US 7,321,271 B2
Voltage-controlled oscillator, radio communication apparatus and voltage-controlled oscillation method for reducing degradation of phase noise characteristic
Koji Takinami, Osaka (Japan); Hisashi Adachi, Osaka (Japan); and Tokio Endoh, Osaka (Japan)
Assigned to Matsushita Electric Industrial Co., Ltd., Osaka (Japan)
Filed on Oct. 01, 2003, as Appl. No. 10/676,654.
Claims priority of application No. 2002-291632 (JP), filed on Oct. 03, 2002.
Prior Publication US 2005/0190002 A1, Sep. 01, 2005
Int. Cl. H03B 5/18 (2006.01)
U.S. Cl. 331—117R  [331/177 V; 331/179] 6 Claims
OG exemplary drawing
 
1. A voltage-controlled oscillator comprising:
an inductor circuit having an inductor;
n pieces (n is two or more) of variable capacitance circuit having a variable capacitance element and having blocking capacitors of interrupting a direct current at both ends thereof, said n pieces of variable capacitance circuit including first, second and third variable capacitance circuits,
a negative resistance circuit, and
reference voltage generation means having m pieces of resistance connected in series between a power supply voltate and a grounding potential wherein:
m is at least two;
said inductor circuit, said n pieces of variable capacitance circuit, and said negative resistance circuit are connected in parallel;
said reference voltage generation means dividing the power supply voltage by use of said m pieces of resistance to supply m pieces of reference voltage to one terminal of the variable capacitance elements of said n pieces of variable capacitance circuit from m pieces of connecting point between adjacent resistances of said m pieces of resistance;
a control voltage of feedback-controlling an oscillation frequency is inputted to the other terminals of the variable capacitance elements of said n pieces of variable capacitance circuits;
said n pieces of variable capacitance circuit are connected in parallel with each other so that each capacitance variation characteristic against said control voltage inputted to said variable capacitance circuit has the same-directed characteristic;
said control voltage inputted to the other terminals of the variable capacitance elements of said n pieces of variable capacitance circuit is the same voltage;
in said reference voltage generation means, a first resistance and a second resistance connected successively are configured so that a first reference voltage is supplied from a connection point positioned between said first resistance and said power supply voltage, a second reference voltage is supplied from the connection point between said first resistance and said second resistance, a third reference voltage is supplied from a connection point positioned between said second resistance and said grounding potential, and the resistance values of said first resistance and said second resistance are different than each other,
of said n pieces of variable capacitance circuits, said first reference voltage is inputted to one of the terminals of said first variable capacitance circuit, said second reference voltage is inputted to one of the terminals of said second variable capacitance circuit, and said third reference voltage is inputted to one of the terminals of said second variable capacitance circuit;
said first reference voltage, said second reference voltage, and said third reference voltage are fixed and respectively; and
a first difference between said first reference voltage and said second reference voltage and a second difference between said second reference voltage and said third reference voltage are each different than each other wherein the linearity of a resonant frequency characteristic of the voltage-controlled oscillator is improved.