實(shí)驗(yàn)七、用雙線性變換法設(shè)計(jì)IIR數(shù)字濾波器

實(shí)驗(yàn)七、用雙線性變換法設(shè)計(jì)IIR數(shù)字濾波器一、源程序程序一clc;clearall;closeall;wp=0.2;ws=0.3;Rp=1;Rs=10;Fs=1000;wp1=2*Fs*tan(wp/2);ws1=2*Fs*tan(ws/2);[N,Wn]=buttord(wp1,ws1,Rp,Rs,'s');[Z,P,K]=buttap(N);[Bap,Aap]=zp2tf(Z,P,K);[b,a]=lp2lp(Bap,Aap,Wn);[bz,az]=bilinear(b,a,Fs);[H,W]=freqz(bz,az);subplot(2,1,1);plot(W/pi,abs(H));grid;xlabel('頻率');ylabel('幅度');subplot(2,1,2);plot(W/pi,20*log10(abs(H)));grid;xlabel('頻率');ylabel('幅度(db)');程序二clc;clearall;closeall;wp=0.2*2*pi;ws=0.3*2*pi;Rp=1;Rs=25;Fs=1;wp1=2*Fs*tan(wp/2);ws1=2*Fs*tan(ws/2);[N,Wn]=buttord(wp1,ws1,Rp,Rs,'s');[Z,P,K]=buttap(N);[Bap,Aap]=zp2tf(Z,P,K);[b,a]=lp2lp(Bap,Aap,Wn);[bz,az]=bilinear(b,a,Fs);[H,W]=freqz(bz,az);subplot(2,1,1);plot(W/pi,abs(H));grid;xlabel('頻率');ylabel('幅度');subplot(2,1,2);plot(W/pi,20*log10(abs(H)));grid;xlabel('頻率');ylabel('幅度(db)');程序三clc;clearall;closeall;wp=0.2*2*pi;ws=0.3*2*pi;Rp=1;Rs=25;Fs=1;wp1=2*Fs*tan(wp/2);ws1=2*Fs*tan(ws/2);[N,Wn]=buttord(wp1,ws1,Rp,Rs,'s');[Z,P,K]=buttap(N);[Bap,Aap]=zp2tf(Z,P,K);[b,a]=lp2lp(Bap,Aap,Wn);[bz,az]=bilinear(b,a,Fs);[H,W]=freqz(bz,az,64);figure(1)subplot(2,1,1);plot(W/pi,abs(H));grid;xlabel('頻率');ylabel('幅度');subplot(2,1,2);plot(W/pi,20*log10(abs(H)));grid;xlabel('頻率');ylabel('幅度(db)');程序四：clc;clearall;closeall;wp=0.2*2*pi;ws=0.3*2*pi;Rp=1;Rs=25;Fs=1;wp1=2*Fs*tan(wp/2);ws1=2*Fs*tan(ws/2);[N,Wn]=buttord(wp1,ws1,Rp,Rs,'s');[Z,P,K]=buttap(N);[Bap,Aap]=zp2tf(Z,P,K);[b,a]=lp2lp(Bap,Aap,Wn);[bz,az]=bilinear(b,a,Fs);[H,W]=freqz(bz,az);figure(1)subplot(2,1,1);plot(W/pi,abs(H));grid;xlabel('頻率');ylabel('幅度');subplot(2,1,2);plot(W/pi,20*log10(abs(H)));grid;xlabel('頻率');ylabel('幅度(db)');bzaz運(yùn)行結(jié)果：bz=0.01790.10720.26810.35750.26810.10720.0179az=1.0000-0.60190.9130-0.29890.1501-0.02080.0025三、實(shí)驗(yàn)總結(jié)：脈沖響應(yīng)不變法和雙線性變換法都是將模擬濾波器變換為數(shù)字濾波器，但前者不可避免的存在頻譜混疊，后者能克服這一缺點(diǎn)，同時(shí)，不能用脈沖響應(yīng)不變法將模擬高通和帶阻濾波器轉(zhuǎn)換為數(shù)字濾波器。雙線性變換法不