A 3D-printed ultra-broadband planar Luneburg lens composed of periodic gradient structures is proposed in this paper. Compared to the previous studies, the proposed lens has a pretty large operating frequency range, spanning from 5 to 22 GHz. The measured results of the near-field and far-field illustrate the feasibility and validity of this lens antenna. High efficiency achromatic sub-diffraction focusing with a full-width at half-maximum of 0.3λ and a highly directive far-field radiation pattern with side lobes below −10 dB are achieved. Triple input and triple output function is also realized experimentally.

中文翻译：

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具有亚衍射分辨率的全电介质超宽带 MIMO Luneburg 透镜

本文提出了一种由周期性梯度结构组成的 3D 打印超宽带平面 Luneburg 透镜。与之前的研究相比，所提出的镜头具有相当大的工作频率范围，从 5 到 22 GHz。近场和远场的实测结果说明了该透镜天线的可行性和有效性。高效消色差子衍射聚焦，半峰全宽为 0.3λ并且实现了旁瓣低于-10 dB的高度定向的远场辐射方向图。还通过实验实现了三输入三输出功能。