Chapter 7 SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)


 

To better reflect the enhancements implemented during the alignment process, for firmware versions >A.10.15 “IF Flatness Alignment” is now referred to as “Channel Equalization” or “Channel Equalization Alignment” (ChanEQ Alignment).

 

SA Mode measures signals at the SA RF IN connector.

 

SA Mode measurements require NO calibration.

 

For a comprehensive SA mode tutorial, see Spectrum Analysis Basics (App Note 150) at https://www.keysight.com/us/en/assets/7018-06714/application-notes/5952-0292.pdf

 

For information on using the FieldFox Remote Viewer which enables you to view the FieldFox from your iOS device, refer to https://www.keysight.com/us/en/assets/7018-04070/application-notes/5991-2938.pdf.

 

Figure 7-1 SA Display with Markers

The graphic above shows an SA display with markers.

Carrier with 5 kHz frequency modulation and deviation of 1 kHz.

 

In this Chapter

“Frequency Range”

“Baseband (N99xxC-Series FieldFox Models Only with Option 350 RTSA or Option 233 SA–Mixed Models)”

“Radio Standard”

“Channel Selection”

“Reverse Swap”

“Scale and Units”

“External Gain”

“Attenuation Control”

“Preamplifier Control (Opt 235)”

“Check for Compressed Measurements”

“Field Strength Measurements”

“Using the Antenna/Cable Editor”

“Source Tracking Offset and Offset Reversal”

“Tune & Listen (AM/FM)”

“Analog Demod (Requires CPU2)”

“Independent Source/Tracking Generator”

“Resolution Bandwidth (Res BW)”

“Video Bandwidth (Video BW)”

“AF RBW (Audio-Frequency Resolution BW)”

“Sweep Type”

“IF Output”

“Sweep Acquisition”

“Very Long Sweep Times”

“Zero Span Measurements”

“Triggering (SA)”

“FFT Gating (Opt 238)”

“Single / Continuous / Restart”

“Points”

“Trace Display States (SA Mode)”

“Average Type”

“Average Count”

“Alignments”

“RF Burst Amplitude Alignment”

“Detection Method”

“Display Line”

“Power Spectral Density (PSD) Function (SA Mode Only)”

“Logarithmic X-axis Limit Line Interpolation (EMI and SA modes Only)”

“Noise Marker”

“Band/Interval Power Marker”

“Frequency Counter at Marker”

“Audio Beep at Marker Power”

“Meas UNCAL Error”

“Old Data Indicator (*)”

“Radio Standards and Channel Measurements”

“Measurement Preset”

“Averaging”

“Traces”

“Channel Power (CHP)”

“How to Set Up EMF Settings (Requires EMF (Option 358), GPS (Option 307), and SA Mode (Option 233–Mixed Analyzers))”

“Spectrum Emission Mask (SEM) — (SA Mode Only)”

“IQ Analysis (Requires Option 351 IQ Analyzer and Option 353 IQ Streaming, SA Mode Only)”

“Effective Isotropic Radiated Power (EIRP) – (SA Mode Only)”

 

See also

Interference Analyzer:

 Refer to the section “Record/Playback (SA Option)" in Chapter 18 Interference Analyzer chapter, in the C-Series N9915-90020 (Unabridged) User's Guide.

Refer to the section “Waterfall Display” in Chapter 18 Interference Analyzer chapter, in the C-Series N9915-90020 (Unabridged) User's Guide.

Refer to the section “Spectrogram Display (SA Option)" in Chapter 18 Interference Analyzer chapter, in the C-Series N9915-90020 (Unabridged) User's Guide.

 

 

Optional Settings:

“All about Markers”

“All about Limit Lines”

“Saving and Recalling Files”

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

  1. Press Mode
  2. 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.

 


 

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

 

The FieldFox can be used with an OML frequency extender. Refer to “Utilities”, the FieldFox Configuration Guide EN, and to “Contacting Keysight”.

 

Available ONLY with Opt. 209 and while in Step sweep, SA mode allows reverse sweeps. This means the Start frequency can be higher than the Stop frequency. In addition, the Reverse Swap feature can be used to quickly reverse the Start and Stop frequencies. Learn how in "Reverse_Swap".

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

How to set Frequency Range

  1. Press Freq/Dist.
  2. Then choose from the following:

 


 

Integration BW (IBW) is coupled to the Frequency Span setting. Frequency Span is 50% wider than the IBW (e.g., if the IBW value is 1 MHz, then the Frequency Span value is 1.5 MHz).

 

 


 

Integration BW (IBW) is coupled to the Frequency Span setting. Frequency Span is 50% wider than the IBW (e.g., if the IBW value is 1 MHz, then the Frequency Span value is 1.5 MHz).

 

Two more ways to change the frequency range

  1. Press Freq/Dist
  2. Then choose from the following:

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.

  1. Press Freq/Dist > More
  2. Then CF Step Auto Manual

 

To change this setting from Manual to Auto, press CF Step twice.

 

How to change from Linear to Log Axis View

  1. Press Freq/Dist > More
  2. Then choose from the following:

 

“Baseband (N99xxC-Series FieldFox Models Only with Option 350 RTSA or Option 233 SA–Mixed Models)”

The SA Receiver has a “Baseband” path, which provides improved sensitivity (i.e., lower DANL), lower phase noise, and less LO Feedthru. The baseband receiver path avoids analog mixing stages, and instead routes the SA input signal (after RF Attenuation) more directly to an Analog to Digital converter. There is no Preamp available in the baseband path. The baseband path is available in both SA and RTSA modes.

 

The baseband path analyzes RF input frequencies up to 6.5 MHz only. When used for RTSA or SA's IQ Analysis measurement, the baseband path is not activated for spans >10MHz. The FieldFox C-Series RTSA and SA IQ Analysis may still have wider IQ bandwidth capability, up to 120 MHz like all B models (requires Option B04 (40 MHz) /B10 (100 MHz)). But, that wider IQ bandwidth is not available in the baseband path.

 

The baseband path, which is available to analyze signals up to 6.5 MHz, is disabled by default, and for Preset. When disabled, the SA Receiver maintains the standard analog mixing stages to analyze this low frequency (<6.5MHz) range.

How to Select the Baseband Path

  1. Press Freq/Dist > More
  2. Then Baseband [Disabled] Press to [Enabled] (Default == Disabled).
  3. To complete the Baseband enabling (activation) process:
      1. Press Meas Setup 4 > IQ Analysis and then [General].
      2. Verify IF Output Use is set to [Narrow].

 

 

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 in “How to set Frequency Range”.

 

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 in “Radio Standards and Channel Measurements”.

 

How to select a Radio Standard

  1. Press Measure 1 OR Freq/Dist then More
  2. Then Radio Standard
  3. Then Radio Standard
  4. Then select a standard using the  arrows  () or rotary knob and press Enter.

Custom Radio Standards

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:

Download and Edit a Custom Radio Standard Template (keysight.com) (Keysight FieldFox Library, Help and Manuals – FieldFox Online Supplemental Help).

 

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

  1. 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.
  2. Press Measure 1 OR Freq/Dist then More
  3. Then Radio Standard
  4. Then Radio Standard
  5. Then Import Radio Standards
  6. Then select the *.csv file 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

  1. Press Freq/Dist > More
  2. Then Unit   Freq Chan

With Unit = Chan, Channel Direction becomes available and CF Step alters to Channel Step.

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.

  1. Press Freq/Dist
  2. Then choose from the following:

 


 

Integration BW (IBW) is coupled to the Frequency Span setting. Frequency Span is 50% wider than the IBW (e.g., if the IBW value is 1 MHz, then the Frequency Span value is 1.5 MHz).

 

Select either Uplink or Downlink Frequencies

Press Freq/Dist then More. 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. In that case, Chan Direction is grayed out.

Channel number X-axis annotation

 

Change Channel Step Size (Optional)

This setting allows you to use the arrows () to increment the channel number by the specified value. The Channel Step softkey appears only when it is valid. Learn how to make it valid in the section, See "How to change the Channel Number of the measurement”.

  1. Press Freq/Dist then More.
  2. Press Channel Step.
  3. Enter a step value using the numeric keypad, the arrows (), or the rotary knob. Then press Enter.

Reverse Swap

Available ONLY with Opt. 209 and while in Step sweep mode. Each press of the softkey causes the Start and Stop frequencies to swap. The Start becomes the Stop and vice versa. Learn more about Step versus FFT sweeps in “FFT Gating (Opt 238)”.

  1. Press Freq/Dist > More.
  2. Then Reverse Swap

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 acquisition 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 acquisition.

How to set Scale

Press Scale / Amptd. Then choose from the following:

Manually set Scale Type, acquisition, and Reference Position.

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.

Antenna correction units are available ONLY by loading or editing an Antenna file that contains the desired units setting. Learn more in “Manage Files”.

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 acquisition) without overloading the SA first mixer.

How to Set External Gain

  1. Press Scale/Amptd
  2. Then More
  3. Then External Gain
  4. 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.

Attenuation Control

Both the RF Attenuation and Preamp functions control the power level into the SA.

 

When too much power is present at the RF Input 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 Input port, 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. Refer to the FieldFox Data Sheet

for your model on

 

Maximum Input Voltages and Power:

 

RF Output Connector: 50V DC, +23 dBm RF

 

Ext Trig/Ref Connector: 5.5 V DC

 

RF Input:

    +27 dBm RF, ±50 VDC Max. (N991xA/B, N9925B, N9926A, N9928A, N993xA/B)

    +23 dBm RF, ±50 VDC Max. (N9923A, N9923AN)

    +25 dBm RF, ±40 VDC Max. (N995xA/B, N996xA/B)

    DC Input: 19VDC, 4ADC, 60 Watts maximum when charging battery

 


 

Learn more about ADC over range warnings by referring to "Chapter 9, “System Settings,” and then to “SA".

 

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

  1. Press Scale/Amptd.
  2. Then RF Atten Auto Man.

 

#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.

