Perfect Boundary Approximation and Thin Sheet Technology
The Perfect Boundary Approximation (PBA) is used for the spatial discretization of the structure. The simulated structure and the electromagnetic fields are mapped to a hexagonal mesh. PBA allows a very good approximation of even curved surfaces within the cubic mesh cells. This works very well as long as the approximated structure is greater than the cell size of the mesh. For PEC structures where details are lower than the method’s resolution, the Thin Sheet Technology (TST) enables more than one non-PEC region within a single cell.
Both these techniques help to avoid extremely small mesh steps and thus positively influences the total simulation time.
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A normal PBA mesh cell face with a single non PEC area. |
TST allows to have two non-PEC areas. |
A cell area with more than two non PEC areas (critical cell) must be filled completely with PEC material. |
Mesh View of critical mesh cells that have been expanded with PEC. |
However, if there are more than two PEC areas in one cell, or if there is one single PEC area that is completely inside of a mesh cell face, the entire critical face or cell must be filled with PEC material. These critical areas / critical cells are then visualized in the mesh view.
PBA and mesh cell size
This works very well as long as the approximated structure is greater than the cell size of the mesh. Because, as in every discrete systems, the resolution of the method is limited by the sampling width. This means, that small details of the structure will be modeled accurately only if the mesh cell sizes are smaller than these details.
If TST is switched off, all critical cells/areas area expanded with PEC.
See also
Mesh View (Hexahedral), Special mesh properties, Hexahedral Mesh
