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A low-power wideband LC VCO has been designed and implemented in a 90-nm CMOS technology. Wide tuning range, low phase noise and low power consumption are achieved thanks to the adopted LC tank, which makes use of shunt-connected switched-coupled inductors and a proper arrangement of varactors. The shunt-connected switched-coupled inductors provide coarse tuning and phase noise optimization without using amplitude calibration loop or trimming of the bias current. The proposed varactors configuration employs accumulation mode thin and thick MOS devices, which has been differently biased to obtain tuning range maximization along with minimization of the amplitude-to-phase noise conversion. The LC-tank topology and inductor layout have been properly designed to attain a die area comparable to a single-inductor VCO, taking advantage of the inductors mutual coupling. The VCO exhibits a phase noise at 1-MHz offset frequency lower than -114 dBc/Hz over the entire tuning range and achieves -126.1 dBc/Hz at 1.2 GHz. It provides a tuning range of 51% from 1.13 GHz to 1.9 GHz with a tuning voltage ranging from 0 to 1.2 V. Despite a very low current consumption, which is 0.88 mA from a 1.2-V supply, the proposed VCO has the outstanding PFTN figure-of-merit of 10. The VCO core die area is 0.5 mm2.
Circuits and Systems I: Regular Papers, IEEE Transactions on (Volume:59 , Issue: 6 )
Date of Publication: June 2012