TH-3 Microwave Radio System: Microwave Integrated Circuits

A series of four high-performance, functionally integrated, microwave circuits has been developed for use in the 6-GHz TH-3 radio system. The circuit designs integrate numerous microwave functions, operating mostly in a strip transmission line medium, into single packages. They replace assemblies of numerous waveguide components used in the design of earlier radio relay systems. The ability to design each function for its specific application and match it to its neighbor allows high performance standards. The resulting reduction in interconnections improves the reliability. Considerable space and cost saving is realized since many common mechanical requirements are satisfied by the same housing. The housings, made of aluminum, are die cast which accounts for a considerable portion of the cost saving. The stripline center conductor and thin film resistors are created by photochemical techniques from a tantalum and gold film. The use of ceramic substrates and thin film technology is important to the achievement of long-term reliability. The inherent precision and low cost of these techniques provide dimensional control and reproducibility and contribute to the overall cost saving. The circuits, three of which are used in each TH-3 radio bay, are 2175