Timing jitter analysis of optimum non-data-aided symbol synchronizer for QAM

Recently, non-data aided synchronizers for QAM with a feedforward structure have been significantly improved by incorporating the prefllter originally proposed by Franks to mitigate the self-noise in analog clock regenerators. Prior to this, D´Andrea proposed a synchronizer with a feedback structure that used Franks´ prefllter. Although not reported in the literature, the earlier D´Andrea´s synchronizer outperforms the more recent feedforward synchronizers, and consequently is believed by the authors to be the optimum non-data aided synchronizer for QAM. An all digital version of D´Andrea´s synchronizer is presented in this paper. The steady state timing jitter is thoroughly analyzed by deriving a closed form expression for the noise power spectrum, as well as a simple expression to estimate the variance of the jitter. Performance comparisons are made.