Spectrum Analyzer  

Configure SA settings

Using Hardkey/SoftTab/Softkey

Using a mouse

1. Press Freq > Main >  SA Setup....

1. Click Stimulus

2. Select SA Setup...

SA Setup Dialog tab help

Sweep Type - Sets the spectrum analysis sweep type. See Type (Sweep).

X-Axis Point Spacing - See X-Axis Point Spacing

Show segments - Displays the segment table at the bottom of the display. Number of points for each segment cannot be specified.

Hide segments - Hides the segment table.

Processing

Resolution Bandwidth - Provides the ability to resolve, or see closely spaced signals. The narrower (lower) the Resolution Bandwidth, the better the spectrum analyzer can resolve signals. In addition, as the Resolution Bandwidth 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 Resolution Bandwidth is narrowed, the sweep speed becomes slower.

Auto - Check to couple Resolution Bandwidth to the frequency span in a ratio based on the Span/RBW setting. As the frequency span is narrowed, the Resolution Bandwidth is also narrowed providing increased ability to resolve signals. Clear to uncouple the settings.

Video Bandwidth - Sets the video averaging factor. The averaging operation is applied after the DFT (Discrete Fourier Transform) and before the image rejection. The trace data is smoothed with the method selected by the Video Averaging Type. More smoothing occurs as the Video BW is set lower. However, as the Video BW is narrowed, the sweep speed becomes slower. The Video Bandwidth can be set from 1.480 Hz to 3 MHz when Auto is deselected. The VBW feature is emulated with averaging (see below the Averaging count). The averaging factor is computed with this equation: Round(0.8 + 0.38 * RBW / VBW).

Auto - Check to couple the Resolution Bandwidth to the Video Bandwidth in a ratio based on the RBW/VBW setting. Clear to uncouple the settings.

Detector Type - A "detector" is an algorithm used to map DFT bins into display buckets. There are typically several DFT bins in a single display bucket, and the detector determines how to translate the multiple DFT values into a single display value.

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

Average - Displays the Root Mean Squared (RMS) average power of all the measurements in each bucket.  This is the preferred method when making power measurements.

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

Normal - Provides a better visual display of random noise than Positive peak and avoids the missed-signal problem of the Sample Mode. Should the signal both rise and fall within the bucket interval, then the algorithm classifies the signal as noise. An odd-numbered data point displays the maximum value encountered during its bucket. An even-numbered data point displays the minimum value encountered during its bucket. If the signal is NOT classified as noise (does NOT rise and fall) then Normal is equivalent to Positive Peak.

NegPeak- Displays the minimum value of all the measurements in each bucket.

Peak Sample - Attempts to determine if the display bucket contains an actual signal, or just noise. If a signal is present, the Peak detector is used, otherwise Sample is applied.

Peak Average - Attempts to determine if the display bucket contains an actual signal, or just noise. If a signal is present, the Peak detector is used, otherwise Average is applied.

Fast Peak - Keeps the x-axis grid untouched and indicates the value of the largest DFT bin from the bucket behind each display point.

Bypass - Check to bypass the Detector Type to view all display points from the DFT. This is only available if the total number of DFT points can be handled by the display.

Video Averaging Type - Determines how to compute the video average. When Auto is selected, the optimum type of averaging for the current instrument measurement settings is selected. It averages the magnitude of the DFT bins. Averaging only applies if the video bandwidth is less than the resolution bandwidth.

Voltage - Selects averaging of the detected signal's magnitude and returns the result.

Power - Selects averaging of the detected signal's squared magnitude and returns the square root of the result.

Log - Selects averaging of the detected signal's natural logarithm of the magnitude and returns the exponentiated value of the result.

Voltage Max - Returns the maximum voltage (signal magnitude) measured during the averaging period.

Voltage Min - Returns the minimum voltage (signal magnitude) measured during the averaging period.

Averaging Count - Reads the number of Video bandwidth sweeps that are averaged together. This readout is displayed to the right of the Averaging Type selection (the small "1" shown in the dialog above). It can be read with the remote interface using the SENS:SA:BAND:VID:AVER:COUNt? command.

Settings

Sets the SA (receiver) frequency range when running Linear Frequency sweep type. Use either of the following pairs of settings to determine the frequency range.

