What am I missing about IIR Filter Design?

A cookbook recipe like pre-warped bilinear transform will do to design "a"
filter for most problems. It's been a standard textbook chapter for two
decades or longer, no one doubts that it works.

This is exactly what has always confused me. I think you are saying that
what I have on my web page is standard textbook material, but I have never
been able to find another web site or text that gives these design
equations explicitly. In other words, the general purpose design equations
for any type of filter where all that is needed are the analog filter
coefficients. 

http://www.iowahills.com/A4IIRBilinearTransform.html

For example, in Randy Allred's "Digital Filters for Everyone", he lists
numerous different equations for very specific filter types. For example,
one set of equations for a Butterworth low pass and another set of
equations for a Bessel low pass. But if I remember correctly, he ends up
with the same filter coefficients that I do.

	 

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>This is exactly what has always confused me. I think you are saying that
>what I have on my web page is standard textbook material, but I have
never
>been able to find another web site or text that gives these design
>equations explicitly. In other words, the general purpose design
equations
>for any type of filter where all that is needed are the analog filter
>coefficients. 

Hi,

for more advanced filter design, you could have a look here:
http://www.nt.tuwien.ac.at/fileadmin/users/gerhard/diss_Lang.pdf
The code examples are available online.
I think there is at least some IIR materal in there. 

Generally, IIR wouldn't be my first choice in most cases (maybe more so, if
a fast 32-bit multiplier is available)	 

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