A 5-6 GHz SiGe HBT monolithic active isolator for improving reverse isolation in wireless systems

A monolithic active isolator combining common-base and common-collector configurations of SiGe heterojunction bipolar transistors (HBT) is used to improve reverse isolation in wireless system applications. This simple active isolator results in an insertion loss of 2 dB and input IP3 of +0.7 dBm over 5-6 GHz with a 1.8-mA current flow for the core circuit of a 3-V supply.