## Cyclic Autocorrelation

For sequences of length , the cyclic autocorrelation operator is defined by

 (7.19)

where and the index is interpreted modulo .

By using zero padding by a factor of 2 or more, cyclic autocorrelation also implements acyclic autocorrelation as defined in (6.16).

An unbiased cyclic autocorrelation is obtained, in the zero-mean case, by simply normalizing by the number of terms in the sum:

 (7.20)

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