Finite element-based hybrid electromagnetic methods for electrically large, complex scattering and radiation structures

When electromagnetic radiation systems are placed on or near highly conducting structures, the radiation characteristics of the systems are significantly influenced by the structure. To take into account the proximity effects in the finite element formulation of a Helmholtz equation, two major numerical issues should be resolved in a multidisciplinary manner: first, obtain an approximate Green's function of the structure; second, minimize the total degrees of freedom in the system of equations. These numerical issues are interrelated and compensatory in the solution process. In this dissertation, a finite element-based hybrid method has been proposed to accommodate these numerical issues in the analysis of electrically large and geometrically complex scattering and radiation structures.; Initially, the hybridization between the finite element method and the method of moment (FEM/MOM) is formulated and implemented for two- and three-dimensional structures. This hybrid method is highly accurate and versatile but limited to radiation systems whose dimensions are small in terms of wavelength. To overcome such limitations, a hybrid method which combines full-wave analysis techniques and high-frequency asymptotic techniques is developed and then supplemented with an iterative algorithm. The method begins with the decomposition of a given computational domain into interior and exterior domains by invoking the field equivalence theorem. For the interior region, the FEM/MOM is formulated to account for the internal interactions involving material and geometrical complexities. As for the exterior region, high-frequency asymptotic techniques are applied on electrically large structures to produce equivalent currents or fields. Finally, the equivalent currents or fields are incorporated into the FEM/MOM as an effective source using a boundary integral formulation. The presented technique is validated with numerical simulations to demonstrate the accuracy and efficiency of the method for two- and three-dimensional scattering and radiation structures.