A Baud-Rate Timing Recovery Scheme With a Dual-Function Analog Filter

This brief presents a baud-rate timing recovery scheme that is aided by signals generated from a dual-function analog filter. The analog filter functions as a simultaneous low-pass and bandpass filter to generate the data and its slope, respectively. Peaking is introduced in the low-pass data path to equalize a lossy channel. The timing recovery loop utilizes the equalized data and slope signals obtained from the dual-function analog filter to recover a clock based on a modified minimum mean squared error (MMSE) criterion. Unlike previously published baud-rate techniques for multigigabit per second nonreturn-to-zero data, this technique can lock to either random or alternating data patterns, even from a closed eye. As a proof of concept, a prototype dual-function analog filter was fabricated in a 0.18-mum CMOS process and used to recover a 2-GHz clock from a 2-Gb/s 231-1 random data sequence based on the modified MMSE criterion