| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of error at the time of active/standby switching even in the case that the carrier phase difference between the transmission modulation wave in an active system and that in a standby system is about 45 deg.. SOLUTION: A phase detection circuit 9 of a frequency error correction control means 21 detects phase deviations of I and Q channel base band signals S4a and S4b from normal signal points. A numerically controlled oscillation circuit (NCO) 11 outputs a phase signal P1 of which the angular speed is changed in accordance with the output value of a loop filter. A signal point area discrimination circuit 13 outputs a phase shift control signal C1 when signal points of I and Q channel base band signals S4a and S4b exist in a specific signal point area in the vicinity of rectangular coordinate axes on a phase plane continuously for a certain time. When receiving the phase shift control signal C1, a 45 deg. phase signal generation circuit 14 outputs a phase signal P2 which shifts the phase at 45 deg.. An addition circuit 15 adds the phase signal P2 to the phase signal P1 and outputs the result as a phase deviation correction value. |
