Chapter 8 Data Analysis Features

The following features can be used after a measurement to analyze the results.

In this Chapter

All About Markers

Markers move along the X-axis range of the measurement trace to provide a numerical readout of each measured data point. Markers also allow you to search for specific Y-axis values.

A trace can contain up to six markers.

The marker readout on the FieldFox screen displays X and Y-axis information for the current active marker ONLY.

A Marker Table can be displayed that allows you to simultaneously view X and Y-axis information for all markers.

Markers can be used in CAT, EMI Measurements, I/Q Analyzer, NA, NF, Phased Array Antenna, RTSA, SA, and Pulse Measurements Modes.

How to Create Markers

1. Press Marker.
2. Then Markers 1...6 to select a marker to activate.
3. Then Normal to activate that marker. A marker is created on the trace in the middle of the X-axis. That marker is now active.
4. Then move the marker using the rotary knob, the  arrows (), or by entering an X-axis position with the number keys.
5. Then press Enter.

How to move a Marker after it is created

• Press Marker.
• Then Markers 1...6 repeatedly until the marker of interest is selected. The OFF, Normal, Peak, or Delta softkey is black to indicate the current setting of each marker.
• Then move the marker as when it was first created.
• Markers can also be moved using one of the marker search functions. Refer to “Searching with Markers”.

Figure 8-1 Marker 2 is Active, marker 1 is NOT active.

About Delta Markers

A Delta marker provides X-and Y-axis readout information that is relative to a ‘reference’ marker.

A Delta marker is created with a D (delta symbol) to distinguish it from the reference marker.

All six markers can be a Delta marker pair.

Peak search functions can be performed using delta markers.

Figure 8-1 A Delta marker and its associated reference marker.

In the graphic above, the marker readout shows the difference between the two markers in frequency and amplitude.

How to Create a Delta Marker

• Create a Normal marker and move it to the reference position.
• Press Delta. The marker becomes the reference marker and fixed in its X-Axis position.
• Move the Delta marker using the numeric keypad, the  arrows (), or the rotary knob.
• Press Enter when finished.

How to move the Reference marker

• Press Normal to turn the Delta marker OFF.
• Move the marker to the new position.
• Then press Delta again, to turn the Delta marker back ON.

Fix the position of the Reference marker (I/Q Analyzer, RTSA, and SA Modes ONLY)

In SA mode, the reference marker can be fixed at the Y-axis position of the data trace when the marker was created, or it can ‘float’ with each sweep at the Y-axis position of the data trace. In CAT and NA mode, the reference marker always floats with the data trace.

• Create a Delta marker.
• From the Mkr ->/Tools menu, press More (SA mode only), then Marker Properties, then Delta Ref Fixed
• OFF – The reference marker floats at the data trace Y-axis position.
• ON – The reference marker is fixed at the Y-axis position of the data trace when the marker was created (default IQA and SA modes).

Signal Track Marker (NF and SA Mode ONLY)

In NF and SA mode, the marker can be peaked at the Y-axis position of the data trace and the marker is centered on the screen. This setting applies to all NF and SA markers.

• Create a Signal Track marker (peak).
• From the Mkr ->/Tools menu, press More, then Marker Search

• OFF – The reference marker floats at the data trace Y-axis position.

• ON – The reference marker is peaked at the Y-axis position of the data trace and the marker is centered on the screen.

Marker Table

The Marker Table can be displayed at the bottom of the FieldFox screen. It can display information for up to 6 markers in a full-width window, and up to 3 markers for a half-width window (NA mode). The marker table “squeezes” the graticule area when activated.

How to display the Marker table

1. Press Marker.
2. Then More
3. Then Marker Table On Off.

Coupled Markers (NA Mode)

I/Q Analyzer (IQA) mode has coupled markers. but the behavior is different than the NA mode Coupled Markers behavior. Refer to “Coupled Markers (Waveform Only)” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.

Coupled Markers, available in NA mode only1 and allows you to simultaneously create and move markers that have the same number for all traces. For example, when marker 2 is created on a trace, a marker 2 is created for ALL traces. When any marker 2 is moved, they all move together to the same X-axis position.

• Coupled markers are allowed only in NA mode and are relevant only in multi-trace configurations.
• You can have markers that are coupled and others that are uncoupled.
• Peak functions move the marker to the peak on the active trace, while all other markers move to the same X-axis position.

Figure 8-3 Coupled Markers move on ALL traces at the same time (NA shown).