Start /Stop - Specifies the beginning and end frequency of the swept receiver range. Start is the beginning of the X-axis and Stop is the end of the X-axis. When the Start and Stop frequencies are entered, then the X-axis annotation on the screen shows the Start and Stop frequencies.

Center /Span - Specifies the value at the center and frequency range. The Center frequency is at the exact center of the X-axis. The Frequency Span places half of the frequency range on either side of center. When the Center and Frequency Span values are entered, then the X-axis annotation on the screen shows the Center and Span frequencies.

Number of Points - Selects the number of trace points on the display. When the Detector is bypassed, the number of display points is read only, it shows the current DFT points to cover the RF span.

Note: When running Segments, the frequency ranges are set by the segment table.

Attenuators

Receiver Attenuation is used to protect the test port receivers from damage or compression. Receiver attenuation causes the applied power at the receiver to be less than the power at the test port by the specified amount of attenuation.

Port 1 is RF In 1, Port 2 is RF In 2. The range is 0 dB to 28 dB, 1 dB step.

SA Source Setup tab help

SA Source Setup is enabled when Src 1/2 out on the front panel is available.

Power On (All Channels)  Check to enable source power for all channels. Only turns power ON if the port State setting is ON.

Source Cells

Name - Src 1/2 Out (Front panel Src 1/2 out)

State

• ON  Source power is ALWAYS ON. Only one port can be turn on unless the unit has the second source or multi-module/unit configuration.  Learn about internal second source restrictions. See also Setting Port Power On/Off for the Second source and Multi Module/Unit configuration.

• OFF  Source power is never ON, regardless of the measurement requirements. Use this setting to prevent damage to a sensitive DUT test port.

Type (Sweep)

CW - The source is set to a CW frequency.

LinFreq - The source is set to sweep from the Start to Stop frequency.

Power - The source is set to a power sweep.

Phase - The source is set to a phase sweep.

LinF+Pwr, Freq+Pha, Pow+Pha, Fr+Pw+Ph - Multi-parameter sweep for the specified parameters. Set the range of sweep for each parameter.

Frequency - Click in the cell, then click Edit, to start the Frequency Settings dialog (below).

Power - Sets the power level at the output of the source. Click in the cell, then click Edit, to start the Power Settings dialog (below).

Phase - Not available on SSA-X

Pulse - Enable/disable pulse measurements. Learn more.

IQMod. - Not available on SSA-X

RF source sweep order

Frequency Power Phase - Sweep from Start to Stop frequency first then sweep power then sweep phase.

Power Frequency Phase - Sweep power first then sweep from Start to Stop frequency then sweep phase.

Phase Frequency Power  - Sweep phase first then sweep from Start to Stop frequency then sweep power.

Phase Power Frequency - Sweep phase first then sweep power then sweep from Start to Stop frequency.

Frequency Phase Power - Sweep from Start to Stop frequency first then sweep phase then sweep power.

Power Phase Frequency - Sweep power first then sweep phase then sweep from Start to Stop frequency.

Buttons

Path Configuration - Not available on SSA-X

Power and Attenuator  Learn more

External Devices  Learn more

SA Coherence Setup tab help

Multitone

The set of Multitone properties enable an enhanced Image Rejection mode that takes benefits of the stimulus test signal knowledge.

If the stimulus test signal is repetitive with a repetition rate of x seconds, it only contains tones that are on a 1/x frequency grid. Example: if the test signal out of an arbitrary wave generator repeats every 1 ms, then it only contains frequencies on a 1 kHz grid (noise is not considered here). We will take this into account here to make the SA DFT analysis grid landing exactly on the same grid.

Moreover we will use the test signal knowledge to adjust the SA LO frequencies in order to avoid having 2 tones from the multitone stimulus signal landing at the same location at the IF side. This makes the image rejection process deterministic.

Enable multitone image rejection

• Enabled (checked) The other parameters of the Multitone dialog are taken into account. Enabling this mode will set the DFT mode to arbitrary, the RBW shape to No Window, the RBW grid to a set of suitable values, and the list of analysis LOs accordingly. This setting is not compatible with the advanced settings “Force ADC record size” or “Force LO to frequency”.

• Disabled (cleared) Legacy stochastic image rejection mode of the SA application. When disabled, the window type is set back to what it was before enabling, and the RBW list is also set to the previous setting.

Tone Spacing - The tone spacing of the multitone signal (Hz).

Waveform Period – 1 over the tone spacing. This is the test signal repetition rate (seconds).