  1. Press Scale/Amptd.
  2. 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.

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 Input 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 because devices other than the ADC, such as the mixer, might be compressed. Increase the RF Attenuation value to prevent the SA receiver from being compressed.

How to Check for a Compressed Measurement

  1. Using a marker at the signal peak, make note of the signal power level.
  2. Increase the RF Attenuation level by 5 dB.

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.

 

Setting Field Strength Measurements

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

Trace 2 - Uncorrected trace (Apply Corr = OFF). The Trace 2 trace state is “View.” For information, refer to “Trace Display States (SA Mode)”

Pink Trace - Current correction factor. See below.

How to select and edit corrections 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.

 

  1. Press Scale/Amptd > More > Corrections.
  2. Then choose from the following:

 

Learn more, see “Selecting and Viewing Corrections”.

 

Selecting and Viewing Corrections

  1. Press Scale/Amptd > More > Corrections > More
  2. View Corrections ON OFF Turn ON and OFF Pink Trace - Antenna/Cable corrections. This is a composite of all cable/antenna corrections that are currently applied. Available as a useful visual aid, the zero “dB” level (no net correction) is mapped to appear at the -50 dBm on-screen level.
  3. Amp Corr Select [Triaxial XYZ] - then choose one of the following:
  1. <Back To return to previous softkey menu.

How to Use the Antenna Softkeys

The following menu appears when any of the above Antenna or Cable softkeys are pressed:

 

When finished, press Back to return to the previous menu.

Using the Antenna/Cable Editor

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

 

Figure 7-2 FieldFox Antenna Editor - E–Field and H-Field Units Displayed

How to use the Antenna/Cable Editor

Before editing the antenna settings, it is important to know whether you are using a magnetic H-field (dB S/m) or electric E-field (dB /m) antenna. When you setup the Antenna Factor Correction table, you will select one of these two units so that the FieldFox knows how to convert the measurement data to various Field Strength Amplitude units.

 

  1. Press Scale/Amptd > More > Corrections then choose:
  1. Then Edit Antenna or Edit Cable to open the Antenna / Cable Editor.
  1. Press New then Yes to clear all data from the existing Antenna or Cable table and reset header information to default settings.
  2. Then use the arrows () to select a field.
  1. Optionally choose from the following:

When the table edits are complete

  1. Press Done to close the Antenna/Cable Editor.
  2. Press Save Antenna or Save Cable to save your changes to the specified Storage Device. Enter a filename using the FieldFox labeler (learn more in “How to use the FieldFox labeler ”). Learn more about Antenna and Cable files below.

Optional:

About Antenna and Cable files

How to create a Cable file from an S21 (NA mode) or an Insertion Loss (CAT mode) measurement

  1. Measure the S21 or Insertion Loss of a cable. In NA mode, select either LogMag, Linear, or VSWR formats.
  2. Use Manage Folders to change the active folder to CABLES. Learn how in “Manage Files”.
  3. While in NA mode, save the measurement as a *.csv file. Learn how in “How to Save a File”.
  4. In SA mode, select Corrections, then recall the *.csv file for correction.

Source Tracking Offset and Offset Reversal

This feature requires:

Source offset tracking is used to offset the Source frequency from the Receiver frequency by a fixed offset at every tune frequency. This feature is used when the DUT contains a frequency translation device or mixer.

How to set Tracking Offset and Offset Reversal

  1. On the Receiver unit, press Measure 1 > Source > Advanced
  2. Then choose one or both of the following:

Tune & Listen (AM/FM)

The Tune & Listen feature can be used to identify an interfering AM or FM signal. Also, AM/FM Metrics displays the demodulated signal and the audio frequency spectrum.

 

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.

 

Figure 7- Tune & Listen ON

 

 

In the graphic above, Tune & Listen ON with Tune Frequency is indicated by a vertical bar (highlighted).

 

This section contains the following:

“How to select Tune & Listen”

“TnL AM SSB Gain”

“Tune Frequency”

“Listen Time”

“To select Listen Time:”

“Volume Control”

“Audio Demod ON and OFF”

“Setting the Marker Counter Gate Softkey”

“Setting the Mkr->TuneFreq Softkey”

 

How to select Tune & Listen

  1. Press Measure 1 > Analog Demod Tune & Listen > Tune & Listen
  2. Then choose a demodulation type. Select a setting based on the type of interfering signal you suspect is being broadcast.

Press Meas Setup 4 > Tnl Demod Type then:

 

See also, “How to select Analog Demod (Metrics)”.

TnL AM SSB Gain

When you select AM USB or AM LSB softkeys, the TnL AM SSB Gain softkey becomes active.

 

The goal is to set the gain as high as possible (to take advantage of the range of the IF and audio paths) without distorting the audio signal. It is recommended that you keep increasing the gain until you hear distortion in the audio and then back off until you no longer hear any distortion.

(Default = 0, Minimum = –50 dB, Maximum = +50 dB)

 


 

The system volume setting should still be used to determine the final desired volume/level of the audio output. Learn more, see also Chapter 9 “System Settings” and then to “Audio (Volume) Control”.

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, sets Tune Frequency to 3.25 GHz (e.g., for a N9914B FieldFox).
  2. Specify Tune Frequency:
    1. Press Meas Setup 4 > Tune Freq
    2. Enter a value using the numeric keypad, arrows (), or the rotary knob. Then select a multiplier key. Learn about multiplier abbreviations “Multiplier Abbreviations”.
  3. Using Mkr->Tune Freq:
    1. Press Mkr->/Tools
    2. Then Mkr->TuneFreq 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 in “Attenuation Control”.

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 > Listen Time

Enter a value using the numeric keypad, arrows (), or the rotary knob. Then select a multiplier key. Learn about multiplier abbreviations.

Volume Control

To increase or decrease the Volume of the demodulated signal:

Press Meas Setup 4 > 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 in “How to set the FieldFox Volume Control”.

Audio Demod ON and OFF

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

Press Meas Setup 4 > Audio Demod ON OFF > OFF

Setting the Marker Counter Precision Softkey

When AM Tune & Listen, FM (narrow) Tune & Listen, or FM (wide) Tune & Listen are selected, you can choose from the following:

 

The Counter Precision softkey is not available when AM Metric or FM Metric are enabled. See also, “Setting the Mkr->TuneFreq Softkey”.

Setting the Mkr->TuneFreq Softkey

When AM Tune & Listen, FM (narrow) Tune & Listen, or FM (wide) Tune & Listen are selected, you can choose from the following:

Press Marker > Normal

Press Mkr->/Tools > Mkr->TuneFreq – The Tune & Listen Frequency becomes the frequency of the active marker (When AM Metrics or FM Metrics are selected this softkey is inactive).

See also, “How to use Marker Functions”.

Analog Demod

The Tune & Listen feature can be used to identify an interfering AM or FM signal. Also, AM/FM Metrics displays the demodulated signal and the audio frequency spectrum.

 

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 Analog Demod spectrum is displayed alongside the SA displayed trace. This enables you to listen and display a carrier frequency and it’s harmonics. The Analog Demod measurement displays a normal SA sweeps for the display while performing audio demodulation at the carrier Frequency. See the “How to select Analog Demod (Metrics)” setting for more information.

 

Figure 7- AM DSB (Metrics) – Demodulation Spectrum

 

In the graphic above, Analog Demod ON and Demod Metrics is indicated above in the x2 displays of carrier spectrum content. For this example, AM Modulation Metrics are displayed in the lower half of the display. See also, Figure 7-5, Figure 7-6, Figure 7-7, and Figure 7-8.

 

This section contains the following:

“How to select Analog Demod (Metrics)”

“How to make Analog Demodulation (Metrics) Settings”

“Setting the Alternate Frequency (AF) Freq/Dist Softkeys”

“Setting the Alternate Frequency (AF) RBW Softkey”

“Setting the Audio Capture Playback Softkeys”

“How to Set the Demod Filters”

“Setting the Marker Counter Gate Softkey”

How to select Analog Demod (Metrics)

Analog demodulation can demodulate AM DSB, AM SSB, FM, FM Stereo / RDS, PM signals. Under analog demodulation metrics the following information is reported for each signal type: Carrier power, modulation rate, SINAD, THD, plus deviation, depth, or RMS depending on the signal. Metrics also displays the demodulated signal and the audio frequency spectrum.

 

Learn more, Chapter 26, “AM/FM Metrics (SA Only and Option 355)” in the C-Series 9915-90020 (Unabridged) User's Guide“.

 

  1. Press Measure 1 > Analog Demod Tune & Listen > Analog Demodulation
  2. Demod Type – Then choose a demodulation metric type. Select a setting based on the type of interfering signal you suspect is being broadcast.

 


 

IMPORTANT! The FieldFox contains only one speaker that supports mono audio output (i.e., if you play a stereo WAVE file, the Left and Right channels are output in mono audio). If you want to output a stereo WAVE file in stereo (to hear the left and right channels separately on the FieldFox) you have to use the headphone jack and stereo headphones (i.e., most earbuds, headphones, etcetera support stereo). Learn more, see also Chapter 9, “System Settings.” and “Audio (Volume) Control”.

 

 


 

When FM Stereo /RDS is selected as the demodulation type, a Warning message is displayed for a few seconds at the start of the sweep; the sweep is 30 to 50 seconds long.

 

The message reads:

"Warning: Slow Measurement. RDS Measurement in Progress."

 

 

 

See also, “How to make Analog Demodulation (Metrics) Settings”.

How to make Analog Demodulation (Metrics) Settings

The following softkeys are available when one of the Analog Demodulation metrics measurements is pressed. See also, “How to select Tune & Listen”.

 

If AM DSB, choose from:

AM Top Y – Determines the Y axis percentage (0% to ±100%) of the AM demodulation waveform is displayed (Default = 100%).