1. IQA mode has coupled markers, but the behavior is different than NA mode’s coupled markers. Refer to “Coupled Markers (Waveform Only)” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.

How to create Uncoupled Markers

Markers are coupled by default.

To create markers that are NOT coupled (move independently on each trace):

1. Press Marker
2. Then More
3. Then Coupled Markers OFF

Marker Colors

As shown in the above image, in NA and CAT Modes, markers are the same color as the trace to which they are assigned. In SA Mode, the marker color is NOT the same as the trace.

Marker colors can NOT be changed.

Marker Trace (CAT, NA, NF Modes)

The Marker Trace setting is used to move markers between the data trace and memory trace.

When Coupled Markers is ON, this setting applies to the active marker for ALL traces that are coupled. Otherwise, this setting applies to the active marker on only the active trace.

How to move a CAT, NA, and NF mode marker between traces

1. With at least one marker present, press Marker then More.
2. Then select the marker to move using Marker 1,2,3,4,5,6.
3. Then toggle Marker Trace Auto Data Mem.

• Auto - Marker resides on data trace when it is visible. Marker resides on memory trace when only IT is visible (Default setting).
• Data - Marker resides on data trace, even when not visible.
• Mem - Marker resides on memory trace, even when not visible.

Marker Trace (IQA and SA Mode)

Marker Trace determines the trace number on which a marker resides. A marker is created on, or can later be changed to, the trace number specified by the Marker Trace selection. When changed, a marker moves to the same X-axis location on the specified trace.

Learn more about IQA Traces in “Trace Display States (IQA Mode)” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.

Learn more about SA Traces in “Trace Display States (SA Mode)”.

How to move an IQ and SA mode marker between traces

1. With two or more traces present, press Marker and Enter to create a marker. The marker is created on the current Marker Trace selection (default setting is 1).
2. Then More
3. Then select the marker to move using Marker 1,2,3,4,5,6.
4. Then toggle Marker Trace 1,2,3,4

• The selected marker is moved to the specified trace.
• When a marker is moved to a ‘blank’ trace (not visible) the marker moves to the same X-axis position at either the Y-axis position of the last data, or to the ZERO position.

Marker Format

The Marker Format setting allows you to choose the format of the marker readout that appears in the upper-right corner of the screen and in the marker table. The marker format can be independent of the trace format, and can be set independently for each trace. All markers on a trace have the same marker format.

How to choose marker format

• Press Marker
• Then More
• Then Marker Format
• For NA Mode measurements, choose from the following:

There are more trace formats available than marker formats. To display marker readouts in more formats than are shown here, change the trace format, then select Default. Learn how to change format in “Format”.

• For TDR (CAT) Mode, choose from Default and Z Mag.

Searching with Markers

Marker Searches are used to move markers to locations on the trace which exhibits the characteristics of the search criteria. Learn What is a 'Peak' in “What Is a ‘Peak’”.

How to Search with Markers

The following menu structure applies to NA Mode. Keystrokes will be slightly different for CAT, Pulse Measurements, and SA Modes.

1. Activate the marker to be used for the search (NOT necessary with Bandwidth search.)
2. Then press Mkr ->/Tools.
3. Then choose one of the following:
• Tracking ON OFF (NA Mode ONLY)
• ON causes the active marker to search for the specified criteria with each new sweep. Search criteria can include: Target, Bandwidth, Peak, Min. The searches begin with the first sweep after Tracking is turned ON, based on the current search type. Trk appears next to the marker number.
• OFF causes a new marker search only when the search feature is re-executed.
• Peak Moves the active marker to the HIGHEST amplitude data point of the trace. Peak Excursion and Peak Threshold value is ignored. In SA Mode, the LO feed-through signal (0 Hz) is also ignored.
• Next Peak Moves the active marker to the next highest amplitude data point of the trace. Peak Excursion value is ignored.
• Mkr -> Center Moves the current active selected marker to the center frequency for the current frequency range displayed.
• Mkr -> RefLev Moves the current active marker to the acquisition.
• Minimum (Not available in DTF, RTSA, SA, or I/Q Analyzer) Moves the active marker to the LOWEST amplitude data point of the trace.
• Min Search (I/Q Analyzer, RTSA, and SA modes Only) Moves the active marker to the LOWEST amplitude data point of the trace. If a marker is turned off, it is turned on before the minimum search is performed.
• Target (NA Mode and Pulse Measurements ONLY) Enter the Target value. The marker moves to the first occurrence of the Target value to the right of its current position. The FieldFox interpolates between measured data points to find the exact Target value to two decimal points. The interpolated X-axis value is displayed in the marker readout or marker table. Subsequent presses of the Target softkey cause the marker to move to the right to find the next occurrence of the Target value. When the marker reaches the end of the stimulus range, it “wraps around” and continues the search from the beginning of the stimulus range.
• Bandwidth ON OFF (NA Mode ONLY) Use to quickly toggle BW Markers ON and OFF. When OFF, the marker table appears showing the X and Y-axis positions of all enabled markers.
• Bandwidth (NA Mode ONLY) Specify the level in dB from the peak or valley where bandwidth is measured.
• Negative numbers search for a Peak bandpass, such as a filter S21 response.
• Either of the following TWO methods can be used to search for a Valley or Notch filter, such as the S11 response of a bandpass filter.
• Negative values search down from the TOP (MAX) of the response.
• Positive values search up from the BOTTOM (MIN) of the notch.
• If you first enter Negative, then Positive values, it may be necessary to press Marker, then More, then Markers All Off.

