A 0.8V 5.9GHz wide tuning range cmos VCO using inversion-mode bandswitching varactors

Abstract

This paper presents a completely integrated 0.8V 5.9GRz CMOS voltage-controlled oscillator (VCO) with inversion-mode MOS (IMOS) bandswitching varactors. IMOS varactors are used to maintain a large tuning range when the supply voltage is lower than 1V. Moreover, a large resistance connects to the bulk of each IMOS varactor to further improve the VCO tuning capability. Through this large resistance, the tuning range increases by 500MHz. A bandswitching topology is used to ameliorate the adverse effects of highly sensitive IMOS varactors. The VCO was simulated with a 0.8V supply with a tuning range of 29.12% from 4.4 to 5.9 GRz when tuned from 0 to 0.8V. The simulated phase noise is -109.65dBc/Hz at 1MHz offset from the carrier frequency of 5.52GHz. The VCO-core power dissipation is 1.2mW. When the supply is reduced to 0.6V, the tuning range becomes 22.64% from 4.7 to 5.9GHz. The VCO-core dissipates 0.9mW, and the phase noise is -105.24dBc/Hz at 1MHz offset from the carrier frequency of 5.65GHz. The VCO circuit has been designed using TSMC 0.18-mu m CMOS technology with deep n-well processing.