High-order QAM fast carrier synchronization by an adaptive decision-directed EKF algorithm

A new Kalman carrier synchronization algorithm is developed for high-order QAM modulated signals which shows fast acquisition times and good frequency tracking performances. The proposed solution relies on a decision directed extended Kalman filter combined with a lock detector which determines the status of the synchronization process, modifying consequently the filter parameters. Simulation results show that, compared to the performance of a basic Kalman synchronization system, a tenfold improvement or better is achieved in terms of acquisition speed, while keeping a low residual phase noise.