Figure 8-4 S21 of a filter with BW Markers and associated readout values. The search criteria is -3 dB.

Figure 8-5 S11 of the same filter with same search criteria: -3 dB.

   The same values would result from a search criteria of approximately +30.4 dB.

After pressing Bandwidth, four markers are automatically created to find the first negative or positive bandpass over the displayed frequency range.

Bandwidth Search can be used ONLY with Log Mag display format.

• The following six values are displayed for Bandwidth Search:

• BW:  Width of the filter. (marker 2 freq) minus (marker 3 freq).
• Center: Marker 4 frequency. Mathematical midpoint between marker 2 and marker 3.
• Q:  Center Frequency / Bandwidth.
• Loss:  Marker 1 amplitude.
• Left: Frequency of marker 2 or 3 (to left of marker 1).
• Right: Frequency of marker 2 or 3 (to right of marker 1).
• Press Back to return to the previous menu.

Press Peak Search then choose from the following:

• Peak Moves the active marker to the HIGHEST amplitude data point of the trace. Peak Excursion value is ignored. In SA Mode, the LO feed-through signal (0 Hz) is also ignored.
• Next Peak Moves the active marker to the next highest amplitude peak from where it currently resides.
• Peak Left (Not IQA) Moves the active marker to the next data point to the left that meets the ‘Peak’ criteria. When no data points to the left meet the ‘Peak’ criteria, the marker does not move.
• Peak Right (Not IQA) Moves the active marker to the next data point to the right that meets the ‘Peak’ criteria. When no data points to the right meet the ‘Peak’ criteria, the marker does not move.

The following applies to DTF Measurements ONLY:

• More then:
• Track Peaks ON OFF When Track Peaks is ON, markers will find the new peak with every sweep. While in this Mode, the markers can NOT be turned OFF or moved.
• Find 3 Peaks Three markers are created and find the highest peaks (faults) on the trace.

The following applies to IQA Measurements ONLY:

• More then:
• Min Search Moves the active marker to the minimum frequency (IQA displays time) currently displayed on the screen.
• Mkr Properties then:
• Peak Criteria then refer to “How to set Peak Criteria”:
• Delta Ref Fixed Enables or disables the delta reference fixed marker.
• Peak Left (IQA Spectrum Only) Moves the active marker to the next data point to the left that meets the ‘Peak’ criteria. When no data points to the left meet the ‘Peak’ criteria, the marker does not move.
• Peak Right (IQA Spectrum Only) Moves the active marker to the next data point to the right that meets the ‘Peak’ criteria. When no data points to the right meet the ‘Peak’ criteria, the marker does not move.

Using Mkr5/Mkr6 to find mins/maxs between Mkr1 and Mkr2 / Mkr3 and Mkr4 (CAT and NA Mode)

Use this feature to search minimum and maximum values within sub-spans defined by Mkr1 and Mkr2, and Mkr3 and Mkr4. This facilitates measuring minimum and maximum values on your uplink and downlink channels, or only in the passband of a DUT. Use in conjunction with marker table and limit lines to verify your DUT’s signals and to adjust or tune as needed. See also, “All about Limit Lines”.

When markers are set to Normal, Mkr5 and Mkr6 can be used to find the minimum and or maximum values between Mkr1 and Mkr2 (using Mkr5) and Mkr3 and Mkr4 (using Mkr6). Refer to Figure 8-6.

