Patent ID: 6072370
Filing Date: 2000-06-06
Classification: H03L,H04L

Abstract:
A clock extraction circuit comprising:a first frequency divider for frequency-dividing a received non-return zero signal by two;an edge detecting circuit for detecting a changing point of a signal outputted from said first frequency divider;a voltage control oscillator for oscillating a clock signal in a frequency region nearly equal to a transmission rate of said non-return zero signal;a second frequency divider for frequency-dividing said clock signal oscillated by said voltage control oscillator by two;a selecting circuit for selecting edge pulses detected by said edge detecting circuit, anda phase comparator for comparing phases between said non-return zero signal frequency-divided by first frequency divider and said clock signal frequency-divided by said second frequency divider based on each of said edge pulses selected by said selecting circuit,wherein said edge pulse selecting circuit includes means for dividing said edge pulses according to cases by using a frequency-divided clock signal phase-shifted by 90 degrees from said frequency-divided clock signal.