Generic transfer function IIR filter design

I need to design an IIR digital filter from a given generic s-domain tranfer function. As it is more complex than a high/low/band-pass filter, how can I do that? Thank you Andrea

Answer 1

[Walter Roberson]

http://en.wikipedia.org/wiki/Infinite_impulse_response

Design of digital IIR filters is heavily dependent on that of their analog counterparts because there are plenty of resources, works and straightforward design methods concerning analog feedback filter design while there are hardly any for digital IIR filters. As a result, usually, when a digital IIR filter is going to be implemented, an analog filter (e.g. Chebyshev filter, Butterworth filter, Elliptic filter) is first designed and then is converted to a digital filter by applying discretization techniques such as Bilinear transform or Impulse invariance.

So... unless you want to put some restrictions on what kind of generic s-domain transfer functions you want to allow, and what kind of processing of them you want to do, you are venturing into Terra Incognita, it appears.

[Andrea Zanelli]

Suppose that the tranfer function to implement is:

R(s)=10(1+10s)(1+5s)(1+s)/s(1+0.4s)^2.

I'd like to learn one way to implement this as an IIR filter using Matlab tools...Can you help me?

[Walter Roberson]

I only know a fairly small amount about IIR filters.

It appears you might be able to convert the tf to a lattice filter using tf2latc http://www.mathworks.com/help/toolbox/signal/tf2latc.html and then use that to do the filter design with latcfilt

Or convert the transfer function to state space, http://www.mathworks.com/help/toolbox/signal/tf2ss.html .

(I do not know enough about IIR to know how to use either of these possibilities in practice.)