How to find autocorrelation function for a mm-sequence ?

I have generated an m-sequence with periodicity 1023 i.e., for order 10. I have successfully generated the m sequence using matlab but got struck while evaluating autocorrelation function of that sequence. I tried using 'xcorr' but it doesn't seem to match the text book i.e., when I use xcorr I get values more than 1. The problem persist even if I try to normalize it i.e., when I divide it by 1023.

If anyone can help me out how to evaluate the autocorrelation function it will be helpful to me. Also, I am wondering if I could evaluate the autocorrelation for specified time value. For example I know matlab calculates the autocorrealtion for discrete values 1,2,3 ... I was wondering if I could calculate it for 0.2,0.4.

Thanks guys in advance.

[Greg Heath]

Please explain the meaning of the terms m-sequence and mm-sequence.

Greg

Answer 1

[Greg Heath]

I do not have xcorr. However, I believe there are at least four options with names like 'unbiased', 'biased' , 'coeff' and 'none' see

help xcorr doc xcorr

for details. Also check to see if you have crosscorr

help crosscorr doc crosscorr

Finally, you can use

crosscorrelation(a,b) = ifft(conj(fft(a)).*fft(b))/N;

Unfortunately, nncorr in the Neural Network Toolbox is buggy.

Hope this helps.

Thank you for formally accepting my answer

Greg