Double Cross Coupled Colpitts VCO with Low Phase Noise using InGaP/GaAs HBT Technology

Abstract

The proposed double cross-coupled differential Colpitts voltage controlled oscillator (VCO) is designed using InGaP/GaAs HBT technology for an adaptive feedback interference cancellation system (AF-ICS). In this paper, two switching transistors were used to steer the bias current and voltage in the VCO core, thereby saving power. The VCO achieves excellent phase noise characteristics of -135 dBc/Hz at 1 MHz offset from carrier frequency (1.630 GHz) when supplied with a control voltage of 0 V Also, its tuning range is around 218 MHz with an output power of -3.91 dBm (including cable loss). It shows the figure of merit (FoM) of -180.5 dBc/Hz. Two pairs of base-collector (BC) diodes are integrated in the tank circuit to increase the VCO tuning range. The optimized chip size is 0.9 mm x 0.9 mm.