[Numpy-discussion] zoom FFT with numpy?

Ray S subscriber100@rjs....
Wed Mar 14 17:02:38 CDT 2007


We'd like to do what most call a "zoom FFT"; we only are interested 
in the frequencies of say, 6kHZ to 9kHz with a given N, and so the 
computations from DC to 6kHz are wasted CPU time.
Can this be done without additional numpy pre-filtering computations? 

If explicit filtering is needed to "baseband" the data, is it worth 
it? It sounds like we need to generate cosine data once for each band 
and N, then multiple with the data for each FFT.

Has anyone coded this up before? I couldn't find any references other 
than http://www.dsprelated.com/showmessage/38917/1.php
and http://www.numerix-dsp.com/siglib/examples/test_zft.c (which uses 
Numerix).

Ray



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