EQUALIZATION OF A HARD-LIMITED SLOWLY-FADING MULTIPATH SIGNAL USING A PHASE EQUALIZER WITH TIME-REVERSAL STRUCTURE

This paper describes a low-complexity equalization technique for improving the reliability of portable radio links in the presence of multipath time delay spread. A technique that operates on hard-limited received signals, with only the phase information available, is presented. The use of passband hard-limiters in radio front-end circuits reduces the complexity of portable radio receivers. Suboptimum receivers based upon a maximum-likelihood estimation criterion are discussed, including a sequence estimator and a decision-feedback phase detector. A low-complexity adaptive phase equalizer structure using decision-directed phase tracking is proposed, which does not require the multiplication operations required in most conventional equalization algorithms. We also propose a receiver that includes a time-reversal structure and a joint estimator for optimum timing recovery and equalizer training. The time-reversal structure plays a crucial role in maximizing the compensation capability of the phase equalizer. The combined use of phase equalization and diversity reception is also considered. Computer simulations confirm the feasibility of the proposed receiver structure.