% spectrogram examples for ECE 802l
%sinusoid;
%logon;
x=logon(64,0.4,128);
tflog=specgram(x,32,128,32,31);
subplot(211);
plot(real(x));
subplot(212);
imagesc(abs(tflog));
pause;
figure
%demo signal;
tfdemo=specgram(demosig,32,200,32,31);
imagesc(abs(tfdemo));
pause
figure;
% effect of the window length;
y=[zeros(1,128),exp(j*0.6*[1:128])];
subplot(411);
plot(real(y));
subplot(412);
tf1=specgram(y,16,256,16,15);
imagesc(abs(tf1));
subplot(413);
tf2=specgram(y,32,256,32,31);
imagesc(abs(tf2));
subplot(414);
tf3=specgram(y,64,256,64,63);
imagesc(abs(tf3));


t=0:0.001:2;                 % 2 secs @ 1kHz sample rate
y=chirp(t,0,1,150);          % Start @ DC, cross 150Hz at t=1sec 
tf1=specgram(y,256,1E3,256,250);

t=-2:0.001:2;                % +/-2 secs @ 1kHz sample rate

y=chirp(t,100,1,200,'q');    % Start @ 100Hz, cross 200Hz at t=1sec 
tf2=specgram(y,128,1E3,128,120); % Display the spectrogram
title('Quadractic Chip: start at 100Hz and cross 200Hz at t=1sec');