Matlab Analog Filter Grpdelay

I designed a analog elliptic filter using Matlab. How do I find the filter grpdelay as a function of freq?

(grpdelay command works only for digital filters)

[Yang Liu]

Maybe you can turn the analog filter to digital filter and then you can use grpdelay function.

Answer 1

[Mathieu NOE]

Compute the group delay response of the filter as the derivative of the unwrapped phase response.

[h,w] = freqs(b,a,1000);

grpdel = diff(unwrap(angle(h)))./diff(w);

clf

semilogx(w(2:end),grpdel)

xlabel('Frequency (rad/s)')

ylabel('Group delay (s)')