杭电实验：离散时间系统的时域特性分析.doc

(1)1)clf;n=0:200;x=cos(20*pi*n/256)+cos(200*pi*n/256);x1=x 0 0;%x1n=xn;x2=0 x 0;%x2n=xn-1;x3=0 0 x;%x3n=xn-2; y=0.5*x1+0.27*x2+0.77*x3;%画出输出和输入信号subplot(2,1,1);stem(n,x);xlabel(时间信号);ylabel(信号幅度);title(输入信号);subplot(2,1,2);stem(y);xlabel(时间信号n);ylabel(信号幅度);title(输出信号);2)clf;n=0:299;x=cos(20*pi*n/256)+cos(200*pi*n/256);num1=0.5,0.27,0.11;num2=0.45 0.5 0.45;den1=1 0 0;den2=1 -0.53 0.46;y1=filter(num1,den1,x);y2=filter(num2,den2,x);%画出输出和输入信号subplot(3,1,1);stem(n,x);title(输入信号);subplot(3,1,2);stem(n,y1);ylabel(信号幅度);title(输出信号);subplot(3,1,3);stem(n,y2);ylabel(信号幅度);title(输出信号);grid(2)n=0:300;N=40;x=cos(20*pi*n/256)+cos(200*pi*n/256);num1=0.5 0.27 0.77;num2=0.45,0.5 0.45;den1=1 0 0;den2=1 -0.53 0.46;y1=impz(num1,den1,N);y2=impz(num2,den2,N);subplot(2,1,1);stem(y1);xlabel(时间序列n);ylabel(信号幅度);title(y1冲激响应);subplot(2,1,2);stem(y2);xlabel(时间序列n);ylabel(信号幅度);title(y2冲激响应);(3) n=0:299; f1=20*pi/256;f2=200*pi/256;x=cos(f1*n)+cos(f2*n); num=0.45 0.5 0.45;den=1 -0.53 0.46;y=filter(num,den,x);subplot(2,1,1); stem(n,x);xlabel(时间信号n);ylabel(信号幅度);title(输入信号);subplot(2,1,2);stem(y);xlabel(时间信号n);ylabel(信号幅度);title(输出信号);系统2为时不变系统。n=0:299;a=2;b=-3;f1=20*pi/256;f2=200*pi/256;x1=cos(f1*n);x2=cos(f2*n);x=x1+x2;num=0.45 0.5 0.45;den=1 -0.53 0.46;y1=filter(num,den,x1);y2=filter(num,den,x2);y=filter(num,den,x);yt=a*y1+b*y2;subplot(2,1,1);stem(n,y);xlabel(时间信号n);ylab