Reference Tone – If the multitone grid does not start from 0 Hz, its offset is set here. To make this more convenient, this dialog accepts as well the frequency of any tone of the multitone grid (Hz).

Reject up to harmonic – Set the number of test signal harmonics you want to be protected against. This adds constraints to the list of LOs used to cover the span.

Nyquist protect order – Enhancement for the deterministic coherent image reject mode. It ensures the Nyquist images of the signal tones in the IF bandwidth are not falling back on top of real signal frequencies. To be able to enable Nyquist protection, the tone spacing of the coherent signal cannot be an integer divider of the ADC sampling clock (100MHz). Enabling this option often results in a larger ADC recordsize (or a smaller DFT tone spacing) at SA receiver side.

Vector Averaging - Average ADC samples by the specified number (≥1) in FPGA memory before the DFT processing. For example, if an ADC record size of 1,000 samples is acquired and Vector Averaging is set to 2, then 1,000 samples will be averaged to 1,000 samples and the result (1,000 samples) will be stored in FPGA memory. In other words, we acquire 2,000 samples form ADCs and send 1,000 averaged samples to the next processing stage. Vector averaging helps to reduce noise and increase dynamic range. However, this feature should only be used when the stimulus frequencies are known and coherent with the current ADC record size. A value of 1 means no averaging. Note this feature behaves like ADC Stacking+1. The maximum vector averaging value is 65536 or below. It depends on the RBW and the decimation.

Check box- Check to enable the ADC sample Vector Averaging to be specified manually.

Note: Vector Averaging and Video Bandwidth averaging cannot be set together. When enabling vector averaging, if the coherent mode is enabled then Video Bandwidth is turned off . The ADC Record Size x Vector Averaging must be ≤ 64 Mega Samples (or ≤ 32 Mega for some multiple receivers configurations).

Note: Vector Averaging is a great averaging method when Coherent Multitone mode is enabled. We recommend increasing it in Coherent Multitone mode instead of reducing the RBW to reduce the noise floor.

Note: Coherent mode (and Vector Averaging too) will work well if and only if the signal source and the analyzer have their reference clocks synchronized. This is usually done by connecting a 10 MHz reference BNC cable between the signal source and the SSA.

Note: Vector Averaging is also known as Stacking. In fact, Vector Averaging = stacking +1.

Data Display

• Show All - Legacy behavior, shows the noise or the spurious between the tones. Note the RBW shape for multitones (No Window) makes the noise or the out of grid spurious amplitude values not accurate.

• Zero the non-tones - All the span frequencies that are not on the multitone grid have their amplitudes set to -200 dBm before correction. This makes band power marker measuring only the power for multitone frequencies, and not the noise power.

• Discard the non-tones - Deletes span frequencies that are not on the multitone grid.

Multitone settings are valid - Displays status of multitone settings.

Tone Phases and Phase Stitching

Compute Phases - Check to enable phase computation.

Note: In the SA tab, Detector Type muse be set to Bypass to compute phases.

Display Phases if Tone Power > - Set the phase display minimum level.

IQ data generation

Compute time domain IQ - Enables/disables computing time domain IQ.

Auto Fill IQ settings button - Fills in the IQ settings automatically. Keep whole sweep data (Processing tab), Compute time domain IQ, Enable multitone, and Compute Phases (Coherence tab) must be enabled before selecting the Auto Fill IQ settings button. If the settings are valid, the Valid IQ Settings under Info (Processing tab) displays OK. Time domain IQ will not be computed until the IQ settings are valid.

Receivers - The receiver list can be either ALL, or a specific valid receiver. This selection determines which receiver data will be transferred to the 89600 VSA.

IQ keeps aligned with SA center, span, coherence - Check to recompute the advanced IQ parameters (IQ center, IQ sample rate, IQ number of points) automatically if a SA sweep parameter change is performed.

VSA Setup... button - Accesses the VSA 89600 Link Setup dialog for connecting the VNA to the VSA. Refer to the topic for information.

Trig. & Pulse Dialog tab help

Trigger... - Accesses the Trigger dialog for setting up triggering.

Hold - The channel accepts NO trigger signals.

Single - The channel accepts ONE trigger signal, then goes into Hold.

Continuous - The channel accepts an infinite number of trigger signals.

