12.9 A 10.2-to-16.2GHz Dual-Mode-Transformer-Based Wideband Series-Resonance VCO Achieving >201.1dBc/Hz FoM T at a 10MHz Offset

This work presents a 28nm CMOS SR-VCO enabled by a dual-mode transformer with magnetic control, achieving a wide tuning range of 10.2 to $16.2 \text{GHz}(45.2 \%)$ and a high $\text{FoM}_{\mathrm{T}} / \text{FoM}_{\text{AT}} {@} 10 \text{MHz}$ of $201.1 / 207.7 \text{dBc} / \text{Hz}$. A transformer optimization method is introduced to ensure consistent performance across modes, achieving less than 2 dB variation in measured PN and FoM at 10 MHz. A sampling PLL incorporating the presented SR-VCO demonstrates rms jitter <18.1fs and $\text{FoM}_{\text{JT}}$ of −265.8 dB.