[SciPy-User] python and filter design: calculating optimal "S" transform

robert somerville rbrt.somerville@gmail....
Tue Jun 1 17:55:03 CDT 2010


Hi;
this is an airy question.

does anybody have some code or ideas on how to calculate the optimal "S"
transform of user specified order (wanting the coefficients)  for a
published filter response curve, ie.

f(s) = (b1*S^2 + b2*S) / (a1*S^2 + a2*S + a3)

I am parameterizing the response of a linear device (Out = Response*In). I
have the measured frequency response for the device (amplitude, phase) for a
range of frequencies.

I wish to model that measured response via a ratio of polynomials in the
s-domain (or Laplace domain), where I define the polynomial orders (for
numerator and denominator).

Something like the "Yule-Walker" method is what I'm after except, to my
knowledge, Yule-Walker approach is strictly for responses involving a
denominator polynomial (i.e. strictly autoregressive) only. I need some
thing to discover both numerator and denominator coefficients.
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