Metasurface Design Using Electromagnetic Inversion

Abstract

This thesis presents the theory and development of a framework for the design of electromagnetic metasurfaces. These metasurfaces can be used to systematically transform an incident electromagnetic field into a different transmitted field, providing new levels of control not typically possible with conventional materials. Although a metasurface is made up of subwavelength scattering elements, it can be macroscopically represented as a homogenized model using effective surface susceptibilities. These tensorial surface susceptibilities define the relationship between the tangential electric and magnetic fields on either side of the metasurface through a set of generalized boundary conditions known as the generalized sheet transition conditions.

On the Use of Electromagnetic Inversion for Metasurface Design

“…We have recently proposed and used the electromagnetic inverse source framework for the design of metasurfaces [32], [33]. In addition to applying the inverse source framework to metasurface design, these works extend it to more practical scenarios: those where the desired specifications are expressed in terms of some performance criteria (e.g., HPBW and null directions) rather than a completely-known desired field pattern.…”

Multi-Plane Magnetic Near-Field Data Inversion Using the Source Reconstruction Method

“…Consequently, they cannot be described by the conventional 2.2. Design and Characterization using Surface Equivalence 22 boundary conditions that describe the field discontinuity between two different types of media, and do not describe a sheet discontinuity in a medium [62,63]. Instead, the generalized sheet transition conditions (GSTCs), which were developed by Idemen [64], can be used to model metasurfaces [65].…”

“…ure 2.1), the subscript t specifies that the tangential components (û and v) of the corresponding quantity are required, ω is the angular frequency of operation, D is the electric flux density, B is the magnetic flux density, and 0 and µ 0 are the permittivity and permeability of free space, respectively. The '∇ t ' operator calculates the gradient with respect to tangential directions only and the '∆' operator can be defined in terms of the transmitted, incident, and reflected fields on the metasurface input and output boundaries [63] (see Figure 2.1)…”

“…Furthermore, it has been shown that a macroscopically valid relation for the electric and magnetic surface polarization densities can be written as [63]…”

“…where χ ee , χ mm , χ em , and χ me are the electric or magnetic (first subscript) surface susceptibility tensors that define the metasurface's response to electric or magnetic (second subscript) field excitations [63,66]. Note that the field quantities are truly those at the position of the metasurface, but they are approximated as the average fields on the input and output metasurface boundaries [62], i.e.…”