Focused microwave power transmission system with high‐efficiency rectifying surface

Abstract

A focused microwave power transmission (MPT) system with high‐efficiency rectifying surface is proposed. This work has two main novel contributions: (i) most of wireless power transmission systems reported so far are non‐focused. This study presents the first focused MPT system with circular polarisation; (ii) a novel high‐efficiency rectifying surface using sub‐wavelength resonant elements is developed. To design a focused transmitting array antenna with high power density at the receiving site and high beam collecting efficiency in the near field, a method based on the optimisation of a partial scattering matrix is employed. A left‐handed circularly polarised microwave power rectifying surface consisting of 8 × 8 sub‐wavelength resonant elements is designed and the measured conversion efficiency reaches 57.74%. To validate the concept, an experimental system including one focused transmitting array antenna and one 2 × 2 elements rectifying surface is implemented and measured, and the improvement of output direct current (DC) power and radiofrequency (RF)‐to‐DC conversion efficiency compared with non‐focused condition is shown. The highest RF‐to‐DC efficiency of 66.5% is achieved in the focused mode, compared to that of 34.8% only in the non‐focused mode as in traditional systems.