Summary form only given. The assembly of arrays including microwave or millimeter-wave monolithic integrated circuit technology has resulted in viable, but not monolithic, solutions. Among the first attempts were several very high risk subarray developments at 20 and 44 GHz that placed microstrip elements, phase shifters, and amplifiers in complete subarrays on GaAs substrates. This multilayer fabrication, 'tile' construction, has the primary advantage of being very thin. Of the several subarrays designed and built in this manner, the first ones suffered yield problems, and were not fully successful. A second construction approach that has found favor if the array can be made somewhat thicker is called 'brick' construction. In this architecture, the array is fabricated on multilayer circuit boards that are mounted perpendicular to the aperture. With either architecture, the array design is dominated by thermal constraints, and so device efficiency and noise figure have become the primary design tradeoffs. This resulted in the development of subarrays and circuits with pseudomorphic HEMT (high electron mobility transistor) and indium phosphide substrates.
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