Major Concerns In Clock Recovery Of Manchester Encoded Data Using a Phase Lock Loop

Abstract

Clock Recovery Circuits are used for recovering clock and data from the signal received which becomes noisy and mistimed while traveling. The target application of this thesis is the recovery of clock and data from Manchester encoded data stream generated by a Manchester Encoder-Decoder designed using the Harsh Environment Cell Library of MSVLSI lab. This thesis also presents its successful test results for temperatures up to 195C. Clock Recovery Systems use PLL whose charge pump generates the control signal for the VCO; any disturbance on its output affects the VCO and locking behavior of the PLL. Thus factors contributing to its non-ideal operation and ways to minimize them are discussed. A new term called "frequency jump", referring to the frequency shifts due to non-ideal charge pump operation, is coined. A technique is proposed which attempts to avoid "kink effect" in 0.5u Peregrine SOS transistors of the VCO as it prevents them from biasing up to the designed levels.