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

A novel topology of a phase detector for applications in clock recovery systems from NRZ data is presented in this paper. The phase detector operates directly on the data stream, without requiring preprocessing, and behaves like a sampling-type phase detector, providing a sinusoidal phase characteristic. The triple-tail principle is exploited to obtain a circuit topology suitable to low-voltage high-speed applications, and a feedback loop is proposed to compensate for data transition density variation. The phase detector 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.