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%------------------------------------------------------------------------------- 
% exa080601.m,  for example 8.5.1 
% 设计一个 8 通道的余弦调制滤波器组; 
% 本程序调用了子程序opt_filter.m 及 ovlp_ripple.m，摘自文献： 
%  S. K. Mitra.  Digital Signal Processing: A Computer-Based Approach. Second Edition, 
%                McGraw-Hill,2001; 清华大学出版社，2001 
%------------------------------------------------------------------------------- 
clear all; 
 
N=127;nbands=8; 
[hopt,H,G]=opt_filter(N,nbands); 
subplot(221) 
stem(hopt,'k');grid; 
 
  h0=H(1,:); 
     h1=H(2,:); 
     h2=H(3,:); 
     h3=H(4,:); 
     h4=H(5,:); 
     h5=H(6,:); 
     h6=H(7,:); 
     h7=H(8,:); 
subplot(223); 
stem(h0,'k.');grid; 
[H0,w]=freqz(h0,1,512,1); 
[H1,w]=freqz(h1,1,512,1); 
[H2,w]=freqz(h2,1,512,1); 
[H3,w]=freqz(h3,1,512,1); 
[H4,w]=freqz(h4,1,512,1); 
[H5,w]=freqz(h5,1,512,1); 
[H6,w]=freqz(h6,1,512,1); 
[H7,w]=freqz(h7,1,512,1); 
 h00=20*log10(abs(H0+0.0000001)); 
 h11=20*log10(abs(H1+0.0000001)); 
 h22=20*log10(abs(H2+0.0000001)); 
 h33=20*log10(abs(H3+0.0000001));  
 h44=20*log10(abs(H4+0.0000001));  
 h55=20*log10(abs(H5+0.0000001));  
 h66=20*log10(abs(H6+0.0000001)); 
 h77=20*log10(abs(H7+0.0000001)); 
subplot(222); 
plot(w,h00,w,h11,w,h22,w,h33,w,h44,w,h55,w,h66,w,h77);grid; 
 
sumh=abs(H0).*abs(H0)+abs(H1).*abs(H1)+abs(H2).*abs(H2)+abs(H3).*abs(H3); 
sumh=sumh+abs(H4).*abs(H4)+abs(H5).*abs(H5)+abs(H6).*abs(H6)+abs(H7).*abs(H7); 
sum=10*log10(sumh); 
subplot(224); 
plot(w,sum);grid;