Effective Mid-Range Wireless Power Transfer with Compensated Radiation Loss

TL;DR

This paper develops a dynamic theory for wireless power transfer that leverages radiation suppression to enable efficient energy transfer over larger distances, expanding the practical range of compact wireless devices.

Contribution

The paper introduces a novel dynamic theory that explains how to suppress radiation effects to improve long-distance wireless power transfer efficiency.

Findings

Radiation suppression enables efficient power transfer at larger distances.

Analytical results are validated by simulations and measurements.

The theory applies to various antenna types and nano-scale energy transfer.

Abstract

In conventional inductive wireless power devices, the energy is transferred via only reactive near fields, which is equivalent to non-radiative F\"orster energy transfer in optics. Radiation from transmitting and receiving coils is usually considered as a parasitic effect that reduces the power transfer efficiency. As long as the distance between the two antennas is small as compared to the antenna size, conventional WPT devices offer rather high power transfer efficiency, of the order of 80-90\%. However, for larger distances, the transfer efficiency dramatically drops, making such devices not practical. In this paper, we develop a dynamic theory of wireless power transfer between two small loop antennas, clarify the role of far-field radiation, and find a possibility to realize efficient wireless power transfer at large distances utilizing the regime of radiation suppression due to optimized mutual dynamic interactions between the transmitting and receiving antennas. The analytical results have been validated by simulations and measurements, and they open a possibility to greatly expand the range of distances of compact wireless power transfer devices. The developed theory can be applied also to coupling between antennas of different types and to energy transfer between nano-objects.