数字信号处理——理论、算法与实现书中 matlab程序

%------------------------------------------------------------------------ % for example 13.3.2，for fig13.3.2 (c),(d) %------------------------------------------------------------------------ clear; %设计IIR滤波器； N=100; wp=.4*pi;ws=.6*pi;Fs=1;rp=1.;rs=40; wap=tan(wp/2);was=tan(ws/2); [n,wn]=cheb1ord(wap,was,rp,rs,'s'); [z,p,k]=cheb1ap(n,rp); [bp,ap]=zp2tf(z,p,k); [bs,as]=lp2lp(bp,ap,wap); [b,a]=bilinear(bs,as, Fs/2); [h,w] = freqz(b,a,512,1); g = 20*log10(abs(h)); %对应并联实现； [r,p,k] = residuez(b,a); [b1,a1]=residuez(r(1:2),p(1:2),0); [b2,a2]=residuez(r(3:4),p(3:4),0); [b3,a3]=zp2tf(0,p(5),r(5)); % 对滤波器系数按4bit量化； bq1 = truncation(b1,4); aq1 = truncation(a1,4); bq2 = truncation(b2,4); aq2 = truncation(a2,4); bq3 = truncation(b3,4); aq3 = truncation(a3,4); kq = truncation(k,4); [h1,w] = freqz(bq1,aq1,512,1); [h2,w] = freqz(bq2,aq2,512,1); [h3,w] = freqz(bq3,aq3,512,1); [h4,w] = freqz(kq,1,512,1); hq=h1+h2+h3+h4; gq = 20*log10(abs(hq)); subplot(221) plot(w,g,'b',w,gq,'r:');grid Ylabel('Gain, dB'); % 对滤波器系数按5bit量化； bq1 = truncation(b1,5); aq1 = truncation(a1,5); bq2 = truncation(b2,5); aq2 = truncation(a2,5); bq3 = truncation(b3,5); aq3 = truncation(a3,5); kq = truncation(k,5); [h1,w] = freqz(bq1,aq1,512,1); [h2,w] = freqz(bq2,aq2,512,1); [h3,w] = freqz(bq3,aq3,512,1); [h4,w] = freqz(kq,1,512,1); hq=h1+h2+h3+h4; gq = 20*log10(abs(hq)); subplot(222) plot(w,g,'b',w,gq,'r:');grid Ylabel('Gain, dB');