基于复合超构表面的宽带圆极化双功能器件设计

多功能器件的设计是推动新一代电磁系统发展的重要力量,而超构表面因其对电磁波的幅度、相位和极化等特性的灵活调控在多功能器件领域备受关注.传统的多功能超构表面是利用各向异性单元对相互正交的线极化波具有不同响应的特性,从而设计出适用于线极化的多功能器件.本文提出了一种缝隙加载的环I形复合超构表面单元,通过单元臂长和旋转角度的调整实现了对圆极化电磁波传输和几何相位的独立控制.利用上述两种相位的共同作用,打破了左旋和右旋圆极化电磁波操控中存在的固有关系,为圆极化双功能器件的设计提供了新的思路.在此基础上,利用复合超构表面分别设计了异面偏折器和定向/涡旋光束产生器,实验结果表明,本文设计的两种反射型圆极化双功能器件在9—13 GHz的宽频带范围内均能良好工作.

Wideband circularly-polarized bifunction devices employing composite metasurfaces

Multifunctional device is powerful for promoting the development of a new generation of electromagnetic systems,and the metasurface has attracted much attention in this field due to its flexible control of amplitude,phase,and polarization of the electromagnetic wave.It is very important to achieve different and arbitrary phase distributions for left-handed and right-handed circularly polarized waves in designing circularly polarized lenses.Here,a strategy to control the propagating phase and the geometrical phase simultaneously and independently is proposed by using a gap-loaded ringshaped composite element.Through adjusting the arm length and the orientation of the unit cell,the propagating phase and geometric phase for the circularly polarized electromagnetic wave can be controlled independently.The combination of above two phases is used to break the inherent relationship between the lefthanded and right-handed circularly polarized electromagnetic wave,which provides a new method of designing bifunctional devices for circular polarization.On this basis,a circularly polarized deflector with reflections in different planes and a generator with directional and vortex-shape beams are built by using the proposed composite elements.Simulated and measured results show that the bifunctional devices for circular polarization proposed in this paper can work well in a wide frequency range of 9–13 GHz.