If AM SSB, choose from:

SSB Top Y – Determines the Y axis voltage (0 nV to ±100mV) of the AM SSB demodulation waveform is displayed (Default = 100 mV).

If FM, choose from:

FM Top Y – Determines the Y axis frequency (1 kHz to 1 GHz) of the FM demodulation waveform is displayed (Default = 100 kHz).

If FM Stereo / RDS, choose from:

FM Top Y – Determines the Y axis frequency (1 kHz to 1 GHz) of the FM demodulation waveform is displayed (Default = 100 kHz).

If PM, choose from:

PM Top Y – Determines the Y axis phase (0 to 100 radians) of the PM demodulation waveform is displayed (Default = 5).

 

For any of the following: AM DSB, AM SSB, FM, FM Stereo / RDS, or PM, choose from:

 

Refer to Figure 7-5, Figure 7-6, Figure 7-7, and Figure 7-8.

 

Setting the Alternate Frequency (AF) Freq/Dist Softkeys

When AM DSB, AM SSB, FM, FM Stereo / RDS, or PM are selected and Demod View = Freq, you can choose from the following:

 

 

Also, you can set the standard Center, Freq Span, and other frequency softkeys.

Setting the Alternate Frequency (AF) RBW Softkey

When AM DSB, AM SSB, FM, FM Stereo / RDS, or PM are selected and Demod View = Freq, you can choose from the following:

Press BW 2 then choose:

AF RBW – Sets the audio frequency (AF) resolution BW for the AM or FM demodulated signal (Manual or Auto; default = Auto).

Setting the Audio Capture Playback Softkeys

The FieldFox analog demodulation audio capture playback feature allows you to capture/record the demodulated audio associated with an analog demodulation measurement (AM DSB, AM SSB, FM, FM Stereo or PM) and save it as an audio file. It also allows you to recall and playback audio files through FieldFox's built-in speaker or headphones.

 


 

Currently, the audio capture playback feature supports WAVE files with mono or stereo LPCM data sampled at 48,000 Hz with 16 bits per sample.

 

If you are unable to hear your audio data files (*.wav), verify that your System 7 > Preferences > Preferences > Audio is set to On.

 

When Analog Demod is selected, you can choose from the following:

 

Press Capture

 

Press Stop to stop the current capture of audio data and depending on the timing of pressing Stop, possibly prevent the audio data from being stored.

 

Press Playback then

 

Then Choose:

Mono (L+R) Sets the audio recording to Mono (single channel) and combining left and right speaker sounds. This is the default.
Stereo (L&R)

Sets the audio recorded to be stereo (two channels).

Left (L)

Sets the audio to be recorded to be the left speaker only.

Right (R)

Sets the audio to be recorded to be the right speaker only.

Difference (L–R) Sets the audio to be recorded to be the value of the left side minus the right side of the audio data (single channel).

 

 

 

For more on file settings refer to Figure 7-9 and to Chapter 10, "File Management”.

How to Set the Demod Filters

The demodulation (Demod) filters and de-emphasis options help you accurately recover and analyze the modulating signal. The demod filters apply to all demod types (AM DSB, AM SSB, FM, FM Stereo and PM), while the de-emphasis options only apply to the FM and FM stereo demod types.

 

None

No lowpass filter is selected.

300 Hz

5-Pole Butterworth LPF with 3 dB cutoff frequency of 300 Hz.

3 kHz

5-Pole Butterworth LPF with 3 dB cutoff frequency of 3 kHz.

15 kHz

5-Pole Butterworth LPF with 3 dB cutoff frequency of 15 kHz.

30 kHz

3-Pole Butterworth LPF with 3 dB cutoff frequency of 30 kHz.

80 kHz

3-Pole Butterworth LPF with 3 dB cutoff frequency of 80 kHz.

100 kHz

3-Pole Butterworth LPF with 3 dB cutoff frequency of 100 kHz.

20 kHz

9-Pole Bessel LPF with 3 dB cutoff frequency of 20 kHz.

300 kHz

3-Pole Butterworth LPF with 3 dB cutoff frequency of 300 kHz.

Custom 5-Pole Butterworth LPF with a custom 3 dB cutoff frequency (determined by the LPF 3 dB Cutoff setting).

 

 

None

No highpass filter is selected.

20 Hz

2-Pole Butterworth HPF with 3 dB cutoff frequency of 20 Hz.

50 Hz

2-Pole Butterworth HPF with 3 dB cutoff frequency of 50 Hz.

300 Hz

2-Pole Butterworth HPF with 3 dB cutoff frequency of 300 Hz.

400 Hz

10-Pole Butterworth HPF with 3 dB cutoff frequency of 400 Hz.

Custom 5-Pole Butterworth HPF with a custom 3 dB cutoff frequency (determined by the HPF 3 dB Cutoff setting).

 

Setting the Marker Counter Gate Softkey

When AM Metric or FM Metric are selected, you can choose from the following:

The Counter Gate softkey is not available when AM Tune & Listen, FM (narrow) Tune & Listen, or FM (wide) Tune & Listen are enabled. Refer to Figure 7-8.

 

See also, “How to use Marker Functions”.

 

Figure 7- AM DSB (Metrics) – Demodulation Waveform

 

 

Figure 7- FM Metrics – Demodulation Spectrum

 

 

Figure 7- FM (Metrics) – Demodulation Waveform

 

 

Figure 7- FM (Metrics) - Counter Gate and FM Demodulation Waveform

 

 

Figure 7- Audio Capture with Annotation Examples

Independent Source/Tracking Generator


 

For best results, when using the independent source feature, InstAlign and the battery saver features should be turned off. Refer to “How to Access Individual Alignments” and “Preferences”.

 

This feature may require an option. For a comprehensive list, view the FieldFox Configuration Guide at: https://www.keysight.com/us/en/assets/7018-06515/configuration-guides/5992-3701.pdf

.

 

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 Output connector and the RF Input connector.

How to make Independent Source Settings

  1. Press Measure 1 > Source
  2. Source Enable ON OFF
  1. Source Mode Choose from the following:
  1. 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 this Trace 4 reference trace, and therefore become relative to it.  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 in “Trace Display States (SA Mode)” on page 198.
  2. Source Power Sets the source power level. Choose from:
  1. 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 IQA and SA sweep and also every 300 seconds during the InstAlign process.

 

To cause the source to stay ON at the end of each sweep, turn battery saver OFF. (Learn more in “How to Access Individual Alignments” on page 205.)

  1. Press System 7 > Preferences > Preferences then
  2. In the table, select Battery Saver. Press Edit then Battery Saver ON OFF

To suspend InstAlign: (Learn more in “How to Access Individual Alignments”.)

  1. Press Cal 5
  2. Then Amptd Alignment 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. See “Very Long Sweep Times”.

How to set Res BW

  1. Press BW 2 > Res BW
  2. Then choose from the following:

 

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 in Appendix B.

 


 

The Res BW setting also affects the Sweep Type setting. Learn how in “Sweep Type”.

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

  1. Press BW 2 > Video BW
  2. Then choose from the following:

.


 

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.

AF RBW (Audio-Frequency Resolution BW)

AF RBW - sets the audio-frequency resolution bandwidth for the selected frequency (Default = Auto).

How to set AF RBW

  1. Press BW 2 > AF RBW
  2. Then choose from the following:

 


 

To change this setting from Man to Auto, press AF RBW twice.

 

The current AF RBW setting is shown at the bottom of the screen.

# AF RBW x.xx XHz (#) means manual setting.

When the Res BW/AF RBW ratio exceeds 10,000, a Meas UNCAL warning may appear to indicate that the AF RBW filter has reached the maximum capacity for averaging.

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 lower-left corner of the FieldFox screen.

For a more comprehensive tutorial, see Spectrum Analysis Basics (App Note 150) at https://www.keysight.com/us/en/assets/7018-06714/application-notes/5952-0292.pdf

How to set Sweep Type

  1. Press BW 2 > Advanced > Sweep Type
  2. Then choose from the following:

Oversweep

In SA mode, the FieldFox uses Oversweep to quickly analyze input signals. Oversweep is meant to verify that your setup is correct, but Oversweep is not meant to be as accurate as FFT and Step sweeps. See also, “How to set Sweep Type”.

How to set Oversweep

  1. Press BW 2 > Advanced then
  2. Press Oversweep – To enable/disable the Oversweep. Over sweep enables you to quickly evaluate your setup.

IF Output

The FieldFox IF (intermediate frequency) can be output for external signal processing. The signal is available from the IF Out connector on the FieldFox right-side panel. See the connector in “Right Side Panel”.

 

The IF Out signal, centered at approximately 33.75 MHz, is simply a down-converted version of the RF Input signal that is present at the tuned frequency.

 

While outputting an IF signal, the FieldFox stops performing the InstAlign process. Therefore, the amplitude of traces on the FieldFox screen is NOT accurate and Meas UNCAL appears on the screen to indicate this. Learn more in “Individual Alignments”. See also Figure 7-10.

 

Learn more about the IF Output frequencies and bandwidths by referring to the FieldFox Supplemental Online Help (Keysight FieldFox Library, Help and Manuals – FieldFox Online Supplemental Help).

 

Figure 7- IF Output Wide with MHz

How to select IF Output

The IF Output signal is useful only in Zero Span. Learn more about Zero Span in “Zero Span Measurements”.

 

At least one sweep must be made in order to tune the FieldFox.

  1. Press BW 2 > Advanced > IF Output Use

  2. Then choose from the following:

Sweep Acquisition

Available only in non-zero span measurements, when Sweep Acquisition is set to Auto, the fastest sweep rate is achieved while maintaining full amplitude accuracy.

 


 

For zero span measurements, refer to “Zero Span Measurements”.

 

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.

 

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.

 

Figure 7- GSM Signal in Framed Data Format

 

In the graphic above, a GSM signal in a framed data format; timeslot zero ON; all others OFF;

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

How to set Sweep Acquisition

SwpAcquisition is NOT an absolute measure of time, but a relative number between 1 (fastest) and 5000 (slowest) sweep time. The actual time that was required to complete a sweep is annotated on the screen.

