I am trying to calculate autocorrelation using fft and xcorr and plot the grafhic with both cases.
autocorr_a=xcorr(signal_1,signal_1);
N1=length(signal_1);
autocorr_b=ifft( fft(signal_1,N1) .* conj(fft(signal_1,N1)));
x1=[0:(2*length(signal_1)-2)]'/(2*length(signal_1)-1);
plot(x1, autocorr_a, x1, autocorr_b)
What is wrong?