A low-voltage low-power low-phase-noise wide-tuning-range 0.18-μm CMOS VCO with high-performance FOMT of −196.3 dBc/Hz

This paper presents a low-voltage low-power low-phase-noise wide-tuning-range VCO in 0.18-μm CMOS. By using analog tuning varactors connected between the drain and source terminations of a cross-coupled pair, and combined with digital switching capacitor banks, the VCO tuning range can be effectively boosted. Moreover, inductors are utilized on top of a cross-coupled pair for enhancing the negative conductance (-G
_m
) and resonate the parasitic capacitors. This design methodology can easily overcome a VCO's start-up condition. Based on the proposed architecture, the fabricated 0.18-μm CMOS VCO exhibits a measured 47.7% tuning range. Operating at 0.65-V low supply voltage, the VCO core consumes 2.99-mW dc power. At this bias condition, the measured phase noise is -115.6 dBc/Hz at 1-MHz offset from a 4.0-GHz oscillation frequency. Compared to recently published VCOs in C band, the proposed VCO can simultaneously achieve low supply voltage, low dc power dissipation, low phase noise, and wide tuning range, leading to a superior figure of merit considering the tuning range (FOM
_T
= -196.3 dBc/Hz).