A 5.0-to-6.36GHz Wideband-Harmonic-Shaping VCO Achieving 196.9dBc/Hz Peak FoM and 90-to-180kHz 1/f3 PN Corner Without Harmonic Tuning

Abstract

Since 2001 [1], LC VCOs have been demonstrating significant improvements of figureof-merit (FoM) and 1/f phase noise (PN) corner [2–5] by exploring common-mode (CM) resonance at twice the oscillation frequency $\left(2 F_{0 s c}\right)$. In addition, for area reduction, the shaping of the impulse sensitivity function (ISF) has evolved from explicit with two coils [1] to implicit with one coil [2]. Yet, as depicted in Fig. 20.1.1, the latter suffers from large CM magnetic-flux cancellation, resulting in a much lower CM impedance $\left|Z_{c M}\right|$ that is $\sim 0.64$ of its differential-mode (DM) impedance $\left|Z_{D M}\right|$. The VCO in [3] achieves a high FoM $_{\circledast 10 \mathrm{M}+\mathrm{z}}$ up to $191.4 \mathrm{dBc} / \mathrm{Hz}$ by boosting $\left|\mathrm{Z}_{\mathrm{CM}}\right|$ at $2 \mathrm{~F}_{0 \mathrm{sc}}$ and $\left|\mathrm{Z}_{\mathrm{DM}}\right|$ at $3 \mathrm{~F}_{{osc. }}$ Yet, to uphold an optimal performance over the tuning range (TR), the VCO in [3]still requires manual harmonic tuning for aligning the $1^{{st }}-t 0-2^{{nd }}$ and $1^{{st }-t 0-3^{{d }} { harmonic resonances. This }}$ denotes a narrowband effect. For the VCO in [4], which features a four-winding transformer with no harmonic tuning, there is a large variation of FoM $_{\circledast 10 \mathrm{MHz}}(190.7 \mathrm{t} \mathrm{t}$ $196.5 \mathrm{dBc} / \mathrm{Hz}$) and 1/f PN corner (60 to 600kHz) across the TR.