Wide-band high isolation subharmonically pumped resistive mixer with active quasi-circulator

A novel subharmonically pumped resistive mixer (SH-PRM) with a core chip dimension of 0.64 × 0.65 mm² is fabricated through a standard 0.18 μm CMOS process. An impedance-transforming active quasi-circulator is monolithically integrated with an nMOS field-effect transistor (FET) to perform up-converter mixing while simultaneously enhancing all port isolation through a broadband operation. The design analysis of impedance-transforming active quasi-circulator is also presented for matching between circulator and resistive transistor. As shown in the measured results, the mixer exhibits a 9-14.5 dB conversion loss. All port-to-port isolations better than 16.5 dB over a radio frequency (RF) of 10-20 GHz can be achieved.