IIR digital and analog filter design given order and critical points.
Design an Nth order lowpass digital or analog filter and return the filter coefficients in (B,A) (numerator, denominator) or (Z,P,K) form.
N – the order of the filter. :
Wn – a scalar or length-2 sequence giving the critical frequencies. :
rp, rs – For chebyshev and elliptic filters provides the maximum ripple :
btype – the type of filter (lowpass, highpass, bandpass, or bandstop). :
analog – non-zero to return an analog filter, otherwise :
ftype – the type of IIR filter (Butterworth, Cauer (Elliptic), :
output – ‘ba’ for (b,a) output, ‘zpk’ for (z,p,k) output. :
SEE ALSO butterord, cheb1ord, cheb2ord, ellipord :