Circular Cross Correlation

CXCORR Circular Cross Correlation function estimates.
CXCORR(a,b), where a and b represent samples taken over time interval T which is assumed to be a common period of two corresponding periodic signals.

a and b are supposed to be length M row vectors, either real or complex.

[x,c]=CXCORR(a,b) returns the length M-1 circular cross correlation sequence c with corresponding lags x.

The circular cross correlation is:
c(k) = sum[a(n)*conj(b(n+k))]/[norm(a)*norm(b)];
where vector b is shifted CIRCULARLY by k samples.

The function doesn't check the format of input vectors a and b!

For circular covariance between a and b look for CXCOV(a,b) in
http://www.mathworks.com/matlabcentral/fileexchange/loadAuthor.do?objectType=author&objectId=1093734

Reference:
A. V. Oppenheim, R. W. Schafer and J. R. Buck, Discrete-Time Signal Processing, Upper Saddler River, NJ : Prentice Hall, 1999.

Author: G. Levin, April 2004.