% AC_PSD.m
% Draw autocorrelation and doppler psd.
function []=AC_PSD(idata, qdata, fm, name)
%******************************  variables ******************************
% idata     Ich data
% qdata     Qch data
% fm        max doppler spead
% name      Title of the figure
%************************************************************************

% calculate autocorrelation
iAC = xcorr(idata, idata);
qAC = xcorr(qdata, qdata);

AC = iAC+qAC;
AC = AC./max(AC);

x=[-length(AC)/2:length(AC)/(length(AC)-1):length(AC)/2];

% Autocorrelation
figure;clf;plot(x, AC);grid on
title(['Normalized Autocorrelation', name]);
xlabel('Normalized Time Delay');
ylabel('Normalized Autocorrelation');


% calculate doppler psd
Doppler_PSD = 10.*log10(abs(fft(AC)));

x=[-fm:(2*fm)/(length(Doppler_PSD)-1):fm];

% Doppler PSD
figure;clf;plot(x, Doppler_PSD);grid on
title(['Doppler PSD', name]);
xlabel('Frequency shift from carrier (Hz)');
ylabel('Doppler psd');

%***************************** end of file *******************************