A 12.9-to-24 GHz Dual-Mode Multi-Coil VCO Achieving 199.2 dBc/Hz Peak FoMT in 65-nm CMOS

This brief reports a mode-switching dual-core multi-coil voltage-controlled oscillator (VCO) with improved frequency tuning range (FTR) and phase noise (PN). Specifically, our VCO utilizes the head transformer (HT) and source center-tap inductor to enable dual-mode operation for FTR extension. Besides, the multi-coil VCO features two-port configuration, where the inherent boosted transformer voltage gain help reducing the PN injection. We also propose a compact HT layout to aid eliminating the parasitic common mode (CM) inductance. The tiny mode-selection switches at the drain terminal introduce negative resistance at the desired mode, averting the oscillation state ambiguity. The VCO fabricated in 65-nm CMOS occupies a core area of
$0.098~{\mathrm{ mm}}^{2}$
while dissipating 16.8 mW at a 0.7-V supply. The measured PN peaks to -129.1 dBc/Hz at 10-MHz offset throughout the entire FTR of 58% (12.9 to 24 GHz) with the corresponding peak
${\mathrm{ FoM}}_{\mathrm{ ~T}}$
of 199.2 dBc/Hz.