plot the frequency responce of a sos Analog chebychev filter using python

Question

I am new to signal processing.
I am using an sos analog Chebychev filter, and I was wondering what would be the result of plotting its frequency response using the sosfreqz function, as it is mentioned that this function works only for digital filters?

Answer 1

To use sosfreqz you would first need to map your poles and zeros that are in the continuous-time s domain to the discrete-time z domain (see this post and this post for further details) using a mapping solution of choice (such as The Method of Impulse Invariance when we want to maintain the same time domain impulse response at the expense of frequency domain aliasing, or the Bilinear Transform when we want to avoid the aliasing but it will be at the expense of frequency warping and will not having a matching impulse response). The distortion in either case will be minimized if you oversample: the higher in sampling rate the more the solution will directly match what is given in the analog continuous-time domain (there is no one-one mapping that can provide an exact match in both domains given the effects of sampling, so when choosing a mapping approach we must balance frequency domain and time domain distortion effects).

Alternatively, and easier, multiply out your second order sections to have a single ratio of polynomials and use the freqs command intended for this purpose.