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Re: digital filter design

The only textbook I know that actually discusses the design of variable (or
controllable) digital filters is S.K. Mitra, "Digital Signal
Processing",  McGraw-Hill, 1998 or 2001.  See section 8.7.

Another text that comes close, without getting quite that far, is S.J.
Orfanidis, "Signal Processing", Prentice Hall, 1996 (section 6.4 on
pole-zero designs, which is very readable).

Apart from these texts, there are occasional papers on the topic, mainly in
the Journal of the Audio Engineering Society over the last 15 or so years,
or occasionally in the IEEE Trans. on Signal Processing (or one of the
associated magazines).  I remember that there are papers in the AES Journal
that treat so-called parametric equalizers of the type mentioned by
Farsheed, but don't have any exact references to hand.

Earlier on there were also a number of papers on tunable analogue filters
(mainly in IEEE publications), and many of these can easily be transformed
to digital form.

The art in all these methods is to design the filter in such a way that
only a small number of parameters need to be varied to achieve a desired
change of the filter behaviour.

The alternative brute force method is to do a complete redesign of the
digital filter each time it is varied, which is not actually out of the
question nowadays.

        Harvey Holmes

At 10:39 30/01/2005, you wrote:
Does someone have a good answer for this student?

Jim Beauchamp

Original message:
> From: Farsheed <hamidito@xxxxxxxx>
> Date: Sat, 29 Jan 2005 16:42:48 -0500
> To: beaucham <beaucham@xxxxxxxxxxxxxxxxxxxxxx>
> Subject: filter design?
> For my senior design project we are working on making a
> touchpad filter equalizer, so that you can boost or attenuate
> frequencies on the fly using your finger.  My question for you
> is, would you recommend any texts to read regarding choosing a
> good DSP filter for such a design?  We would like to be able
> to control Q, boost/attenuation, and frequency for a
> bandstop/bandpass filter directly, using one algorithm only.
> Thank you,
> Farsheed
> ***************************************
> Farsheed Hamidi-Toosi
> Student, University of Illinois at Urbana-Champaign
> Webpage: http://www.midnightparking.com