Broadband monolithic GaAs-based HEMT diode mixers

Broad-band monolithic diode mixers covering 17.5-33 GHz with different topologies are designed, fabricated and tested. The topologies under investigation include the singly balanced mixer with 90° and 180° coupler and the sub-harmonically pumped (SHP) mixer. These monolithic microwave integrated circuits are fabricated using a 0.2-μm pseudomorphic HEMT foundry process on a 4-mil thick GaAs substrate, and thus the measurement results for each topology are evaluated on a fair basis. The SHP mixer, with a miniature size of 1.3 mm×1.1 mm, demonstrates 10-12 dB conversion loss at 17.5-33 GHz of RF with 2.5-GHz IF and both LO-to-RF, LO-to-IF isolations of both better than 25 dB. It outmatches the singly balanced approaches, as well as achieves rival performance compared with previously reported results at similar frequencies