Output coupling circuit for a cavity oscillator

摘要

A microwave oscillator has a cavity resonator enclosed by conducting walls and containing a microwave oscillator element therein. A biasing device applies a bias voltage to the microwave oscillator element to generate a microwave signal. A microwave coupling circuit takes the microwave signal from the resonator in a direction which is perpendicular to the direction of the propagation of the microwave signal in the resonator and applies the taken-out microwave signal to an output means. The microwave coupling circuit is located at a position corresponding to one of the nodes of the electric field appearing in the cavity. The coupling circuit also is preferably at a position on the resonator wall which is a quarter wavelength away from the oscillator element. The undesired signals can be effectively suppressed in the output means, by -44 dB, or more, without making use of a filter. The suppressed signals especially include an electro-magnetic energy component of the second harmonics signal appearing at a frequency band which is twice as high as the fundamental oscillating frequency.