 

  1. Press Sweep 3.
  2. Then SwpAcquisition Auto Man.
  3. Then choose from the following:

 

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 in “Temperature Control Mode”.

 

Learn more about SA mode SwpAcquisition time by referring to the FieldFox Supplemental Online Help (Keysight FieldFox Library, Help and Manuals – FieldFox Online Supplemental Help).

Very Long Sweep Times

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

 

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.

 


 

For non-zero span measurements, refer to “Sweep Acquisition”.

 

Figure 7- GSM Signal, Framed Data Format

 

The graphic above shows a GSM signal, framed data format, with 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

How to change Sweep Time in Zero Span

  1. Press Sweep 3
  2. Then Sweep Time
  3. Enter a value using the numeric keypad. Sweep time is limited to 1000 seconds for N991xC/2x/3xC models.
  4. Then select a multiplier key. Learn more in “Multiplier Abbreviations”.

 

Learn more about SA mode Sweep Time by referring to the FieldFox Supplemental Online Help (Keysight FieldFox Library, Help and Manuals – FieldFox Online Supplemental Help).

Triggering (SA)


 

SA STEP sweeps do not have trigger behavior. So, they are essentially always in "FREERUN" mode. If you try to set a trigger (other than FREERUN) in SA Step sweep, the FieldFox displays the following popup message:

"Note: Trig Type has no effect while in STEP sweep mode"

 

External, Video, and RF Burst triggering allows you to initiate an SA mode sweep using an external event such as a signal burst.

 

All three trigger types can be used in either Zero Span (time domain) or FFT frequency sweeps. Learn more in “Zero Span Measurements”. Learn more in “Sweep Type”.

 

FFT Gating is available for non-zero span measurements. Learn more about FFT Gating in “FFT Gating (Opt 238)”.

Trigger Type

  1. Press Sweep 3 > Trigger Settings > Trig Type
  2. Then choose from the following:

 

The following two selections are similar in that they both trigger a sweep from a signal at the SA RF Input connector. Experiment with both selections to find the best trigger type for your application.

 

Sync


 

The Sync softkey is ONLY available when Trigger Type is set to Periodic. SA STEP sweeps do not have trigger behavior. So, they are essentially always in "FREERUN" mode. If you try to set a trigger (other than FREERUN) in SA Step sweep, the FieldFox displays the following popup message:

"Note: Trig Type has no effect while in STEP sweep mode"

 

Selects the type of signal the periodic trigger is synchronized.

Trigger Slope


 

This softkey is unavailable when Trigger Type is set to Periodic.

 

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

  1. Press Sweep 3 > Trigger Settings > Trig Slope
  2. Then choose from the following:

Trigger Delay

After a valid trigger signal is received, the sweep begins after the specified Trigger Delay time.

 

To see the rising edge of a repetitive signal which is triggered on that edge, enter a negative trigger delay value (also known as pre-trigger). Adjust the sweep time to observe the pre-trigger time if necessary.

 

  1. Press Sweep 3 > Trigger Settings > Trig Delay
  2. Enter a value using the numeric keypad, the  arrows (), or the rotary knob.
  3. Then select a multiplier key or press Enter. Learn more in “Multiplier Abbreviations”.

 

In Zero span, you can use Trigger Position as an easy way to set Trigger Delay by positioning the trigger event on the FieldFox screen. See “Triggering (SA)”.

Period


 

This softkey is ONLY available when Trigger Type is set to Periodic.

 

Sets the length of time in seconds before a waveform repeats. (default = 20.00 ms).

Offset


 

This softkey is ONLY available when Trigger Type is set to Periodic.

 

Sets the periodic trigger offset. (default = 0.00s).

Trigger Level

Used with Video and RF Burst triggering, a sweep is initiated when an incoming signal crosses this level. The units depend on the Units setting. Learn more in “Scale and Units”.

 

RF Burst Trigger Level uses an alignment process which is performed in the background to set the detected signal level accuracy. Learn more in “RF Burst Amplitude Alignment”. Video Trigger Level is a zero span signal level comparison. Therefore, the sweep will trigger close to the displayed level in zero span measurements. In non-zero 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.

  1. Press Sweep 3 > Trigger Settings > Trig Level

  2. Enter a value using the numeric keypad, the  arrows (), or the rotary knob.
  3. Then select a multiplier key or press Enter. Learn more in “Multiplier Abbreviations”.

Auto Trigger Time

While waiting for a valid trigger signal, Wait is annotated in the top left corner of the FieldFox screen.

 

If a valid 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 trigger signal is received.

  1. Press Sweep 3 > Trigger Settings > Auto Trigger [current setting]
  2. Enter an Auto Trig Time using the numeric keypad.
  3. Then select a multiplier key. See “Multiplier Abbreviations”.

Trigger Position

Available ONLY in zero span measurements, this setting is an easy way to automatically set the Trigger Delay by positioning the trigger event (also known as T-zero) at any graticule along the X-axis. With T-zero in the center of the screen, you can zoom in and out by increasing or decreasing the sweep time. Using the Trigger Position and Sweep Time settings is a quick and efficient way to examine artifacts of a pulse, much easier than trying to set the Trigger Delay manually.

 

When Trigger Position is set to OFF, the Trigger Delay softkey is not available. The amount of Trigger Delay that is being used is displayed on the softkey. The Trigger Position is annotated on the screen. Learn how in the following section.

  1. Press Sweep 3 > Trigger Settings
  2. Then Trig Position. If Sweep Time is longer than 0.15 sec, this softkey is grayed out.

Trigger Settings Annotation

Trigger settings are annotated on the FieldFox screen as highlighted in red in the following image:

FFT Gating (Opt 238)

Time-gated spectrum analysis allows you to obtain spectral information about signals occupying the same part of the frequency spectrum that are separated in the time domain. Using an external trigger signal to coordinate the separation of these signals, you can perform the following operations:

 

 

FFT Gating is a simple, efficient way to set the proper amount of trigger delay and capture time so that signal artifacts of a repeating waveform or pulse can be examined in the frequency domain. Learn more about trigger settings in “Triggering (SA)”.

 

For best results, Auto Trigger should be used with this feature to ensure that the sweep does not wait indefinitely for a trigger. Set Auto Trigger to a time that is longer than the expected periodic rate of the signal.  This is especially important when using RF Burst or Video triggering in wider spans, because the signal providing those triggers has limited bandwidth. Learn more about Auto trigger in “Auto Trigger Time”.

 

For more conceptual information on this topic, please refer to Spectrum Analysis Basics (App Note 150), pages 31 - 35, at https://www.keysight.com/us/en/assets/7018-06714/application-notes/5952-0292.pdf.

How to Set FFT Gating

  1. Create a non-zero span measurement. Wider frequency spans take more time to acquire.
  2. Press Sweep 3 > Trigger Settings > FFT Gating Setup
  3. Then choose from the following:

 

When you have properly setup the Gate Trigger, Width, and Delay using the Gate View measurement, you can turn Gate View OFF to return to the full screen non-zero span measurement with FFT Gating ON, the RBW set, and the Trigger settings active.

Single / Continuous / Restart

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 or Continuous

  1. Press Sweep 3.
  2. Then choose one of the following:

Points

Points is the number of measurements that are displayed along 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

  1. Press Sweep 3 > Points [current setting]
  2. Then choose from:

Trace Display States (SA Mode)

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. See also “Marker Trace (IQA and SA Mode)”.

 

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 the Trace States

  1. Press Trace 6.
  2. Then Trace 1,2,3,4 repeatedly to select a trace number to display or change its state. Traces are displayed in the following colors:
  1. Then State [current setting]
  2. Then choose from the following Trace States:
  1. 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 (“Independent Source/Tracking Generator") or using Field Strength antenna or cable corrections (“Field Strength Measurements”).

Average Type

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

There are three types of mathematical averaging that can be performed – Log, Linear, or Voltage (see “How to set Average Type”). Select ONE of these types and it is used for all of the above averaging processes.

How to set Average Type

  1. Press Meas Setup 4 > Average Type [current setting]
  2. Then choose from the following:

Average Count

The Average Count setting is used mainly with the Average Trace State described in “Trace Display States (SA Mode)”. 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

  1. Press Meas Setup 4 > Average Count
  2. Enter a value from 1 to 10,000 using the numeric keypad, the  arrows (), or the rotary knob.
  3. Press Enter

Alignments


 

To better reflect the enhancements implemented during the alignment process, for firmware versions >A.10.15 “IF Flatness Alignment” is now referred to as “Channel Equalization” or “Channel Equalization Alignment” (ChanEQ Alignment).

 

This section contains the following:

Overview

The alignments softkeys are located by pressing the Cal 5 hardkey.

 

All Alignment or Align All Now corrects for receiver drift over temperature and time. SA measurement applications monitor changes in internal temperature and the time since last alignment update and trigger the need for a new update when the alignment becomes stale. The alignment is deemed stale after a significant change in temperature or a significant time elapsed from the last update. The temperature change and time duration necessary to trigger an alignment update is predetermined in the factory. Until the update is performed, annotation indicating “questionable amplitude” is displayed AMPTD?.

 

When All Alignment is enabled (by default) the FieldFox performs an alignment process using the internal RF source. Although some sweeps are delayed, measurement results are never disturbed.

 

If the Independent Source (tracking generator) is enabled for your measurement, it will be borrowed to perform the alignment. Again, the measurement results are not disturbed. Learn about the Independent Source in “Independent Source/Tracking Generator”.

 

The alignment process can be disabled. You may want to do this, for example, if you are analyzing the amplitude stability of a signal.

SA and all modes built on its infrastructure require three types of alignments:    

These are referred to as Individual Align.

