Optimization of Wireless Power Transfer Systems Enhanced by Passive Elements and Metasurfaces

Abstract

Abstract-This paper presents a rigorous optimization technique for wireless power transfer (WPT) systems enhanced by passive elements, ranging from simple reflectors and intermediate relays all the way to general electromagnetic guiding and focusing structures, such as metasurfaces and metamaterials. At its core is a convex semidefinite relaxation formulation of the otherwise nonconvex optimization problem, of which tightness and optimality can be confirmed by a simple test of its solutions. The resulting method is rigorous, versatile, and general -it does not rely on any assumptions. As shown in various examples, it is able to efficiently and reliably optimize such WPT systems in order to find their physical limitations on performance, optimal operating parameters and inspect their working principles, even for a large number of active transmitters and passive elements.

Wireless power transfer system rigid to tissue characteristics using metamaterial inspired geometry for biomedical implant applications

“…Recent advancements in WPT systems have focused on the deployment of meta-surface 13 – 15 , or metamaterial 17 – 21 . Such meta-surfaces or -materials have negative or near-zero effective permeability or permittivity characteristics that help to improve the coupling between the TX and RX to enhance the performance of the WPT system.…”

“…The active routing-based meta-surface 14 enabled the adaptive location of the receiver during operation. Lang and Sarris 15 proposed a semidefinite-relaxation-based method to determine the optimum loading reactance of the meta-surface unit cells. The resulting meta-surface showed enhanced efficiency when utilized as a passive relay in a reference WPT system when compared to that WPT system without meta-surface 15 .…”

A Novel Coding Metasurface for Wireless Power Transfer Applications

“…The authors designed the unit-cell with two layers, in which each layer contains a switchable diode for providing 2-bit control ability. Recently, there has been an increasing number of research works which focus on using metasurface in wireless power transfer [16][17][18][19][20][21][22]. Nevertheless, these works are just able to do fixed focusing and are definitely inapplicable for mobile devices.…”

Analysis of coupling between magnetic dipoles enhanced by metasurfaces for wireless power transfer efficiency improvement

“…Since non-radiative WPT basis is based on energy transmission through near-field coupling between coils, so WPT efficiency can be enhanced by manipulating electromagnetic waves. One of the suitable solutions to WPT efficiency improvement is using the multiple passive elements cooperatively for example to form near-filed guiding structure 18 . Another solution to manipulating electromagnetic waves is using metamaterial which possesses the property of evanescent wave amplification 19 , 20 .…”

“…In 13 , the effect of metamaterial on WPT efficiency improvement has been investigated employing a simplified geometry such as an infinitely large slab and point dipoles for the source and receiver to obtain a closed form and analytical expressions. Another original approach to manipulating electromagnetic wave for WPT efficiency enhancement is use of metasurface instead of metamaterial slab 18 , 32 , 33 . Three-dimensional metamaterials can be extended by engineering sub-wavelength resonators, whose spectral response can be controlled independently by tailoring the element size and shape into a two-dimensional pattern at a surface or interface.…”