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.