Adour V. Kabakian

Surface-Wave Waveguides

We present simulations and measurements of surface-wave waveguides (SWGs) for guiding surface waves (SWs) along a constrained path. In its simplest form, the SWG is a two-dimensional analog to a dielectric waveguide where a low-index material surrounds a high-index material. The most common method for realizing materials with differing SW index is to use a grid of metallic patches of varying size on a dielectric substrate. Using asymmetric patches results in a tensor SW index. We show simulations of how the phase front of the guided surface wave can be precisely controlled using a combination of SW-index grading and rotation of the SW-index tensor. We present measurements of straight and curved SWGs showing how SWG width and curvature affect guiding properties.

Implementation of Discontinuous Galerkin (DG) method for antenna applications

In this paper, we have presented representative applications of the DG based TEMPUS solver for modeling and simulation of complex broadband antennas. Numerical results demonstrate the excellent performance of the code in typical antenna applications such as monopole, microstrip and cavity-backed slots. The code has a powerful underlying structure enabling its applicability to large and complex geometry problems in antennas and scattering.

Multiphysics simulation of microstructure formation by self-propagating photopolymer waveguides

A 3D multiphysics solver which combines beam propagation with chemical kinetics for simulating self-propagating photopolymer waveguides is presented. The solver is shown to predict various experimentally observed phenomena and is used to simulate the formation of micro-truss structures consisting of intersecting photopolymer waveguides.

Backscatter reduction of long thin bodies by surface impedance modulation

We present a method for controlling the scattering of surface waves induced on long, thin, conductive bodies by grazing-angle illumination. We consider such bodies as travelling wave antennas and apply a modulated impedance coating to radiate the surface waves away from the illumination source, thus eliminating the large near nose-on monostatic scattering (backscatter). The effect on bistatic scattering is shown. We demonstrate the proposed concept with full-wave simulations.

Surface-wave waveguides

We present simulations and measurements of surface-wave waveguides (SWGs) for guiding surface waves (SWs) along a constrained path. In its simplest form, the SWG is a two-dimensional analog to a dielectric waveguide where a low-index material surrounds a high-index material. The most common method for realizing materials with differing SW index is to use a grid of metallic patches of varying size on a dielectric substrate. Using asymmetric patches results in a tensor SW index. We show simulations of how the phase front of the guided surface wave can be precisely controlled using a combination of SW-index grading and rotation of the SW-index tensor. We present measurements of straight and curved SWGs showing how SWG width and curvature affect guiding properties.

Discontinuous Galerkin Method for the Time-domain Maxwell’s Equations

A parallel, unstructured, high-order discontinuous Galerkin method is developed for the time-dependent Maxwell’s equations, using simple monomial polynomials for spatial discretization and a fourth-order Runge-Kutta scheme for time marching. Scattering results for a number of validation cases are computed employing polynomials of up to third order. Accurate solutions are obtained on coarse meshes and grid convergence is achieved, demonstrating the capabilities of the scheme for time-domain electromagnetic wave scattering simulations.

Large-Scale Parallel Simulations in Computational Electromagnetics

The ability to predict the electromagnetic response from complex structures with layered material media over a wide frequency range (100 MHz to 20 GHz) is a critical technology need for the development of stealth platforms. There are three basic approaches to numerical simulation of Maxwell’s equations: 1) high frequency asymptotics, which treats scattering and diffraction as local phenomena; 2) solution of an integral equation for radiating sources on (or inside) the scattering body, which couples all parts of the body through a multiple scattering process; and 3) the direct integration of the differential form of Maxwell’s equations in time. The integration of Maxwell’s equations in time offers the most direct and general solution for broadband radar scattering and propagation of electromagnetic pulses in real materials. The challenge for time-domain methods has been to maintain global accuracy in the phase and amplitude of waves scattered by large, complex structures.