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In summary, keep the following in mind when executing FFT:
Perform fourier transforms on trace A, B, or C, or user-defined traces containing 1008 elements
automatically creates a 1008 point array from trace A, B, or C.)
FFT is designed to be used in transforming zero span information into the frequency domain. Performing FFT on a
frequency sweep will result in inaccurate FFT data.
Define a trace window with the TWNDOW command before performing an FFT on a trace.
It is possible to get numbers outside the boundaries of the screen (0 - 1023) after executing an FFT. If the destina-
tion trace is trace A, then the results are automatically clipped. For traces B, C, and user-defined traces, the results
are not automatically clipped. When using these traces, avoid writing in locations outside the boundaries of the
screen.
To get an FFT frequency readout on the FFT trace, use the Marker Read command (MKREAD Fm,,) .
The following is an example of an FFT program.
10
OUTPUT 718; "TFLDEF W-INDOW, 1008;"
20
OUTPUT 718;"TWNDOW WeINDOW,HANNING;"
21
30
OUTPUT 718;"FFT TFLB,TRA,W-INDOW,"
31
40
E N D
Line 10:
A trace array of 1008 points is defined as W-INDOW.
Line 20:
The trace array is formatted according to the HANNING algorithm.
Line 30:
An FFT is performed on trace A and the results are stored in trace B.
(Continued) FFT
(FFT
only.
P r o g r a m m i n g 1 1 3
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