 

All three or a subset of the individual alignments are required for each specific mode, depending on the type of measurement supported by it:

SA:

RTSA:

Channel Scanner:

EMI Measurements:

ERTA:     

 IQA:

Built-in Power meter

 

Default settings and recommended use model for many applications:

 

For special cases, the individual alignments can be accessible via the front panel soft-keys using the Preference setting SA - Individual Alignment Control  > On/Off. This enables a soft-key for access to Individual Alignments when this preference is set to ON: Cal 5 > Individual Align. For more refer to “Preferences”, in Chapter 9 System Settings.

 

The individual alignments may be:

 

Each of the individual alignments:

All Alignment and Align All Now


 

IMPORTANT! It is recommended that you use Align All Now, because it includes the individual alignment InstAlign Amptd Align Now, as well as, Burst Align Now, and ChanEQ Align Now. But, if you would prefer to have manual control over the individual alignments, then refer to the SA Individual Alignment Control setting in “Preferences”, in Chapter 9 System Settings.

 

The notification AMPTD? displayed on screen means the InstAlign amplitude alignment or channel equalization is stale (if its state is Hold) and requires an update or it is in the OFF state. This situation does not occur when the respective alignment is in the Auto state. To clear this notification, press the Align All Now softkey.

 

How to set All Alignment and Align All Now

  1. Press Cal 5
  2. Then All Alignment [Auto] (to enable or disable the All Alignment) – Default is Auto.

or

Then Align All Now (to manually perform an Align All Now.) This performs an alignment on all three individual alignments: Amptd Align Now, Burst Align Now, and ChanEq Now). Refer to “Individual Alignments”.

  1. Press Back

If you want to disable the All Alignment [Auto], you can do so in the FieldFox preferences (i.e., you may want to do this, for example, if you are analyzing the amplitude stability of a signal).

 

Refer to the SA Individual Alignment Control setting in “Preferences”, in Chapter 9 System Settings. See also, “Individual Alignments”.

Individual Alignments


 

IMPORTANT! It is recommended that you use All Alignment [Auto] or Align All Now in lieu of the individual alignments (Amptd Align Now, Burst Align Now, and ChanEQ Align Now), because All Alignment [Auto] and Align All Now includes the individual alignment InstAlign Amptd Align Now, Burst Align Now, and ChanEQ Align Now. But, if you would prefer to have manual control over the individual alignments, then refer to the SA Individual Alignment Control setting in “Preferences”, in Chapter 9 System Settings.

 

The Individual Alignment softkey is only available, when the preference SA - Individual Alignment Control is set to On in the FieldFox Preferences menu. Refer to “Preferences”, in Chapter 9 System Settings.

How to Access Individual Alignments

This section assumes access to individual alignments was activated using the FieldFox’s system settings’ Preferences. Once enabled, an Individual Alignments softkey is displayed. Refer to “Preferences”, in Chapter 9 System Settings.

  1. Press Cal 5
  2. Then Individual Align
  3. Then Amptd Align Now or

Then Burst Align Now or

Then ChanEq Align Now

  1. Press Enter

How to make Amplitude Alignment settings


 

During continuous sweep (“acquisition” for IQA) operation, automatic Alignments will NOT interrupt the ongoing measurement, but when necessary, will occur opportunistically as settings are changed. When no automatic alignment updates occur, existing alignments can become stale over time and temperature drift, so a warning annotation on the left panel will light up indicating that alignments need updating.

 

SA, IQA, RTSA, and other modes use a proprietary amplitude alignment algorithm to make extremely accurate amplitude measurements over the full frequency range of the FieldFox.

 

These settings do NOT survive a Preset or Mode Preset.

  1. Press Cal 5 > Individual Align > Amptd Alignment
  2. Then choose from the following:

 

Some examples of the conditions when alignments occur are: This could be a Center frequency change, or it could be as simple as requesting a Single sweep. Also, unique alignments are required at different FieldFox receiver frequency bands, so even if the temperature hasn't changed, an alignment may be required when one changes the Center frequency.

 

If a needed alignment cannot be performed, the user is notified about questionable amplitude AMPTD?.

 

 

Amptd? is annotated in the lower left corner of the FieldFox screen when amplitude alignment is questionable. This is always true when OFF, and is conditionally true in Auto or Hold when the most recent alignment is deemed stale.

RF Burst Amplitude Alignment

RF Burst alignment calibrates the circuitry to provide accurate external RF Burst triggering. Learn more about RF Burst triggering in “Triggering (SA)”.

 

When enabled (by default) the FieldFox performs an alignment process using the internal RF source. Although some sweeps are delayed, measurement results are never disturbed.

 

If the Independent Source is enabled for your measurement, it will be borrowed to perform the alignment. Again, the measurement results are not disturbed. Learn about the Independent Source in “Independent Source/Tracking Generator”.

 

The alignment process can be disabled. You may want to do this, for example, if you are analyzing the amplitude stability of a signal.

How to use git Burst Alignment settings

These settings do NOT survive a Preset or Mode Preset.

 

  1. Press Cal 5 > Individual Align > Burst Alignment
  2. Then choose from the following:

 

Burst Align Now An alignment is performed once and applied to subsequent sweeps.

Channel Equalization (IQA and RTSA Only)


 

During continuous sweep operation for RTSA and continuous acquisition for IQA, automatic Alignments will NOT interrupt the ongoing measurement, but when necessary, will occur opportunistically as settings are changed. When no automatic alignment updates occur, existing alignments can become stale over time and temperature drift, so a warning annotation on the left panel will light up indicating that alignments need updating. When alignments need updating, you will see a “Channel Equalization” or “ChanEq” error message displayed.

 

IQA and RTSA modes use proprietary channel equalization algorithms to make extremely accurate channel measurements over the full frequency range of the FieldFox.

How to use Channel Equalization Alignments settings

These settings do NOT survive a Preset or Mode Preset.

 

  1. Press Cal 5 > Individual Align > ChanEq Alignment
  2. Then choose from the following:

 

When you press ChanEq Align Now An alignment is performed immediately.

 

The Amptd? annotation lights up whenever the current channel equalization is deemed stale.

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 Points setting. Learn more in “Points”.

 

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.

 

Figure 7- Detection using One Bucket

 

In the graphic above there is one bucket showing Positive peak, Sample, and Negative peak Detection methods.

 

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.

 

  1. Press Trace_6 > Detector
  2. Then choose from the following:

Display Line

A display line is a simple, horizontal line that can be placed at any amplitude level on the SA screen or set to any level in IQA. 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 more in “All about Limit Lines”.

 

Figure 7- Display Line with Annotations

 

How to create and move a Display Line

  1. Press Limit __8 > Display Line OFF ON
  2. 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.

 

Learn more,  “All about Limit Lines”.

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 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 Detector is set to Auto. Learn more in “Detection Method”.

 

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 in “All about Markers”.

How to measure Noise with a marker

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

Then More > Marker Function > Noise ON OFF.

 

Power Spectral Density (PSD) Function (SA Mode Only)

The Power Spectral Density Function (PSD Function) is a way to normalize the SA measurement to a 1 Hz Bandwidth. Every SA Resolution Bandwidth is characterized by an “Equivalent Noise Bandwidth” (ENBW) that in general is a few percent wider than the Resolution Bandwidth itself. To normalize the measurement to this ENBW, an offset is added in this amount:       

PsdOffset = -10 * Log10( ENBW )

 

This offset is added to the Reference Level, the Trace values, and Marker values and s  annotation is updated with “/Hz” or “(1Hz)” as an indication that the results are now normalized to 1Hz. This is similar to what the Noise Marker function does, but the Noise Marker also first averages several trace points around the marker location. Similar to a Noise Marker, the PSD Function will also auto-couple the Detector to RMS.

 

See also, “Noise Marker”.

 

How to measure the PSD function:

Press Scale/Type > More > PSD Function ON OFF (Default == OFF).

 

Logarithmic X-axis Limit Line Interpolation (EMI and SA modes Only)

Normally, limit lines are interpolated linearly between the defined limit points (i.e., as a delta dB per Hz). Sometimes the user may want to change the limit line interpolation so that it is logarithmic vs. X (i.e., as a delta dB per log10(Hz)). The “AUTO” state for this control will automatically switch to logarithmic interpolation, if the Trace is being drawn on a logarithmic frequency axis (Log Freq Axis X, available by Freq/Dist > More for SA and EMI modes). The “OFF” state keeps limit line interpolation happening linearly, regardless of the current choice of logarithmic frequency axisX.

 

Learn more, see “How to change from Linear to Log Axis View”.

 

How to set Logarithmic X-axis Interpolation (Log Freq AxisX)

  1. Press Limit 8 > Options > LogX Interp Auto Off – Enables/disables logarithmic interpolation of the X–axis (Default == Auto).
  2. Then choose from the following:

Band/Interval Power Marker

A Band/Interval Power marker—available in IQA and SA Modes—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 (“Channel Power (CHP)”).

 

When the frequency span is set to Zero span, the marker is referred to as an Interval Band 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 in “Zero Span Measurements”.

 

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 in “Detection Method”, and Averaging Type in “Average Type”.

 

Summary:

How to measure Band/Interval Power with a marker

  1. Press Marker to create or select a Normal or Delta marker to use to measure Band/Interval Power.
  2. Then press More > Marker Function > Band/Int Power > Band (or Interval) Span
  3. Then choose from the following:

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 in “Frequency Reference Source”.

 

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

  1. Press Marker
  2. Press Normal, Delta, or Peak, or select an existing marker to use as a frequency counter.
  3. Locate the marker somewhere on a CW signal. It does NOT have to be on the peak.
  4. Then More > Freq Count ON
  5. 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.

Time Zero Fixed Marker

This feature was created to allow recall of vintage instrument states (older than Rev. 7.0) that included Zero span sweep with a trigger delay and at least one marker. Before Rev. 7.0, these instrument states were saved and recalled with the equivalent of the ON state of this setting. The default setting is OFF. Learn more about Triggering with negative delay in “Triggering (SA)”.

