A 18.5-to-22.4GHz Class-F23 VCO Achieving 189.1dBc/Hz FoM Without 2nd/3rd-Harmonic Tuning in 65nm CMOS

This paper presents a class-F
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voltage-controlled oscillator (VCO) to improve the phase noise performance without manual $2^{\mathrm{n}\mathrm{d}_{-}}$ or $3^{\mathrm{r}\mathrm{d}}-$harmonic tuning. By leveraging a three-coil transformer, a differential-mode (DM) resonance expansion at $3^{\mathrm{r}\mathrm{d}}-$harmonic frequency is achieved while maintaining the class-F operation. Meanwhile, by utilizing a two-coil transformer-based resonator for the tail filtering, a wideband common-mode (CM) resonance at $2^{\mathrm{n}\mathrm{d}}-$harmonic frequency is realized. Prototyped in 65-nm CMOS process, the proposed VCO achieves a frequency tuning range of 19.1% from 18.5 to 22.4 GHz with 1-MHz offset phase noise from -110.7 to -106.1 dBc/Hz, while consuming 5 mW at 0.5 V. The figure-of-merit (FoM) is 189.1 dBc/Hz, and the chip area is 0.061 m$\mathrm{m}^{2}$.