图3-3-8 滤波器的幅频特性和相位特性.txt

二阶数字谐振器的频率特性和滤波器的幅频特性和相位特性和预畸变在双线性变换中的作用

clear;
%[例3-3-5]
fs=10000;
Wp = 1000/(fs/2); Ws = 2000/(fs/2);
Rp = 1; Rs = 50;
[n,Wn] = buttord(Wp,Ws,Rp,Rs);
[b1,a1] = butter(n,Wn);
[h1,f1]=freqz(b1,a1,512,fs);

[n,Wn] = ellipord(Wp,Ws,Rp,Rs)
[b2,a2] = ellip(n,Rp,Rs,Wn);
[h2,f2]=freqz(b2,a2,512,fs);
subplot(2,1,1);
plot(f1,20*log(abs(h1)));
hold on;
plot(f2,20*log(abs(h2)),'r');
hold on;

subplot(2,1,2);

plot(f1,unwrap(angle(h1)));
hold on;
plot(f2,unwrap(angle(h2)),'r');
hold on;

%%%%%%%%%%%
[gd,w] = grpdelay(b1,a1,512);							%数字滤波器频响
plot(w/pi,gd);		
hold on;
[gd,w] = grpdelay(b2,a2,512);							%数字滤波器频响
plot(w/pi,gd);		
hold on;