192 Agilent InfiniiVision 5000 Series Oscilloscopes Programmer's Reference
3Commands by Subsystem
:FUNCtion:WINDow
(see page 530)
Command Syntax :FUNCtion:WINDow <window>
<window> ::= {RECTangular | HANNing | FLATtop}
•The RECTangular window is useful for transient signals, and signals
where there are an integral number of cycles in the time record.
•The HANNing window is useful for frequency resolution and general
purpose use. It is good for resolving two frequencies that are close
together, or for making frequency measurements. This is the default
window.
•The FLATtop window is best for making accurate amplitude
measurements of frequency peaks.
The :FUNCtion:WINDow command allows the selection of three different
windowing transforms or operations for the FFT (Fast Fourier Transform)
function.
The FFT operation assumes that the time record repeats. Unless an
integral number of sampled waveform cycles exist in the record, a
discontinuity is created between the end of one record and the beginning
of the next. This discontinuity introduces additional frequency components
about the peaks into the spectrum. This is referred to as leakage. To
minimize leakage, windows that approach zero smoothly at the start and
end of the record are employed as filters to the FFTs. Each window is
useful for certain classes of input signals.
Query Syntax :FUNCtion:WINDow?
The :FUNCtion:WINDow? query returns the value of the window selected
for the FFT function.
Return Format <window><NL>
<window> ::= {RECT | HANN | FLAT}
See Also •"Introduction to :FUNCtion Commands" on page 182