여기서 N은 기본주기이고, L/N은 의무 주기(duty cycle)이다

a) L과 N으로 을 표현해보자.

b) 인 경우에 대해 크기 을 그려라.

ex5_2.cem

/*   Chapter 5: Example 5.02*/
 
//L = 5; N = 20;
//x = [ones(1,L), zeros(1,N-L)];
//xn = x' * ones(1,3);
//xn = (xn(:))';
//n = -N:1:2*N-1;
//subplot(1,1,1);subplot(2,1,2);
//stem(n,xn,"-"); xtitle("n"); ytitle("xtilde(n)")//title("Three periods of xtilde(n)") 
 
subplot(1,1,1)// Part (b)1L = 5; N = 20;
xn = [ones(1,L), zeros(1,N-L)];
Xk = dfs(xn,N);
magXk = abs([Xk(N/2+1:N) Xk(1:N/2+1)]);
k = [-N/2:N/2];
subplot(2,2,1); stem(k,magXk,"-"); 
xtitle("k"); ytitle("Xtilde(k)")
title("DFS of SQ. wave: L=5, N=20")// Part (b)2L = 5; N = 40;
xn = [ones(1,L), zeros(1,N-L)];
Xk = dfs(xn,N);
magXk = abs([Xk(N/2+1:N) Xk(1:N/2+1)]);
k = [-N/2:N/2];
subplot(2,2,2); stem(k,magXk,"-"); 
xtitle("k"); ytitle("Xtilde(k)")
title("DFS of SQ. wave: L=5, N=40")// Part (b)3L = 5; N = 60;
xn = [ones(1,L), zeros(1,N-L)];
Xk = dfs(xn,N);
magXk = abs([Xk(N/2+1:N) Xk(1:N/2+1)]);
k = [-N/2:N/2];
subplot(2,2,3); stem(k,magXk,"-"); 
xtitle("k"); ytitle("Xtilde(k)")
title("DFS of SQ. wave: L=5, N=60")// Part (b)4L = 7; N = 60;
xn = [ones(1,L), zeros(1,N-L)];
Xk = dfs(xn,N);
magXk = abs([Xk(N/2+1:N) Xk(1:N/2+1)]);
k = [-N/2:N/2];
subplot(2,2,4); stem(k,magXk,"-"); 
xtitle("k"); ytitle("Xtilde(k)")
title("DFS of SQ. wave: L=7, N=60")