%Ellip函數：設計橢圓濾波器
Wp1=500;
Wp2=800;
Ws1=600;
Ws2=700;
Wp=[Wp1 Wp2];
Ws=[Ws1 Ws2];
Rp=0.1;
Rs=50;
Fs=2000;
[N,Wn]=ellipord(2*Wp/Fs,2*Ws/Fs,Rp,Rs);         %確定濾波器的最小階數
[num,den]=ellip(N,Rp,Rs,Wn,'stop');
[H,W]=freqz(num,den);
plot(W*Fs/(2*pi),abs(H));grid;
xlabel('頻率/Hz'),ylabel('幅度');