|
EDA365欢迎您登录!
您需要 登录 才可以下载或查看,没有帐号?注册
x
3 {2 i% l7 I& N6 a M周期方波的表达式我就不提炼了,既然你来看文章了,我就不信你周期方波都不知道。# w) B0 J2 Y; {" Q b9 I6 ?+ R
: g1 F5 G9 t6 O9 M
占空比定义为:L/N,N为周期,下面我们对 L = 5,N = 20; L = 5,N = 40;L = 5,N = 60;L = 7,N = 60分别画出它们的DFS图作比较。
! ?2 J: S! V* n/ F
. A% I: r1 {+ [4 I: J我觉得有必要先把对应的周期方波给出来(每幅图都只给出一个周期):
3 j! B4 E p) X1 D* H
% x6 @/ O0 {5 x, P& }- clc;clear;close all;
- % Periodic square wave parameters L = 5,N = 20
- L = 5;
- N = 20;
- n = 0:N-1;
- xn = [ones(1,L),zeros(1,N-L)];
- subplot(2,2,1)
- stem(n,xn);
- title('L = 5,N = 20');
- xlabel('n');ylabel('xtilde(n)');
- % Periodic square wave parameters L = 5,N = 40
- L = 5;
- N = 40;
- n = 0:N-1;
- xn = [ones(1,L),zeros(1,N-L)];
- subplot(2,2,2)
- stem(n,xn);
- title('L = 5,N = 20');
- xlabel('n');ylabel('xtilde(n)');
- % Periodic square wave parameters L = 5,N = 60
- L = 5;
- N = 60;
- n = 0:N-1;
- xn = [ones(1,L),zeros(1,N-L)];
- subplot(2,2,3)
- stem(n,xn);
- title('L = 5,N = 20');
- xlabel('n');ylabel('xtilde(n)');
- % Periodic square wave parameters L = 7,N = 60
- L = 7;
- N = 60;
- n = 0:N-1;
- xn = [ones(1,L),zeros(1,N-L)];
- subplot(2,2,4)
- stem(n,xn);
- title('L = 5,N = 20');
- xlabel('n');ylabel('xtilde(n)');
# r6 Q% a* D+ k/ R( q" Q 7 j# @5 ]3 Z% c. A0 W; I! I) a* h
) p6 }0 j+ X4 X' q; x+ w
2 Q3 s8 K1 j6 l上面程序中的DFS函数定义在另一篇博文中:【 MATLAB 】离散傅里叶级数(DFS)及 IDFS 的 MATLAB 实现; m, R! r9 J2 R5 ^" e# |* f6 k) D
6 Z+ n0 b6 E( j4 G6 S9 a% {
6 |' E# w0 }2 _/ m: S
H3 B' g( f, { ~/ ]/ J- o3 M6 H( F) ^
直接给出MATLAB脚本:
+ \ ^ }- i4 _3 ?& |, x% Z
% l, O' }1 ?0 T3 V9 R3 C- clc;clear;close all;
- % Periodic square wave parameters L = 5,N = 20
- 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);
- title('DFS of Square: L = 5,N = 20');
- xlabel('k');ylabel('Xtilde(k)');
- % Periodic square wave parameters L = 5,N = 40
- 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);
- title('DFS of Square: L = 5,N = 40');
- xlabel('k');ylabel('Xtilde(k)');
- % Periodic square wave parameters L = 5,N = 60
- 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);
- title('DFS of Square: L = 5,N = 60');
- xlabel('k');ylabel('Xtilde(k)');
- % Periodic square wave parameters L = 7,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);
- title('DFS of Square: L = 7,N = 60');
- xlabel('k');ylabel('Xtilde(k)');
/ {* t$ F0 W7 e8 `" c* V7 [' @
E2 }/ t5 j) ^# d1 M( Z
9 K" V* U p3 U) R( U$ T9 S) a
7 Y2 o1 E, f* A' d3 \3 s# l2 E+ x" }* ]* g6 G
]4 D, e- L1 I- h# {9 p% k
+ K# x0 C0 u* e0 S: {. f% s: n5 D3 C& c |
|