%qusetion %Make changes with the code below for %Design IIR Filter (HPF, BPF, band stop filter) by using the Butterworth approximation. Ab=6; As=20; A=10^(As/20) beta=((sqrt(10^(As/10)-1))/(sqrt(10^(Ab/10)-1))) ebslon=sqrt(A^2-1)/beta; elpha=3/2; N=5 d1=2*((10^(Ab/10)-1)^(-1/10)); d2=3*((10^(As/10)-1)^(-1/10)); wc=max(d1,d2)/pi; [zb,pb,kb]=butter(N, wc,'s') [bb, ab]=zp2tf(zb,pb,kb) %zero pol to trans function [hb,w]=freqs(bb,ab); plot(w,mag2db(abs(hb)))