Agilent Technologies Signal Analyzer N9030a - Manual (Page 1172)

6 RLC Swept SA Measurement Front-Panel & SCPI Reference
Sweep/Control
FFT Width
This menudisplays and controls the width of the FFT’s performed while in FFT mode. The “FFT
width” is the range of frequencies being looked at by the FFT, sometimes referred to as the “chunk
width” -- it is not the resolution bandwidth used when performing the FFT.
It is important to understand that this function does not directly set the FFT width, it sets the
limit on the FFT Width. The actual FFT width used is determined by several other factors
including the Span you have set. Usually the instrument picks the optimal FFT Width based on
the current setup; but on occasion you may wish to limit the FFT Width to be narrower than that
which the instrument would have set.
This function does not allow you to widen the FFT Width beyond that which the instrument might have
set; it only allows you to narrow it. You might do this to improve the dynamic range of the measurement
or eliminate nearby spurs from your measurement.
Note that the FFT Width setting will have no effect unless in an FFT sweep.
See "More Information" on page 1173
Key Path Sweep/Control, Sweep Setup
Remote Command [:SENSe]:SWEep:FFT:WIDTh <real>
[:SENSe]:SWEep:FFT:WIDTh?
Example SWE:FFT:WIDT 167 kHz sets this function to “<167.4 kHz”
Notes The parameter is in units of frequency.
For values sent from SCPI, the analyzer chooses the smallest value that is at least as great as
the requested value.
Examples:
Parameter 3.99 kHz is sent over SCPI. Analyzer chooses ≤4.01 kHz
Parameter 4.02 kHz is sent over SCPI. Analyzer chooses ≤28.81 kHz
Parameter 8 MHz is sent over SCPI. Analyzer chooses 10 MHz
Dependencies In some models, the analog prefilters are not provided. In these models the FFT Width function
is always in Auto. The FFT Width key is blanked in these models, and the SCPI commands are
accepted without error but have no effect.
In Zero Span, this key is irrelevant and cannot be accessed (because the whole Sweep Setup
menu is grayed out in Zero Span). However, its settings can be changed remotely with no error
indication.
Couplings
The FFT Width affects the ADC Dither function (see Meas Setup key) and the point at which the
instrument switches from Swept to FFT acquisition.
Preset The Preset is Auto, but Preset will also pick Best Dynamic Range and hence this function will be
set to ~Maximum
1172 Remote Language Compatibility Measurement Application Reference