Patent ID: 7888974

Claim:
A frequency synthesizer comprising: a voltage-controlled oscillation unit for oscillating a frequency signal having a frequency corresponding to a supplied voltage; a frequency-divider for subjecting the frequency signal to 1/N (N represents an integer) frequency division in accordance with a set frequency of the voltage-controlled oscillation unit; an analog/digital converter for sampling a sinusoidal signal having the frequency corresponding to 1/N of the output frequency of the voltage-controlled oscillation unit on the basis of a reference clock signal and outputting a sampling value of the sampled sinusoidal signal as a digital signal; a vector extracting unit for subjecting the frequency signal corresponding to the output signal from the analog/digital converter to orthogonal detection based on a digital signal of a sinusoidal signal having a frequency of ω0/2π, and extracting a real number part and an imaginary number part of a rotation vector rotating at the frequency corresponding to the frequency difference between the frequency of the frequency signal concerned and ω0/2π when the rotation vector concerned is represented by complex notation; a parameter output unit for calculating the frequency of the rotation vector when the output frequency of the voltage-controlled oscillation unit is equal to a set value, and determining, on the basis of the calculated frequency, a frequency for rough adjustment set at a rough frequency pitch and a frequency for fine adjustment set at a fine frequency pitch; a slow-speed rotation vector obtaining unit for multiplying an inverse rotation vector rotating inversely to the rotation vector by the frequency for rough adjustment calculated by the parameter output unit and obtaining a slow-speed rotation vector rotating at a differential frequency from the rotation vector; an integrating circuit unit for integrating a value corresponding to the difference between the frequency of the slow-speed rotation vector obtained by the slow-speed rotation vector obtaining unit and the frequency for fine adjustment; and a feedback unit for feeding back, to the voltage-controlled oscillation unit, a voltage signal corresponding to the integration value obtained by the integrating circuit unit, whereby PLL is formed by the voltage-controlled oscillation unit, the rotation vector extracting unit and the feedback unit, and when PLL is locked, an output frequency of the voltage-controlled oscillation unit is adjusted to a set frequency.