边界

littleant

What is the difference between "open" and "open add space" if shapes touch the boundary? (Faq #102)
) ^; c/ o! K; W) A. R! dThe PML "open" boundary operator extends the cross section found at the bounding box to infinity, thus  an inifite ground plane can be simulated for example. Therefore if you want to model a finite structure, it should not touch the open boundary. The "open add space" boundary is a very convenient way to introduce an additional spacing that is sufficiently large to guarantee correct operation of the open boundary operator.

When and how to use conducting walls? (Faq #107)
Conducting walls are most helpful if the structure under investigation is non-radiating (e.g. straight microstrip lines) and cost-effective closed boundaries instead of the PML shall be used. In contrast to electric/magnetic boundaries unwanted box modes can be suppressed after introducing small conductivities in the order of 1E3. We recommend to check all results carefully and to adjust the setting if necessary.
1 T$ z% k3 g% h8 F- M
Can instabilities be produced by wrong settings for the PML boundary? (Faq #108)
8 u/ b9 B% d% cTo ensure the proper function of the PML, a certain distance between the source of radiation and the bounding box as well as a resonable thickness/grading of the PML layer is necessary. Otherwise parts of the energy leaving the calculation domain might be reflected instead of being absorbed. This can cause inaccuracies or in rare cases numerical instabilities.

% ]8 u. c7 v( c( s" Y) sInstabilities due to the PML typically come up at a late stage of a calculation. If problems like this are observed, please consider to increase the size of the bounding box. We alternatively recommend to reduce slightly the "Factor for active comp." which is multiplied to the active components of the PML boundary.

yin123

边界