setup 4

 Then

Average Count

 Enter a value from 1 to 10,000 using the numeric keypad, the ▲|▼ arrows, or the rotary knob.

 Press Enter

Detection Method

In SA Mode, the X-axis is comprised of data points, also known as “buckets”. The number of data points is specified using the Resolution setting. Learn how on

page 89.

Regardless of how many data points are across the X-axis, each data point must represent what has occurred over some frequency range and time interval.

From the frequency span of the measurement, the span of each data point is calculated as (frequency span / (data points-1)). The detection method allows you to choose how the measurements in each bucket are displayed.

One bucket showing Positive peak, Sample, and Negative peak Detection methods.

SA (Spectrum Analyzer) Mode 91

How to set Detection Method

The current Detection method is labeled on the left edge of the screen. When a method is selected manually, a # precedes the label. For example: # Nrm means that Normal was selected from the softkeys.

 Press Trace__6

 Then

Detector

 Then choose from the following

: o

Auto

Displays the most appropriate Detection method based on other settings. [ # is NOT shown] o

Normal

[Nrm] Provides a better visual display of random noise than

Positive peak and avoids the missed-signal problem of the Sample Mode.

Should the signal both rise and fall within the bucket interval, then the algorithm classifies the signal as noise. An odd-numbered data point displays the maximum value encountered during its bucket. An evennumbered data point displays the minimum value encountered during its bucket. If the signal is NOT classified as noise (does NOT rise and fall) then

Normal is equivalent to Positive Peak. o

Positive Peak

[Pk] Displays the maximum value of all the measurements in each bucket. This setting ensures that no signal is missed. However, it is not a good representation of the random noise in each bucket. o

Negative Peak

[NPk] Displays the minimum value of all the measurements in each bucket. o

Sample

[Smp] Displays the center measurement of all the measurements in each bucket. This setting gives a good representation of the random noise in each bucket. However, it does not ensure that all signals are represented. o

Average

[#RMS] Displays the Root Mean Squared (RMS) average power of all the measurements in each bucket. This is the preferred method when

making power measurements. Learn more on page 161.

Display Line

A display line is a simple, horizontal line that can be placed at any amplitude level on the SA screen. Use a display line as mental guide for visual feedback. A display line is similar to a Limit Line, except that no PASS/FAIL testing occurs.

A display line is easier to create than a Limit Line. Learn about Limit lines on

page 162.

92 N9912A FieldFox User’s Guide

Display line with annotation

How to create and move a Display Line

 Press Limit __8

 Then

Display Line OFF ON

 Then enter a Y-axis value using the ▲|▼ arrows or the rotary knob, then press

Enter

. Or enter a value using the numeric keypad and press a suffix key or press Enter.

Noise Marker

For comparison purposes, electronic noise measurements are often displayed as though the measurement was made in a 1 Hz Res BW. However, making an actual measurement at a 1 Hz Res BW is impossible, and at 10 Hz, extremely slow.

A Noise Marker, unique to SA Mode, mathematically calculates the noise measurement as though it were made using a 1 Hz bandwidth.

Several data points (or ‘buckets’) are averaged together to calculate the Noise

Marker readout. To accurately measure noise, the Noise Marker should NOT be placed on, or too close to, a signal. The distance from a signal depends on several factors. To know if an accurate reading is being made, move the Noise Marker until consistent measurements are displayed in adjacent data points.

In addition, when a Noise Marker is displayed, the Detection method is automatically switched to Average and

PAvg

is shown on the FieldFox screen.

This occurs only when Detection is set to Auto. Learn more on page 91.

With a Noise Marker present, the Res BW can be changed and the displayed noise floor will also change, but the Noise Marker readout will remain about the same.

Noise Markers can be used like regular markers. A Noise Marker is distinguished from a regular marker by (1Hz) after the marker readout value. Learn more about

regular markers on page 152.