Advanced Settings Dialog tab help

Properties

RBW Shape - Selects the digital filter (window) to apply to the time domain IF signal. The filter effectively "shapes" the signal before application of the DFT to help avoid discontinuities which add unwanted frequency content to the spectrum. Each filter has its own advantages and disadvantages.

Gaussian - Selects a Gaussian window. The Gaussian window has good frequency separation and moderate amplitude accuracy. This window provides higher dynamic range because it has much lower side lobes. It is used for general-purpose measurements and when high dynamic range is required.

Flat Top - Selects the flat top window for amplitude measurement of sinusoidal frequency components. The flat top window has moderate frequency separation and excellent amplitude accuracy. It is typically used for narrowband signals when measuring the amplitude of a particular frequency component with greater amplitude accuracy.

Kaiser - Selects the Kaiser window which is an approximation of a Slepian window using Bessel functions. This window has a relatively high dynamic range and is similar to the Blackman window.

Blackman - Selects the Blackman window. This window has a relatively high dynamic range and is similar to the Kaiser window.

No Window - The No Window selection does not modify the time-domain data in any way before applying the DFT. This selection is very fast but may yield a significant number of side lobes in the frequency domain because of spectral leakage. This selection has a rectangular shape and does not attenuate any portion of the time record.

Image Reject Type - Sets the minimum number of distinct DFT acquisitions to use when computing an actual signal. As the number of DFT acquisitions increases from the None, LO Low setting to the Max setting, an increased number of erroneous signals are eliminated. Therefore, the Better and Max settings provide the highest confidence that what remains are actual signals, at the expense of slower measurements.

None, LO High - Selects 1 acquisition with the LO higher than the receiver frequency.

Note: Selecting None, LO High with full span is not possible. See SA Warning Messages.

None, LO Low - Selects 1 acquisition with the LO lower than the receiver frequency.

Note: Selecting None, LO Low with full span is not possible. See SA Warning Messages.

Min - Selects 2 acquisitions.

Min, LO High - Selects 2 acquisitions (like Min) and both acquisitions consider that the LO is higher than the receiver frequency.

Min, LO Low- Selects 2 acquisitions (like Min) and both acquisitions consider that the LO is lower than the receiver frequency.

Normal - Selects 4 acquisitions.

Better - Selects 6 acquisitions.

Max - Selects 8 acquisitions.

Image Reject Strength - Sets the image rejection strength. During the image rejection process, several LO acquisitions overlap at the same RF frequency (depending on the Image Reject Type). As a result, different RF signal values can be returned. This feature sets the acceptable power differences between measurements performed with different LOs in determining actual signals. Possible values are Weak, Normal, Strong. Weak accepts more difference between measurements, and strong less difference.

Auto RBW/VBW - Sets the ratio of Resolution Bandwidth to Video Bandwidth when the Video Bandwidth is in Auto mode.

Span/RBW - Sets the ratio of Span to Resolution Bandwidth when the Resolution Bandwidth is in Auto mode.

CF Step Size - Manually sets the amount Center frequency change that occurs when ▲|▼ is clicked (next to the value).

Auto - Each press of the ▲|▼ arrows increments or decrements the Center frequency by 5% of the current frequency span.

Occupied BW search min - Sets the minimum search frequency to use during an Occupied BW search measurement. Power below this frequency is ignored. See Occupied BW Ratio for information about setting up this measurement type.

Advanced >> button - Accesses the IF, Processing, ADC & LO, and Data dialogs.

IF Dialog tab help

IF Gain

Auto - Selects the appropriate amount for gain versus RF frequency bands for each receiver IF Path.

Or select a specific amount of gain (in dB) for IF receiver paths.

Couple all IF paths - (Two port only) When checked, all receivers assume the same setting. When cleared, each receiver can assume an individual setting.

IF Bandwidth

DFT Bandwidth Auto - Enables the default values for DFT bandwidth.

With Auto checked, the default values are:

Wide - 1 MHz to 30 MHz

With Auto unchecked, the values can be entered manually. The ranges are:

Wide - 1 Hz to 44 MHz

Processing Dialog tab help

DFT Type - Sets the DFT record size type. The types include:

Power of 2 - Sets the DFT record size to the next power of 2 greater than or equal to the current ADC record size. This is the fastest DFT processing available; the power of 2 record size allows for very efficient computation shortcuts (also known as the FFT algorithm).

Fastest - Sets the DFT record size as close as possible to the ADC record size (larger or equal) while optimizing processing speed.

