| This dissertation work is primarily concerned with the numerical simulation of radiating structures using the time-domain finite-element method (TDFEM). As far as radiation problems are concerned, three major numerical challenges are addressed in this thesis. The first one is the truncation of the unbounded free space for the open-region problems. The second one is the accurate modeling of the antenna feeding structures, which is of great importance for the characterization of the antenna impedance and scattering parameters. The third one is the necessity to handle very large computation domains, which is often encountered in the simulation of electrically large antennas and large antenna arrays. In this thesis, new methodologies and techniques are developed to provide potential solutions to aforementioned challenges and enable the TDFEM as a versatile and efficient simulation tool in the analyses of a variety of antenna structures, especially large antenna and antenna arrays.;The dissertation first introduces the basics of an implicit TDFEM formulation. Then it focuses on the radiation problems and describes the truncation of open free space using the perfectly matched layers and the modeling of the waveguide feed using the waveguide port boundary condition. To handle large computation domain efficiently, a novel dual-field domain decomposition (DFDD) method is developed for the TDFEM. The method is then applied to the simulation of large antennas and antenna arrays. For large finite arrays, a specialized array solver is developed for an even better efficiency. Finally, an explicit TDFEM is derived from the DFDD and its advantages and disadvantages are discussed. |
