A 2.75–6.25GHz low-phase-noise quadrature VCO based on a dual-mode ring resonator in 65nm CMOS

This paper presents a low-phase-noise wide-tuning-range quadrature voltage-controlled oscillator (QVCO) using a dual-mode ring resonator. In contrary to the conventional approaches that use transistor-coupled LC oscillators, the proposed resonator inherently provides quadrature signals by employing both magnetic and capacitive couplings in a ring structure, resulting in low phase noise performance and high quadrature accuracy. Additionally, it offers two oscillation modes which are exploited to realize a wide-tuning-range QVCO. The implemented prototype in a 65-nm CMOS process shows 2.75-6.25 GHz continuous tuning range, phase noise figure-of-merit (FoM) of 188.2 dB at 3 GHz and better than 184 dB across the entire operating frequency range, 1.5° maximum phase error while consuming 9.7-15.6 mA from 0.6-V supply. The QVCO occupies an active chip area of 0.35 mm².