Artificial materials for electromagnetic wave-front manipulation applied to antenna systems

RWTH Publications (RWTH Aachen)

Abstract

Artificial surfaces are engineered structures consisting of two-dimensional arrangements of subwavelength scattering elements that enable electromagnetic wave manipulation. They can be designed for many applications, including impedance matching surfaces, antenna beam scanning, and beam focusing lenses. With respect to the type of their interaction with incident electromagnetic waves, they can be categorized into three groups: wave guiding, transmission, and reflection. Artificial surfaces are challenging to model and optimize using full-wave simulations as they represent a multi-scale problem. They consist of subwavelength unit cells (micro-scopic scale) that require dense geometrical meshes to capture all physical details. At the same time, the entire surface is electrically large (macroscopic scale). This highlights the need to develop a simple and efficient modeling method to analyze three-dimensional arbitrarily shaped artificial surfaces with any kind of polarization. In this work, we focus only on artificial surfaces that are periodic or continuous and can be considered as infinitely extended in one spatial dimension perpendicular to the plane of wave propagation. The three-dimensional physical problem is simplified to a two-dimensional equivalent problem considering only the plane where the fields are not uniform. The subwavelength metallic patterns of the artificial surfaces are homogenized and represented by zero-thickness impedance sheets with equivalent electric currents. Thus, the two-dimensional equivalent model consists of the cross-sections of multilayer arbitrarily curved zero-thickness impedance sheets separated by dielectric layers. The fields within the dielectric regions are described by equivalent polarization currents according to the volume equivalent principle. A volume-surface integral equation is proposed to analyze the electromagnetic scattering by the two-dimensional equivalent model due to the equivalent currents. The continuous volume-surface integral equation is discretized and solved numerically using the method of moments (MoM). The MoM is formulated for both TE and TM polarized excitations. Since the problem is two-dimensional, the volume integrals of the original three-dimensional problem reduce to surface integrals over the cross-sections of the structure, and the surface integrals reduce to line integrals over the boundaries of the two-dimensional cross-sections. To validate and evaluate the accuracy and efficiency of the proposed MoM modeling method, three illustrative examples are studied. 1. Guiding of waves along artificial surfaces. 2. Manipulation of electromagnetic waves passing through transmissive metasurfaces. 3. Manipulation of electromagnetic waves by reflective metasurfaces.

Authors 1

1. Taher Badawy corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen