Novel Miniature and Broadband Millimeter-Wave Monolithic Star Mixers

In this paper, three monolithic star mixers using a new miniature dual balun are proposed. The first one is a double spiral transformer mixer, and the second one is a trifilar transformer mixer. Both of these are fabricated using a commercial GaAs pseudomorphic HEMT process. The third is a 3-D transformer mixer, which is fabricated using a commercial CMOS process. These mixers exhibit bandwidths over 25-45 GHz (57%) with local oscillator isolations better than 20 dB. These star mixers are smaller than (lambda/6timeslambda/6) for the mixer core area. Compared with traditional star mixers, these mixers demonstrate 80% size reduction, and achieve good performance with the smallest chip size among all star mixers using monolithic microwave integrated circuit processes.