FREQUENCY MODULATION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide the frequency modulation circuit in which deterioration in a modulation characteristic at a low frequency is compensated in a frequency modulation state by a PLL and which is suitable for FSK modulation. SOLUTION: In the frequency modulator in which a PLL is operated as the frequency modulator by providing a modulation signal to the PLL circuit, the modulation signal is fed to the PLL via a compensation circuit 4 consisting of a plurality of connecting filters of the same type as a loop filter 12 used for the PLL 5 so as to allow the PLL circuit to conduct frequency modulation thereby allowing the compensation circuit 4 to compensate deterioration in the modulation characteristic.