实验三数字信号处理.doc

1. 假设系统用下面差分方程描述： y(n)=x(n)+ay(n-1)假设a=0.7, 0.8, 0.9 ， 分别在三种情况下分析系统的频率特性，并打印幅度特性曲线。解：B=1;A=1,-0.7;subplot(3,3,3);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)-0.7y(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,2);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,6);subplot(3,3,1);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性);B=1;A=1,-0.8;subplot(3,3,6);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)-0.8y(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,5);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,6);subplot(3,3,4);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性);B=1;A=1,-0.9;subplot(3,3,9);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)-0.9y(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,8);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,6);subplot(3,3,7);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性); 图形如下所示：2. 假设系统用下面差分方程描述： y(n) = x(n) +ax(n-1)假设a=0.7, 0.8, 0.9 ， 分别在三种情况下分析系统的频率特性，并打印幅度特性曲线。解：B=1,0.7;A=1;subplot(3,3,3);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)+0.7x(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,2);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,2);subplot(3,3,1);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性);B=1,0.8;A=1;subplot(3,3,6);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)+0.8x(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,5);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,2);subplot(3,3,4);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性);B=1,0.9;A=1;subplot(3,3,9);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=x(n)+0.9x(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,3,8);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(0,2,0,2);subplot(3,3,7);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性); 图形如下所示：3. 假设系统函数用下式描述： y(n)=1.273y(n-1)-0.81y(n-2)+x(n)+x(n-1)试分析它的频率特性，要求打印其幅度特性曲线，并求出峰值频率和谷值频率。解：B=1,1;A=1,-1.273,0.8;subplot(3,1,3);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title(y(n)=1.273y(n-1)-0.81y(n-2)+x(n)+x(n-1)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,1,1);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(-0.1,2.1,0,15);subplot(3,1,2);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性); 图形输出如下：4. 假设系统函数用下式描述：（另加的一个） y(n)=0.66y(n-7)-0.77y(n-8)+0.88x(n)-0.99x(n-5)试分析它的频率特性，要求打印其幅度特性曲线。解：B=0.88,0,0,0,0,-0.99;A=1,0,0,0,0,0,0,-0.66,0.77;subplot(3,1,3);zplane(B,A);xlabel(实部Re);ylabel(虚部Im);title( y(n)=0.66y(n-7)-0.77y(n-8)+0.88x(n)-0.99x(n-5)传输函数零、极点分布);grid onH,w=freqz(B,A,whole);subplot(3,1,1);plot(w/pi,abs(H),linewidth,2);grid on;xlabel(omega/pi);ylabel(|H(ejomega)|);title(幅频响应特性);axis(-0.1,2.1,0,15);subplot(3,1,2);plot(w/pi,angle(H),linewidth,2);grid on;axis(-0.1,2.1,-3,3);xlabel(omega/pi);ylabel(phi(omega);title(相频响应特性);