Patent ID: 6628174
Filing Date: 2003-09-30
Classification: H03B

Abstract:
A voltage-controlled oscillator comprising:an oscillation part performing oscillation; and a tuning part resonating within the oscillation frequency band of said oscillation part, wherein said tuning part includes: an impedance transformer including a transmission line, and a variable reactance circuit, connected between an end of said transmission line and said oscillation part, including a variable capacitance element having a capacitance value varying with a control voltage and an inductive component, a locus drawn by the impedance of said tuning part as viewed from the node between said oscillation part and said tuning part in response to change of said control voltage includes a point where reactance reaches substantially zero, and the characteristic impedance of said transmission line is so set that the rate of change of the capacitance value of said variable capacitance element with respect to change of the oscillation frequency is minimized within a prescribed range of the characteristic impedance of said transmission line.