An Unbounded Frequency Detection Mechanism for Continuous-Rate CDR Circuits

A continuous-rate clock and data recovery (CDR) circuit with unbounded frequency detection mechanism is proposed herein. The unbounded frequency detection mechanism combines the digital quadricorrelator frequency detection and subharmonic tone frequency detection techniques. By adopting the unbounded frequency detector, this reference-less CDR circuit has no locking range limitation and provides an automatically bidirectional frequency detection characteristic. In addition, the CDR circuit can detect the frequency-hopping information without an additional transmitted control signal. Based on the proposed frequency detection methodology, a proof-of-concept CDR circuit is implemented to demonstrate the feasibility and effectiveness of the proposed design.