A Ka-Band Colpitts–Clapp VCO With 30% Tuning Range and High Output Power

This letter presents a systematic design strategy for SiGe bipolar voltage-controlled oscillators (VCOs) with a wide tuning range (TR). As a proof of concept, a Colpitts–Clapp VCO with an ultra-wide continuous TR of 30.2% and center frequency of 35.5 GHz is presented in a 0.13-
$\mu \text{m}$
SiGe BiCMOS technology. The measured phase noise of the free-running VCO at 1 MHz offset is better than −99 dBc/Hz over the entire TR. A peak output power of 12.6 dBm is measured with 19.8% of DC-RF efficiency. The VCO exhibits a figure-of-merit (FoMPT) of −193 dBc/Hz. To the best of the authors’ knowledge, the proposed VCO shows the best FoMPT, highest output power and DC-RF efficiency among the reported SiGe VCOs at this frequency range.