[Numpy-discussion] zoom FFT with numpy?

Nadav Horesh nadavh@visionsense....
Thu Mar 15 04:53:49 CDT 2007

A long time ago I translated a free code of chirp z transform (zoom fft)
into python.
Attached here the source and two translations (probably one of the is


On Wed, 2007-03-14 at 14:02 -0800, Ray S wrote:

> 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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