%程序7.1
%橢圓IIR低通濾波器設計
%
Wp=input('歸一化通帶截止頻率＝');
Ws=input('歸一化阻帶截止頻率＝');
Rp=input('單位為dB的通帶波紋＝');
Rs=input('單位為dB的最小阻帶衰減＝');
[N,Wn]=ellipord(Wp,Ws,Rp,Rs)
[b,a]=ellip(N,Rp,Rs,Wn);
[h,omega]=freqz(b,a,256);
plot(omega/pi,20*log10(abs(h)));grid;
xlabel('\omega/\pi');ylabel('增益,dB');
title('橢圓IIR低通濾波器');