Hermetically sealed oscillator with dielectric resonator tuned through

Abstract

Microwave dielectric resonator apparatus which, for example, may be a microwave oscillator frequency stabilized by a dielectric resonator or may be a microwave filter whose critical frequency is determined by a dielectric resonator, has the dielectric resonator environmentally protected in a hermetic chamber. As the hermetic integrity of the chamber would be destroyed by having a tuning slug therein at the end of a screw threaded into a tapped hole through a chamber wall for rotation by a screwdriver outside the chamber, the tuning slug is instead located within a non-hermetic chamber at the end of a screw threaded into a tapped hole through a wall of the non-hermetic chamber serving also as an outer wall of a housing enclosing both chambers. The chambers have an interface which is transparent to microwave fields and proximate the dielectric resonator and tuning slug. The interface preserves the hermetic integrity of the hermetic chamber and transmits part of the microwave field developed by the dielectric resonator, when it resonates, to the non-hermetic chamber to be variously interfered with by the tuning slug as the slug is moved by rotation of the screw into different positional relationships of interference with the transmitted field part. As known per se, such interference alters the distribution and amount of microwave energy stored in the resonating dielectric resonator, and thereby alters the microwave frequency at which the dielectric resonator resonates. By using a puck of barium titanate as the dielectric resonator, a resonant frequency of 12 gigahertz is typically obtainable with a range of stable adjustment thereabout in the vicinity of 20 megahertz.