Agilent Technologies Signal Analyzer N9030a - Manual (Page 1190)

6 RLC Swept SA Measurement Front-Panel & SCPI Reference
Sweep/Control
Backwards
Compatibility SCPI [:SENSe]:SWEep:FFT:SPAN:RATio <integer>
[:SENSe]:SWEep:FFT:SPAN:RATio?
This is the legacy “FFTs per Span” command, because in the PSA, this is what you set rather
than the FFT Width. The behavior of the analyzer when it receives this command is to compute
the “intended segment width” by dividing the Span by the FFTs/Span parameter, then
converting this intended width to an actual width by using the largest available FFT Width that is
still less than the intended segment width. The “Span” used in this computation is whatever the
Span is currently set to, whether a sweep has been taken at that Span or not.
Initial S/W Revision Prior to A.02.00
Modified at S/W
Revision A.04.00
Key Path Sweep/Control, Sweep Setup
Remote Command [:SENSe]:SWEep:FFT:WIDTh:AUTO OFF|ON|0|1
[:SENSe]:SWEep:FFT:WIDTh:AUTO?
Example :SWE:FFT:WIDT:AUTO ON
Couplings Pressing Auto Couple always sets FFT Width to Auto.
Preset ON
State Saved Saved in instrument state
Initial S/W Revision Prior to A.02.00
More Information
An FFT measurement can only be performed over a limited span known as the “FFT segment”.
Several segments may need to be combined to measure the entire span. For advanced FFT control
in the X-Series, you have direct control over the segment width using the FFT Width control.
Generally, in automatic operation, the X-Series sets the segment width to be as wide as possible,
as this results in the fastest measurements.
However, in order to increase dynamic range, most X-series models provide a set of analog
prefilters that precede the ADC. Unlike swept measurements, which pass the signal through a
bandpass before the ADC, FFT measurements present the full signal bandwidth to the ADC,
making them more susceptible to overload, and requiring a lower signal level. The prefilters act to
alleviate this phenomenon - they allow the signal level at the ADC to be higher while still avoiding
an ADC overload, by eliminating signal power outside the bandwidth of interest, which in turn
improves dynamic range.
1190 Remote Language Compatibility Measurement Application Reference