Design and realization of a millimeter-wave Si/SiGe HBT frequency multiplier

In this paper, the design of an active millimeterwave frequency doubler using an Si/SiGe heterojunction bipolar transistor (HBT) as the active device is studied. Simulations are made using a developed physics-based large-signal model for Si/SiGe HBT's, which includes thermal dependence. Despite the high-output operating frequency of the fabricated doubler being close to [f.sub.max] 67 GHz for the Si/SiGe HBT, the conversion efficiency in a not completely optimized circuit is found to be better than -12 dB. The 3-dB bandwidth for the doubler is approximately 7.4%. These results are found to be comparable to a heterojunction field-effect transistor (HFET) doubler operating equally close to its [f.sub.max].Simulated results of the doubler performance with varied terminating impedances for the HBT are presented as design aids.