Patent ID: 8638172

Claim:
A local oscillator comprising: a digitally-controlled oscillator configured to output an oscillation signal with a predetermined oscillation frequency and to control variably the oscillation frequency by using a first oscillator control value and a second oscillator control value that are digital values, an amount of change in the oscillation frequency per unit second oscillator control value being equal to a product of an amount of change in the oscillation frequency per unit first oscillator control value multiplied by a second coefficient, the oscillation frequency being equal to a sum of a product of the first oscillator control value multiplied by the amount of change in the oscillation frequency per unit first oscillator control value, and a product of the second oscillator control value multiplied by the amount of change in the oscillation frequency per unit second oscillator control value; a rough adjustment controller configured to roughly adjust the oscillation frequency to a roughly adjusted frequency by adjusting the second oscillator control value on the basis of a reference signal and the oscillation signal; a phase data generator configured to output, as phase difference data of a digital value, a phase difference between the reference signal and the oscillation signal; a subtractor configured to subtract the phase difference data from the set frequency data obtained by dividing a set frequency by a reference frequency of the reference signal, and to output the subtraction result as phase error data; a loop filter configured to output a normalized control value obtained by filtering the phase error data; a multiplier configured to multiply the normalized control value by a first coefficient to obtain the first oscillator control value and output the first oscillator control value to the digitally-controlled oscillator in fine adjustment; and a coefficient calculator configured to set a value as the first coefficient in the multiplier before the fine adjustment, the value being calculated on the basis of the second oscillator control value used to roughly adjust the oscillation frequency to the roughly adjusted frequency, the second coefficient, and the set frequency data.