A 335-GHz Subharmonic Quadrature Mixer MMIC Based on GaAs Schottky Diode Technology

This letter presents a 335-GHz quadrature mixer with monolithic microwave integrated circuit (MMIC) utilizing the GaAs Schottky diode technology. By using two identical double-sideband (DSB) subharmonic mixer units and a 90° phase shift line co-designed with an on-chip double-RF probe, a quadrature phase relationship downconversion is achieved on a single GaAs chip. The conversion loss of the mixer is approximately 16 dB in the 330–350-GHz frequency range. The amplitude imbalance is less than 3 dB within the 333–342-GHz range, while the phase imbalance is less than 10° in the 330–340-GHz range. The quadrature mixer exhibits a reasonable performance with an MMIC structure and the smallest chip area compared with mixers made by two substrates.