Inductor characterization in RF LC-VCOs

This paper analyzes the characterization of inductors in resonant radio frequency (RF) circuits, with emphasis in LC voltage-controlled oscillators (VCOs). We will demonstrate how inductor quality factor is often underestimated in the vicinity of self-resonance frequency, because its capacitive parasitic contribution is not properly considered. In consequence, some valid inductor geometries could be incorrectly discarded during the initial circuit optimization process. To overcome this design space limitation, the paper presents an alternative method to characterize inductors at the wanted resonant frequency. The comparison between the conventional and the proposed methods is illustrated with the characterization of a complete inductor library in a commercial 90nm CMOS RF technology.