Patent ID: 7587180

Claim:
An FM modulator for FM-modulating a signal containing a modulation component and outputting, as an output signal, a signal having been FM-modulated, comprising: a reference signal generator for generating a reference signal; a voltage controlled oscillator for outputting, as the output signal, a signal in accordance with a control voltage being applied thereto; and a control circuit for converging, to a predetermined frequency, an oscillation frequency of the voltage controlled oscillator using the reference signal, and, after the oscillation frequency has been converged to the predetermined frequency, changing, in accordance with the signal containing the modulation component, the control voltage to be applied to the voltage controlled oscillator, and causing the voltage controlled oscillator to output the output signal having been FM-modulated, wherein the control circuit includes a correction section for measuring, using the oscillation frequency of the voltage controlled oscillator and the control voltage to be applied to the voltage controlled oscillator, an f-V characteristic representing a relationship between the oscillation frequency and the control voltage, and applying, to the voltage controlled oscillator, the control voltage having been corrected in accordance with the f-V characteristic having been measured, the correction section measures the f-V characteristic while the oscillation frequency is being converged to the predetermined frequency, and applies, to the voltage controlled oscillator, the control voltage having been corrected in accordance with the f-V characteristic having been measured such that the voltage controlled oscillator outputs a signal equivalent to a signal outputted by a voltage controlled oscillator having a linear f-V characteristic, and the FM modulator further comprises a characteristic measurement time control section for notifying the correction section of a time at which the f-V characteristic is to be measured.