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Date: Tue, 30 Aug 2022 00:04:51 -0400
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Subject: Re: [geda-user] Active filter
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From: "Dan McMahill (dan AT mcmahill DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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On 8/11/2022 3:44 PM, karl AT aspodata DOT se [via geda-user AT delorie DOT com] wrote:
> David: Schultz:
> ...
>> My go to reference is the "Active Filter Cookbook" by Don Lancaster.
> 
> That seems to be a nice book, but currently I'm more interested in
> how to calculate the tables used.
> 
>> If I need something not covered there, then it is time to dust off the
>> ol' college text by Van Valkenburg
> 
> Ok, I'll look into that.
> 
> Thanks,
> /Karl Hammar
> 

If you're looking for more details on topics like approximation methods 
for filter design, then two textbook resources on my "must read" list are:

Adel Sedra and Peter Brackett, "Filter Theory And Design: Active and 
Passive", Matrix Publishers, 1978

Richard Daniels, "Approximation Methods for Electronic Filter Design", 
McGraw-Hill, 1974

The Daniels book is fairly obscure, the programming examples are in a 
language that hasn't been used for almost 50 years (Telcomp), and a fair 
amount of the math is in a special purpose transformed variable domain 
(no, not the standard Laplace domain from school, but a transformation 
that tends to spread out poles for better numeric stability).  That 
said, this book really covers the details that produce the tables found 
in most other filter text books.  It also goes into detail on a pole 
placer algorithm that can do some pretty cool stuff with real world 
applications.  For example, suppose you want to produce a 0.15 dB 
equiripple passband, you want a notch at a fixed frequency, and you have 
a piecewise constant stop band spec.  With the pole placing algorithm, 
you can design optimal polynomials for the design.  This is the magic 
behind part of what S/FILSYN can do.  It also helps engineers who 
weren't trained in the 50's and 60's understand the language of tools 
like S/FILSYN.

The Sedra and Brackett book covers a lot of the same material but it is 
mostly presented in the more familiar Laplace domain.

Both books give some attention to synthesis methods for going from a 
polynomial to an actual circuit.

There have been more recent developments for addressing things like 
numeric instability in both approximation and synthesis.  In addition, 
today's compute power makes some approaches more practical now than they 
were pushing 50 years ago.  But these are still great books.

-Dan