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Mathematical Problems in Engineering
Volume 2015, Article ID 382483, 7 pages
Research Article

A Wide Tuning-Range CMOS VCO with a Tunable Active Inductor

Department of Electronic Engineering, Chang Gung University, Taoyuan City 33302, Taiwan

Received 9 August 2014; Accepted 26 December 2014

Academic Editor: Zhenhai Shao

Copyright © 2015 Hsuan-Ling Kao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This study describes a wide tuning-range VCO using tunable active inductor (TAI) topology and cross-coupled pair configuration for radio frequency operation. The TAI used two feedback loops to form a cascode circuit to obtain more degrees of freedom for inductance value. The TAI-VCO was fabricated using a 0.18 μm CMOS technology. The coarse frequency tuning is achieved by TAIs while the fine tuning is controlled by varactors. The fabricated circuit provides an output frequency range from 0.6 to 7.2 GHz (169%). The measured phase noise is from −110.38 to −86.01 dBc/Hz at a 1 MHz offset and output power is from −11.11 to −3.89 dBm within the entire frequency range under a 1.8 V power supply.