Optimized Radix - Sets the DFT record size to the minimum integer number larger or equal than the ADC record size that can be decomposed with 2,3,5,7,11,13 radixes (also known as the 13-smooth numbers). The Intel CPUs have shared-coded trigonometric values for 2, 3, 5, 7,11, 13 fractional angles; the DFT code takes benefits from that for efficient DFT processing.

Arbitrary - Sets DFT record size equal to the ADC record size. If the current ADC record size is a large prime number, then the DFT can be very slow. Sometimes, the record size will be increased more than the minimum number required to match the 13-smooth condition, if the whole processing of the sweep is faster with a record size that has a faster DFT time. There is a trade-off here: increasing the record size to speed up the DFT will increase the amount of data to process for the further steps of the SA processing (image rejection, detection).

Additional comments:

There is a given ADC record size that gives a given RBW (for a given window type), the RBW evolves as 1/ADC record size. If the DFT record size must be greater, depending on the DFT mode, some zeros will be added to the ADC record size. This is the difference that can be noted between the ADC record size and the DFT record size on the Advanced Processing dialog.

When running the coherent mode of SA, the Arbitrary mode will always be selected, to make sure the DFT bins frequencies exactly land on the coherent signal tones.

The Power of 2, Optimized Radix, and Fastest mode have the same behavior regarding the RBW setting: These 3 modes are increasing the ADC record size to the next best match. This is more sensitive with Power of 2 mode, as the density of available ADC record size is sparse.

The Power of 2 mode makes the SA computation behave exactly like some tools based on FFT processing; this is a use case of this mode. The other use case is to get the fastest processing time that can be useful for intensive spurious search measurements. The penalty is the small number of RBW values available.

The Optimized Radix mode is currently the default mode, this is the one that gives the most accurate RBW setting. The Fastest is to be tried if speed matters for a given non-coherent SA setting.

For example: running 100 kHz RBW with Gaussian filter, the ADC record size must be 1988 samples. Here are the DFT lengths for the different algorithms:

• Power of 2: 2048

• Fastest: 2048

• Optimized Radix: 2000

• Arbitrary: 1988

End of Sweep Processing

The End of Sweep Processing function is used to keep the memory buffer of the last full sweep in memory for further processing. This is not done by default because keeping the whole data in memory requires large amounts of memory and processing (for example, in the case of wide span or low RBW).

Before the implementation of this function, raw data could be sent to a file (ascii or binary) or the fifo, as this can be done while sweeping with no need to keep the whole data in memory. This option is still available.

With each sweep, the data buffers are filled, and are erased if a new sweep is started. In other words, this feature works well in the logic of “Single” sweep. You must ensure that a full sweep is in the buffers before pulling out raw data.

Receivers - The receiver list can be either ALL, or a specific valid receiver. Only the receivers currently defined for measurement traces can be kept in memory.

Keep whole sweep data - Check to keep last full sweep data in memory.

Info

Acq. Time for 1 LO - Displays the LO acquisition time which is the ADC Record Size x ADC Sampling Frequency (10 nsec or 40 nsec) x (1 + Stacking) x (Video Averaging Coefficient). When settings affecting this value are changed, the displayed value is not updated automatically and will become grayed out. To update the value, close then open this dialog. The analyzer must be sweeping to update values.

Span Acq. Time - Displays the total acquisition time to perform a SA sweep. For simple cases, it is the acquisition time of one LO multiplied by the number of LOs. When running Multiple recording coherent pulse mode, the acquisition time here takes into account the duty cycle of the pulses.

Span LOs count - Displays the number of LO acquisitions determined by the Image Reject selection and the span. When settings affecting this value are changed, the displayed value is not updated automatically and will become grayed out. To update the value, close then open this dialog. The analyzer must be sweeping to update values.

Span bins count - Displays the current span DFT bin count, the number of DFT points processed across the total RF span. When the Detector is bypassed, this is the number of points that are sent to the display.

DFT resolution - Displays the DFT resolution.

DFT record size - Displays the current DFT record size.

ADC record size - Displays the ADC record size value.

ADC with average - Displays the ADC acquisition time of one LO multiplied by the averaging (vector averaging or video averaging) factor. It is the straight ADC acquisition time that has to go into the ADC memory for further processing.

ADC frequency - Displays the ADC frequency.

Coherence ratio - Displays the coherence ratio value.

