PURPOSE: To enable automatic frequency control even under a condition where ambient temperature changes by storing data for several positions in a storage device in advance within a frequency fluctuation range of a temperature compensation voltage controlled crystal oscillator and sweeping the data as initial data when the automatic frequency control is started.
CONSTITUTION: Plural data Vdn deciding a control voltage Vc of a temperature compensation voltage controlled crystal oscillator 5 are stored in a storage device 72 in a control arithmetic device 7 so that a deviation in a frequency fo being an output of a frequency converter 1 is within a frequency error detection range ±Δf1 of a frequency error detection section 2. Then control data Vdn are extracted from the storage device 72 when the automatic frequency control is started and a control voltage Vcn generated by the data Vdn is applied to the temperature compensation voltage controlled crystal oscillator 5 to obtain a reference signal of a PLL synthesizer circuit 3 so that an error of the difference signal fo of the frequency conversion section 1 is set within a frequency error detection rage of the frequency error detection section 2 in the automatic frequency control loop.
YAMADA JUN
TAKIZAWA KAZUYUKI
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