A 19.5-GHz 28-nm Class-C CMOS VCO, With a Reasonably Rigorous Result on 1 / f Noise Upconversion Caused by Short-Channel Effects

Abstract

Class-C operation is leveraged to implement a K-band CMOS voltage-controlled oscillator (VCO) where the upconversion of 1 / f current noise from the cross-coupled tran- sistors in the oscillator core is robustly contained at a very low level. Implemented in a bulk 28-nm CMOS technology, the 12%-tuning-range VCO shows a phase noise as low as −112 dBc/Hz at 1-MHz offset ( −86 dBc/Hz at 100 kHz offset) from a 19.5 GHz carrier while consuming 20.7 mW, achiev- ing a figure of merit (FoM) of −185 dBc/Hz. The design is complemented by a theoretical investigation of 1 / f noise upconversion caused by short-channel effects in the cross-coupled transistors, obtaining the first instance of a closed-form phase noise expression in the 1 / f 3 region.