A Capacitively Coupled Noise Circulating VCO

A capacitively coupled noise circulating voltage-controlled oscillator (VCO) is proposed. Through capacitive coupling from the
LC
tank to the gates of the active devices, a simple inductor-based resonator can realize the same noise circulating effect as the conventional transformer-based topology, leading to a more compact chip area, as well as larger tuning range. The proposed VCO is fabricated with a 28-nm CMOS process using only thick-oxide devices. The core chip area is 0.09 mm
²
. The measured oscillation frequency ranges from 6.17 to 10.45 GHz, and the phase noise at 1-MHz offset is from −121.6 to −115 dBc/Hz, with a power dissipation from 32 to 41 mW under a 1.8-V supply voltage across the frequency tuning range. The achieved figure-of-merit with tuning range (FoM
$_{T}$
) is from 193.1 to 196.4 dBc/Hz.