A 5-8 GHz Wideband and Low Phase Noise Cross-Coupled LC VCO Using 6-bit DCCA in 40nm CMOS Process

Abstract

This paper presents a broadband and low phase noise LC voltage-controlled oscillator (VCO) implemented in SMIC 40nm CMOS process. The VCO uses 6-bit digitally-controlled capacitor array (DCCA), achieving a large tuning range of 47.5% and a maximum tuning sensitivity of only 80MHz/V. Besides, by optimizing the layout of DCCA, it achieves a low phase noise of - 121.7dBc/Hz at 1MHz frequency offset at 8 GHz output frequency at room temperature. The fluctuation value of phase noise is less than 3.5dBc/Hz in the temperature range of -55°C to 125°C. Meanwhile, in order to improve the control voltage variation range, the varactor transistor adopts the one with the withstand voltage value of 2.5 V, and the quiescent current of the circuit is around 11mA at 1.2V, and the layout area is around 0.21×0.35mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .