Movahhedi Mostafa, Komjani Nader
Opt Express. 2020 Apr 13;28(8):12424-12438. doi: 10.1364/OE.391380.
The holographic technique is a promising way to manipulate light distribution and wave-front in the optical regime. In recent years, many researchers have extended this concept to microwave regime to manipulate phase, amplitude, and polarization of waves in a convenient way revealing diverse intriguing applications. Unlike the previous studies with optimization-based schemes, in this paper, we propose a simple route to design dual frequency dual-polarization holographic metasurfaces with negligible interference between the operating (lower and upper) frequencies. For this purpose, a Jerusalem-shape unit-cell is used to realize two distinct impedance distributions which yield two decoupled field profiles over the aperture of the metasurface at each frequency band. Consequently, the proposed metasurface radiator can operate in two frequency bands, independently. Each set of horizontal (vertical) cross-bars of the Jerusalem-shape unit-cell is illuminated by a vertical (horizontal) feeding network from one side of the metasurface. Side feeding has a null-free advantage, this undesired null emerges in central feeding metasurfaces and leads to an undesirable rabbit's ears phenomenon. As the proof-of-concept, a prototype of the metasurface radiator for operating at 11.5 GHz and 14 GHz is fabricated and measured. The experimental results depict a good agreement with the full-wave simulations.
全息技术是在光学领域中操纵光分布和波前的一种很有前景的方法。近年来,许多研究人员已将这一概念扩展到微波领域,以便以一种便捷的方式操纵波的相位、幅度和极化,从而展现出各种有趣的应用。与以往基于优化方案的研究不同,在本文中,我们提出了一种简单的方法来设计双频双极化全息超表面,使工作(低频和高频)频率之间的干扰可忽略不计。为此,采用耶路撒冷形状的单元结构来实现两种不同的阻抗分布,这会在每个频段的超表面孔径上产生两个解耦的场分布。因此,所提出的超表面辐射器可以在两个频段独立工作。耶路撒冷形状单元结构的每组水平(垂直)横杆由来自超表面一侧的垂直(水平)馈电网络照明。侧边馈电具有无零点的优势,这种不期望的零点出现在中心馈电超表面中,并导致不期望的兔耳现象。作为概念验证,制作并测量了一个工作在11.5GHz和14GHz的超表面辐射器原型。实验结果与全波模拟结果吻合良好。