| 摘要 |
PURPOSE:To eliminate spurious signal and to improve carrier noise by providing a voltage controlled oscillator whose frequency of oscillated signal is changed while receiving an error signal from the 1st input circuit and a control signal from the 2nd input circuit. CONSTITUTION:The operating characteristic of the voltage controlled oscillator (VCO)5 corresponding to unit level changes of a control signal V'i are as shown by curves b1, b2- in Fig. When the frequency of a reference signal fr(input signal) and an oscillating signal fo is locked at a point on the curve b1 in Fig., an error signal Vi is limited between levels V1 and V2. In increasing the frequency of the signal fr, the level of the error signal Vi reaches the level V2 being an upper limit threshold value. In this case, a constant voltage diode 15 of an error signal level limiter 10 is operated, the mode becomes the up mode, an up-down counter 23 is incremented, the level of the control signal V'i is increased by 1 unit, the operating characteristic of the VCO5 becomes the curve b2 from the curve b1, the frequency is locked up at one point on the curve b2 and the error signal f0 becomes between the levels V1 and V2. |
