Near-Field Shielding Analysis of Single-Sided Flexible Metasurface Stopband TE: Comparative Approach

Near-field (NF) studies comprising four common 10 GHz stopband frequency selective surfaces (FSSs) of single-sided, single-layer metasurfaces are conducted. The studies are to determine the NF efficiency of the metasurfaces for electromagnetic shielding applications. First, the FSSs' shielding performance in both far-field (FF) and NF zones is considered using the finite element method (FEM) based on the cell shielding effectiveness (SE). Analytical derivations of the FF- and NF-SE are presented, incorporating the equivalent circuit model and infinitesimal electric/magnetic source model, respectively. A nonlinear regression learning approach is utilized to predict an acceptable NF model. In the comparison study, the edge diffraction effects due to the finite structures are taken into consideration for 1-D and 2-D diffractions. The NF-SE performance of conformal structures is analyzed based on the radii of curvature. When the structure is bent, the movement of the desired transmission zero in the NF region intensely degrades the NF-SE, which may lead to a highly unstable shielding performance. Moreover, data sets are extracted for efficient usage of the structures under test by introducing two useful reconfigurable parameters, distance and radius. For verification, the FEM results are compared with the method of moment (MOM) results. The developed scenarios create a reliable criterion for further advancements of the flexible shielding surfaces from the NF point of view.