Abstract: Provided is a phase-locked loop frequency synthesizer, including: a reference oscillator; a voltage controlled oscillator; a variable frequency divider that divides the high frequency signal in frequency to output a feedback signal; a phase comparator that compares the reference signal and the feedback signal with each other to output a phase comparison signal; a loop filter that outputs a control signal of the voltage controlled oscillator based on the phase comparison signal; and a frequency/phase control circuit that generates frequency division number control data in synchronism with any one of the feedback signal and the reference signal based on setting data which is input from an external to give an output frequency and setting data which is input from the external to give a phase to the reference signal, to thereby output the frequency division number control data to the variable frequency divider.

Abstract: Provided is a phase-locked loop frequency synthesizer, including: a reference oscillator; a voltage controlled oscillator; a variable frequency divider that divides the high frequency signal in frequency to output a feedback signal; a phase comparator that compares the reference signal and the feedback signal with each other to output a phase comparison signal; a loop filter that outputs a control signal of the voltage controlled oscillator based on the phase comparison signal; and a frequency/phase control circuit that generates frequency division number control data in synchronism with any one of the feedback signal and the reference signal based on setting data which is input from an external to give an output frequency and setting data which is input from the external to give a phase to the reference signal, to thereby output the frequency division number control data to the variable frequency divider.

Abstract: A voltage-controlled oscillator has a tuned circuit for controlling the oscillation frequency. The tuned circuit has a variable-capacitance element whose capacitance varies in response to a control voltage and a negative capacitance circuit whose impedance frequency characteristics have opposite characteristics to those of a normal capacitance, and which is connected to the variable-capacitance element. The configuration enables increasing the variation ratio corresponding to the control voltage of the combined capacitance composed of the variable-capacitance element and negative capacitance circuit, thereby broadening the oscillation frequency band.

Abstract: A voltage-controlled oscillator has a tuned circuit for controlling the oscillation frequency. The tuned circuit has a variable-capacitance element whose capacitance varies in response to a control voltage and a negative capacitance circuit whose impedance frequency characteristics have opposite characteristics to those of a normal capacitance, and which is connected to the variable-capacitance element. The configuration enables increasing the variation ratio corresponding to the control voltage of the combined capacitance composed of the variable-capacitance element and negative capacitance circuit, thereby broadening the oscillation frequency band.