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

The paper presents a completely integrated 0.8 V 5.9 GHz 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 1 V. 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 500 MHz. A bandswitching topology is used to ameliorate the adverse effects of highly sensitive IMOS varactors. The VCO was simulated with a 0.8 V supply with a tuning range of 29.12% from 4.4 to 5.9 GHz when tuned from 0 to 0.8 V. The simulated phase noise is -109.65 dBc/Hz at 1 MHz offset from the carrier frequency of 5.52 GHz. The VCO-core power dissipation is 1.2 mW. When the supply is reduced to 0.6 V, the tuning range becomes 22.64% from 4.7 to 5.9 GHz. The VCO-core dissipates 0.9 mW, and the phase noise is -105.24 dBc/Hz at 1 MHz offset from the carrier frequency of 5.65 GHz. The VCO circuit has been designed using TSMC 0.18-μm CMOS technology with deep n-well processing.