| 摘要 |
PURPOSE:To attain the frequency modulation of an RF output synchronously with the frequency of a reference signal by providing a shift cancelling circuit and varying the frequency division ratio of a frequency divider so as to cancel the frequency shift caused due to a level of a frequency modulation signal. CONSTITUTION:An integration device built in a shift cancel circuit 10 integrates a voltage of a frequency modulation signal, the circuit 10 selects one frequency division ratio of either a frequency divider C8 or a D9 depending on the polarity of the output voltage when its output voltage exceeds a prescribed value and restores the frequency division ratio when the frequency shift is cancelled. Then a voltage cancelling the integration voltage corresponding to the cancelled voltage is fed simultaneously to the built-in integration device. The shift cancel circuit 10 varies the frequency division ratio of the frequency dividers C8 and D9 so as to cancel the frequency shift caused due to the level of the frequency modulation signal in this way, thereby bringing the output voltage of the integration 4 to be a value producing an RF output synchronously with the frequency of a reference signal without the case of the frequency modulation at all times. Thus, the RF output synchronously with the frequency of the reference signal i s frequency-modulated. |
