On AR equalization with the constant modulus criterion

This work studies the CM criterion applied to equalization with AR channel receivers motivated by recently proposed blind IIR algorithms [6], [7], but may also be used for initializing a blind adaptive DFE. Blind IIR equalization is of practical interest for two main reasons: the IIR structure not only provides a parsimonious representation of a linear receiver, but may also be used for switching to DFE mode. We begin by showing that, unlike the FIR case, AR-CM receivers are equivalent to Wiener receivers for Gaussian sources. For sub-Gaussian input signals, however, due to the requirements of causality and stability of the receiver, characterization of CM solutions appears to be a complex problem. Thus, for sub-Gaussian sources, analysis is restricted to the special case of a MA(1) channel and AR(1) equalizer. Nevertheless, this study provides insight into the properties of AR-CM receivers by making the connection to the popular IIR-MMSE receivers.