ms13r4.m

《数字信号处理实验(MATLAB版)》这

%方法2,用DFT求时域循环卷积

xn1=[5,4,-3,-2];      %建立x1(n)序列
xn2=[1,2,3,0];        %建立x2(n)序列
N=length(xn1);      
n=0:N-1;k=0:N-1; 
Xk1=xn1*(exp(-j*2*pi/N)).^(n'*k);  %由x1(n)的DFT求X1(k) 
Xk2=xn2*(exp(-j*2*pi/N)).^(n'*k);  %由x2(n)的DFT求
Yk=Xk1.*Xk2;                       %Y(k)=X1(k)X2(k) 
yn=Yk*(exp(j*2*pi/N)).^(n'*k)/N;   %由Y(k)的IDFT求y(n)
yn=abs(yn)
subplot(2,3,1),stem(n,xn1);
title('x1(n)');
subplot(2,3,2),stem(n,xn2); 
title('x2(n)');
subplot(2,3,3),stem(n,yn); 
title('y(n)');
subplot(2,3,4),stem(k,abs(Xk1)); 
title('|X1(k)|');
subplot(2,3,5),stem(k,abs(Xk2)); 
title('|X2(k)|');
subplot(2,3,6),stem(k,abs(Yk)); 
title('|Y(k)|');