| 摘要 |
PURPOSE:To always pass an intermediate frequency signal through the center frequency of a band pass filter by controlling a reception local oscillator and a voltage control oscillator on the basis of the oscillation frequency of a highly stabilized intermediate frequency oscillator. CONSTITUTION:The reception input signal supplied to a terminal 9 is amplified by a high frequency amplifier 1 and mixed with the output wave fed from a reception local oscillator 14 by a reception mixer to be converted into an intermediate frequency signal. This signal is amplified up to a prescribed level through a BPF4 and an intermediate frequency amplifier 5 containing an automatic phase controller and then undergoes phase detection through a phase detector 6 by means of the output wave of a voltage control oscillator 11. Thus a base band signal is extracted at a terminal 10. The phase comparison is carried out between a partial output of the oscillator 11 and the output wave of a highly stabilized intermediate frequency oscillator through a phase comparator 13 to obtain error voltage. Both oscillators 14 and 11 are controlled by said error voltage to obtain the prescribed value for both the frequency of an intermediate frequency signal and the oscillation frequency of the oscillator 11. The variance component of the intermediate frequency signal is absorbed by varying the oscillation frequency of the oscillator 14. Thus the intermediate frequency signal always passes through the center frequency of the BPF4. |
