| 摘要 |
PURPOSE:To remarkably reduce the power consumption even if the subject circuit is used in the environment in which a temperature variation is severe by allowing a capacitor of an LPF part for generating a frequency control voltage of a voltage control oscillating circuit to have a temperature characteristic for offsetting a temperature variation of this oscillator. CONSTITUTION:A free-running frequency of a voltage control oscillator VCO 5 is varied by a temperature. The capacity and the induction element reactance of a variable capacity diode 19 have a positive temperature coefficient, and work in the direction for lowering a self-oscillation frequency as a temperature rises, therefore, a temperature compensation of the circuit 5 is executed as follows. That is, within a prescribed time from the time when pull in is ended, from the point that an accumulated charge is kept constant in a capacitor 17, and from the point that a characteristic of the capacitor 17 is varied by a temperature, as for a temperature characteristic of the capacitor 17, that which offsets a temperature variation of the VCO is selected. Subsequently, by varying the capacity of the variable diode 19 by a voltage variation based on a capacity variation of the capacitor varied in accordance with a temperature variation, the reactance of a VCO 20 is compensated. |
