CIRCUIT FOR CAPTURING FRAME SYNC SIGNAL IN RECEIVER

摘要

A demodulator (1) produces I and Q symbol streams from a received PSK signal which is a time-multiplexed signal composed of a 20-symbol-long BPSK frame sync signal, a 20-symbol-long BPSK superframe identification signal, and an 8PSK digital signal. BPSK demappers (3) produce bit streams B0-B3 demapped according to a base criterion, which allows signal points to be the same along the Q-axis in the I-Q phase plane, and to criterions obtained by shifting the base criterion counterclockwise by pi /4, 2 pi /4 and 3 pi /4. First comparators (60-63) capture, from the bit streams B0-B3, patterns being different few bits at most than the frame sync signal. A predetermined time later, second comparators (64-67) capture patterns being different few bits at most than the superframe identification signal. A frame sync capture signal (SYN) is then produced by a generator (90).