Carrier independent blind initialization of a DFE

This paper is concerned with the blind initialization of a decision feedback equalizer (DFE) in a practical setting. We present a DFE architecture with forward and feedback filters which operate in the passband so that equalization can be done completely independent of carrier phase. The constant modulus algorithm (CMA) error term is used to update the forward and feedback equalizer parameters of a linear infinite impulse response (IIR) equalizer structure in order to acquire an equalizer parameterization which is in the neighborhood of the optimum DFE setting. Methods for coarse tuning of a decision directed (DD) carrier loop during acquisition are also described. Laboratory experiments with test silicon demonstrate the similarity in equalizer parameter settings between CMA in a linear IIR structure with those of the DD least mean squares algorithm (DD-LMS) in a linear IIR structure and in a non-linear DFE structure.