How to measure Noise with a marker

 Press Marker to create or select a Normal or Delta marker to use to measure

Noise.

SA (Spectrum Analyzer) Mode 93

94

 Then

More

.

 Then

Marker Function

 Then

Noise ON OFF

.

Band/Interval Power Marker

A Band/Interval Power marker, unique to SA Mode, accumulates the power that is measured over several adjacent data points (or ‘buckets’). The range of buckets being measured is displayed with vertical posts around the marker. This Band

Span value is selectable.

This feature is very similar to a channel power measurement (page 97).

When the frequency span is set to Zero span, the marker is referred to as an

Interval marker because it averages power over a specific time interval. In this case the range is specified as the Interval Span. Learn more about Zero span

measurements on page 86.

If the Detection method and Averaging type are set to Auto when you enable a

Band/Interval Power marker, the Detection method will change to Average

(RMS) and Averaging type will change to Power average. Other Detection methods or Averaging type settings will usually cause measurement inaccuracy.

Learn more about Detection method on page 91, and Averaging Type on page 90.

Summary:

 In Zero span, an Interval Power Marker yields the average power over the specified time interval.

 In non-Zero span, a Band Power Marker yields the total power over the specified frequency range.

How to measure Band/Interval Power with a marker

 Press Marker to create or select a Normal or Delta marker to use to measure

Band/Interval Power.

 Then press

More

 Then

Marker Function

 Then

Band/Int Power

 Then

Band (or Interval) Span

 Then choose from the following: o

Auto

Measures power over 5% of the displayed span, or ½ graticules. The

Band Span is automatically updated to remain at 5% when you change the frequency span. o

Man

Enter a frequency or time value using the ▲|▼ arrows or the rotary knob, then press Enter. Or enter a value using the numeric keypad and select a frequency or time suffix. The Band Span remains at the frequency or time value that you set as the span changes.

N9912A FieldFox User’s Guide

Frequency Counter at Marker

Available in SA Mode ONLY. Use any existing marker to make highly-accurate frequency counter readings. For highest accuracy, lock the FieldFox to a stable

external frequency reference. Learn how on page 186.

When Frequency Counter is ON, the FieldFox uses background sweeps to zoom on the signal, measure the signal peak with 1 Hz resolution, and display the frequency of the signal peak in the marker annotation area. The marker does not move to the signal peak.

When Freq Counter is ON, measurement sweeps are considerably slower.

How to use Frequency Counter

 Press Marker.

 Press Normal, Delta, or Peak, or select an existing marker to use as a frequency counter.

 Locate the marker somewhere on a CW signal. It does NOT have to be on the peak.

 Then

More

 Then

Freq Count ON

 With Freq Count ON, you can scroll through the existing markers that are located on a discrete CW signal, and read the frequency of the signal peak.

However, each frequency count update requires another sweep. If the FieldFox is in HOLD, press

Single

to update the frequency count results.

Audio Beep at Marker Power

When enabled, the Audio Beep feature emits a repetitive beep sound which varies in tone pitch and repetition rate to indicate the relative power level of the active marker. The highest tone pitch and fastest beep rate occurs when the marker Y-axis position is at the top of the display. Conversely, the lowest pitch and repetition rate occurs at the bottom of the display. Therefore, it is important to scale the signals that you intend to measure between the top and bottom of the

screen. Learn more about Scale on page 74.

Audio Beep can be used with any marker type or function, including

Band/Interval Power. Learn more on page 94.

How to use Audio Beep

 Press Marker

 Optionally, press

Marker 1 2 3 4 5 6

to select an existing marker to use with

Audio Beep. A marker will be created if one does not already exist.

 Then

More

 Then

Marker Function

 Then

Audio Beep ON OFF

Audio Beep does NOT beep when the FieldFox is in Hold mode.

While Audio Beep is ON, press

Marker 1 2 3 4 5 6

to toggle Audio Beep through the existing markers.

SA (Spectrum Analyzer) Mode 95

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