| 摘要 |
PROBLEM TO BE SOLVED: To quickly and stably attain automatic frequency control while narrowing an AFC pull-in range without the need for using an expensive highly stable local oscillator. SOLUTION: The method of this invention comprises reading an initial reference control voltage from a storage circuit 156 or other reference control voltage as required, giving the read voltage to a digital/analog converter 158 via an addition/ subtraction circuit 157, converting the voltage into a control voltage, applying the control voltage to a voltage-controlled crystal oscillator 141, which oscillates a local oscillation signal with a corresponding frequency. A detection circuit 152 detects the received signal after frequency conversion, restores a phase modulation signal to detect phase information, an angle difference detection circuit 153 detects a deviation in the reception frequency from the angle difference and an addition/subtraction circuit corrects the reference control voltage so as to eliminate the deviation. When the reception is performed, the output reference control voltage information from the adder/subtraction circuit corresponding to the base station identification information detected by a base station ID detection circuit 155 is registered to the storage circuit as the reference control voltage information particular to the base station. The AFC operation at reception next time can be quickened.
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