An Investigation of the Use of Inverse-Mode SiGe HBTs as Switching Pairs for SET-Mitigated RF Mixers

The capability of inverse-mode (IM) silicon- germanium (SiGe) heterojunction bipolar transistors (HBTs) for the mitigation of single-event transients (SETs) under large-signal operation was investigated in an RF down-conversion single- balanced mixer using a through-wafer, two-photon absorption pulsed-laser beam experiment and TCAD heavy-ion simulations. The IM SiGe HBTs replace conventional forward-mode (FM) SiGe HBTs in the differential pair, which provides full current steering for frequency mixing operation. Under steady-state conditions, the IM SiGe HBT differential pair exhibits smaller transient peaks with shorter durations compared to the FM SiGe HBTs. In addition, under the injection of a local oscillator (LO) signal with large swing, the IM SiGe HBTs show faster recovery (50% reduction in the best case) from the impact of SETs. In the frequency domain, it is observed that IM SiGe HBTs produce less distortion at the output for an intermediate frequency below 1 GHz. Based on the performance comparison between FM and IM SiGe HBT down-conversion mixers, system design guidelines to compensate the noise figure degradation associated with using IM SiGe HBTs are discussed.