Demodulator for differential phase shift keying signal using a maximum likelihood sequence estimator

摘要

The present invention is directed to a differential phaseshift keying (PSK) signal demodulator in which an error rate provided when a signal modulated according to a π/4-shift DQPSK modulation system is demodulated can be improved. The differential PSK signal demodulator includes means (4 to 10) for judging changing traces of signal points from outputs of an I-axis level discriminating device (1) and a Q-axis level discriminating device (2) to select an optimum path, thus making it possible to reduce a bit error rate (BER).