An X-Band CMOS VCO Using Ultra-Wideband Dual Common-Mode Resonance Technique

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
$2^{\mathbf {nd}}$
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
²
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
$_{\mathbf {T}}$
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
³
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
²
.