If your Markers are positioned and in Normal marker mode, no changes are made to the Mkr1 through Mkr4 settings.   If your Markers are not previously positioned and in Normal marker mode, when you select the Mkr5 and Mkr6 maximum and minimum setting, your markers are set as follows: Markers are all set to Normal Mkr1 and Mkr3 are set to 1/4 full span Mkr2 and Mkr4 are set to 3/4 full span

How to use the Mkr5 and Mkr6 markers to find maximums and minimums between your Normal markers (CAT and NA Mode):

This section assumes you understand the previous marker features. And, that you have previously positioned your markers (Mkr1 and Mkr2 or and Mkr3 and Mk4) and set the markers up as Normal markers using “How to create Markers” and other previous marker sections. For example, if your markers are set to Delta, change to Normal, and verify the marker positions are correct. Refer to Figure 8-6.

• Then press Mkr ->/Tools.
• Then More (For DTF, TDR measurements, and NA Mode, skip this step and proceed to the next step.)
• Then Mkr5 & Mkr6 Search
• For Mkr1 & Mkr2 maximum or minimum value search:
• Then Mkr5 Peak or
• Mkr5 Min

Or for Mkr3 & Mkr4 maximum or minimum value search:

• Then Mkr6 Peak or
• Mkr6 Min

Figure 8-6 CAT Mode Mkr5 and Mkr6 Search Example

What Is a ‘Peak’

You define what the FieldFox considers a “peak” by setting the Peak Threshold and Peak Excursion and for I/Q Analyzer Only Cont Peak Search.

These two peak criteria settings are set individually for each trace and for each mode (CAT, SA, or NA).

These settings do NOT survive a FieldFox or Mode Preset.

The Peak Threshold and Excursion settings are NOT available in DTF measurements. To make these settings, create a non-DTF CAT mode measurement, then change the measurement back to DTF.

How to set Peak Criteria

• Press Mkr ->/Tools.
• In CAT and NA modes:
• Then Peak Search.
• Then Peak Criteria
• In IQA (Spectrum) and SA mode:
• Then More
• Then Mkr Properties
• Then Peak Criteria
• In IQA (Waveform) mode:
• Then Mkr Properties

• Then Peak Criteria

After selecting Peak Criteria for CAT, IQA, NA, or SA mode:

• Then select the following:

• Peak Threshold Minimum amplitude (dB). To be considered valid, the peak must be above the threshold level. The valley on either side can be below the threshold level.

• Default =  –190 for CAT and NA Modes; –90 for SA Mode.

CAT mode Loss measurements are displayed in positive values. In these cases, the Peak Threshold setting is inverted. For example, Peak Threshold = -20 will consider any peak that has less Loss than 20 dB to be valid.

• Peak Excursion The vertical distance (dB) between the peak and the valleys on both sides. To be considered a peak, data values must “fall off” from the peak on both sides by the excursion value. Default = 0.5 dB for CAT and NA Modes; 6 dB for SA Mode.
• Cont Peak Search (I/Q Analyzer Only) Enables or disables the Continuous Peak Search marker. When Continuous Peak Search is on, a peak search is automatically performed for the selected marker after each sweep. The rules for finding the peak are exactly the same as for Peak Search, including the use of peak criteria rules. See also, “Using Markers (IQA)” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.
• Delta Ref Fixed Enables or disables the delta reference fixed marker.

Peak Excursion and Peak Threshold example—the settings for the trace in the following image are:

• Threshold: –10 dB
• Excursion: 1 dB
• Scale = 1 dB / Division.

Peak A = Valid Peak (Above Threshold and Excursion Settings)

Peak B = Invalid Peak (Below 1 dB Excursion Setting)

Peak C = Invalid Peak (Below –10 dB Threshold Setting)

Marker Functions

Marker functions are used to change FieldFox frequency or distance settings to those of the active marker.

How to use Marker Functions

1. Activate the marker to move.
2. Then press Mkr ->/Tools
3. Then Mkr -> (this step not required for I/Q Analyzer mode)
4. Then choose one of the following:

• Mkr -> Center (Not available in DTF, I/Q Analyzer (waveform), or SA mode with zero span) The center frequency of the measurement becomes the value of the active marker. The frequency span is adjusted accordingly.

• Mkr -> Delay (NA mode ONLY.) The group delay value of the active marker becomes the electrical delay setting of the trace. Learn how to set group delay format in “Calibration Settings”. Learn more about electrical delay in “Electrical Delay”.

• Mkr-> RefLev (IQ Analyzer (NOT waveform) and SA mode ONLY) The acquisition becomes the magnitude of the active marker.

