Agilent Technologies Infiniium 8000A, Programmer'S Reference Manual

Page: 356 / 934

16-14
Function Commands
FFT:WINDow
FFT:WINDow
Command :FUNCtion<N>:FFT:WINDow {RECTangular | HANNing |
FLATtop}
The :FUNCtion<N>:FFT:WINDow command sets the window type for the FFT
function.
The FFT function assumes that the time record repeats. Unless there is an
integral number of cycles of the sampled waveform in the record, a discontinuity
is created at the beginning of the record. This introduces additional frequency
components into the spectrum about the actual peaks, which is referred to as
spectral leakage. To minimize spectral leakage, windows that approach zero
smoothly at the beginning and end of the record are employed as filters to the
FFTs. Each window is useful for certain classes of input waveforms.
• The RECTangular window is essentially no window, and all points are
multiplied by 1. This window is useful for transient waveforms and
waveforms 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.
• The FLATtop window is best for making accurate amplitude measurements
of frequency peaks.
<N>
An integer, 1 - 4, representing the selected function. This command presently
selects all functions, regardless of which integer (1-4) is passed.
Example
This example sets the window type for the FFT function to RECTangular.
10 OUTPUT 707;":FUNCTION<N>:FFT:WINDOW RECTANGULAR
20 END