A High-Level Model for Capacitive Coupled RC Oscillators

Abstract : In this paper a high-level model is proposed for quadrature oscillators that are based on two RC oscillators with capacitive coupling. The capacitive coupling technique has the advantages of being noiseless and not increasing the power requirements, which are important features for low power receivers. This coupling technique was already study for LC oscillators but not for RC oscillators. Simulations showed that the behavior of capacitive coupling in RC oscillators is different than for LC. In opposition to what was expected, in RC oscillators, the oscillation frequency increases almost linearly and proportional to the coupling capacitances. This behavior can be explained by the presented model. Simulations are presented to validate the model in respect to the oscillation frequency and to the output phases of the oscillator.