Far-field predictions from near-field measurements using the three dimensional finite element and boundary integral methods.
|Title:||Far-field predictions from near-field measurements using the three dimensional finite element and boundary integral methods.|
|Abstract:||Characterizing antenna designs in their operational modes has been a classic problem for electromagnetic engineers for many years. The far-field pattern is of great importance in antenna characterization, but in many cases, it is impossible or at least impractical to measure directly. This thesis presents a numerical technique whereby near-field measurements can be transformed into far-field solutions. The finite element method (FEM), and an integral formulation, solution to the scattering problem, are used separately to solve the open boundary wave propagation problem in three dimensions. The near-field of a known source is sampled over a mesh of points and used as data for both methods. The integral formulation yields the far-field solution for homogeneous problems without the need for space discretization. The finite element method uses tetrahedral elements for discretizing the domain of interest and second order interpolation functions. It is complemented by the application of an absorbing boundary condition (ABC) which allows truncation of the domain. Classical ABCs of the local type are applied to the three dimensional problem. A new non-local ABC is obtained from the integral formulation and is coupled to the finite element approach. Computed field strengths obtained with the different approaches are compared with the analytical results obtained from the excitation source's analytical expression. The agreement was very good with maximum error percentages of about 10% for the FEM method and 2.5% for the integral formulation.|
|Collection||Thèses, 1910 - 2010 // Theses, 1910 - 2010|