%利用FFT计算WVD分布(非平稳随机信号分析与处理第45页)
clc
clear all
NN=100;
w1=0.001;
a1=0.0005;
w2=0.001;
a2=-0.005;
j=sqrt(-1);
nn=-3*NN-1:1:3*NN-1; %构造信号
%n=nn-3*NN;
x=exp(j*(2*pi*(w1*nn+1/2*a1*nn.^2))); %s1=ss1(nn-3*NN)
%ss1c=conj(ss1);
L=64; %加矩形窗
N=2*L;
w=zeros(N);
w(1)=0;
l=-(L-1):1:(L-1);
w(2:length(l))=1; %2L-1窗
%s1=ss1(3*NN-(L-1)+1:3*NN+(L-1)+1);
Wx=zeros(N,N);
G=zeros(N,N);
GG=zeros(N,N); %conj(G)
f=zeros(N,N);
for n=0:N-1 % n=nn-3*NN
% l=-(L-1):1:(L-1)
% G=w.*x(3*NN+n+l) %G(n,l)=w(l).*x(n+1)
%for
l=0:1:L-1;
% ll=L+l;
% nn=3*NN+n;
G(n+1,l+1)=w(L+1+l).*x(3*NN+n+L+1+l);
GG(n+1,l+1)=conj(w(L+1-l).*x(3*NN+n+L+1-l));
f(n+1,l+1)=G(n+1,l+1).*GG(n+1,l+1);
l=L:1:2*L-1;
G(n+1,l+1)=w(L+1+l-2*L).*x(3*NN+n+L+1+l-2*L);
GG(n+1,l+1)=conj(w(L+1-l+2*L).*x(3*NN+n+L+1-l+2*L));
f(n+1,l+1)=G(n+1,l+1).*GG(n+1,l+1);
end
F=f'; %FFT按列计算矩阵的傅立叶变换
Wx=fft(F);
Wx=Wx';
n=0:N-1;
k=0:N-1;
figure;
grid;
mesh(n,k,Wx);
figure;
contour(Wx);
D90
