资源描述：
《实验四IIR数字滤波器设计及软件实现.doc》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、fc1=250;fm1=15;fc2=500;fm2=50;fc3=1000;fm3=100;N=800;Fs=10000;Ts=1/Fs;n=[0:N-1];t=n*Ts;x11=cos(2*pi*fc1*t);x12=cos(2*pi*fm1*t);x1=x11.*x12;subplot(3,1,1);plot(t,x11,'g');plot(t,x12,'r');plot(t,x1,'b');legend('载波','调制波','已调');xlabel('t/s');ylabel('波形')x=
2、cos(2*pi*fc1*t).*cos(2*pi*fm1*t)+cos(2*pi*fc2*t).*cos(2*pi*fm2*t)+cos(2*pi*fc3*t).*cos(2*pi*fm3*t);subplot(3,1,2);plot(t,x);X=fft(x)subplot(3,1,3)k=[0:(N-1)/2]stem(k*2/N,abs(X(k+1))/max(abs(X(k+1))),'.');axis([0,0.3,0,1]);xlabel('omega/pi');ylabel('幅度
3、');wp=[0.04,0.06];ws=[0.03,0.07];rp=0.1;rs=60;[N1,wp]=ellipord(wp,ws,rp,rs);[B,A]=ellip(N1,rp,rs,wp);y1=filter(B,A,x);figuresubplot(3,1,1);plot(t,x);xlabel('t/s');title('3路混合信号波形')subplot(3,1,2);[H1,w1]=freqz(B,A,N);plot(w1/pi,20*log10(abs(H1)));axis([0
4、,0.5,-80,1]);xlabel('omega/pi');ylabel('
5、H(e^jomega)
6、');title('中心频率为250Hz的频率响应');subplot(3,1,3);plot(t,y1);xlabel('t/s');ylabel('y1(t)');title('中心频率为250H的滤波信号')wp=[0.08,0.12];ws=[0.07,0.13];rp=0.1;rs=60;[N1,wp]=ellipord(wp,ws,rp,rs);[B,A]=ellip(N1,rp
7、,rs,wp);y1=filter(B,A,x);figuresubplot(3,1,1);plot(t,x);xlabel('t/s');title('3路混合信号波形');subplot(3,1,2)[H1,w1]=freqz(B,A,N);plot(w1/pi,20*log10(abs(H1)));axis([0,0.5,-90,2]);xlabel('omega/pi');ylabel('
8、H(e^jomega)
9、');title('中心频率为500Hz的频率响应')subplot(3,
10、1,3);plot(t,y1);xlabel('t/s');ylabel('y1(t)');title('中心频率为500H的滤波信号')wp=[0.17,0.23];ws=[0.16,0.24];rp=0.1;rs=60;[N1,wp]=ellipord(wp,ws,rp,rs);[B,A]=ellip(N1,rp,rs,wp);y1=filter(B,A,x);figuresubplot(3,1,1);plot(t,x);xlabel('t/s');title('3路混合信号波形');subplo
11、t(3,1,2);[H1,w1]=freqz(B,A,N);plot(w1/pi,20*log10(abs(H1)));axis([0,0.5,-100,10]);xlabel('omega/pi');ylabel('
12、H(e^jomega)
13、');title('中心频率为1000Hz的频率响应')subplot(3,1,3);plot(t,y1);xlabel('t/s');ylabel('y1(t)');title('中心频率为1000H的滤波信号')
