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1、实验三：滤波器的设计实验三：滤波器的设计第五题： fp=6000;fs=12000;ap=3;as=25;wp=2*pi*fp;ws=2*pi*fs;N,WC=buttord(wp,ws,ap,as,s)B,A=butter(N,WC,s) x=20*log10(abs(H);y=angle(H);f=0:20;w=2*pi*f;H=freqs(B,A,w);subplot(2,1,1);plot(f,x)axis(0,20,-10.0e-16,1.0e-16);xlabel(f/HZ);ylabel(幅度/dB); grid onsubplot(2,1,2);plot(f,y) grid o
2、naxis(0,5,-9.8e-04,0);xlabel(f/HZ);ylabel(相位); 第六题： clear,clc,close allfp=12000;fs=6000;ap=1;as=40;wp=2*pi*fp;ws=2*pi*fs;N,WC=cheb1ord(wp,ws,ap,as,s)B,A=cheby1(N,ap,WC,high,s)f=2000:18000;w=2*pi*f;H=freqs(B,A,w);x=20*log10(abs(H);y=angle(H);subplot(2,1,1);plot(f,x)axis(2000,18000,-50,2);xlabel(f/HZ)
3、;ylabel(幅度/dB); grid onsubplot(2,1,2);plot(f,y)grid onaxis(2000,18000,-5,5);xlabel(f/HZ);ylabel(相位);第七题： clear,clc,close allfp=20000,40000;fs=10000,50000;ap=1;as=40;wp=2*pi*fp;ws=2*pi*fs;N,WC=ellipord(wp,ws,ap,as,s)B,A=ellip(N,ap,as,WC,s)f=10000:60000;w=2*pi*f;H=freqs(B,A,w);x=20*log10(abs(H);y=angl
4、e(H);subplot(2,1,1);plot(f,x)axis(10000,60000,-100,100);xlabel(f/HZ);ylabel(幅度/dB); grid onsubplot(2,1,2);plot(f,y)grid onaxis(10000,60000,0.2:0.01:0.3);xlabel(f/HZ);ylabel(相位);第八题： clear,clc,close allfp=20000,40000;fs=10000,50000;ap=1;as=40;wp=2*pi*fp;ws=2*pi*fs;N,WC=buttord(wp,ws,ap,as,s)B,A=butte
5、r(N,WC,s)f=10000:60000;w=2*pi*f;H=freqs(B,A,w);x=20*log10(abs(H);y=angle(H);subplot(2,1,1);plot(f,x)axis(10000,60000,-110,110);xlabel(f/HZ);ylabel(幅度/dB); grid onsubplot(2,1,2);plot(f,y)grid onaxis(10000,60000,-4,4);xlabel(f/HZ);ylabel(相位);第九题：ap=0.5;as=50; wp=0.4;ws=0.6; N,WC=buttord(wp,ws,ap,as);
6、B,A=butter(N,WC); f=10:40;w=2*pi*f; H=freqz(B,A,w); hn,n=impz(B,A,20); y=20*log10(abs(H); subplot(3,1,1); stem(f,y) axis(10,20,-7e-15,-4e-15); xlabel(f/HZ);ylabel(幅度/dB); grid on subplot(3,1,2); stem(f,angle(H) xlabel(f/HZ);ylabel(相位); grid on subplot(3,1,3); stem(n,hn) xlabel(f/HZ);ylabel(单位脉冲响应);
7、grid on第十题： ap=1;as=40; wp=0.25,0.75;ws=0.35,0.65; N,WC=cheb1ord(wp,ws,ap,as); B,A=cheby1(N,ap,WC,stop); t=10:40;w=2*pi*t; H=freqz(B,A,w); hn,n=impz(B,A,30); y=20*log10(abs(H); subplot(3,1,1); stem(t,y); axis(10,20,1.05e-15,2.25e-15); xlabel(f/HZ);ylabel(幅度/dB); grid on subplot(3,1,2); stem(t,angle(
8、H); xlabel(f/HZ);ylabel(相位); grid on subplot(3,1,3); stem(n,hn); xlabel(f/HZ);ylabel(单位脉冲响应); grid on第十一题： ap=1;as=40; wp=0.35,0.65;ws=0.25,0.75; N,WC=ellipord(wp,ws,ap,as); B,A=ellip(N,ap,as,WC); t=5:40;w=2*pi*t; H=freqz(B,A,w); hn,n=impz(B,A,20); y=20*log10(abs(H); subplot(3,1,1); stem(t,y); axis(
9、5,40,-42,-38); xlabel(f/HZ);ylabel(幅度/dB); grid on subplot(3,1,2); stem(t,angle(H); xlabel(f/HZ);ylabel(相位); grid on subplot(3,1,3); stem(n,hn); xlabel(f/HZ);ylabel(单位脉冲响应); grid on第十二题：ap=0.1;as=40; fp=4500;fs=5500;Fs=15000; wp=2*fp/Fs;ws=2*fs/Fs; N,WC=ellipord(wp,ws,ap,as); B,A=ellip(N,ap,as,WC); t=0:20;w=2*pi*t; H=freqz(B,A,w); hn,n=impz(B,A,30); y=20*log10(abs(H); subplot(3,1,1); stem(t,y); axis(0,20,-4.2e-15,-3.7e-15); xlabel(f/HZ);ylabel(幅度/dB); grid on subplot(3,1,2); stem(t,angle(H); xlabel(f/HZ);ylabel(相位); grid on subplot(3,1,3); stem(n,hn); xlabel(f/HZ);ylabel(单位脉冲响应); grid on
