example3_3.m

西交大刘树棠写的《数字信号处理》那本书的所有源代码

L=5;N=20;k=[-N/2:N/2];
xn=[ones(1,L),zeros(1,N-L)];
Xk=dfs(xn,N);
magXk=abs([Xk(N/2+1:N),Xk(1:N/2+1)]);
subplot(2,2,1);stem(k,magXk);axis([-N/2,N/2,-0.5,5.5]);
xlabel('k');ylabel('Xtilde(k)');
title('DFS L=5,N=20');

L=5;N=40;k=[-N/2:N/2];
xn=[ones(1,L),zeros(1,N-L)];
Xk=dfs(xn,N);
magXk=abs([Xk(N/2+1:N),Xk(1:N/2+1)]);
subplot(2,2,2);stem(k,magXk);axis([-N/2,N/2,-0.5,5.5]);
xlabel('k');ylabel('Xtilde(k)');
title('DFS L=5,N=40');

L=5;N=60;k=[-N/2:N/2];
xn=[ones(1,L),zeros(1,N-L)];
Xk=dfs(xn,N);
magXk=abs([Xk(N/2+1:N),Xk(1:N/2+1)]);
subplot(2,2,3);stem(k,magXk);axis([-N/2,N/2,-0.5,5.5]);
xlabel('k');ylabel('Xtilde(k)');
title('DFS L=5,N=60');

L=7;N=60;k=[-N/2:N/2];
xn=[ones(1,L),zeros(1,N-L)];
Xk=dfs(xn,N);
magXk=abs([Xk(N/2+1:N),Xk(1:N/2+1)]);
subplot(2,2,4);stem(k,magXk);axis([-N/2,N/2,-0.5,7.5]);
xlabel('k');ylabel('Xtilde(k)');
title('DFS L=7,N=60');