A 1.9–3 GHz broadband LC VCO with low phase noise for wireless communications

Abstract

In this paper, a Broadband LC Voltage Controlled Oscillator (VCO) with low phase noise for wireless communications is realized by a 0.18-μm CMOS process. In order to optimize the turning curve, reduce the phase noise, and increase the linearity, a cross-coupled LC structure is selected. At the same time, a capacitor working in accumulation area and an inverter buffer are applied. The proposed circuit is designed and manufactured in standard 0.18-μm RF-CMOS process. To cover all the bands, the VCO should have an oscillation range of 1.9∼3.05 GHz, the relative bandwidth is 48%. With a 4-bits control word, the VCO is divided into 16 sub-bands. The experimental results show that the proposed VCO design can reach the frequency as high as 3.04 GHz, meeting the requirements of 3.05 GHz. The phase noise in the whole frequency stage is less than −122.9 dBc/Hz.