A high-speed low-voltage phase detector for clock recovery from NRZ data

A novel topology of phase detector (PD) for applications in clock recovery systems from nonreturn-to–zero data is presented in this paper. The PD operates directly on the data stream, without requiring preprocessing, and behaves like a sampling-type PD, providing a sinusoidal phase characteristic. The triple-tail cell principle is exploited to obtain a circuit topology suitable to lowvoltage high-speed applications, with a very simple structure and thus limited jitter generation. A model is proposed to understand circuit behavior and optimize its design. The PD has been used in a clock-and-data recovery circuit for 10-Gb/s optical communications, and measurements in agreement with SONET specifications are reported.