[SciPy-User] FIR filter with arbitrary frequency response

Warren Weckesser warren.weckesser@enthought....
Sat Nov 20 22:09:02 CST 2010


On Sat, Nov 20, 2010 at 9:43 PM, Nathaniel Smith <njs@pobox.com> wrote:

> I was wondering if anyone has already written Python code to design
> FIR filters with arbitrary (given) frequency response via
> IDFT+windowing, a la 'fir2' in octave/matlab?
>  http://octave.sourceforge.net/signal/function/fir2.html
>  (Theory: http://www.dspguide.com/ch17/1.htm)
>
> I don't see it in scipy, but it seems generally useful. (I might end
> up writing it if no-one else has, but I'm not sure yet whether it's
> actually useful for my problem.)
>
>

Hi Nathaniel,

There is one implemented as the function firwin2 currently under review in
this ticket:
    http://projects.scipy.org/scipy/ticket/457
It will eventually be added to scipy.signal.  Included in the ticket is a
patch file that can be applied to the latest version of the scipy source,
and also a copy of just the updated file fir_filter_design.py.  You could
grab that and try it stand-alone (but you would have to comment out the
local import of sigtools, which is used by the remez function in
fir_filter_design.py).

Feedback would be appreciated, so if you try it, be sure to write back with
comments or questions.

Warren
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