An <i>X</i>-Band CMOS VCO Using Ultra-Wideband Dual Common-Mode Resonance Technique
Feifan Hong, Hao Zhang, Dixian Zhao
Abstract
In this paper, the dual common-mode (CM) resonance technique is proposed for lowering the phase noise (PN) and flicker PN corner of LC voltage-controlled oscillators (VCOs) across wide tuning range. The dual CM resonator can provide high and resistive input impedance across a wide <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{\mathbf {nd}}$ </tex-math></inline-formula> harmonic band without dedicated tuning. It can both prevent the tank-loading effect and reshape the output waveform. Novel implementation methods are demonstrated to realize dual CM resonance at high frequencies. For comparison, both the dual CM resonance VCO and a reference one with a tail filter are fabricated in 65-nm CMOS, achieving the measured frequency range of 8-11.15 and 7.98-11.3 GHz, respectively. In 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> region, the proposed VCO shows an average PN of −139 dBc/Hz and the FOM of 190-192.3 dBc/Hz across the band, leading to an excellent FOM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {T}}$ </tex-math></inline-formula> of larger than 200.3 dBc/Hz. The reference VCO shows the average PN and FOM of -137.7 and 190.5 dBc/Hz. In 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> region, the former exhibits a low flicker PN corner of 280–350 kHz while the latter’s flicker PN corner varies largely from 290 to 950 kHz across the band. Both VCOs’ cores consume about 5 mW at 1 V supply and occupy approximately 0.13 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .