20.1 A 5.0-to-6.36GHz Wideband-Harmonic-Shaping VCO Achieving 196.9dBc/Hz Peak FoM and 90-to-180kHz 1/f<sup>3</sup> PN Corner Without Harmonic Tuning
Hao Guo, Yong Chen, Pui‐In Mak, Rui P. Martins
Abstract
Since 2001 [1], LC VCOs have been demonstrating significant improvements of figureof-merit (FoM) and 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> phase noise (PN) corner [2-5] by exploring common-mode (CM) resonance at twice the oscillation frequency (2F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OSC</sub> ). 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 |Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CM</sub> | that is -0.64 of its differential-mode (DM) impedance |Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DM</sub> |. The VCO in [3] achieves a high FoM@10MHz up to 191.4dBc/Hz by boosting |Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CM</sub> | at 2F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OSC</sub> and |Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DM</sub> | at 3F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OSC</sub> . Yet, to uphold an optimal performance over the tuning range (TR), the VCO in [3]still requires manual harmonic tuning for aligning the 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> -to-2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> and 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> -to-3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">@10MHz</sub> (190.7 to 196.5dBc/Hz) and 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> PN corner (60 to 600kHz) across the TR.