A Low Phase Noise 28 GHz VCO Using Transformer-based Q-enhanced Active Impedance Converter

This paper presents a low phase noise 28 GHz voltage-controlled oscillator (VCO) using a transformer-based active impedance converter to enhance the quality factor (Q) of the capacitor in the resonator. The active impedance converter can enhance the Q of a capacitor bank and varactor by 25-40% across the VCO's tuning range. The proposed VCO is fabricated using the proposed transformer-based Q-enhancement impedance converter in a standard 65 nm CMOS process. The VCO achieves a 15.9% measured fractional frequency tuning range and phase noise of −107.6 dBc/Hz at 1 MHz offset from 28 GHz oscillation frequency while occupying only 0.05 mm2 area (200 μm ß 250 μm). The VCO consumes 5.1 mW power, resulting in an excellent figure-of-merit (FoM) of 189.4 dBc/Hz and a figure-of-merit-with-area (FoMA) of 202.8 dBc/Hz.