A comparison period detecting unit (11) defines, as a comparison period, a period between a rising edge of a first clock signal and a rising edge of a second clock signal, and detects the presence or absence of transition of a data signal during the comparison period. A phase relationship detecting unit...http://www.google.com/patents/US8149974?utm_source=gb-gplus-sharePatent US8149974 - Phase comparator, phase comparison device, and clock data recovery system
