| 摘要 |
PURPOSE:To reduce an inter-code interference caused by a shift of the center frequency of a band pass filter. CONSTITUTION:An AFC circuit 1 executes the following operations after 32 executes synchronization of a transmitting frequency fTX to a receiving frequency fRX. To a ROM 11, a shift from a center frequency at each temperature of a BPF 30 is set together with that which is caused by a manufacturing error. A temperature sensor 12 allows the ROM 11 to output a deviation value at a detected temperature. An adding circuit 10 adds a count value of a counter 52 and an output value of the ROM 11. A large/small relation of its added value and a prescribed value is decided by a magnitude comparator 13, and based on a result of its decision, a prescribed pulse is outputted from a pulse generator 14, the number of its pulses is subjected increase/decrease count by an up/down counter 15, its count value is analogized by a C/A converter 16, and an oscillation frequency of an oscillator 2 is set. The oscillator 2 generates a second local frequency f2LO in a state synchronized with the center frequency of the BPF 30. As a result, the center frequency of the BPF 30 and a second IF frequency f2IF coincide with each other, and an inter-code interference is reduced. |
