FFT Program for Turbo-C
By
Steve Sampson
Version 2.6, November 1988
The FFT program and test signal generators included in the archive, can
be
used to perform signal analysis in the frequency domain, using samples in
the
time domain. Historically the applications have ranged from music to
radar.
I recently have been doing some research in the radar field using this FFT
to
perform relative velocity measurements. This program can be further
refined
to meet your needs.
I initially uploaded a fairly basic program, and through feedback have
made some improvements. It's pretty complete now as far as a start for
making
your own specific version. Earlier Unix compatability has been removed in
favor of IBM graphics adaptors.
This program uses graphics to present a 256 filter window. My current
application required complex data and resulted in 256 complex points. You
may
use this with real data which results in 128 significant points. If you
feed
the FFT real data only (Imaginary data set to zero), then the output will
be a
mirror image, and you can ignore the left side.
Some papers I found on the subject of FFTs are included at the end. There
are
several books devoted to the subject also.
For an example try:
sine in
1000
3000
Which will sample the 1 Khz data every 333 microseconds (1 / 3 Khz).
Note: The
sample frequency should be greater than 2 times the input frequency
(Nyquist
and all that...).