• Mkr->TuneFreq (SA mode with Tune & Listen ONLY) The Tune & Listen Frequency becomes the frequency of the active marker.

The following applies to DTF Measurements ONLY:

• More then:

• Mkr->Start Distance The Start Distance of the measurement becomes the value of the active marker. Markers that would no longer appear on the screen are moved to the new Start Distance.

• Mkr->Stop Distance The Stop Distance of the measurement becomes the value of the active marker. Markers that would no longer appear on the screen are moved to the new Stop Distance.

I/Q Analyzer (IQA) Marker Functions

The following Marker Functions are available in I/Q Analyzer Mode ONLY (exceptions are noted):

• Noise Marker (Available in SA mode)
• Band/Interval Power Marker (Available in SA mode)
• Coupled Markers
• Band Span
• Interval Band Span
• Continuous Peak Search

Learn more about Noise and Band/Interval Power marker functions starting in the IQA chapter here: “Noise Marker” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.

SA Marker Functions

The following Marker Functions are available in SA Mode ONLY (exceptions are noted):

• Noise Marker (Available in I/Q Analyzer mode)
• Band/Interval Power Marker (Available in I/Q Analyzer mode)
• Frequency Counter at Marker
• Audio Beep with Marker
• Time Zero Fixed Marker

Learn more about these marker functions starting in the SA chapter here: “Noise Marker” in Chapter 11 "IQ Analyzer (IQA) – Option 351 (CPU2 Only)", of the A-Series N9927-90020 (Unabridged) User's Guide.

All About Limit Lines

Limit lines are visual representations, drawn on the FieldFox screen, of the specified limits for a measurement. With this capability, you can easily compare measured data versus specifications. Optionally, you can enable an audible beep and display Pass or Fail information for each measurement.

The following are Limit Options for Limit Lines in CAT, NA, NF, RTSA, and SA. But, RTSA mode has some exceptions: –When using the Spectrogram measurement, Limit lines are only available when the display Measurement Type for Spectrogram View used is: Overlay. –RTSA mode does not support any PASS or FAIL features. –Beep, Warning, and Margin softkeys are grayed out (not active) in RTSA mode.

IMPORTANT! For CAT and NA modes, limit lines do not apply where F1 = F2.

• You can have up to as many limit line segments as there are data points for each measurement trace allowing you to test all aspects of your measurements.
• Limit lines are available in CAT Mode, NA Mode, NF Mode, and SA Mode. Power Meter Mode uses different limit settings. Learn more in “Limits” in Chapter 22 "Power Meter (USB/LAN) Mode – Option 302", of the A-Series N9927-90020 (Unabridged) User's Guide.
• Limit lines and limit testing are NOT allowed in NA Mode with Smith Chart or Polar display formats.
• A simple Display Line is also available in I/Q Analyzer, NF, and SA Modes ONLY. Learn more in “Display Line (I/Q, NF, and SA Modes Only)”.
• Limit lines can be saved and recalled with an *.sta file. Learn more in “How to Save and Recall Limits”.  Learn more in “How to Save and Recall Limits”. .*sta files can also be saved and recalled independently from the Limit softkeys. Learn more in Chapter 10 "File Management", of the A-Series N9927-90020 (Unabridged) User's Guide.

How to Create Fixed Limit Lines

The following are Limit Options for Limit Lines in CAT, NA, NF, RTSA, and SA. But, RTSA mode has some exceptions: –When using the Spectrogram measurement, Limit lines are only available when the display Measurement Type for Spectrogram View used is: Overlay. –RTSA mode does not support any PASS or FAIL features. –Beep, Warning, and Margin softkeys are grayed out (not active) in RTSA mode.

There are two ways to build a Fixed limit line:

1. Build (limits) From a Trace. Learn how in “Build From Trace”.
2. Enter X/Y data points into the on-screen editor. The limit line is formed as the FieldFox ‘connects the dots’ on the screen. To create frequency gaps that are NOT tested, use separate limit lines. The X-axis values for two lines can overlap.
3. Press Limit 8 > Edit Limits. A limit line table appears.
4. Use the Up / Down arrows () and rotary knob to navigate the cursor to the following editable cells.

• Description - Press Edit, then enter a description for the limit line using the FieldFox labeler. Learn how in “How to use the FieldFox labeler ”.
• Fixed/Relative – Press Edit to toggle between the following:
• Fixed - the limit line does not move. The X/Y coordinates are absolute locations on the screen.
• Relative - the limit line moves relative to the center frequency and acquisition.

