A high 2LO-RF isolation SiGeBiCMOS sub-harmonic Gilbert mixer using stacked-LO-stage topology

Abstract

A 5.2 GHz SiGe BiCMOS stacked-LO-stage CMFB (Common Mode Feedback) sub-harmonic mixer is demonstrated in this letter. The stacked-LO-stage and the active loads are used to improve the 2LO-RF isolation and the conversion gain, respectively. The SiGe mixer includes five levels of transistors stacked together at the supply voltage of 3.3 V because of the low knee-voltage characteristic of the SiGe HBTs (Heterojunction Bipolar Transistors). The mixer demonstrated achieves 23 dB conversion gain and -78 dB 2LO-RF isolation.