One-transmitter–multiple-receiver system for wireless power transfer using an exceptional point of degeneracy

In wireless power transfer systems, robust transfer efficiency under various operating conditions remains a fundamentally important challenge. This becomes even more critical when transferring power to groups of inductively coupled receivers. We propose a method for efficient wireless power transfer to multiple receivers, exploiting the concept of exceptional points of degeneracy (EPDs) in a self-oscillating system. In previous studies based on parity-time (PT) symmetry, a receiver's operation has been divided into the strong and weak coupling regimes, and the power transfer efficiency is constant in the strong coupling regime when varying the coupling factor. Here, the concept of strong and weak coupling and constant power transfer efficiency is extended to a system of multiple receivers that do not follow PT symmetry. The transmitter has saturable nonlinear gain, and the EPD is analyzed when the system oscillates after reaching saturation. We show that the important feature for achieving roughly constant power transfer efficiency independent of the positions of the receivers, is the existence of an EPD that separates the weak and strong coupling regimes. Our proposed method produces a system with less sensitivity to changes in coupling than a conventional system without an EPD when the receivers and their couplings to the transmitter are not necessarily identical.