A 1.8-GHz low-phase-noise CMOS VCO using optimized hollow spiral inductors

TLDR

The VCO is built with integrated spiral inductors fabricated on only two metal layers without etching, and its high‑frequency magnetic field effects and substrate losses were modeled by finite‑element analysis, enabling a 250‑MHz tuning range using standard junction capacitances. The fully integrated 1.8‑GHz VCO achieves a phase noise of –116 dBc/Hz at 600 kHz offset while consuming only 6 mW.

Abstract

A completely integrated 1.8-GHz low-phase-noise voltage-controlled oscillator (VCO) has been realized in a standard silicon digital CMOS process. The design relies heavily on the integrated spiral inductors which have been realized with only two metal layers and without etching. The effects of high-frequency magnetic fields and losses in the heavily doped substrate have been simulated and modeled with finite-element analysis. The achieved phase noise is as low as -116 dBc/Hz at an offset frequency of 600 kHz, at a power consumption of only 6 mW. The VCO is tuned with standard available junction capacitances, resulting in a 250-MHz tuning range.