IQ record duration - Displays the current duration of the IQ record.

VSA IQ pairs count - Displays the number of IQ pairs transferred to the VSA.

Valid IQ Settings - Displays whether the IQ settings are valid or not. If valid, OK is displayed.

Misc

Display image reject traces - Check to display the data acquired by each LO. The minimum number of meaningful traces is determined by the "Image Reject" setting (described in the Advanced dialog above).

About Image Reject Traces

These traces display the spectral content of the measured signal for each LO frequency used in the acquisition. The number of ImageReject traces you want to look at is tied to the 'Image Reject' setting. For example, 'Normal' setting is at least 4 ImageReject traces, and 5 more generally.

This function is intended to be used as a diagnostic tool if something looks suspicious.

Note: Mixer calibration and user calibration are not applied to the image rejection traces, thus the amplitude readout value is not accurate.

About Acquisition Time and Sweep Time

The Acquisition time for 1 LO is really the duration of the ADC acquisition run for one LO setting. Depending on the SA span and the image rejection mode, the number of LOs required for a given SA frequency span changes. This number is reported as Span LOs count. So the total ADC acquisition time for a given span, aka Sweep Acq. Time, is the product of Acquisition time for 1 LO x Span LO count (unless Multiple Recording mode is running, then the Multiple Recording  multiplication factor is to be considered).

The entire sweep time is a significantly larger number than the Sweep Acq. Time. Each time the LO is moved, there is a settling time required for LO stabilization. Then each time some raw ADC data is acquired, there is some time to move the data across the buses (the data amount is multiplied by the number of ADCs at work, when several RF receivers are acquired). All the further processing (windowing, DFT, IF calibration, Image Rejection, User calibration) is CPU time consuming, the lowest the RBW the more time it takes to process the DFT samples (there are more DFT samples).

The Image Rejection mode MIN instead of Normal (when not running coherent mode) is a popular way to speed up the sweep time, as roughly half of the LOs count is required, at the cost of higher likelihood of false spectrum spurious (but real signal spurious are still always detected).

The video averaging is digital, it runs several times the ADC acquisitions and windowing and DFT and then averages. The number of times this extra processing is done for video averaging is indicated at the Video averaging count at the SA main page.

When available, the vector averaging is done at the FPGA side, it multiplies by the averaging factor the ADC acquisition time, and it doubles the data amount across the data buses (32 bits instead of 16 bits ADC data representation). The following parts of the processing are not impacted, the quantity of data to process at host CPU side is not increased. Thus the vector averaging is a very efficient way to get lower noise floor with minimum additional CPU time.

The display processing is a very significant part of the sweep time. The number of display points can be set (defaults to 1001), then the code often has to do a data reduction to go from millions of DFT points to 1001 display points. This is the so-called detector processing. This process is CPU intensive, especially the Peak detector that recomputes an X-axis frequency grid each sweep to align each x-axis point to the local interpolated peak. FastPeak is less frequency accurate for the peak points positions but very significantly faster. If the span is narrow, bypassing the detector can speed up the sweep. Turning off the display is another option, it bypasses most detection and display algorithms, thus speeds up the sweep in remote programming modes.

The status bar of the channel shows the last measured SA sweep time, and if some settings are changed, the first sweep after a change shows an estimate with a ~ preceding the timing.

ADC & LO Dialog tab help

ADC Sampling

ADC Sample Frequency - Fixed to 100 MHz

ADC Dithering - Check to add dither.

Overrange warning percent - Sets the percentage of the ADC input full scale. SA sweeps require thousands (or millions) of ADC samples processed by the FFT. The maximum ADC sample value is kept for the whole sweep, as it is an image of the peak voltage in the IF chain of the instrument. Instead of calibrating this value to Volts, a percentage value of the ADC input full scale is used. If the value is too high, reduce the IF gain or add RF attenuation to maintain the linearity of the instrument. If the value is too low, the signal amplitude to too low and under-utilizing the ADC range. Increasing the IF gain may increase the measurement quality (reducing the noise floor).

Show ADC Ranges... - Displays the ADC ranges of the current receivers from the last sweep if the Trigger mode is currently on Hold.

