Improved carrier acquisition in 64 QAM systems

Several phase and frequency detectors (PFDs) are presented for improved carrier acquisition in 64 QAM (quadrature amplitude modulation) systems. Some of them are based on rectangular signal representation and are direct extension to 64 QAM of the PFDs previously proposed by the authors for 16 QAM systems. The others are new and use a phase detector based on polar-coordinate representation of the demodulated complex signal. A 34 Mb/s laboratory breadboard was used to evaluate the performance of each detector. The best performance was obtained with the PFDs derived from the polar phase detector. As compared with the original phase detector, these PFDs led to a five- or sixfold increase of the loop acquisition range.<>