PURPOSE: To provide a frequency synthesizer with low power consumption capable of an intermittent operation as holding carrier output even at the time of high-speed changeover for a TDAM system for monitoring adjacent cells inside a communication frame.

CONSTITUTION: A voltage coarse adjustment part 3 by a D/A converter is provided on the negative electrode side of the capacitor of the loop filer (LPF) 6 of a PLL loop part 2. The charging/discharging operation of the capacitor of the LPF 6 for the variation of the control voltage values of a voltage controlled oscillator 5 is reduced at the time of changing channels, the influence of dielectric absorption is eliminated and the open-loop/intermittent operation holding the carrier output stabilized by a capacitor charge voltage is performed.