Mid-range wireless power transfer: anapoles or magnetic dipoles?

Abstract

For short-range wireless power transfer (WPT) one recently suggested so-called anapole antennas that practically do not create fields in the far zone, eliminating radiation loss. Enhancements of power transfer efficiency (PTE) compared to traditional WPT systems based on magnetic dipole antennas were claimed for distances of the order of one-tenth of the wavelength or smaller. In this Letter, we theoretically show that a system of two properly engineered magnetic dipole antennas grants a similar PTE for this range of distances and a higher PTE for larger distances. In addition, we demonstrate that at mid-range distances, the radiation from magnetic-dipole-based WPT systems can be made drastically lower than the radiation from a single magnetic dipole antenna. This regime offers an alternative for reduction of far-field radiation.