A 4.21-to-15.18GHz Pure Magnetic-Coupling and Fully Symmetrical Quad-Core Quad-Mode VCO Achieving 220.5dBc/Hz FoMTA@10MHz

This work proposes a wide frequency tuning range (FTR) and low phase noise (PN) quad-core quad-mode voltage-controlled oscillator (VCO) which features pure magnetic-coupling technique and fully symmetrical topology. The proposed centrosymmetric transformer, which integrates four coupled inductors and an embedded switched inductor, enables quad-mode operation through pure magnetic coupling without causing any FTR degradation due to extra electrical coupling. Furthermore, the fully symmetrical inductive, capacitive, and active elements, as well as the routing layout, minimize mismatches among the VCO cores and effectively synchronize each core, optimizing phase noise in quad-core operation. The proposed quad-core quad-mode VCO achieves an FTR of 113.2% (4.21 to 15.18 GHz), a PN of $-141.4 \mathrm{dBc} / \mathrm{Hz}$ at a 10 MHz offset from 4.28 GHz, a peak $\mathrm{FoM}_{\mathrm{T}}$ of $211.6 \mathrm{dBc} / \mathrm{Hz}$ and a peak $\mathrm{FoM}_{\text {TA }}$ of $220.5 \mathrm{dBc} / \mathrm{Hz}$ at a 10 MHz offset.