High-Isolation Millimeter-Wave Subharmonic Monolithic Mixer With Modified Quasi-Circulator

This study presents a 21-40-GHz broadband subharmonic gate-pumped mixer using the standard 0.18-μ m CMOS process. A modified quasi-circulator is monolithically integrated with an nMOS field-effect transistor to perform down-converter mixing while enhancing all port isolations through a broadband operation. The proposed configuration has a chip size of less than 0.9 mm². The measured results demonstrate a low conversion loss from 8.3 to 14.2 dB, a local oscillation (LO)-to-RF isolation greater than 50 dB, and a high 2LO-to-RF isolation of 48 dB to 65 dB over the 21-40-GHz RF bandwidth at a 10.5-dBm LO power level.