test0806stft3.m

信号处理实例

%---------------------------------------------------------------------------------------
% test0806stft3.m,  for  example 08.06
% two sinus signal and its STFT
% 2006.12.18 LYB
%----------------------------------------------------------------------------------------
clear;
n=256;
%------------------------
% example1:two sinus signal
w=pi/4; %f=1,fs=32
t=1:n;w1=t*w; part=n/2;
   for k=1:part; sig(k)=sin(k*w); end;
   for k=(part+1):2*part, sig(k)=sin(2*k*w); end;
sig=sig';

p=8;
for ni=1:p
    N=2^ni-1;
    h=ones(N,1);
    %h=hanning(N);
    %tfrstft(sig,1:128,128,h);
    [TFR,T,F]=tfrstft(sig,1:n,n,h);
    %figure(4);
    subplot(3,p/2,ni+4);
    imagesc(T,F,abs(TFR(1:n/2,1:n)).^2);
    title(['N=',num2str(N)]);
    hidden off;
    clear TFR;
end;

ftreal=abs(fft(sig));

subplot(3,2,1);
plot(1:n,real(sig(1:n)));
axis([0 n-1 -1.2 1.2]);
title(' the signal x(t)');

subplot(3,2,2);
plot(1:n/2,ftreal(1:n/2));
axis([0 127 0 80]);
title(' the spectrum of x(t)');


%tfrreal=abs(TFR);
%figure(3);
%subplot(211);
%plot(ftreal);
%subplot(212);
%plot(tfrreal(1:127,1))

%imagesc(abs(TFR).^2);