A new suppressed carrier synchronizer with reduced phase jitter for QAM systems

A new simple carrier phase synchronizer for QAM systems with reduced phase jitter is proposed. A solution based on the extended Kalman filter (EKF) is applied as a near optimal solution for the tracking of time- varying phase of the carrier. In a conventional DPLL (digital phase lock loop) used in carrier phase recovery, the loop filter gain is a constant while in the new method the gain is adaptively changed such that a greatly reduced phase jitter variance is achieved. We derive the new scheme and compare it to the conventional first order DPLL, both analytically and by simulations for QAM modulations. We test the case of 16-QAM as an example. Simulation results show that the obtained phase error variance is much smaller in moderate and high SNR case, also with high carrier phase noise than the one achieved with a constant loop filter gain.