A 9.1–12.7 GHz VCO in 28nm CMOS with a bottom-pinning bias technique for digital varactor stress reduction

Abstract

A wide tuning range class-B VCO in 28nm CMOS targeted for software defined radio applications demonstrates a technique for minimizing device stress while simultaneously optimizing off-state Q in digitally switched tank capacitor cells. The proposed digital varactor structure can be implemented using only capacitors and NMOS transistors, resulting in a very compact layout. The VCO operates between 9.1 - 12.7 GHz, achieving a tuning range of 32% and phase noise of -163.2 dBc/Hz at 20 MHz offset referred to a 915 MHz carrier while consuming 9.5 mW for a FoM of -187 dBc/Hz.