Note: It is easiest to first create Fixed Limits, then change this setting to Relative. Learn more “Relative Limit Lines”.

• Upper/Lower – Press Edit to toggle between the following:
• Upper:
• All modes except RTSA: (Default) FAILS any measured data point ABOVE the line.
• RTSA mode: (Default) Draws visible “ears” going upward from any measured data point BELOW the line.
• Lower:

• All modes except RTSA: FAILS any measured data point BELOW the line.

• RTSA mode: Draws visible “ears” going downward from any measured data point ABOVE the line.

• Off/On – Press Edit to toggle between the following:
• On:

• All modes except RTSA: Limit line is drawn on the screen and PASS/FAIL testing occurs.

• RTSA mode: Limit line is drawn on the screen, but no PASS/FAIL testing occurs.

• Off - All modes: Limit line is NOT drawn on the screen and testing does NOT occur.
• Frequency – Enter a numeric X-axis value of the data point.
• Amplitude – Enter a numeric Y-axis value of the data point.

5. Then optionally choose from the following:

• Press Add then choose from the following:
• Add Point - Adds a blank X/Y data point below the cursor.
• Add Limit - Adds a default limit line below the current limit.
• Press Clear then choose from the following:
• Clear Point - Removes the X/Y data point on which the cursor resides.
• Clear Limit - Removes the limit Line on which the cursor resides.
• Clear All - Removes ALL limit lines.
• Press <Back to return to the Limit menu.

Relative Limit Lines

Relative limit lines are X/Y coordinates that are referenced to the center frequency (X-axis) and acquisition (Y-axis).

Use relative limits to test devices or signals that are identical except for the center frequency or amplitude. With relative limit lines in place, you change the center frequency of the measurement and the limits look as though they are in the same location.

The same is true for acquisition. When you expect to measure a different power level, instead of changing the Y-axis value of all of the fixed limits, simply change to relative limits. The limits will then remain a constant Y-axis distance from the acquisition.

Each limit line can be changed at any time from Fixed to Relative, and Relative to Fixed.

How to Create a Relative Limit Line

The easiest way to create a Relative limit line is to create a Fixed Limit at a specific center frequency and acquisition. Learn how “Relative Limit Lines”. Then change the limit line to Relative. The X/Y data points will be re-calculated relative to the center frequency and acquisition.

Build From Trace

A limit line can be built from an existing trace. One X/Y point is made from each measured data point. Then, using an offset value, you can shift the limit line UP for upper limits or DOWN for lower limits.

Once limit lines have been built from the trace, changes that you make to the trace, such as frequency range, do NOT change the limits. However, the limit line properties can be edited just like standard limit lines.

Figure 8-7 A lower limit line (red) built from the trace (yellow) shifted down 5 dB.

How to Build Limit Lines from a Trace

Build from Trace is NOT allowed for traces with more than 1001 data points.

1. Select the trace from which limits will be built.
2. Press Limit 8 > Edit > Build From Trace. A limit line table appears.

Figure 8-8 Build From Trace (1 of 2)

3. Use the  arrows () to select ON.
4. Use Offset to shift the limit line UP or DOWN. Learn how below.

Figure 8-9 Build From Trace (2 of 2)

Limit Options

The following are Limit Options for Limit Lines in CAT, NA, NF, RTSA, and SA. But, RTSA mode has some exceptions: –When using the Spectrogram measurement, Limit lines are only available when the display Measurement Type for Spectrogram View used is: Overlay. –RTSA mode does not support any PASS or FAIL features. –Beep, Warning, and Margin softkeys are grayed out (not active) in RTSA mode.

How to set Limit Options

1. Press Exit if the limit table is visible.
2. Then Options.
3. Then choose from the following:

• Beep
• On Pass Audible beep sounds when a sweep passes.
• On Fail Audible beep sounds when a sweep fails.
• Off No audible beep sounds.
• Warning On Off Shows Pass or Fail indication on the display with each sweep. Data points that fail are highlighted.
• Limit Type Then Fixed or Relative.
• Offset Shifts the limit line up or down. Enter an offset value using the rotary knob, the  arrows (), or by entering a value with the number keys.
• Enter a positive offset to shift the limit line UP, usually used with UPPER limits.
• Enter a negative offset to shift the limit line DOWN, usually used with LOWER limits.
• Margin Shifts the limit line up or down like an offset, but only virtually. The limit line does NOT appear to move. Enter a Margin value using the rotary knob, the  arrows (), or by entering a value with the number keys.

