Three‐Dimensional Integral Equation‐based GSTC Method for Composite Structure With Arbitrary‐Shaped Nonpenetrating Metasurface

ABSTRACT This study proposes a novel three‐dimensional integral‐equation‐based electromagnetic solver with surface susceptibilities of metasurfaces that satisfy the generalised sheet transition conditions (GSTCs). The metasurface is replaced by an equivalent zero‐thickness sheet with surface susceptibilities, which can be extracted using the retrieval method deduced from the GSTCs. We consider the problems of composite structures with metasurfaces for greater generality and applicability. The integral equations of the problems are formulated and discretised using Rao–Wilton–Glisson (RWG) basis functions through Galerkin's testing procedure. We also propose a technique for enforcing the boundary condition at the interface, which should be carefully considered within the problem formulation of composite structures. The proposed method is validated by using a circuit‐analog‐based absorber to extract the surface susceptibilities. Composite structures, including flat and curved metasurfaces, are employed to verify the IE‐GSTC solver, and numerical simulation results are compared with those obtained from a commercial finite‐element method‐based simulation (FEM‐HFSS).