Metasurface (MTS) antennas are based on the transformation of a cylindrical-wavefront surface wave (SW) into a general wavefront leaky wave (LW). The MTS aperture is constituted by a grounded dielectric slab printed with an electrically dense distribution of subwavelength patches realizing space-variable, homogenized tensor impedance boundary conditions (IBCs). One of the challenges in this type of antenna is related to obtaining dual polarization operations by using the same impedance modulation. In this article, we explore and compare three simple approaches to obtain two beams with orthogonal polarizations by feeding two ports. A first known method is based on exciting both a transverse electric (TE) and a transverse magnetic (TM) SW mode on the same modulated impedance. A second method exploits the concept of impedance modulation sharing, according to which two distinct modulations, designed to radiate different polarizations when properly illuminated by distinct offset feeding points, are superimposed on the same aperture. A third method consists in duplexing an outward (radially diverging) and an inward (converging to the center) SW. Simple analytical formulas are presented for the synthesis of the impedance that allows for the control of the inward/outward waves to ensure balanced radiation performances in terms of aperture efficiency for the two polarizations. A comparison in terms of performances between the latter two approaches is presented.

中文翻译：

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双极化超表面天线的设计方法：三种简单的方法


超表面（MTS）天线基于圆柱波前表面波（SW）到一般波前漏波（LW）的转换。 MTS 孔径由接地电介质板构成，电介质板印刷有电致密分布的亚波长贴片，实现空间可变、均匀张量阻抗边界条件 (IBC)。这种类型天线的挑战之一与通过使用相同的阻抗调制来获得双极化操作有关。在本文中，我们探索并比较了通过馈送两个端口来获得具有正交偏振的两个光束的三种简单方法。第一种已知方法基于在相同的调制阻抗上激励横向电（TE）和横向磁（TM）SW模式。第二种方法利用阻抗调制共享的概念，根据该概念，将两种不同的调制叠加在同一孔径上，两种不同的调制被设计为当被不同的偏移馈电点正确照射时辐射不同的偏振。第三种方法包括使向外（径向发散）和向内（会聚到中心）SW成双工。提出了用于合成阻抗的简单分析公式，该阻抗允许控制向内/向外波，以确保两种偏振的孔径效率方面的平衡辐射性能。给出了后两种方法之间的性能比较。