Enter a positive margin to virtually shift the limit line UP.

Enter a negative margin to virtually shift the limit line DOWN.

• LogX Interp Auto Off – Enables/disables the logarithmic X-axis interpolation trace (default == Auto). Learn more, refer Chapter 7, “SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)” and to “Logarithmic X-axis Limit Line Interpolation (EMI and SA modes Only)”.

How to Save and Recall Limits

1. Press Save/Recall 9 then Device to set the Device (Internal, SD card, or USB flash drive) to be used for the Save or Recall. Learn more in “Set File Type and Select Device”  in Chapter 9 "System Settings", of the A-Series N9927-90020 (Unabridged) User's Guide.
2. Press Limit 8.
3. Then choose from the following:

• Save Limits After limit lines have been defined, this saves the line definition to a file on the specified device (e.g., *.xml).
• Recall Limits Recalls a limit Line definition from the specified device (e.g., *.csv).

Recall can recall both *.xml or *.csv file types. But, Save can only save files as *.xml.

Creating and Importing *.csv Limit Line Files

This sections defines the procedure for creating a importable *.csv file that defines the limit lines for your current trace.

Data delimiter Usage: – Data delimiters of “,” or “;” can be used. – Data delimiters must be consistent in a file: Either “,” or “;” can be used. – Data delimiters are auto-detected. – If the “;” data delimiter is detected, then the numeric format is assumed to use “.” as the grouping separator. – When “,” is used as the decimal separator (e.g. 1,103.45 would be written as 1.103,45 or 1.4e8 is written as 1,4e8).

1. Define your measurement (e.g, expected maximum and minimum power levels, frequency band breaks, etcetera).
2. Create and save a *.csv file to your PC using these values using parameters defined in Table 8-1 and similar to the example in Figure 8-8.
3. Copy the limit line *.csv file from your PC to a CD card or USB storage device.
4. Remove the SD card or USB storage device from your PC.
5. Install the SD card or USB storage device into the FieldFox.
6. Set the device type (SD Card or USB storage device) by referring to “Set File Type and Select Device” in  in Chapter 9 "System Settings", of the A-Series N9927-90020 (Unabridged) User's Guide.
7. Press Limit 8 > All Limits ON > Recall Limits or

press Limit 8 > Recall Limits

1. Use the  arrows () or the rotary knob to select the limit lines *.csv file to display on the FieldFox.
2. Look for the following messages:

• When successful, the FieldFox displays a message similar to this:

“Recalled [USBDISK]:\LimitLineExample.csv”.

• If unsuccessful, the FieldFox displays a message similar to this:

“212, Operation failed. Possible file content error.”

For an example trace with limit lines, refer to Figure 8-9.

Table 8-1 Example: Limit Line Formatting (*.csv)

Figure 8-8 Example: Table Limit Line Formatting in actually LimitExample.csv

Figure 8-10 Example: Recalled Limit Line Formatting LimitExample.csv

Display Line (I/Q, NF, and SA Modes Only)

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 8-11 Display Line with Annotations (SA mode shown, but others are similar)

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.

All About Trace Math

Trace Math is available in CAT (excluding DTF measurements), NA Mode, and FOPS (under USB Power Meter mode).

Noise Figure (NF—Option 356) does not have trace math, but does have the ability to display data and memory traces. Refer to “How to display data and memory traces”.

A trace is a series of measurement data points that are connected to form a line. This ‘live’ data trace is updated as data points are measured.

A memory trace is a live trace that has been stored in the FieldFox volatile memory. It then becomes static, meaning it is not updated with measurements. It can be displayed on the screen by itself, or with a data trace for comparison purposes.

• In NA mode, memory traces are the same color as data).
• In CAT mode and FOPS, the data trace is displayed in yellow and the memory trace is displayed in blue.

How to display data and memory traces

1. Press Trace 6.
2. Press Math and Memory then Data->Mem to store the current live trace into memory. A ‘beep’ sounds to confirm the data trace has been saved to memory. There is no display annotation that indicates that the memory trace has been stored.
3. Then choose from:

• Press Data to view only the data trace.
• Press Memory to view only the memory trace.
• Press Data & Memory to view both the live trace and the stored memory trace.

How to perform Trace Math

Trace math is performed between a live trace and a memory trace. When one of the following math operations are selected, the yellow data trace displays the current measurement with the selected trace math applied. The math operation symbol indicated below in [brackets] is displayed on the lower left corner of the screen.

