Timing extraction circuit and communication system utilizing the same

摘要

A timing clock extraction circuit for extracting from a multilevel code signal, transmitted at a predetermined baud rate, in which cross timings with a reference level are generated at frequency timings several times the baud rate, a clock pulse train at the baud rate and obtaining discriminative data from the multilevel code signal in accordance with the extracted clock pulse train. The timing clock extraction circuit includes a detector for detecting cross timings between the multilevel code signal and a predetermined threshold value; a synchronization control circuit for outputting a clock pulse train having a frequency several times said baud rate in synchronism with the cross timings; a clock generator for dividing the several-time clock pulses to generate a plurality of trains of baud rate clock pulses in different phase from each other; and a decision unit for distinguishing a baud rate clock pulse train from the plurality of trains of baud rate clock pulses which are synchronized with discriminative points of the multilevel code signal by using the cross timings and the clock pulse train having a frequency several times the baud rate.