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From: fazleh on 21 May 2010 03:50
Hi

I needed to plot the spectrogram of the tau_gate, frequency, and the Power. I have tried to get that but with fail. I even asked the same question in a previous thread but I was pointed the wrong direction. Really need help. Thanks in advance.

CODE:


Fs=800;
t = -20:1/Fs:20;

%Carrier Sine Wave
lambda = 1550e-9;
freq= ((3*10^8)/lambda)*1e-12;

%Gaussian Function
tau_pulse = 0;
FWHM_pulse = 10;
A_pulse = 1;
sigma_pulse = FWHM_pulse/(2*sqrt(2*log(2)));
Ip = A_pulse*exp(-((t-tau_pulse)/(2*sigma_pulse)).^2); %Gaussian input puls

for tau_gate=-30:1:30;

FWHM_gate = 10;
A_gate = 1;
sigma_gate = FWHM_gate/(2*sqrt(2*log(2)));
SGorder_gate = 3;
Ig = A_gate*exp(-((t-tau_gate)/(2*sigma_gate)).^(2*SGorder_gate)); %Gate

% Plot pulse and gate intensities
subplot(2,2,1)
plot(t,Ip);
xlabel('Time')
ylabel('Amplitude')
hold on
plot(t,Ig,'r')
hold off

%Carrier And Gausian
Ep = (sqrt(Ip).*cos(2*pi*freq*t));
Eo = Ig.*Ep;
subplot(2,2,3)
plot(t,Eo);
axis([-20 20 -1.1 1.1]);
xlabel('Time')
ylabel('Amplitude')

%Fourier Transform
m = length(Ip);% Window length
n = pow2(nextpow2(m));

% Transform length
z = fft(Eo,n); % FFT
z=fftshift(z);%Shift zero-frequency component of discrete Fourier transform to center of spectrum

f=([-n/2:n/2-1]/n*Fs);
power = z.*conj(z)/n;
power = power./max(power);

% PSD of the DFT figure(4);
subplot(2,2,4)
plot(f,power);
axis([190 197 0 1.1]);
xlabel('Frequency')
ylabel('Power')

pause(0.1)

loopi =loopi + 1;

end
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