Small-signal characterization of SiGe-HBT fT-doubler up to 120 GHz

In this brief, small-signal characterizations of selectively implanted collector (SIC) and non-SIC SiGe-heterojunction bipolar transistors (HBT) f_T-doublers up to 120 GHz are measured, analyzed, and compared with those of the corresponding single devices. The measured results confirm a great improvement in transit frequency with almost no considerable decrease in the maximum stable gain/maximum available gain, and maximum oscillation frequency. Since the f_T-doubler can be used easily instead of a single transistor, a much higher transit frequency and RF power can be achieved while using a technology with a moderate f_T.