The ability to create estimates of the cross-covariance function that are both unbiased and normalized is not available in the Signal Processing Toolbox.
To work around this issue, create unbiased estimates and normalize by the zero lag term manually, as in the following example:
ww = randn(1000,1);
N = 10;
[cov_ww,lags] = xcov(ww,N,'unbiased');
cov_ww = cov_ww / cov_ww(N+1);
stem(lags,cov_ww)
