PURPOSE: To provide a method for controlling oscillation frequency of a digitally controlled oscillator circuit capable of easily using even a crystal oscillator whose frequency-temperature characteristics are substantially different from a reference value.
CONSTITUTION: In this method of controlling the frequency of the digitally controlled oscillator circuit 1 for detecting the temperature change of the crystal oscillator by a temperature sensor 2 and controlling the oscillation frequency to be fixed by controlling a voltage to be impressed to a variable capacitive element for the deviation of a resonance frequency due to the temperature change of the crystal oscillator, a storage circuit 7 is provided, the temperatures of appropriate three points are selected, a control voltage for correcting the frequency deviation of the crystal oscillator is measured, the correction curve of a cubic expression is obtained by the measured values of the three points and the coefficient is stored in the storage circuit 7 beforehand. By calculating the control voltage corresponding to the measured temperature of the temperature sensor 2 from the correction curve of the cubic expression, impressing it to the variable capacitive element and controlling the capacitance, the oscillation frequency is maintained constant.
NONAKA YOJI
SUWA YOJI
HIRAMOTO JUICHI
