A Broadband Waveguide Thermal Isolator

This paper describes a new, compact, waveguide thermal isolator. The isolator is based on a recently developed microwave bandgap joint, a periodic structure which suppresses microwave fields propagating between two parallel conducting surfaces. When such a structure is placed between a pair of waveguide flanges, the flanges can be separated by a few percent of a wavelength before the leakage and mismatch become significant. The thermal isolator is relatively immune to misalignment and cocking. Simulations and measurements on WR-10 thermal isolators indicate excellent performance over the entire waveguide band. The design is readily scalable to other waveguide bands.