Theoretical Modeling of Complicated Inductive Wireless Power Transfer Systems

Abstract

Inductive RF power transfer designs can be incredibly versatile, designed with a multiplicity of geometries and current paths to focus and enhance the transfer of power. However, most inductive systems in engineering practice are limited to either two-flat-loop systems or several basic coils with simplifying symmetry aspects. Complicated loop designs are largely ignored or untried by engineers because they are notoriously difficult to understand and model. This paper presents a foundational model for inductive systems with an arbitrarily large number of mutually-coupling loops. For the first time, comprehensive first-principle expressions for calculating voltage gain, s-parameters, and transfer efficiencies for these arbitrarily complicated inductive systems are presented and compared to measurements. The final result is a set of tools for designing the next-generation inductive RFID and wireless power transfer systems.