The use of constant modulus normalization for digital echo cancellation within RF repeaters

The use of constant modulus normalization for adaptive echo cancellation within a digital repeater is investigated. Echo cancellation coefficients are estimated iteratively from the phase information within the cross spectrum. This is an alternative to normalizing the cross spectrum by the power spectrum. Constant modulus and power spectrum normalizations show comparable echo cancellation results, both preventing frequency-dependent biases often associated with an input spectrum whose power varies over frequency. Both methods compensate for the bandwidth reduction associated with a digital sub-band filter. The constant modulus normalization has the advantage of fewer computations.