homew4.m

西交大刘树棠写的《数字信号处理》那本书的所有源代码

b=[1,1];
a=[1,0.9,-0.81];%
[H,w]=freqz(b,a,100);
magH=abs(H);phaH=angle(H);
subplot(211);plot(w/pi,magH);grid;
title('系统函数H的幅频曲线');
xlabel('freq');ylabel('amp');
subplot(212);plot(w/pi,phaH/pi);grid;
title('系统函数H的相频曲线');
xlabel('freq');ylabel('pha');

n=0:200;
x=sin(pi/3*n)+5*cos(pi*n);
y=filter(b,a,x);
k=-200:200;w=(pi/100)*k;
X=x*exp(-j*pi/100.*(n'*k));
Y=y*exp(-j*pi/100.*(n'*k));
magY=abs(Y);angY=angle(Y);
figure(2);
subplot(211);plot(w/pi,magX);grid;
title('输入信号x的幅频曲线');
xlabel('Frequency');ylabel('amplitude');
subplot(212);plot(w/pi,angX);grid;
title('输入信号x的相频曲线')
xlabel('Frequency');ylabel('angle');
figure(3);
subplot(211);plot(w/pi,magY);grid;
title('输出信号y的幅频曲线');
xlabel('Frequency');ylabel('amplitude');
subplot(212);plot(w/pi,angY);grid;
title('输出信号y的相频曲线');
xlabel('Frequency');ylabel('angle');