Patent ID: 7558355

Claim:
A syncword detecting circuit for detecting a predetermined syncword in an input baseband signal, comprising: a matched-bit-number comparing circuit that determines a number of bits in the baseband signal that match bits of a predetermined syncword, and that compares said number with a first threshold; a comparing-result-change detecting circuit that samples a result of said matched-bit-number comparing circuit by a clock having a frequency equivalent to an integer N greater than or equal to two times a symbol transmission rate of the baseband signal, and that detects a change of said result of said matched-bit-number comparing circuit; a detected-result storing circuit that stores sequentially a result of said comparing-result-change detecting circuit and to also store historical data of results of said comparing-result-change detecting circuit of previous cycle periods; a total-number detecting circuit that detects a total number of said results of said matched-bit-number comparing circuit from a present cycle period and the previous cycle periods, said results of said matched-bit-number comparing circuit being included in cycle periods of said clock surpassing said first threshold, based on the results of said comparing-result-change detecting circuit stored in said detected-result storing circuit; and a syncword detecting circuit that detects said predetermined syncword based on a total-number result of said total-number detecting circuit, and that selects an intermediate phase of a cycle period having a maximum number of bits that match as a detection phase.