function psd=PCspectrum(Signal,Bw,T,Rs)
% function psd=PCspectrum(Bw,T,Rs)
% Pulse Compression Spectrum using FFT
% Parameters:
% Signal -- the signal on time plan
% Bw  -- Bandwidth (Hz)
% T   -- Pulsewidth (s)
% Rs  -- Sample Rates (b/s)
%psd  -- Power Spectral Density



% Set Rs to power of 2
if Rs<256
    Rs=256;
else Rs=256*(ceil(Rs/256));
end

% Solve Fourier Spectrum of PCs
fsig=fftshift(fft(Signal,2*Rs));

% Solve Power Spectral Density
psd=fsig.*conj(fsig)/Rs;
Amp=max(psd); % Normalize to 1
len=length(fsig);
flabel=(1/T)*(-(len-1)/2:(len-1)/2);

% plot
t=0:1/Bw:T;
maxs=max(Signal);mins=min(Signal);
figure;
subplot(211);
plot(t,Signal(1:length(t)));
% plot(Signal);
axis([0 T mins maxs]);
title('Chirp Waveform');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(212);
plot(flabel,psd/Amp);
grid on;
axis([-Bw Bw 0 1]);
title('Pulse Compression Spectrum');
xlabel('Frequency (Hz)');
ylabel('Amplitude');