Ka‐band multi‐focus and pattern manipulation in near‐field based on three‐dimensional printed transmit‐array antenna

A simple method to achieve multi-focus and pattern manipulation in antenna near field (NF) is proposed in this study, whose effectiveness is then validated by measurements based on different transmit-array antennas. The radiating aperture is divided into several regions and each region corresponds to one assigned focal point, thus achieving multi-focusing performance. Then, the superposition principle is employed and constrains the multiple foci into a certain area to get a contoured pattern. Three examples are investigated. Ant-A presents four balanced focal spots simultaneously, while Ant-B presents two unbalanced foci. A square flat-top field pattern is obtained for Ant-C. Three-dimensional printing technology is employed to fabricate these lenses, resulting in a low cost and light weight. Measured results coincide well with the numerical design and simulation. The proposed method provides a simple and effective alternative for NF power redistribution and owns great value in such applications as radio-frequency identification, wireless power transmission, millimetre-wave imaging etc.

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