fp1=1000;
fp2=2000;
ap=3;
N=3;
[z,p,k]=cheby1(N,ap,[fp1,fp2]*2*pi,'s')
omega=abs([p(1),p(3),p(5)])
Q=omega./(-2*real([p(1),p(3),p(5)]))
H0=k/omega(1)/omega(2)/omega(3)*Q(1)*Q(2)*Q(3)
H01=H0^(1/3)
