Voltage-controlled oscillator

Abstract

A voltage-controlled oscillator includes a resonator section in which a plurality of types of variable capacitance elements having different structures and capacitance variation characteristics are connected in parallel and capacitance values of the plurality of types of variable capacitance elements are controlled simultaneously by a control voltage; and an amplifier section for maintaining oscillation produced by the resonator section. Varactor diodes and MOS varactors can be used as the variable capacitance elements.

1 . A voltage-controlled oscillator comprising a resonator section, and an amplifier section that maintains oscillation produced by said resonator section, wherein said resonator section comprises:
 an inductor;   a first MOS varactor and a second MOS varactor connected between respective ones of two ends of said inductor and a common node;   a first varactor diode and a second varactor diode connected between respective ones of two ends of said inductor and a power supply so as to be reverse biased;   a first resistor connected directly at its one end to the common node and directly at its other end to a voltage control terminal; and   second and third resistors connected between respective ones of two ends of said inductor and the voltage control terminal.   
     
     
         2 . The voltage-controlled oscillator according to  claim 1 , further comprising third and fourth varactor diodes which, when the power supply is one of either a high-potential power supply or a low-potential power supply, are connected between the other one of these power supplies and respective ones of two ends of said inductor so as to be reverse biased. 
     
     
         3 . The voltage-controlled oscillator according to  claim 1 , wherein gate terminals of said first and second MOS varactors are connected to the common node. 
     
     
         4 . The voltage-controlled oscillator according to  claim 1 , wherein said amplifier section comprises a first and a second input/output terminals, and wherein the ends of said inductor are connected to respective ones of input and output terminals of said amplifier section. 
     
     
         5 . A voltage-controlled oscillator comprising a resonator section, and an amplifier section that maintains oscillation produced by said resonator section, wherein said resonator section comprises:
 a first inductance connected between a power supply and a first node;   a second inductance connected between the power supply and a second node;   a first varactor diode connected between a third node, which is connected to a voltage control terminal via a resistor, and the first node so as to be reverse biased;   a second varactor diode connected between the third node and the second node so as to be reverse biased;   a first MOS varactor and a second MOS varactor each having a first end directly connected to the third node;   a first fixed capacitor connected between a second end of said first MOS varactor and the first node; and   a second fixed capacitor connected between a second end of said second MOS varactor and the second node.   
     
     
         6 . The voltage-controlled oscillator according to  claim 5 , wherein a fixed bias is applied to the second end of each of said first and second MOS varactors. 
     
     
         7 . The voltage-controlled oscillator according to  claim 5 , wherein gate terminals of said first and second MOS varactors are connected to the third node. 
     
     
         8 . The voltage-controlled oscillator according to  claim 5 , wherein said amplifier section comprises a first and a second input/output terminals, and wherein the first node and the second node are connected to said first and second input/output terminals, respectively.