Finite element modeling of electromagnetic radiation

Download
2007
Özgün, Özlem
The Finite Element Method (FEM) is a powerful numerical method to solve wave propagation problems for open-region electromagnetic radiation/scattering problems involving objects with arbitrary geometry and constitutive parameters. In high-frequency applications, the FEM requires an electrically large computational domain, implying a large number of unknowns, such that the numerical solution of the problem is not feasible even on state-of-the-art computers. An appealing way to solve a large FEM problem is to employ a Domain Decomposition Method (DDM) that allows the decomposition of a large problem into several coupled subproblems which can be solved independently, thus reducing considerably the memory storage requirements. In this thesis, two new domain decomposition algorithms (FB-DDM and ILF-DDM) are implemented for the finite element solution of electromagnetic radiation/scattering problems. For this purpose, a nodal FEM code (FEMS2D) employing triangular elements and a vector FEM code (FEMS3D) employing tetrahedral edge elements have been developed for 2D and 3D problems, respectively. The unbounded domain of the radiation/scattering problem, as well as the boundaries of the subdomains in the DDMs, are truncated by the Perfectly Matched Layer (PML) absorber. The PML is implemented using two new approaches: Locally-conformal PML and Multi-center PML. These approaches are based on a locally-defined complex coordinate transformation which makes possible to handle challenging PML geometries, especially with curvature discontinuities. In order to implement these PML methods, we also introduce the concept of complex space FEM using elements with complex nodal coordinates. The performances of the DDMs and the PML methods are investigated numerically in several applications.

Suggestions

Finite element modeling of electromagnetic radiation
Yılmaz, Asım Egemen; Kuzuoğlu, Mustafa; Department of Electrical and Electronics Engineering (2007)
In this thesis, quadratic hexahedral edge elements have been applied to the three dimensional for open region electromagnetic scattering problems. For this purpose, a semi-automatic all-hexahedral mesh generation algorithm is developed and implemented. Material properties inside the elements and along the edges are also determined and prescribed during the mesh generation phase in order to be used in the solution phase. Based on the condition number quality metric, the generated mesh is optimized by means o...
Design and implementation of microwave lumped components and system integration using MEMS technology
Temoçin, Engin Ufuk; Akın, Tayfun; Department of Electrical and Electronics Engineering (2006)
This thesis presents the design and fabrication of coplanar waveguide to microstrip transitions and planar spiral inductors, and the design of metal-insulator-metal capacitors, a planar band-pass, and a low-pass filter structures as an application for the inductors and capacitors using the RF MEMS technology. This thesis also includes a packaging method for RF MEMS devices with the use of “benzocyclobutene” as bonding material. The transition structures are formed by four different methods between coplanar ...
Magnetic resonance current density imaging using one component of magnetic flux density
Ersöz, Ali; Eyüboğlu, Behçet Murat; Department of Electrical and Electronics Engineering (2010)
Magnetic Resonance Electrical Impedance Tomography (MREIT) algorithms using current density distribution have been proposed in the literature. The current density distribution can be determined by using Magnetic Resonance Current Density Imaging (MRCDI) technique. In MRCDI technique, all three components of magnetic flux density should be measured. Hence, object should be rotated inside the magnet which is not trivial even for small size objects and remains as a strong limitation to clinical applicability o...
Analysis of coupled lines in microwave printed circuit elements
Piroğlu, Şefika Özkal; Dural Ünver, Mevlüde Gülbin; Department of Electrical and Electronics Engineering (2007)
Full wave analysis of microstrip lines at microwave frequencies is performed by using method of moments in conjunction with closed-form spatial domain Green’s functions. The Green’s functions are in general Sommerfeld-type integrals which are computationally expensive. To improve the efficiency of the technique, Green’s functions are approximated by their closed-forms. Microstrip lines are excited by arbitrarily located current sources and are terminated by complex loads at both ends. Current distributions ...
The dual reciprocity boundary element solution of helmholtz-type equations in fluid dynamics
Alsoy Akgün, Nagehan; Tezer Sezgin, Münevver; Department of Mathematics (2013)
In this thesis, the two-dimensional, unsteady, laminar and incompressible fluid flow problems governed by partial differential equations are solved by using dual reciprocity boundary element method (DRBEM). First, the governing equations are transformed to the inhomogeneous modified Helmholtz equations, and then the fundamental solution of modified Helmholtz equation is used for obtaining boundary element method (BEM) formulation. Thus, all the terms in the equation except the modified Helmholtz operator ar...
Citation Formats
Ö. Özgün, “Finite element modeling of electromagnetic radiation,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.