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

## TL;DR

This paper introduces a rigorous convex optimization method for enhancing wireless power transfer systems using passive elements and metasurfaces, enabling efficient performance optimization and fundamental limit analysis.

## Contribution

It develops a general semidefinite relaxation approach that does not rely on assumptions, allowing reliable optimization of complex WPT systems with passive and active components.

## Key findings

- Optimized WPT systems achieve improved efficiency and range.
- The method confirms the physical limits of system performance.
- Applicable to systems with many passive and active elements.

## Abstract

This paper presents a rigorous optimization technique for wireless power transfer (WPT) systems enhanced by passive elements, ranging from simple reflectors and intermedi- ate 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.