Example Program 2 - Channel Power Measurement Using Immediate - Keysight Technologies M9393A Programming Manual

Close Driver for VSA
Using FFT Acquisition Mode in Channel Power Measurements
Advantages of using FFT Acquisition Mode in Channel Power Measurements
The
averaged FFT on the fly. The resultant FFT data is processed in fast capture
memory in hardware. Although this FFT process is limited in length, it is very good
for producing very fast channel power measurements. This process differs with the
Spectrum Acquisition mode,
Baseband tuning within the digitizer is another feature of using FFT Acquisition
mode
digitally inside the digitizer to shift off the center frequency. In addition, while doing
this, the local oscillator in the downconverter doesn't have to move, while you are
doing baseband tuning. Tuning digitally inside the digitizer has the advantage that
it does not require any settling time. This offset frequency matches the offset
frequency on all the other acquisition modes.
Pseudo code
The following pseudo code is a modification of the Example Program 2 - Pseudo-
code. Use this and Example Program 2 - Channel Power Measurement Using
Immediate Trigger as a reference for coding.
Initialize Driver for VSA, Check for Errors
Keysight M9393A PXIe Performance Vector Signal Analyzer
Sample Rate
Duration
Channel Filter
Apply Method to Send Changes to Hardware
Wait for Hardware to Settle
Send Arm Method to VSA
Send Read Power Method to VSA
FFT Acquisition mode uses a feature in the digitizer DSP to do a high speed
for making channel power measurements. Baseband tuning can be made
Send RF Settings to VSA Driver
Frequency: (range 9 kHz to 27 GHz)
Level: (range -170 dBm to 24 dBm)
Peak to Average Ratio: (range 0 dBm to 20 dBm)
Conversion Mode: (choose between Single High Side, Single Low
Side, Image Protect, or Auto)
IF Bandwidth: (choose between 40 MHz and 160 MHz)
Set Acquisition Mode to "FFT"
Send FFT Acquisition Setting to VSA Driver
FFT Length: select 64, 128, 256, or 512. Typically use 256
Sample Rate:
Usable bandwidth of FFT is 80% of sample rate
which does an FFT in the host controller.
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