I am trying to design a digital ButterWorth filter for the given specifications.
rp=3;
rs=15;
FS=1;
wp=0.5*pi;
ws=0.75*pi;
pwp=2*FS*tan(wp/2);
pws=2*FS*tan(ws/2);
[n,wn]=buttord(pwp,pws,rp,rs,'s')
[b,a]=butter(n,wn,'s');
[bn,an]=bilinear(b,a,FS);%error
freqz(bn,an,512,FS);
If I design a filter manually i am getting different values for bn
and an
but Matlab gives different answer. Can anybody please help me?