| 摘要 |
PURPOSE:To prevent false leading-in easily to extend the synchronization leading-in width of the phase synchronous circuit, by adding differential frequency DC components between the reference oscillator and the voltage control oscillator to the center frequency control voltage of the voltage control oscillator directly. CONSTITUTION:An AFC circuit is constituted by low-pass filter 11 and amplifier 12. The output of voltage control oscillator 5 and the output of reference oscillator 9 are mixed by mixer 10 to generate the differential frequency. The control voltage of oscillator 5 is controlled by DC components of the differential frequency. Since the oscillation frequency is moved to the center frequency of oscillator 5, the phase synchronous circuit leads it into the normal input frequency to prevent false leading- in. |
