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Topic: Looking For: Numerical Frequecy Detectors
Replies: 1   Last Post: Dec 5, 1996 11:46 PM

 Richard Williams Posts: 1 Registered: 12/15/04
Re: Looking For: Numerical Frequecy Detectors
Posted: Dec 5, 1996 11:46 PM

:
: I am looking for numerical routines to solve the following problem
:
: 1) Limited RAM (< 40 bytes available)
: 2) Limited Processor (68HC11)
: 3) Limited Time (real time app)
: 4) Given a small number of samples (10?) determine if a given frequency
: is present.
:
: Before I get a million FFT answers the following is important: I only
: care about 1 frequency and a yes/no threshold detector result would be
: OK (though a magnitude would be prefered ;->). Is there a very
: efficient way to solve this?
:
: chuckb

Look at the Goertzel algorithm. This is a very simple way to compute
the FFT in real time at a single frequency. It uses a second order
IIR filter. Given your severe constraints, you probably will be limited
to some kind of IIR filtering, but you may be able to use a higher order.
The Goertzel algorithm is described in standard DSP texts such as
Discrete Time Signal Processing by Oppenheim and Schafer, or the book
by Proakis and Manolakis.