matlab高手请进

Posted 2023-03-14

用DFT计算连续周期信号的频谱：
x(t)=1-cos(pi*t)+2sin(2*pi*t)+cos(3*pi*t);
其中周期和采样点数我都算了为:2s和14点
谢谢大家
把程序附上,追加分!!

参考技术A 先建立M-file
function [Xk]=dft(xn,N)
%Computes Discrete fouriwe transform
%----------------------------------
%[Xk]=dft(xn,N)
%Xk=DFT coeff. array over 0<=k<=N-1
%xn=N-point finite-duration sequence
%N=length of DFT
%
n=[0:1:N-1];
k=[0:1:N-1];
WN=exp(-j*2*pi/N);
nk=n'*k;
WNnk=WN.^nk;
Xk=xn*WNnk;

再在command window中输入
>> n=0:1:13;
>> N=14;
>> T=2/14.*n;
>> x=1-cos(pi*T)+2*sin(2*pi*T)+cos(3*pi*T);
>> X=dft(x,N);
>> magX=abs(X),phaX=angle(X)*180/pi

计算的结果
magX =

Columns 1 through 7

14.0000 7.0000 14.0000 7.0000 0.0000 0.0000 0.0000

Columns 8 through 14

0.0000 0.0000 0.0000 0.0000 7.0000 14.0000 7.0000

phaX =

Columns 1 through 7

0 180.0000 -90.0000 -0.0000 44.2152 141.5463 -84.4725

Columns 8 through 14

4.9331 68.1986 -96.5819 -18.1219 0.0000 90.0000 -1本回答被提问者采纳