A Trifilar Transformer-Based Class-F23 VCO With Noise-Circulating Technology

This article presents a low-phase noise (PN) trifilar transformer-based Class-F₂₃ voltage-controlled oscillator (VCO) with noise-circulating technology. The topology minimizes the side effect of the parasitic capacitors that incorporates an uncontrollable common-mode (CM) path in the conventional noise-circulating VCOs, and reduces the magnitude of the noise sources injected into the tank by simultaneously switching on/off the source degeneration. Additionally, the PN is reduced because the proposed trifilar transformer-based tank can provide extra drain-to-gate gain. The proof-of-concept prototype is a 5.2–6.1 GHz VCO in 65 nm CMOS. It exhibits a −146.6 dBc/Hz PN at 10 MHz offset, consuming 7.92 mW from a 0.9 V power supply at 5.9 GHz. The corresponding figure of merit (FoM) at 10 MHz offset is 193 dBc/Hz. It achieves a slight supply frequency pushing of 13.3 and −18.7 MHz/V at the lowest and highest frequency, respectively. The occupied compact core area is 0.12 mm².