s31.m

数字信号处理的MATLAB仿真加实验指导

%a20.m
wp=0.2*pi;wr=0.4*pi;Ap=3;Ar=20;
T=1;
Omegap=(2/T)*tan(wp/2);Omegar=(2/T)*tan(wr/2);
ep=sqrt(10^(Ap/10)-1);
Ripple=sqrt(1/(1+ep*ep));
Attn=1/(10^(Ar/20));
%双线性变换法设计Butterworth数字低通滤波器
[cs,ds]=afd_butt(Omegap,Omegar,Ap,Ar);
[b,a]=bilinear(cs,ds,T);
[C,B,A]=dir2cas(b,a)
[db,mag,pha,w]=freqz_m(b,a);
subplot(2,2,1);plot(w/pi,mag);
title('数字滤波器幅度响应|H(w)|'); axis([0,1,0,1.1]);
subplot(2,2,2);plot(w/pi,db);
title('数字滤波器衰减响应(dB)');axis([0,1,-40,5]);
subplot(2,2,3);plot(w/pi,pha/pi);title('数字滤波器相位响应');
[b,a]=afd_butt(wp,wr,Ap,Ar); 
[C,B,A]=sdir2cas(b,a);
[db,mag,pha,w]=freqs_m(b,a,pi);
subplot(2,2,4);plot(w/pi,mag);
title('模拟滤波器幅度响应|H(Omega)|');