Absorbing boundaries in frequency domain TLM method and their application to analysis of planar structures.

摘要

For the first time in literature, the concept of absorbing boundary conditions is introduced to the Frequency-Domain Transmission Line Matrix (FDTLM) method, thus extending its scope of analysis to open and radiating microwave structures. Three different approaches are considered in this thesis: Zero-Reflection Termination (ZRT), Berenger's Perfectly Matched Layer (PML), and anisotropic PML. The ZRT technique is the simplest one of the three. It is specific to the TLM method because of its unique discretization mesh which is a 3D network of transmission lines. The absorbing boundaries are simulated simply by setting the reflection coefficients to zero at the outer branches of the mesh. Therefore, no additional nodes are needed for modeling the boundary, which is the main advantage of this technique. Although assumed perfectly reflectionless, numerical reflections from ZRT boundaries exist due to the finite discretization. These reflections cannot be reduced, but their effects can be decreased. (Abstract shortened by UMI.).