Near-field focusing metasurface design based on wireless energy transmission

This article proposes an improved near-field focused metasurface for wireless energy transmission, which solves the problems of large phase value calculation and complex phase distribution in traditional phase gradient near-field focused metasurface array units. The metasurface adopts a hybrid periodic element with a cross and open ring structure, and achieves a 360° linear phase shift by changing the angle of the outer open ring with parasitic branches at the end. A near-field focusing metasurface with 13×13 periodic elements and an effective area of 117 mm ×117 mm is designed and processed by fully covering the phase values using seven simplified elements. The measured results show that the maximum focusing efficiency of 62.91% and transmission efficiency of 94.1% are achieved within a relative bandwidth of 13.72%, and a focal depth of 61.4 mm is achieved at a working frequency of 14 GHz. The measured results are in good agreement with the simulation results. The designed metasurface exhibits 360° phase control of x and y polarized electromagnetic waves, achieving an average transmission loss of −0.52 dB. This metasurface has the characteristics of simple design, high transmission efficiency, and high focusing efficiency, providing a solution for the simplified design of near-field focusing metasurface.