  1. Press Mkr->/Tools > More > Mkr Properties > Time Zero Fixed
  2. Then choose from the following:

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 in “Scale and Units” on page 167.

 

Audio Beep can be used with any marker type or function, including Band/Interval Power. Learn more in “Audio”.

How to use Audio Beep

  1. Press Marker
  2. 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.
  3. Then More > Marker Function > 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.

 

To set FieldFox speaker volume control, press System > Preferences > Preferences > Audio then Volume. Learn more in “Audio”.

Meas UNCAL Error

Meas UNCAL appears in the lower-left corner of the screen when the FieldFox can NOT display accurate measurement results with the current settings. Usually, the part of the trace that is inaccurate is shown at –200 dB.

 

The following situation can produce Meas UNCAL:

Old Data Indicator (*)

In SA mode, when the current trace does not exactly match the annotation that is on the screen, an asterisk is displayed in the upper-right corner of the screen graticule area. This would occur, for example, when the Res BW setting is changed while in sweep Hold mode. The annotation is changed immediately, but the trace is not updated until the next sweep occurs. Therefore, the current data trace does not match the screen annotation. See the asterisk in Figure 7-1.

Channel Measurements

The following Channel Measurements are offered in SA Mode:

 

Channel Power                “Channel Power (CHP)”

Occupied Bandwidth              “Occupied Bandwidth”

Adjacent Channel Power Ratio  “Adjacent Channel Power Ratio (ACPR)”

Radio Standards and Channel Measurements

To tune the frequency range of any of the Channel Measurements using channels instead of frequency, first select a Radio Standard, then select Units = CHAN. Learn how to select a Radio Standard and channels in “How to select a Radio Standard”.

 

When you first select a Radio Standard, then select a Channel Measurement:

 

When you first select a Channel Measurement, then select a Radio Standard, the BW, Offset, RRC, Integration BW, and Span settings are changed to those of the standard. In addition, Res BW can also change when set to ‘Auto(couple)’. However, center frequency is NOT changed unless you first select Units = CHAN.

Measurement Preset

Measurement Preset allows you to easily reset any of the channel measurements to its default settings. The Center Frequency, Preamp ON|OFF, RF Attenuation, Markers, Limits, and Radio Standard settings are NOT reset.

How to select Measurement Preset:

Press Preset > Mode Preset.

Averaging

By default in ALL Channel measurements, averaging is enabled and set to display the average of the last 15 measurements. When enabled, this average setting is automatically making the following ‘averaging’ settings in order to provide the most accurate power measurements:

 

 

Any of these settings can be changed manually during a Channel measurement. Learn more about these settings starting in “Average Type”.

 

To change Averaging:

  1. Press Meas Setup 4
  2. Then Average Enable ON OFF OFF effectively sets the Average Count to 1.
  3. Then Average Count
  4. Enter a value between 1 and 10,000 using the numeric keypad,  arrows (), or the rotary knob.
  5. Press Enter.

Traces

Only one measurement trace can be displayed in Channel Measurements.

Channel Power (CHP)

Channel Power measures total power over the specified Integrated BW. The Integration Bandwidth (IBW) can be adjusted to measure the power over multiple channels.

 

Figure 7- Channel Power Measurement

 

The following two Channel Power levels are displayed:

How to select Channel Power

  1. Press Measure 1
  2. Then Channel Measurements
  3. Then Channel Power

 

When Channel Power is selected, the following settings are maintained from a previous measurement: Center Frequency, Preamp ON|OFF, and RF Attenuation.

Integration Bandwidth

When Channel Power is selected, vertical posts appear on the display to mark the current Integration Bandwidth setting. The displayed Channel Power and Power Spectral Density values are measured and calculated over the specified Integration Bandwidth.

 

By default, the displayed frequency span is automatically coupled to the Integration Bandwidth. As you change the Integration Bandwidth, the frequency span is adjusted so that the vertical posts appear to NOT move. However, when you manually change the frequency span, the Integration Bandwidth is no longer coupled to the frequency span.

 

When a Radio Standard is selected, the appropriate Integration Bandwidth is set automatically. Learn more about Radio Standards in “Radio Standard”.

 

To change Integration Bandwidth:

 

  1. Press Meas Setup 4 > Integrating BW (Integrating Bandwidth)
  2. Enter a value between 100 Hz and 5 GHz using the numeric keypad,  arrows (), or the rotary knob.
  3. Press Enter

Other Channel Power Settings

All relevant FieldFox settings are made automatically to ensure the highest accuracy, such as ResBW, VideoBW, and sweep (SwpAcquisition) speed. These, and all other SA Mode settings, can be changed manually in a Channel Power measurement.

 

Occupied Bandwidth

Occupied Bandwidth measures the power of the displayed frequency span and displays vertical posts at the frequencies between which the specified percentage of the power is contained. The frequency span between the two vertical posts is the Occupied Bandwidth. The Occupied Power, the power that is contained between the two posts, is also displayed in dBm.

 

Figure 7- Occupied Bandwidth Measurement

 

The graphic above shows an OBW measurement; Chan 190 Downlink; GSM850 Radio Standard.

How to Select Occupied Bandwidth

  1. Press Measure_1
  2. Then Channel Measurements
  3. Then Occupied BW

 

When Occupied Bandwidth is selected, the following settings are maintained from a previous measurement: Center Frequency, Preamp ON|OFF, and RF Attenuation.

Frequency Span

Occupied BW is calculated from power that is measured over the entire displayed Frequency Span. The frequency span can be entered using arbitrary frequencies or by using a Radio Standard in conjunction with channel numbers. Learn how to select a Radio Standard and channels in “Channel Selection”.

 

To change Frequency Span:

  1. Press Freq/Dist > Freq Span
  1. Enter a value using the numeric keypad,  arrows (), or the rotary knob.
  2. Press Enter

Power Percent

This setting specifies the percentage of total measured power to display between the vertical posts. The measurement defaults to 99% of the occupied bandwidth power. The remaining power (1% of default setting) is evenly distributed;.5% of the power on the outside of each side of the vertical posts.

 

To change Power Percent:

  1. Press Meas Setup 4 > Power Percent
  2. Enter a value between 10 and 99.99 using the numeric keypad,  arrows (), or the rotary knob.
  3. Press Enter.

Other Occupied Bandwidth Settings

All relevant FieldFox settings are made automatically to ensure the highest accuracy, such as ResBW, VideoBW, and sweep (SwpAcquisition) speed. These, and all other SA Mode settings, can be changed manually in a Occupied Bandwidth measurement.

Adjacent Channel Power Ratio (ACPR)

ACPR measures the power of a carrier channel and the power in its adjacent (offset) channels. The measurement results can help you determine whether the carrier power is set correctly and whether the transmitter filter is working properly.

 

You can measure the channel power in one, two, or three adjacent (offset) channels on the low frequency and high frequency side of the carrier channel.

 

Limits can be used to quickly see if too much power is measured in the adjacent channels.

 

Figure 7- GSM 850-Ch 251-Up with one Offset

In the graphic above, red frequencies (MHz) are added to illustrate offset and integ BW.

 

Data in the ACPR graphical chart is always presented in dBm for the carrier, and dBc (dB below the carrier) for the offsets. This can NOT be changed. Use the Meas Type setting (next page) to change how the data is presented in the table below the graph.

How to select ACPR

  1. Press Measure_1
  2. Then Channel Measurements
  3. Then Adjacent Channel Power

 

When ACPR is selected, the following settings are maintained from a previous measurement: Center Frequency, Preamp ON|OFF, and RF Attenuation.

Frequency Range/Channel

When a Radio Standard is selected, the appropriate center frequency or channel and span is set automatically. The frequency or channel number can then be changed from the Freq/Dist menu. Learn how to select a Radio Standard and channels in “Radio Standard”.

 

The frequency range of an ACPR measurement can also be entered using arbitrary frequencies.

 

When a Radio Standard is NOT selected, the center frequency of a previous measurement is maintained when ACPR is selected.

 

Changing the Integration Bandwidth

The Integration Bandwidth of the carrier and offsets is the frequency span over which power is measured.

To change Integration Bandwidth:

  1. Press Meas Setup 4 > Integrating BW
  2. Enter a value between 100 Hz and 100 MHz using the numeric keypad,  arrows (), or the rotary knob.
  3. Press Enter

How to define adjacent (Offset) channels

An offset represents a difference in center frequencies of the carrier channel and its adjacent channel to be measured. The frequency range for each offset is specified with an Offset Freq and Integ BW. Each offset that is created has a Lower (carrier MINUS Offset Freq) and Upper (carrier PLUS Offset Freq) set of frequencies.

 

  1. Press Meas Setup 4 > Offsets
  2. Press Offset 1 2 3 to select an offset.
  3. Then Offset State to set that offset ON or OFF.
  4. Select Offset Freq This is the difference between the carrier center frequency and the center frequency of the offset channel. Then enter a value using the numeric keypad.
  5. Select Offset Integ BW This is the frequency range over which power is measured in that offset; half of the range below and half above the Offset Freq.

How to set limits for adjacent channels

You can set a unique threshold power for each of the offsets that will cause a FAIL indication (RED bar). This occurs when the calculated dBc power (on top of the offset bar) is ABOVE the specified level.

 

To set limits, with an ACPR measurement on the screen:

  1. Press Limit 8 > Then Offset (1,2,3)
  2. Then choose from the following:
  1. Then enter a value using the numeric keypad,  arrows (), or the rotary knob.
  1. Then Limit Test ON OFF

Measurement Type

This setting determines how the measured carrier and offset power levels in the table are presented. (Data in the graphical chart is always presented in dBm for the carrier and dBc for the offsets.)

 

To select Meas Type:

  1. Press Meas Setup 4 > More.> Meas Type
  2. Then choose from the following:

For both Meas Types, choose the reference for the offset data.