1. Press Trace 6.
2. If not already stored, press Data->Mem to store the current live trace into memory.
3. Then Data Math.
4. Then choose one of the following:

• Data + Mem [D+M] Current measurement data is added to the data in memory.
• Data – Mem D-M] Current measurement data is subtracted from the data in memory.
• Data / Mem [D/M] Current measurement data is divided by the data in memory.
• Math Off [Data] Displays trace data with NO math applied.

About Math Operations

Data / Memory and Data - Memory math operations are performed on complex linear data before it is formatted. Because data is often viewed in log format, it is not always clear which of the two math operations should be used. Remember: dividing linear data is the same as subtracting logarithmic data. The following illustrates, in general, when to use each operation.

Use Data / Memory for normalization purposes, such as when comparing traces “before” and “after” a change is made or when measuring trace noise. In the following table, the Data/Mem values intuitively show the differences between traces. It is not obvious what Data-Mem is displaying.

Use Data - Memory to show the relative differences between two signals. Use for comparison of very small signals, such as the S11 match of two connectors.

In the following table, Data/Mem shows both pairs of connectors to have the same 2 dB difference. However, the second pair of connectors have much better S11 performance (–50 and –52). The relative significance is shown in Data-Mem.

All About Scale Settings

IMPORTANT! Some of the scale settings do not apply to all of the modes.

How to Use Scale Settings

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

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

How to set Scale

1. Press Scale / Amptd.
2. Then choose from the following three methods:

• Autoscale Automatically adjusts the Y-axis to comfortably fit the Minimum and Maximum amplitude of the trace on the screen.
• Set Scale, acquisition, and Reference Position:
• Scale Manually enter a scale per division to view specific areas of the trace.
• Ref Level Manually set the value of the reference line. Enter a negative value by pressing Run/Hold (+/-) either before or after typing a value.
• Ref Pos Manually set the position of the reference line. Values must be between 0 (TOP line) and 10 (BOTTOM line).
• Range Manually set the absolute power (dBm).
• Set Top and Bottom graticule values. The scale per division is calculated.
• Top to set the value of the Top graticule.
• Bottom to set the value of the Bottom graticule.
• Enter a negative value by pressing Run/Hold (+/-) either before or after typing a value.

Scale annotation on the FieldFox screen Reference Line = red arrow Ref Level = -40 dB Ref Position = 1 Scale = 2 dB per division

Averaging (CAT, NA, Power Meter, Channel Scanner, and Pulse Measurement Modes Only)

Trace Averaging helps to smooth a trace to reduce the effects of random noise on a measurement. The FieldFox computes each data point based on the average of the same data point over several consecutive sweeps.

Average Count determines the number of sweeps to average; the higher the average count, the greater the amount of noise reduction.

An average counter is shown in the left edge of the screen as Avg N. This shows the number of previous sweeps that have been averaged together to form the current trace. When the counter reaches the specified count, then a ‘running average’ of the last N sweeps is displayed. Average Count = 1 means there is NO averaging.

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

Averaging is often used to increase the dynamic range of a measurement. To achieve the highest dynamic range, select NA mode and reduce the IF Bandwidth setting. Learn more about dynamic range in “Increase Dynamic Range”.

How to Enable/Disable Averaging

1. Press BW 2.
2. Then choose from:
• Channel Scanner: Then Average OFF ON change to ON to enable averaging (Default = OFF).
• Power Meter, Pulse Measurements: Then Average Auto MAN OFF change to Auto or Man to enable averaging (Default = Auto, Auto == FieldFox sets the average count based on current mode settings).
• CAT, NA: Then Average 1 change to a number >1 to enable/set averaging (Default = 1 (OFF)).
3. Press Enter.

Refer to “How to set Trace Averaging”.

How to set Trace Averaging

1. Press BW 2.
2. Then choose from:
• Channel Scanner: Then Average OFF ON change to ON to enable averaging and then set the current count, using Average Count softkey.
• Power Meter, Pulse Measurements: Then Average Auto MAN OFF change to Auto or Man to enable averaging (Default = Auto, Auto == FieldFox sets the average count based on current mode settings).
•  Or set the current count, using the Num Averages softkey
• CAT, NA: Then Average 1 change to a number >1 to enable/set averaging (Default = 1 (OFF)).
3. Enter a value using the numeric keypad. Enter 1 for NO averaging.
4. Press Enter.
5. While Trace Averaging is in process, press Sweep 3 then Restart to restart the averaging at 1.