Patent ID: 7538628

Claim:
A harmonic oscillator comprising: a transmission line resonator in which an oscillation frequency depends on an electrical length of a transmission line and both ends of the transmission line are electrical open ends; and an active element for oscillation as a negative resistance connecting to the transmission line resonator, the harmonic oscillator using the transmission line resonator in which each standing wave of a fundamental wave of the oscillation frequency and odd-order harmonics related to the fundamental wave has a minimum voltage displacement portion at a midpoint portion of the transmission line resonator and maximum voltage displacement portions in opposite phase to each other at both ends and the standing wave has a voltage displacement distribution which is odd-symmetric with respect to the midpoint portion; each standing wave of even-order harmonics related to the fundamental wave has a maximum voltage displacement portion at the midpoint portion of the transmission line resonator and maximum voltage displacement portions in phase or opposite phase in relation to the midpoint portion at both ends and the standing wave has a voltage displacement distribution which is symmetric with respect to the midpoint portion; and an output line is connected to the midpoint portion of the transmission line resonator to suppress output levels of the fundamental wave and odd-order harmonics, and the even-order harmonics are obtained on the output line, wherein in the transmission line resonator, suppressing means is provided for suppressing a voltage displacement distribution of second harmonic among the even-order harmonics; and the suppressing means is provided at a position between the midpoint portion and either ends of the transmission line resonator, the position being at least a minimum voltage displacement portion for the second harmonic.