an oscillator, oscillating a resonator and generating a first oscillation signal; and

a PLL circuit, adjusting a ratio between a first frequency of the first oscillation signal and a second frequency of a second oscillation signal output from a voltage controlled oscillator, and controlling the oscillator based on a loop filter voltage being an input voltage of the voltage controlled oscillator, wherein the PLL circuit comprises:

a frequency divider circuit, adjusting the ratio between the first frequency and the second frequency so that the loop filter voltage becomes a spurious oscillation equivalent voltage, wherein the spurious oscillation equivalent voltage is the loop filter voltage when the resonator produces a spurious oscillation.