Midrange Radiative Wireless Power Transfer Based on the Improved Half-Fisheye Lens

Abstract

An improved half-fisheye lens (HFL) is proposed to achieve efficient midrange radiative wireless power transfer (RWPT). First, the study analyzes the factors that impede the attainment of optimal power transfer efficiency (PTE) in a mirror-symmetric RWPT system composed of a pair of conventional HFLs under practical feeding conditions. Subsequently, the field distribution conditions requisite for achieving optimal PTE in the HFL-based RWPT system are derived. Guided by these conditions, a mirror-symmetric RWPT system comprising a pair of improved HFLs is designed to achieve optimal PTE under practical feeding conditions. The improved HFL consists of a redesigned HFL and a transition layer. The transition layer not only mitigates the impedance mismatch at the interface but also achieves a time-reversal symmetric field distribution required for optimal PTE. The redesigned HFL undergoes axial compression and refractive index distribution modification, thereby reducing the lens’s refractive index while maintaining its profile height. Finally, to validate the effectiveness of the proposed design, a midrange RWPT prototype based on the improved HFL is designed and fabricated. The experimental results show that the RWPT system based on the improved HFL can achieve a PTE of 41% at a transfer distance of $d=8\lambda $ when fed by a horn antenna, demonstrating a 70% PTE improvement compared to the RWPT system based on the conventional HFL.