Voltage controlled oscillator circuit and frequency synthesizer

摘要

According to one embodiment, a voltage-controlled oscillation (VCO) circuit includes a current source, an oscillation core unit, an amplitude detection unit, a current control unit, a low pass filter, and a switch. The current source supplies a bias current to the oscillation core unit in accordance with a current control signal. The oscillation core unit oscillates according to the bias current and outputs an oscillation signal. The amplitude detection unit outputs a detection voltage according to an amplitude of the oscillation signal. The current control unit outputs a control signal so that the detection voltage is equal to a reference voltage. The low pass filter generates the current control signal by filtering the control signal, and then supplies the current control signal to the current source. The switch is connected in parallel with the low pass filter.

主权项

1. A voltage-controlled oscillation (VCO) circuit connected to a coarse adjustment circuit configured to perform a coarse adjustment of a frequency of an oscillation signal to a target frequency, a phase-locked loop (PLL) circuit configured to perform a fine adjustment of the frequency of the oscillation signal to the target frequency, and a control unit configured to cause the coarse adjustment circuit to perform the coarse adjustment during a predetermined coarse adjustment period and the PLL circuit to perform the fine adjustment at a time after the performance of the coarse adjustment, said VCO circuit comprising:
a current source configured to supply a bias current in accordance with a current control signal; an oscillation core unit configured to oscillate in accordance with the bias current and to output the oscillation signal; an amplitude detection unit configured to output a detection voltage in accordance with an amplitude of the oscillation signal; a current control unit configured to output a control signal so that the detection voltage is equal to a reference voltage; a low pass filter configured to filter the control signal to generate the current control signal and to supply the current control signal to the current source; and a switch that is connected in parallel with the low pass filter, wherein the switch is controlled within the coarse adjustment period to turn to an on state from an off state and to turn back to the off state.