Temperature compensated microwave resonator

A cavity resonator comprising:

• a waveguide body formed from a material having a relatively high co-efficient of thermal conductivity, said body having a cavity sized to maintain electromagnetic waves of one or more selected resonant frequencies;
• means for coupling electromagnetic energy into and out of the resonator;
• at least one tuning screw for adjusting the resonant frequency of the cavity,
• temperature-compensating structure within the cavity configured to undergo temperature-induced dimensional changes which substantially minimize the resonant frequency change which would otherwise be caused by the temperature-induced dimensional change of the waveguide body cavity and also including temperature responsive means for varying the effective diameter of the at least one tuning screw to substantially minimize temperature induced frequency changes.

A coupling iris assembly for use in a cavity resonator and comprising:

• (a) a base of material having a pair of opposing faces, and an electromagnetically transparent slot communicating with said faces adapted to couple electromagnetic energy through the base when the coupling iris is positioned within a cavity resonator;
• and
• (b) a first structure which further comprises a generally bow-shaped, generally annular member coupled about its outer and inner peripheries to the base, the first structure including material having a higher temperature expansion co-efficient than the base and positioned on a face of the base to protrude into the cavity from the base when the base is mounted in the cavity resonator,
• the position and expansion co-efficient of the first structure material being such that it increasingly protrudes into the cavity in response to increasing temperature sufficiently to substantially minimize temperature-induced resonant frequency changes of the cavity.