[Numpy-discussion] Zoom fft code
Stéfan van der Walt
stefan@sun.ac...
Mon Jan 5 07:58:11 CST 2009
2009/1/5 Neal Becker <ndbecker2@gmail.com>:
> I was not aware that chirp-z transform can be used to efficiently compute DFT over a limited part of the spectrum. I could use this. Any references on this technique?
The only reference I have is the one mentioned in the source:
Rabiner, L.R., R.W. Schafer and C.M. Rader.
The Chirp z-Transform Algorithm.
IEEE Transactions on Audio and Electroacoustics, AU-17(2):86--92, 1969
The discrete z-transform,
X(z_k) = \sum_{n=0}^{N-1} x_n z^{-n}
is calculated at M points,
z_k = AW^-k, k = 0,1,...,M-1.
You can think of the z_k's as a spiral, where A controls the outside
radius (starting frequency) and W the rate of inward spiralling.
Regards
Stéfan
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