Generation of Non-diffractive Beam by Using Metasurface for Wireless Power Transfer (WPT) Applications

A transmission metasurface that can generate a non-diffractive focusing beam with direction control in the nearfield regime is proposed. It is designed for WPT at 5.8GHz, which utilizes cells with high transmission efficiency and can obtain an accurate phase distribution required to form a non-diffractive beam by controlling the size of each cell. The metasurface is composed of 10×10 unit cells, and the focusing range obtained by simulation is about 120mm, which is much larger than the distance of point focusing. Meanwhile, a method for calculating the focusing efficiency is also proposed, showing a focusing efficiency of about 47% in the plane with the best focusing effect (Z = +60mm). In addition, according to the generalized refraction law, a beam deflected approximately 15° from the normal direction is achieved, which vividly demonstrates the flexibility of beam direction control. The design has the advantages of long focusing distance, flexible beam control and simple manufacture, thus providing a practical solution for long-distance wireless power transfer.