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% exa110702_specgram.m ,for example 11.7.2  and fig11.7.1 
% to test specgram.m  
%------------------------------------------------------------------------- 
%clear; 
%t=0:0.001:1.024-.001;  
%N=1024;  
 
% 得到两个Chirp 信号，并相加； 
%y1=chirp(t,0,1,350); 
%y2=chirp(t,350,1,0); 
%y=y1+y2; 
%subplot(211);plot(t,y1); 
%ylabel(' Chirp signal y1') 
 
% 求两个Chirp 信号和的短时傅里叶变换； 
%[S,F,T]=specgram(y,127,1,hanning(127),126);  
%subplot(212); 
%surf(T/1000,F,abs(S).^2) 
%view(-80,30); 
%shading flat; 
%colormap(cool); 
%xlabel('Time') 
%ylabel('Frequency') 
%zlabel('spectrogram') 
load tf.dat; 
pt=tf(:,1);pf=tf(:,2);      %分离出时间和幅值信号 
%subplot(311); 
%plot(pt,pf); 
title('Time Domain');   %绘制原时域信号图 
[S,F,T]=specgram(pf,64,1E3,hanning(64),0); 
subplot(311); 
surf(T/1000,F,abs(S).^2); 
view(-80,30); 
shading flat; 
colormap(cool); 
xlabel('Time'); 
ylabel('Frequency'); 
zlabel('spectrum'); 
 
 
[S,F,T]=specgram(pf,128,1E3,hamming(128),0); 
subplot(312); 
surf(T/1000,F,abs(S).^2); 
view(-80,30); 
shading flat; 
colormap(cool); 
xlabel('Time'); 
ylabel('Frequency'); 
zlabel('spectrum'); 
 
 
[S,F,T]=specgram(pf,256,1E3,hamming(256),0); 
subplot(313); 
surf(T/1000,F,abs(S).^2); 
view(-80,30); 
shading flat; 
colormap(cool); 
xlabel('Time'); 
ylabel('Frequency'); 
zlabel('spectrum'); 
 
 
%[y,f,t,p] = spectrogram(pf,256,250,F,1E3,'yaxis'); 
%subplot(313); 
%surf(t,f,10*log10(abs(p)),'EdgeColor','none'); 
%axis xy; axis tight;colormap(jet);view(0,90); 
%xlabel('Time'); 
%ylabel('Frequency(Hz)') 
 
      %t=0:0.001:2;                    % 2 secs @ 1kHz sample rate 
      %x=chirp(t,0,1,150);             % Start @ DC, cross 150Hz at t=1sec  
      %F = 0:.1:100; 
      % [y,f,t,p] = spectrogram(x,256,250,F,1E3,'yaxis');  
      % NOTE: This is the same as calling SPECTROGRAM with no outputs. 
      %surf(t,f,10*log10(abs(p)),'EdgeColor','none');    
      %axis xy; axis tight; colormap(jet); view(0,90); 
      %xlabel('Time'); 
      %ylabel('Frequency (Hz)')