Modeling of fine geometric details and singular field regions in TLM




Tardioli, Giampaolo

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Numerical modeling of electromagnetic fields is becoming an important topic in such diverse areas as microwave and RF engineering, antenna design, bio-electromagnetics, and electromagnetic compatibility and interference (EMC/EMI). Among several techniques, time-domain schemes are of particular interest, due to their high flexibility and ease of implementation. This thesis is focused on the Transmission Line Matrix (TLM) method, based on a space and time discrete formulation of Maxwell's equations. The objective of this thesis is to develop, implement and test a number of techniques aimed to the enhancement of the accuracy of the method without increasing the computational load. The link between the electromagnetic theory and the TLM updating equations is first investigated, creating a solid background for the implementation of hybrid schemes characterized by better accuracy. The problem of coarseness error is in particular addressed. Two methods are proposed and analyzed. In the first approach the knowledge of the relationship between field equations and TLM equations is exploited to incorporate the static field behavior in the vicinity of singularities into the three-dimensional TLM mesh. Secondly, the field distribution around a corner is represented in terms of an equivalent circuit derived from a quasi-static approximation of the Green's functions for an infinite conductive wedge. As a result, relatively coarse TLM meshes, in combination with hybrid schemes, can be used to obtain highly accurate results, within the dispersion error margin, across a wide frequency range. By taking advantage of these techniques it is possible to incorporate more information of the structure under study into the TLM solution, thus creating an accurate and efficient CAD tool.



Telecommunication lines, Electrical engineering, Electromagnetic theory