Abstract
Large-scale three-dimensional (3D) electromagnetic simulations are commonly used as design and investigation tools in a wide variety of technological fields. It is not uncommon for both excitations and observation quantities to be expressed in terms of particular field profiles of feed waveguides. These may then be used to evaluate, e.g. scattering parameters. These field profiles must be obtained as a pre-processing task before the main simulation. Use of a theoretical field profile as an excitation to a discretised structure will typically cause a non-physical reflection. It is therefore more desirable in practice to use a field profile that is consistent with both the discretisation of the geometry and the 3D method of simulation. The authors present an approach to extracting these 2D field profiles from large-scale 3D unstructured meshes which are to be simulated with the unstructured transmission line modelling method. Discretised slices from the 3D mesh are extracted and incrementally extruded into a form suitable for consistent pre-processing. The impacts of all the parameters of the approach are investigated. Benchmarking is undertaken on both coaxial cable and microstrip waveguide feed structures showing that good quality results can be obtained straightforwardly.
Highlights
Large-scale numerical computational electromagnetic methods have rapidly evolved to become a mainstay of design and simulation activities in a broad range of disciplines, [1,2,3,4]
We demonstrate how to effectively extract particular 2D field profiles from a 3D meshed geometry which are necessary to specify a class of excitations and observations when using the Unstructured Transmission Line
This paper has presented for the first time a methodology for extracting waveguide mode parameters using the 3D Unstructured Transmission Line Modelling (TLM) approach
Summary
Large-scale numerical computational electromagnetic methods have rapidly evolved to become a mainstay of design and simulation activities in a broad range of disciplines, [1,2,3,4]. Second (Fig. 1b), shows a Lange coupler which is excited at one of its ports by a fundamental microstrip mode and its performance is characterised in terms of a 4-port scattering matrix, [7, 8] In both cases, the 3D simulation is being performed using an algorithm that discretises the problem space using an unstructured tetrahedral mesh. For example, an excitation is imposed in the form of a field profile which is not a waveguide-like eigen-solution of Maxwell’s equations discretised in exactly the same manner as that used by the 3D algorithm, a numerical impedance mismatch will occur. This corresponds to use of a power-voltage definition of impedance [21]
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