Graphical method for the optimization of CMOS quadrature VCO

Abstract

This paper describes a graphical method for the optimization of Quadrature Voltage Controlled Oscillators (QVCOs) based on the coupling of two LC-tank VCO. A three-dimensional phase noise analysis diagram and graphical optimization approach is presented, to optimize QVCO phase noise while satisfying design constraints such as power dissipation, tank amplitude, tuning range and start up condition. The obtained QVCO can be tuned between 2.2GHz and 2.58GHz, and shows a phase noise of −129 dBc/Hz at 1MHz offset from a 2.4 GHz carrier, for a current consumption of 9.25mW. The equivalent phase error and amplitude error between I and Q signals are respectively 0.65° and 1.87%.