autocorrelation_pic.asv

calculation of the autocorrelation peak sidelobe levels and corsscorrelation. CE sequence, frank aut

function autocorrelation_pic(L,S)

m=power_integer_2(L);
nfft=2^(m);

% sfft=fft(S,nfft);
% Ac=fftshift(abs(ifft(sfft.* conj(sfft)))/L);
% figure(1);
% time=(-(nfft/2)):1:(nfft/2-1);
% plot(time,Ac);

S=[S, zeros(1,(nfft-L))];
x=zeros(41,nfft);
col=0;
for fdT=-2:.1:2
   col=col+1;
   for row=1:nfft
      Sr(row)=S(row)*exp(i*2.*pi*(row-1)*fdT/L);
   end
   x(col,:) = fftshift(abs(ifft(fft(Sr).* conj(fft(S))))/L);
end
% 
% test if the autocorrelation figure in the fdT=0 right matched the former Ac computered   
% figure(1);
% time=(-(nfft/2)):1:(nfft/2-1);
% plot(time,Ac);
% hold all
% plot(time,x(:,21),'--r');

time=(-(nfft/2)):1:(nfft/2-1);
fdT=-2:.1:2;
figure(1);
mesh(time,fdT,x);
xlabel('sample shift');
ylabel('Doppler shift fd*T');
zlabel('Autocorrelation function');
figure(2);
contour(time,fdT,x);
xlabel('sample shift');
ylabel('Doppler shift fd*T');