A 18-GHz silicon bipolar VCO with transformer-based resonator

Abstract

A silicon bipolar voltage-controlled oscillator for 17-GHz ISM band is presented. The VCO is composed of a core oscillating at 9 GHz followed by a frequency doubler. It adopts a transformer-based topology to obtain both wide tuning range and low noise performance. The VCO exhibits a tuning range of 4.1 GHz from 16.4 to 20.5 GHz and a phase noise as low as -109 dBc/Hz at a 1-MHz frequency offset from a carrier of 18.5 GHz. To design and optimize the resonator, a lumped scalable model for differentially driven inductors and transformers was used. This model is presented and validated up to 20 GHz by comparison with experimental data