A Triple-Band SiGe HBT Cross-Coupled Differential VCO Using a Novel Element-Switching Technique

A triple-band SiGe HBT cross-coupled VCO has been developed for the next generation multi-band and/or multimode wireless radios. It employs a novel triple-band resonator comprised of a HPF-type LC resonator with element-selective transistors. The element-selective transistor is a two-terminal device with base and collector short-circuited and therefore can provide three different conditions of open, short and small capacitance. A triple-band resonation can be accomplished by connecting the element-selective transistor in parallel with circuit elements and controlling a bias condition. The implemented 0.35- μm SiGe HBT cross-coupled differential VCO has achieved a low-band oscillation from 0.64 to 0.84 GHz, a middle-band oscillation from 0.66 to 0.96 GHz and a high-band oscillation from 0.68 to 1.04 GHz. The phase noise at 100 kHz offset varies from -98 to -107dBc/Hz for all bands. The novel triple-band resonator having the element-selective transistor would be widely applied to the design of the multi-band VCOs.