| 摘要 |
PURPOSE:To prevent an S/N from being reduced in the case of demodulating a spread spectrum signal by performing rough frequency correction at a synchronism capture part and performing much preciser frequency correction at a phase comparator later. CONSTITUTION:The synchronism capture part 9 supplies a spectrum frequency value exceeding a prescribed value to a correcting circuit 13, a control voltage is supplied from the circuit 13 to a local oscillator 3 as a first control signal based on the value, and the oscillation frequency of the oscillator 3 is roughly adjusted so that the frequency of an inverse spread signal can be the central frequency f1 of a band pass filter 10 at all times. On the other hand, a phase comparator 15 compares the phase of a signal J from a multiplier 6 with the phase of an intermediate frequency signal from an oscillator 16 and after the first control signal from the circuit 13 is supplied to the oscillator 3, a control voltage corresponding to the phase difference is supplied to the oscillator 3 as a second control voltage. Thus, the oscillation frequency of the oscillator 3 is adjusted, and the frequency of the signal J can be more exactly adjusted to the central frequency f1 of the filter 10. |
