A Carrier Recovery Algorithm for High Order QAM Signals

The carrier recovery is one key technique in the demodulation of high order quadrature amplitude modulation (QAM) signals. A carrier recovery algorithm which switches between multi-threshold polarity decision mode and decision directed mode according to the standard deviation of the frequency of numerically controlled oscillator (NCO) is proposed. The proposed algorithm can detect a proper time for the mode switch to yield lower steady state error. The simulation results demonstrate the effectiveness of the proposed algorithm in improving the performance of blind carrier recovery.