A 9.9-11.8 GHz CMOS Dual-Core Class-F₂₃ VCO Achieving 190.4 dBc/Hz FoM With Inter-Core-Shaping

This paper presents a complementary-NMOS-PMOS (CMOS) dual-core inter-core-shaping class- ${F}_{23}$ voltage controlled oscillator (VCO) with low phase noise and high figure-of-merit (FoM). In contrast to the traditional class- ${F}_{23}$ VCO employing single-ended capacitors in the common-mode (CM), a CM excitation is introduced between CMOS transistor pairs with high-Q differential capacitors, thereby suppressing flicker noise up-conversion and improving phase noise performance. Moreover, a circular-geometry quad-coil transformer is designed to control the $3^{\text {rd }}$ harmonic in the differential mode (DM) for the waveform shaping, and counteract the magnetic flux between the inner and outer coils in CM, which eliminates parasitic effects on the $2^{\text {nd }}$ harmonic resonance. Fabricated in a 65-nm CMOS process, the dual-core $F_{23}$ VCO could cover a 17.5% frequency tuning range from 9.9 to 11.8 GHz. Consuming 12.7 mW from a 1.2 V voltage supply, the $1 / \mathbf{f}^{3}$ corner is about 240 kHz and a phase noise ranging from -118.7 to $-121.5 \mathrm{dBc} / \mathrm{Hz} {\text {@}} 1 \mathrm{MHz}$ offset is achieved, resulting in a FoM of $\mathbf{- 1 9 0. 4 d B c} {\text {@}} 1 M H z$ offset.