Efficient Carrier Recovery for High-Order QAM

A novel carrier recovery algorithm for high-order quadrature amplitude modulation (QAM) is proposed in this paper. Besides the traditional decision-directed phase detector, the algorithm employs an improved polarity-based phase detector to extend the acquisition range of carrier frequency offset. And when combined with a dual-mode adaptive equalization algorithm, it can be used in the application over multi-path channels. Simulation results demonstrate that it can deal with carrier frequency offset up to 960 kHz@256QAM over AWGN channels and 690 kHz@256QAM over typical coaxial cable channels at a baud rate of 6.9 Msps. Meanwhile, its complexity is quite low.