ADC Raw data

Force ADC record size - Sets the ADC record size which is dependent on the Resolution Bandwidth and ADC Sampling Frequency:

Check box - Check to enable the ADC record size to be specified manually. Doing so sets the resolution bandwidth. The size range is 64 Samples to 32 or 64 MegaSamples depending on the selected receivers. The DFT size will be recomputed accordingly to the DFT Type setting. When not checked, the value displayed is the current ADC record size. This feature is not compatible with Coherent Multitone mode.

Stacking - Stack ADC samples by the specified number (≥1) and store result in memory. For example, if an ADC record size of 1,000 samples is acquired and Stacking is set to 1, then 1,000 samples will be added to 1,000 samples and the result (1,000 samples) will be stored in memory. In other words, we acquire 2,000 samples form ADCs and send 1,000 stacked samples to the next processing stage. Stacking helps to reduce noise and increase dynamic range. However, this feature should only be used when the stimulus frequencies are known and coherent with the current ADC record size. A value of 0 means no stacking.

Check box- Check to enable the ADC sample stacking to be specified manually.

Note: Stacking and Video Bandwidth averaging cannot be set together; Video Bandwidth has precedence. The ADC Record Size x (Stacking + 1) must be ≤64 Mega Samples.

Note: Stacking is a great averaging method when Coherent Multitone mode is enabled. We recommend increasing the stacking in Coherent Multitone mode instead of reducing the RBW in order to reduce the noise floor.

LO

Randomized LO - Check to allow dithering of the LO values used when taking a sweep. Allowing randomized LO makes it less likely that erroneous signals will appear in the final measurement.

Enable baseband X-axis mode (LO independent sweep) - Enables baseband sweep independent of the LO sweep to allow signals down to 1 Hz to be analyzed.

Force LO to Frequency - Sets the LO to a specified frequency. This check box can only be set if Image Reject is set to None, LO Low or None, LO High or Enable baseband X-axis mode (LO independent sweep) is checked.

Check box - Check to enable the LO frequency to be specified manually.

Data Dialog tab help

Data Format -

Float LogMag (dB) - Sets the data format to log magnitude in dBm.

Float LinMag - Sets the data format to linear magnitude in volts.

Integers - Sets the data format to Packed Integers (each value is a short 16 bit integer, the equation to compute the dBm value is: dBm = Xshort/200.0 - 36.165.

Export receivers - Select the data to export from a specific receiver or all receivers.

Don't save data below threshold - Set data level threshold mode and threshold level in dBm. For text file output with verbose mode, only the frequencies with power greater than this threshold setting will be written to the file.

DFT bins count - Displays the current DFT bin count, the number of DFT points processed across the total RF span. When the Detector is bypassed, this is the number of points that are sent to the display.

Receivers count - Displays how many receivers are currently being exported. The number here can be less than the number of receivers specified in Export Receivers, if some of them at not selected in the channel.

Export to binary file - Set data to be exported to a binary file. Data is not exported until the next new sweep occurs.

Export to text file - Exports data only. Data is not exported until the next new sweep occurs.

Verbose mode - Exports frequency and data. Data is not exported until the next new sweep occurs.

Erase files each new sweep - Selecting this option will erase the data after each sweep. If this option is not checked, the data from each sweep will continue to be appended to the output data file which can create a very large file size (and fill the disk, with many unwanted consequences).

File name prefix - The receiver selected in Export receivers will be appended to the prefix name specified in this field with either ".txt" if a text file is exported or ".bin" if a binary file is exported. For example, if C:\Temp\SA_DATA_OUT is entered into the File name prefix field and the "B" receiver data is exported to a text file, the data will be exported to a file called SA_DATA_OUT_B.txt.

Record size (bytes) - This is the byte size of binary data output.

Export markers with data files - Adds marker data and data to the text file (*.txt) output.

Export all markers to a single file - Adds all marker data to a single text file (*.txt) output.

Export to FIFO buffer - Exports data to the FIFO (First-IN, First-OUT) data buffer. FIFO is a circular buffer that allows very fast Read-Write access.

Export to shared memory - Exports data to shared memory (Microsoft Windows feature) which is the fastest way to transfer data between applications. The application that is retrieving data has to register itself to Microsoft Windows with the same share name.

Share name - Assigns a specified name to the shared data.

How to select and configure Measurement Parameters

Using Hardkey/SoftTab/Softkey

Using a mouse

1. Select a trace by pressing Trace > Trace N >  Trace N.

2. Press Trace > Trace Setup >  Measure....

3. Select a parameter.

1. Right-click on a trace.

2. Select a parameter