[SciPy-User] [signal] zpk -> s domain?

[cassiope]

On Feb 11, 8:23 am, Neal Becker <ndbeck... at gmail.com> wrote:
> Sorry for the cryptic question - for an engineer working in my field it would
> not be cryptic.
>
> I have a digital filter design, which is specified as poles and zeros in the z-
> transform domain (zpk).
>
> k (z-z0)(z-z1)...
> -----------------
> (z-p0)(z-p1)...
>
> I want it expressed in the s domain (laplace transform), in a form such as:
>
> (s-a)(s-b)...
> -----------
> (s-c)(s-d)...
>
> or
>
> s^3 + a s^2 + b s + c
> ---------------------
> s^3 + d s^2 + e s + f
>
> or similar

There is no unique solution; probably the most common way would be to
use the bilinear transform.
See, for example, http://en.wikipedia.org/wiki/Bilinear_transform .