A carrier recovery algorithm based on multi-threshold polarity decision for QAM

Quadrature Amplitude Modulation(QAM) is widely applied in modern communications systems.The carrier recovery is one of the key factors,which decides the overall performance of the receiver.A multi-threshold polarity decision algorithm is proposed for QAM carrier recovery having the advantage of increasing convergence speed and minimizing the lock error.This algorithm fully utilizes the signal points with zero lock error on the diagonal lines of the QAM constellation so that adds the number of symbol set to distill the phase error.It is indicated from the analysis and simulation results that compared with traditional decision directed carrier recovery algorithms,multi-threshold polarity decision algorithm can further increase convergence speed while maintaining the large frequency acquisition range and the advantage of the polarity decision carrier recovery algorithm.