%雙譜例子
clear all;
N=64;
n=0:N-1;
f1=0.1;f2=0.15;f3=0.25;f4=0.4;
fai1=pi/6;
fai2=pi/3;
fai3=pi/2;
fai4=pi/4;
s1=cos(2*pi*f1*n+fai1);
s2=cos(2*pi*f2*n+fai2);
s3=cos(2*pi*f3*n+fai3);
s4=cos(2*pi*f4*n+fai4);
x=s1+s2+s3+s4;
subplot(2,2,1);
plot(x)
X=fft(x);
X=fftshift(X);      %下面的Fy才是數(shù)據(jù)Y的傅立葉變換 Fy=fftshift(fft(Y)); 取幅值相位[mag,pha]=bode(sys,w) 
subplot(2,2,2);
plot((n-N/2),abs(X));grid on;
subplot(2,2,3);
[bspec,waxis]=bispeci(x,10);
subplot(2,2,4);
mesh(abs(bspec));
%bspec=bispecd(x);figure;mesh(abs(bspec))