  1. Press Ref Value to toggle between these settings:

Other ACPR Settings

All relevant FieldFox settings are made automatically to ensure the highest accuracy, such as ResBW, VideoBW, and sweep (SwpAcquisition) speed. These, and all other SA Mode settings, can be changed manually in a ACPR measurement.

RRC Weighting

RRC, or Root-Raised-Cosign weighting, is offered with Channel Power and ACPR measurements.

 

When RRC Weighting is applied to transmitted and received power, the edges of the channel are ‘smoothed’ to help prevent interference. To accurately measure a channel that has RRC weighting, set the same value of RRC weighting as that used in the transmitter and receiver.

 

Figure 7- Channel power measurement with.22 RRC applied

RRC Weighting is set and enabled automatically when included in a selected radio standard.

 

To set and enable RRC Weighting:

  1. Press Meas Setup 4 > RRC Weighting ON OFF > More > RRC Alpha [current setting]
  2. Enter a value between 0 (no smoothing) and 1 (most smoothing) using the numeric keypad, arrows (), or the rotary knob. A standard level of filtering is 22.
  3. Press Enter.

 

How to Set Up EMF Settings (Requires EMF (Option 358), GPS (Option 307), and SA Mode (Option 233–Mixed Analyzers))

If OTA or SA mode does not detect an EMF Option 358 license, then the EMF application and the USB antenna’s axes must be set up manually. This use model is not recommended or supported by Keysight.

 

The USB antenna’s cable loss is not included, in the antenna’s correction factors. For an accurate EMF measurement, the cable loss values should be accounted for. Refer to “Editing Cable Correction Factors and Adding New Cable Factors”.

 


 

IMPORTANT! The USB triaxial antenna—or equivalent—is required for EMF measurements. Refer to Chapter 15, “USB Antennas –”, in the C-Series N9915-90020 (Unabridged) User's Guide.

 

EMF mode measures signals at the SA RF Input Port 2 connector.

 

EMF mode requires the FieldFox to have SA mode (Option 233 on combination analyzers)), GPS (Option 307), and CPU2 installed.

 

Recommended, but not required, preamplifier (Option 235) to improve receiver sensitivity.

 

With Option 358 (EMF), network designers can measure and verity the RF exposure compliance as required by each country.

 

If SA mode is licensed for EMF Option 358, the primary measurement performed is Channel Power (CHP) which automatically switches amongst the 3 TriAxial antenna axis (X/Y/Z), to provide a summation of “total power” detected, using unique Antenna supplied corrections for the individual axis, with results in FieldStrength units. This is accomplished within the existing SA Channel Power measurement.

 

With or without license EMF Option 358, the System Utilities menu enables one to Import Corrections and manually drive the Antenna to a particular axis (X, Y, or Z). The manual control thus allows any SA Receiver measurement to sweep that axis just like any other antenna transducer, however without license the imported corrections are not usable from the Apps. But with license the SA provides for easy use of the imported XYZ corrections, thus allowing presentation of correctly compensated FieldStrength measurements, for 1 axis at a time.

 

This section reviews the steps in setting up an EMF measurement, using a USB antenna. If you are not familiar with this process or would like more information, refer to Chapter 15, “USB Antennas – ”, in the C-Series N9915-90020 (Unabridged) User's Guide.

 

This section consists of:

EMF Features

EMF has the following features:

EMF Measurement Results:

 

EMF uses the following data formats:

                         

Figure 7- Example of EMF with Triaxial Antenna

EMF Setup Procedure


 

When the USB antenna correction factors are imported, EMF (Option 358) couples many settings to ease setting up the EMF measurement (e.g., Apply Corrections is enabled, all X, Y, and Z antenna axes are enabled, and Amp Corr Select is set to TriAxial XYZ).

 

  1. Setup the FieldFox Spectrum Analyzer for a Channel Power measurement.
    1. Press Mode > SA >
    2. Press Measure 1 > Channel Measurements > Channel Power

 

See also, “Channel Measurements”.

 


 

If necessary, this step can be skipped and done after the USB antenna is set up.

 

  1. Connect a USB antenna’s RF cable to the SA RF Input, port 2 and the USB connector to a FieldFox USB port. See also, Figure 7- on page 238 and to Chapter 15, “USB Antennas – ”, in the C-Series N9915-90020 (Unabridged) User's Guide.

 

Only Agos Advanced Technologies SDIA–6000 Triaxial Isotropic USB antenna is currently compatible with EMF (Option 358).

 

  1. Importing and selecting the X/Y/Z antenna factors:
    1. Press System > Utilities > EMF Antennas

 


 

If the antenna factor import is successful, the FieldFox displays: "Success: Antenna Factors Imported: Tri-Ax Antenna ID: ->[R] Antenna ID: SDIA-6000-1006 ->[]". The last 4-digits will vary for each antenna (i.e., “1006” value will vary).

 

If the FieldFox displays this error Error: USB antenna Error: Not found or Unable to communicate with antenna. Ensure it is connected. is displayed, verify the USB antenna is connected correctly. See also, “Troubleshooting” in the C-Series N9915-90020 (Unabridged) User's Guide.

 

 

  1. Enabling the imported USB antenna factors and Cable factors:
    1. Verify that the Channel Power measurement is set: Press Measure 1 > Channel Measurements > Channel Power
    2. To enable the Triaxial antenna for EMF: Press Meas Setup 4 > EMF Off > EMF Triaxial [OFF] > Sum All

 

With Sum All, the field strength from all three axes is summed and displayed. The RF measurements are switched between the three different antennas (three dipoles), and the resulting summation of the total power collected, and averaged.

 

Alternatively, you can select either of three axes to individually measure the field strength in the one direction.

 

    1. Else, to manually set one of the triaxial antenna’s three axes to individually measure the field strength in one direction.
      1. Press Meas Setup 4 > EMF Off > EMF Axis Select [OFF] then
      2. Select a single Axis X, Axis Y, or Axis Z antenna dipole for uncorrected use. [X, Y, or Z] is displayed to indicate which one of the X/Y/Z dipole axes is enabled. If for example the X axis has been selected in the System > Utilities > EMF Antennas menu, then Antenna Axis [X] is displayed to indicate the X axis measurement (i.e., this uncorrected manual mode is typically used when no EMF Option 358 is installed). Refer to Figure 9-. See also step f.

 

Figure 7- SysCtrl Triaxial [N] Softkey – With the X–Axis Dipole Selected

 

    1. Modifying the Amplitude Correction Selection:

 

Press Scale/Amptd > More > Corrections > More then

 

    1. Optional (Triaxial XYZ Antenna):

 

Verifying antenna and cable corrections are applied:

      1. Press Scale/Amptd > More > Corrections

 

Yes – Choose Yes to overwrite the current cable data

No – Choose No to exit the cable data edit table view

 

 

    1. Optional: Example of editing X, Y, and Z axes manually.

 


 

The USB antenna factors stored in the triaxial antenna itself cannot be overwritten. The antenna factors on FieldFox imported into FieldFox can be modified. To reset the antenna factors in FieldFox to the original factors, re-import the antenna factors.

 

 

  1. Modifying the EMF settings:

Press Meas Setup 4 > More > EMF Off then

 

For more details on editing the USB antenna, refer to Chapter 15, “USB Antennas – ”, in the C-Series N9915-90020 (Unabridged) User's Guide.

Editing Antenna Correction Factors and Adding New Antenna Factors

This section contains two procedures illustrating how to edit the Antenna Factors settings table values.

 


 

If New is selected under the X, Y, or Z Antenna or Cable softkey menu, whatever antenna or cable factors that have been imported as the default values and are displayed in the Settings table.

 

  1. Selecting an antenna softkey menu:

 

Press Scale/Amptd > More > Corrections then choose one of these softkey menus:

 

  1. For this example, the X axis Antenna softkey menu has been selected:

 

 

Refer to next step for details on editing the antenna Settings table.

 

  1. Use the  arrows (), the rotary knob, or numeric keypad to select the table cell value to be edited (i.e., the Frequency Interpolation value is not editable). Then:

 

press New to add a a new antenna’s factors or to write over your existing antenna’s file (i.e., Overwrite existing Antenna data? is displayed above the table).

  1. Press Done when finished editing to exit.

 

    1. Press Save Antenna to save your changes. See also “File Saving Naming Options” and then to “Alpha Numeric Editing”.

 

For more information:

 

Figure 7- Example Editing and Adding a New X axis antenna is shown.

 

Editing Cable Correction Factors and Adding New Cable Factors

This section contains two procedures illustrating how to edit the Cable Factors settings table values.

 


 

If New is selected under the X, Y, or Z Antenna or Cable softkey menu, whatever antenna or cable factors that have been imported as the default values and are displayed in the Settings table.

 

  1. Selecting an cable softkey menu:

 

Press Scale/Amptd > More > Corrections then choose one of these softkey menus:

 

 

  1. For this example, the Cable Off softkey menu has been selected:

 

    1. Then press Cable Off > Edit Cable to edit the existing cable’s Frequency and Cable Loss table values that are stored in the FieldFox [:Internal]:\Cable\ directory (Refer to Figure 9-21). Then you can edit the following:

 

 

Refer to next step for details on editing the cable Settings table.

 

    1. Use the  arrows (), the rotary knob, or numeric keypad to select the table cell value to be edited (i.e., the Frequency Interpolation value is not editable). Then:

 

      1. Press Edit Cable to edit your existing cable loss data or

press New to add a a new antenna’s factors or to write over your existing antenna’s file (i.e., Overwrite existing Cable data? is displayed above the table).

      1. Press Add Row to create additional Frequency and Cable Loss values.
      1. Press Delete/Clear then choose one of these:

 

      1. Press Done when finished editing to exit.

 

  1. Press Save Cable to save your changes. See also “File Saving Naming Options” and then to “Alpha Numeric Editing”.

 

For more information:

 

Figure 7- Example: Editing and Adding a New X axis antenna is shown. But, the Cable Loss table is similar.

