Analysis of magnetically coupled wireless power transfer between two resonators based on power conservation

Based on an equivalent circuit in which the necessary elements for a magnetically coupled wireless power transfer (WPT) system are considered, its overall characteristics are formulated and analyzed. In particular, the WPT efficiencies are conveniently expressed as a function of a figure of merit and a load deviation factor, re-emphasizing the use of an optimal load for the maximum efficiency. Some useful closed-form formulas for extraction of circuit parameters and coupling coefficients are also presented. The theoretical and EM-simulated WPT efficiencies are shown to be in good agreement, validating the circuit modeling and presented formulation.