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Surface Impedance Boundary Conditions is perhaps the first effort to formalize the concept of SIBC or to extend it to higher orders by providing a comprehensive, consistent, and thorough approach to the subject. The product of nearly 12 years of research on surface impedance, this book takes the mystery out of the largely overlooked SIBC. It provides an understanding that will help practitioners select, use, and develop these efficient modeling tools for their own applications. Use of SIBC has often been viewed as an esoteric issue, and they have been applied in a very limited way, incorporated in computation as an ad hoc means of simplifying the treatment for specific problems. Apply a Surface Impedance "Toolbox" to Develop SIBCs for Any Application The book not only outlines the need for SIBC but also offers a simple, systematic method for constructing SIBC of any order based on a perturbation approach. The formulation of the SIBC within common numerical techniques—such as the boundary integral equations method, the finite element method, and the finite difference method—is discussed in detail and elucidated with specific examples. Since SIBC are often shunned because their implementation usually requires extensive modification of existing software, the authors have mitigated this problem by developing SIBCs, which can be incorporated within existing software without system modification. The authors also present: Conditions of applicability, and errors to be expected from SIBC inclusion Analysis of theoretical arguments and mathematical relationships Well-known numerical techniques and formulations of SIBC A practical set of guidelines for evaluating SIBC feasibility and maximum errors their use will produce A careful mix of theory and practical aspects, this is an excellent tool to help anyone acquire a solid grasp of SIBC and maximize their implementation potential.
A point-matching technique is employed to obtain the electromagnetic fields scattered from a surface whose height profile is periodic. The surface impedance or Leontovich boundary condition is assumed to apply in a local sense. Thus the results are restricted to situations where the lower medium is well conducting (e. g., sea water). It is indicated that the convergence of the computational process is very good in the cases tested thus far.
This book comprehensively describes a variety of methods for the approximate simulation of material surfaces.
The paper deals with the methods of investigating waves propagated above the earth. Such a problem generally requires different degrees of approximation of conditions existing on the earth's surface. The present discussion is based on the assumption that the earth surface can be approximated as being flat. The Hertz vector is used for the solution of the problems relating to the theory of electromagnetic wave propagation. Two transformations relating the Hertz vector to vectros of electric and magnetic fields are given. A vertical electric dipole is located in space as the next step and the conditions of the interphase surfaces are then formulated. Construction of precise and approximate solutions is discussed for two locations of the dipole: one in the upper half-space and the other in the lower half-space. Two methods of selecting proper constants are reviewed. (Author).
A comprehensive survey of boundary conditions as applied in antenna and microwave engineering, material physics, optics, and general electromagnetics research. Boundary conditions are essential for determining electromagnetic problems. Working with engineering problems, they provide analytic assistance in mathematical handling of electromagnetic structures, and offer synthetic help for designing new electromagnetic structures. Boundary Conditions in Electromagnetics describes the most-general boundary conditions restricted by linearity and locality, and analyzes basic plane-wave reflection and matching problems associated to a planar boundary in a simple-isotropic medium. This comprehensive text first introduces known special cases of particular familiar forms of boundary conditions — perfect electromagnetic conductor, impedance, and DB boundaries — and then examines various general forms of boundary conditions. Subsequent chapters discuss sesquilinear boundary conditions and practical computations on wave scattering by objects defined by various boundary conditions. The practical applications of less-common boundary conditions, such as for metamaterial and metasurface engineering, are referred to throughout the text. This book: Describes the mathematical analysis of fields associated to given boundary conditions Provides examples of how boundary conditions affect the scattering properties of a particle Contains ample in-chapter exercises and solutions, complete references, and a detailed index Includes appendices containing electromagnetic formulas, Gibbsian 3D dyadics, and four-dimensional formalism Boundary Conditions in Electromagnetics is an authoritative text for electrical engineers and physicists working in electromagnetics research, graduate or post-graduate students studying electromagnetics, and advanced readers interested in electromagnetic theory.
A method is derived for obtaining parameters which characterize higher order surface wave mode propagation on cylindrical columns with radially inhomogeneous permittivity bounded by a homogeneous medium. The method is well suited for application to boundary value problems where conventional Green's function techniques or expansions in series of known functions cannot be used since it works directly with the coefficients of a particular set of differential equations. The only theoretical restriction on the permittivity function is that it ust be non-singular. Numerical results were obtained for some permittivity models as a demonstration of the application of the method. (Author).
This dissertation presents procedures for implementing high order boundary conditions in time and frequency domains for solving exterior problems governed by the Helmholtz equation and the wave equation exterior to a perfectly conducting scatterer. Solving problems governed by two and three-dimensional wave equations in exterior domains is a complex task. There are techniques to reduce the computational complexities; one technique is On-Surface Radiation Boundary Conditions (OSRBC). There has been a recent interest in revisiting this technique for two and three-dimensional problems. In this research, we explore the implementation of a new high order OSRBC based on the high order local boundary conditions introduced in for two and three dimensions to solve the wave equation in exterior domains. As will be seen later, the OSRBC implementations require normal derivatives of the scattered field on the surface of the scatterer. For the two-dimensional case, we develop a Fourier spectral method based on discrete Fourier transform to find the normal derivative of the electromagnetic field on the surface of the scatterer. The method involves transforming the high order time dependent local boundary conditions to frequency-domain and implementing it on the surface of the scatterer. The normal derivative of the scattered field is needed for applications such as the calculation of the radar cross-section and the surface current. We consider the two-dimensional problem for a perfectly conducting scatterer with arbitrary cross section. The numerical implementations and their performances for a wide range of frequencies are demonstrated and compared to the frequency-domain integral equation for the scattered field. The advantage of the new method is that the On-Surface Radiation Boundary Conditions (OSRBCs) is applicable to a wide range of frequencies. A series of numerical tests demonstrate the accuracy and efficiency of these conditions to a wide range of frequencies. Both the exact solutions, as well as the high order local boundary conditions solutions, are compared. For the two and three-dimensional time dependent wave equations cases, we simulate exact solutions in a large exterior domain because explicit solutions are not available. The implementation involves a new novel approach based on bilinear transformation, which simplified the implementation process and lead to higher accuracy compared to the different types of finite difference schemes used to approximate the first and second order partial derivative in the new high order OSRBC and the auxiliary functions that define the high order boundary conditions. A series of numerical tests demonstrate the accuracy and efficiency of the new high order OSRBC for two and three-dimensional problems. Both the long domain solutions, as well as the OSRBC solutions, are compared.