Maximizing the Power Transfer for a Mixed Inductive and Capacitive Wireless Power Transfer System

Nowadays, near-field wireless power transfer is realized by inductive or capacitive coupling. Power transmission is respectively accomplished by a time-varying magnetic or electric field as medium. Recently, mixed or hybrid near-field wireless power transfer is being developed as a possible mean to increase the power density of the system by utilizing both the magnetic and the electric near-field. The fundamental basics of mixed coupling are well understood. However, the implications of the mixed coupling theory on wireless power transfer applications is not rigorously described. Moreover, no general description is available that allows for a detailed comparison between current hybrid systems, especially for a series topology of inductive and capacitive coupling. In this work, we analytically solve a general mixed wireless power transfer configuration with series topology. We determine the optimal load to maximize the amount of power transfer and calculate the maximum achievable output power. The analytical derivation is validated by numerical simulation in SPICE. Our solution provides insight in the mixed wireless link and can serve as a reference point to evaluate the performance of mixed systems with regard to power transfer.