Surface Susceptibility Synthesis of Metasurface Skins/Holograms for Electromagnetic Camouflage/Illusions

Abstract

A systematic numerical framework based on Integral Equations and Generalized Sheet Transition Conditions (IE-GSTCs) is presented in 2D to synthesize closed metasurface holograms and skins for creating electromagnetic illusions of specified objects and as a special case, to camouflaging them against their backgrounds. The versatile hologram surface is modeled using a zero-thickness sheet model of a generalized metasurface expressed in terms of its surface susceptibilities, which is further integrated into the GSTCs and the IE current-field propagation operators. To estimate the effectiveness of the illusions, the notion of a scene constructed by an observer is developed from first principles and a simple mathematical model, referred to as a Structured Field Observation (SFO), based on spatial Fourier transform is proposed.Using numerical examples, it is shown that to recreate the reference desired fields everywhere in space using a closed metasurface hologram/skin, an internal illumination must be applied inside the hologram, in addition to the applied external illumination fields. Finally, several numerical examples are presented for simple, angle-dependent and dynamic illusions. Finally, a dynamic camouflaged region of space, which can freely move inside a given complex scene without being detected by the observer is demonstrated.

Accelerated IE-GSTC Solver for Large-Scale Metasurface Field Scattering Problems using Fast Multipole Method (FMM)

“…This integral equation based approach coupled with GSTCs, is referred to here as the IE-GSTC field formulation. For numerical computation, these equations are discretized by segmenting the surfaces following Boundary Element Method (BEM) techniques and assembled in a matrix form for further processing [8], [9], [27], [28].…”

“…However, several practical system level applications require large area metasurface sizes beyond laboratory scale experiments. Two examples are that of creating electromagnetic illusions and camouflage [8], [9], and using metasurfaces to engineer the wireless environment, for instance [8], [10]- [12]. In both cases, the metasurfaces are operated in larger environments with variety of scattering objects of different shapes and sizes present.…”

“…On the other hand, Integral Equation (IE) based methods are particularly attractive as large simulation domains can be handled, since no volumetric meshing is used and only surfaces are discretized [27]- [29]. Consequently, zero thickness sheet models implemented using GSTCs in IE solvers (IE-GTSC) have been shown to very efficiently reproduce the macroscopic field behavior of practical metasurfaces with large number of unit cells, when compared to standard brute-force full-wave computer simulations [8], [9], [30]- [32].…”

“…If other objects made of PEC, conductors or dielectric are also part of the scattering problem, then appropriate boundary conditions must be used, in addition to the GSTCs for the respective surfaces. See[8],[32] 3. Both Electric and Magnetic fields, which are coupled by the GSTCs, unlike standard EFIE, MFIE or CFIE formulations.…”

Application of cylindrical IE-GSTC to physical metasurfaces

“…Recently asymptotic methods (GO, GTD)was applied to electrically large metasurfaces [20]. Even though mathematically rigorous, none of these works [10]- [12], [14], [19]- [23] have used physical metasurfaces.…”