24GHz CMOS Frequency Source with Differential Colpitts Structure-Based Complementary VCO for Low Phase Noise

Abstract

In this paper, a 24GHz frequency source for low phase noise is presented in a 0.18µm CMOS process. The 24GHz frequency source chip is composed of a 12GHz voltage controlled oscillator (VCO) and a 24GHz balanced frequency doubler with class B gate bias. Compared to a conventional complementary VCO, the proposed 12GHz VCO has phase noise improvement by using resistor current sources and substituting the nMOS cross-coupled pair in the conventional complementary VCO for a gm-boosted nMOS differential Colpitts pair. The measured phase noise and fundamental frequency suppression are -107.17dBc/Hz at a 1MHz offset frequency and -20.95dB at 23.19GHz frequency, respectively. The measured frequency tuning range is from 23.19GHz to 24.76GHz drawing 2.72mA at a supply voltage of 1.8V not including an output buffer.