Patent ID: 8249198

Claim:
A demodulation circuit for demodulating a differential phase shift keying (DPSK) modulated received signal, the circuit comprising: a phase difference data generator which compares phase data representing a phase of the received signal input at every predetermined sampling time with previous phase data preceding by one symbol period to generate phase difference data representing a phase shift amount between the phase data and the previous phase data; and a symbol selection unit which evaluates the phase difference data generated at every sampling time to select as a symbol, wherein the symbol selection unit selects, as a subsequent symbol, (1) a phase difference data at a sampling time delayed by one symbol period from a sampling time of a current symbol, when the phase difference data Di at the sampling time of the current symbol corresponds with a phase difference data Di−1 preceding by one sampling period from the sampling time of the current symbol, and the phase difference data Di corresponds with a phase difference data Di+1 delayed by one sampling period from the sampling time of the current symbol, (2) a phase difference data at a sampling time delayed by a first period shorter than the symbol period from the sampling time of the current symbol, when the phase difference data Di does not corresponds with the phase difference data Di+1, and (3) a phase difference data at a sampling time delayed by a second period longer than the symbol period from the sampling time of the current symbol, when the phase difference data Di does not corresponds with the phase difference data Di−1.