Patent ID: 8217690

Claim:
A frequency synthesizer apparatus comprising: a voltage controlled oscillator circuit that varies an oscillation frequency thereof by a control voltage supplied thereto, the voltage controlled oscillator circuit including: a variable capacitance element; and a capacitor bank that includes a plurality of weighted capacitance elements and a plurality of switches controlled as being turned ON and OFF based on a plurality of control bit signals corresponding to the plurality of weighted capacitance elements, respectively; a phase comparator that performs a phase comparison between an output signal fed back from the voltage controlled oscillator circuit and a reference signal supplied thereto, the output signal from the voltage controlled oscillator circuit being fed back directly or via a frequency divider to an input of the phase comparator; a loop filter that generates a control voltage for supply to the voltage controlled oscillator circuit, based on a result of the phase comparison; a temperature compensation block that includes: a first correction potential generation circuit that generates a correction potential for parasitic capacitance of the capacitor bank of the voltage controlled oscillator circuit; a second correction potential generation circuit that generates a correction potential for the variable capacitance element; and a weighting circuit that performs weighting processing, based on the control bit signals; and a combining circuit that combines effects of said first and second correction potential generation circuits and said weighting circuit.