Analysis of electromagnetic scattering from anisotropic impedance boundaries

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Doctoral thesis (article-based)
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Analysis of electromagnetic scattering from complex surfaces is an often encountered problem in electrical engineering. Solving such problems is usually difficult, and generally numerical solution methods are needed. Impedance boundary condition (IBC) can often be used to simplify the original scattering problem, if only the fields outside the scatterers are of interest. In this thesis the focus of the research has been on the analysis of scattering from anisotropic impedance surfaces. The research was divided into two parts. The first part concentrates on the theoretical analysis of scattering using complex boundary conditions. The Perfectly Anisotropic Boundary (PAB) is defined and a possible realization for it is introduced. Similarly, a realization for the previously introduced Generalized Soft-and-Hard Surface (GSHS) is introduced. The scattering properties of these boundaries are studied, especially regarding the polarization transforming properties. The second part of the research concentrates on the numerical analysis of scattering from anisotropic impedance boundaries. Surface integral equation formulations for the Soft-and-Hard Surface and a specific IBC surface are presented and the scattering properties of these surfaces are studied. The second part of the research also necessitated the study of the accurate numerical integration techniques, and new results regarding these are given. In scattering computations the number of unknowns often grows beyond practical limits due to the electrically large size and the complex nature of the studied objects. Thus, more efficient computational methods are needed. The Multilevel Fast Multipole Algorithm (MLFMA) is a very popular such method. In latter part of the thesis a novel and efficient way to compute the translator operator in MLFMA is introduced.
anisotropic impedance boundary, electromagnetic scattering, surface integral equations
  • [Publication 1]: Ismo V. Lindell, Ari H. Sihvola, and Ilari Hänninen, Perfectly anisotropic impedance boundary, IET Microwaves, Antennas & Propagation, Vol. 1, no. 3, pp. 561-566, 2007. © 2007 The Institution of Engineering and Technology (IET). By permission.
  • [Publication 2]: Ilari Hänninen, Ismo V. Lindell, and Ari H. Sihvola, Realization of generalized soft-and-hard boundary, Progress in Electromagnetics Research, Vol. 64, pp. 317-333, 2006. © 2006 EMW Publishing. By permission.
  • [Publication 3]: Ilari Hänninen, Matti Taskinen, and Jukka Sarvas, Singularity subtraction integral formulae for surface integral equations with RWG, rooftop and hybrid basis functions, Progress in Electromagnetics Research, Vol. 63, pp. 243-278, 2006. © 2006 EMW Publishing. By permission.
  • [Publication 4]: Ilari Hänninen, Mikko Pitkonen, Keijo I. Nikoskinen, and Jukka Sarvas, Method of moments analysis of the backscattering properties of a corrugated trihedral corner reflector, IEEE Transactions on Antennas and Propagation, Vol. 54, no. 4, pp. 1167-1173, 2006. © 2006 IEEE. By permission.
  • [Publication 5]: Ilari Hänninen and Keijo Nikoskinen, Implementation of method of moments for numerical analysis of corrugated surfaces with impedance boundary condition, IEEE Transactions on Antennas and Propagation, Vol. 56, no. 1, pp. 278-281, 2008. © 2008 IEEE. By permission.
  • [Publication 6]: Ilari Hänninen and Jukka Sarvas, Efficient evaluation of the Rokhlin translator in multilevel fast multipole algorithm, Helsinki University of Technology, Electromagnetics Laboratory Report Series, Report 485, Espoo, Finland, 13 pages, November 2007. IEEE Transactions on Antennas and Propagation, accepted for publication with minor modifications. © 2007 by authors.
  • [Errata file]: Errata of publication 3