[SciPy-dev] complex-valued remez

Chuck Harris Chuck.Harris at sdl.usu.edu
Wed Feb 5 15:46:02 CST 2003


> -----Original Message-----
> From: Travis Oliphant [mailto:oliphant at ee.byu.edu]
> Sent: Wednesday, February 05, 2003 2:17 PM
> To: scipy-dev at scipy.net
> Subject: RE: [SciPy-dev] complex-valued remez
> 
> 
> > Depends...
> >
> > I used the code I posted to design complex-hermitean filters,
> > i.e., the filter coefficients were complex but the transfer
> > function was real and arbitrary from zero the sampling frequency.
> > The Remez code in sigtools will design filters whose transfer
> > functions are symmetric or antisymmetric about the Nyquist 
> frequency.
> >
> > The Remez code I posted can be made considerably more efficient for
> > the special case of filter design. It was made for the general case.
> >
> > Chuck
> 
> 
> I was going back to check on this code, and noticed that it 
> is posted in
> base64 encoding.
> 
> I'm not sure how to decode the file.
> 
> I would like to incorporate it into signal as a separate function.
> 
> Can you resend it in ascii format or tell me how to decode it?
> 
> Thanks,
> 
> -Travis

Oops, I thought I just sent the (Python) text file as text. This
particular version should probably go into the optimization 
directory. The general setting is the space of real continuous
functions on a compact subset of the real line in the sup norm.
Given a point in this space and a special sort of finite dimensional
subspace (Chebychev system), it finds the unique closest point in the subspace. Without the restriction to Chebychev systems the closest 
points are not necessarily unique. Anyhow, its a type of optimization.

For the signals tools, the best version is probably an adaptation of
the current algorithm with either complex barycentric interpolation
instead of the current real version, or a combination of this with
the fft. I've given some thought to these, but haven't actually
coded them up beyond bits and pieces.

I can work these over a bit and send them in if you think they would 
be useful.

Chuck 



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