Closed-loop gain analysis of LC Quadrature VCO for the accurate prediction of oscillation frequency

An accurate feedback system analysis method is used as a tool for analyzing submicron CMOS LC-tank Quadrature VCOs. A simplified analysis for the closed-loop gain and oscillation frequency is developed, and good agreement is found between the feedback theorem and simulation results. The insight closed-loop gain is used to explore circuit design trade-offs.