 

Spectrum Emission Mask (SEM) — (SA Mode Only)

This section explains how to make the spectrum emission mask, (SEM), measurement. SEM compares the total power level within the defined carrier bandwidth and offset channels on both sides of the carrier frequency, to levels allowed by standard. Results of the measurement of each offset segment can be viewed separately.

 

Purpose

 

The Spectrum Emission Mask measurement includes the in-band and out-of-band spurious emissions. It is the power contained in a specified frequency bandwidth at certain offsets relative to the total carrier power. It may also be expressed as a ratio of power spectral densities between the carrier and the specified offset frequency band.

 

The spectrum emission mask measurement is a composite measurement of out-of-channel emissions, combining both in-band and out-of-band specifications. It provides useful figures-of-merit for the spectral regrowth and emissions produced by components and circuit blocks.

 

Measurement Method

 

The spectrum emission mask measurement measures spurious signal levels in up to 8 pairs of offset/region frequencies and relates them to the carrier power.

 

The integration bandwidth method is used to perform a data acquisition. The reference channel integration bandwidth (Meas BW) is analyzed using the user defined resolution bandwidth (Res BW), which is much narrower than the channel bandwidth. The measurement computes an average power of the channel or offset/region over a specified number of data acquisitions, automatically compensating for resolution bandwidth and noise bandwidth.

 

This measurement requires the user to specify the measurement bandwidths of carrier channel and each of the offset/region frequency pairs up to 12 (A - L). Each pair may be defined with unique measurement bandwidths. The results are displayed both as relative power in dBc and as absolute power in dBm.

 

Summary

 

Similar to other Radio Channel measurements, SEM sweeps and measures the total power within a Reference channel. It also optionally performs sweeps of user defined offset segments both above and below the reference channel. The peak signals within the offsets are compared against limits, to determine PASS or FAIL results. Tabular data is presented showing individual offset segment results, one row for each offset. A final trace is displayed that contains all of offset segment sweeps and the reference channel sweep is formed and plotted along with the limits.

 

The following are displayed:

 

 

Figure 7- SEM Example

 

Figure 7- SEM Example FAIL Data - Absolute Limit (Blue), Relative Limit (Violet), Trace (Yellow), and Tabular Data

 

How to select Spectrum Emission Mask (SEM) Measurement

 

When SEM is selected, the following settings are maintained from a previous measurement: Center Frequency, Preamp ON|OFF, and RF Attenuation.

 

Setting up the FieldFox for Spectrum Emission Mask (SEM) Measurement

  1. Press Measure 1 > Channel Measurements > Spectrum Emission Mask
  2. Press Meas Setup 4 then optionally select:

 

 

Measurement Type (Meas Type) enables the user to select the method used to calculate the reference power level.

 


 

The displayed green power (dBm)/frequency (Hz) text changes as the Meas Type is toggled.

 

 

 

 

 

 

 

  1. Setting Center Frequency and Span

 


 

Frequency control menu (Center and Span) provides an SEM Auto Span control (defaulted to ON) which automatically tracks the necessary span to cover all enabled offset segments. In the example in Figure 9-, the necessary span is 16 MHz. But the you can de-couple the span simply by narrowing or widening Span it in order to zoom.

 

The Carrier Frequency (Ref Channel Center) by default tracks the specified Center Frequency, but can be forced to “Hold” at a particular location which would then allow the user Center Frequency to pan above or below for reasons similar to zooming with span.

 

Press Freq/Dist then choose

 

  1. Setting the Limit Lines

 

Two Limit traces are available, an Absolute Limit and a Relative Limit. Both are defined and applied only over the Offset measurement regions. There is no Limit definition or application for the Reference Channel itself. The final Limit Trace displayed is a concatenation of all the individual Offset Limit segments, just as the final measurement trace is. Success or Failure is determined by Fail Mask per offset, to be based on either Relative or Absolute limits, Both (Abs AND Rel), or Either (Abs OR Rel).

 

Press Limit 8 then

 

The Limits per offset are determined by Start/Stop Amplitude level endpoints, which correspond exactly to the user specified Start/Stop frequency locations in the Offsets sub-menu. So each offset segment is a LINE defined by its two endpoints. In the Limit menu “Auto” means to match the Start limit value, hence creating a FLAT (horizontal) Limit Line segment. But the Stop value can be manually set as well, creating sloped Limit segments.

 


 

The reference power level is displayed in green. The reference power level type can be selected through Measure 1 > Meas Type, and the reference power settings defined through Meas Setup > Ref Channel.

 

Example: If the reference power level reads -15 dBm, and Rel Start is set to -10 dB, the level is -25 dBm. Since this limit line type is relative, it moves with the reference power reading.

 

 

  1. Setting the Detectors

 

The Trace menu shows that two Detector controls are available, one for the Reference Channel (default Auto is Average to facilitate the Power Integration), and another for all the Offset segments (default Auto is PEAK, to facilitate finding PEAK signal energy when comparing against Limits).   There is only 1 Trace available, and like the other Channel Measurements, it is set to average.

 

Press Trace 6 then

IQ Analysis (Requires Option 351 IQ Analyzer and Option 353 IQ Streaming, SA Mode Only)

This feature’s intended use is that the Streamed data will be sent to another computer. That computer or another one will act as a SCPI controller and is required for actually controlling the streaming, in particular setting up network configuration data and starting and stopping the streaming.

 


 

IMPORTANT!

– IQ Streaming is used by configuring the desired setup and then starting the acquisition/data stream. In order to make measurement changes (bandwidth, center frequency, etcetera) streaming must be stopped, the new setup configured, and then streaming restarted.

– During streaming, the data displayed on the FieldFox is not updated.

– For both Decodio and VITA49, FieldFox encodes all streamed I and IQ data as 32-bit IEEE 754 floating point values.

– FieldFox does not support TCP networking.

– Data for both protocols is 2 floating point values per sample (I and Q).

– Except for the 32-bit floating point only option for I and Q data, FieldFox implements VITA 49A a subset of the VITA 49.2 protocol.

– While in any IQ Analysis mode, the sample rate to frequency span will stay locked/coupled in a ratio of 1.25:1.

How to Select IQ Analysis

  1. Press Meas Setup 4
  2. Then IQ Analysis then choose from

 

When IQ Analysis is selected, the following settings are maintained from a previous measurement: Center Frequency, Span, BW, Sample Rate, Preamp ON|OFF, and RF Attenuation.

How to Setup IQ Analysis General

General setup for IQ Analysis:

 

  1. Press Meas Setup 4 > IQ Analysis > General
  2. Press IQE Sample Rate > Auto (default).
  3. Press Average Count > 10 (default). Learn more Chapter 19 Interference Analyzer (SA Mode) - Option 236 and to “Adjusting the Measurement Setup Settings”, in the C-Series N9915-90020 (Unabridged) User's Guide.
  4. Press Average Type > Auto (default). Learn more Chapter 19 Interference Analyzer (SA Mode) - Option 236 and to “Adjusting the Measurement Setup Settings”, in the C-Series N9915-90020 (Unabridged) User's Guide6.
  5. Press Freq/Dist > Center > 1 GHz
  6. Press Freq Span > 1 MHz (default).

How to Setup IQ Analysis Streaming

This feature’s intended use is that the Streamed data will be sent to another computer. That computer or another one will act as a SCPI controller and is required for actually controlling the streaming, in particular setting up network data and starting and stopping the streaming.

 

The feature provides continuous streaming of IQ data up to 1.25 MSamples/sec over the Ethernet port in either VITA49A or Decodio formats.

 

If locked to GPS, will populate the timestamp applied to streamed data packets. If not locked to GPS, the system clock time is used to stamp the streamed data packets. Refer to Chapter 9, “System Settings” and to “Frequency Reference”.

 

General setup for IQ Streaming:

 

  1. Press Meas Setup 4 > IQ Analysis > Streaming
  2. Then IQE SampRate > Manual > 1.25 MHz (default when set to Auto).
  1. Configure Center Frequency, Span, Preamp, and RF Attenuation
    1. Press Freq/Dist > Center > 1 GHz
    2. Press Freq Span > 1 MHz (default).

This forces the Span to be:

Span = 1.25 * Span.

 

    1. Then to adjust receiver gain:

 

Typically, the goal is to be able to see the desired signal that you want to capture as close as possible to the top of the display grid on the screen, without causing an ADC over range to be displayed. This maximizes the signal-to-noise ratio.

 

 

Press Scale/Amptd then

or

To adjust manually:

 

  1. Setup IQ Streaming protocol, destination host, and port:

 

To set the destination host, IQ streaming protocol, and samples per packet, refer to the [:SENS]:IQST subsystem commands in the FieldFox Handheld Analyzer SCPI Programming Guide on www.keysight.com.

 

 

  1. Start Streaming: Refer to the FieldFox Handheld Analyzer SCPI Programming Guide on www.keysight.com.
  1. When done press Exc to stop streaming or refer to the FieldFox Handheld Analyzer SCPI Programming Guide on www.keysight.com.

 

Or via the FieldFox front panel, choose:

Or simply choose:

Effective Isotropic Radiated Power (EIRP) – (SA Mode Only)

How to Select Effective Isotropic Radiated Power (EIRP)

  1. Press Measure 1
  2. Then Channel Measurements > EIRP Off to open a menu of softkeys to set up EIRP.

 

How to Setup EIRP (Effective Isotropic Radiated Power)

General setup and an example for EIRP:

 

For this example we are using an isotropic antenna with the following specifications:

 

  1. Press Measure 1 > Channel Measurements > Channel Power > EIRP Off then choose from the following:

 

  1. Configure Center frequency, Span, Preamp, and RF Attenuation

 

  1. Configure Center frequency, Span, Preamp, and RF Attenuation

 

  1. Summary of EIRP setup, per step 1.

 

  1. Start EIRP: Press Restart

 

  1. When done press:

 

  1. Optional: To clear the saved horizontal and vertical EIRP values press:

Clear H & V