ms12_2.m

《数字信号处理实验(MATLAB版)》这

xn=[0,1,2,3,4,5,6,7];
N=length(xn);
n=0:4*N-1;k=0:4*N-1;
xn1=xn(mod(n,N)+1);               %xn1=[xn,xn,xn,xn];            
Xk=xn1*exp(-j*2*pi/N).^(n'*k);    %离散傅里叶变换
subplot(2,2,1),stem(xn,'k');      %显示序列主值
title('原主值信号x(n)');
subplot(2,2,2),stem(n,xn1,'k');   %显示周期序列
title('周期序列信号');
axis([-1,4*N,1.1*min(xn1),1.1*max(xn1)]);
subplot(2,2,3),stem(k,abs(Xk),'k');  %显示序列的幅度谱
title('|X(k)|');
axis([-1,4*N,1.1*min(abs(Xk)),1.1*max(abs(Xk))]);
subplot(2,2,4),stem(k,angle(Xk),'k');%显示序列的相位谱
title('arg|X(k)|');
axis([-1,4*N,1.1*min(angle(Xk)),1.1*max(angle(Xk))]);