Guilin Sun
Ansys Employee

I maybe confused by this description:


I guess you mean when you use PMP it diverges around 30,000 fs to 35,000 fs.If so, it is not dt factor issue.


Have you checked the time monitor spectrum before it diverges? It may have resonance not in the interested source bandwidth.

You may need to try 64 layer SttepAngle PML.

Divergence is subtle: KB gave two typical types of diverging: dt factor and PML. Other causes could be:

large mesh aspect ratio;

large diffraction angle

strong resonance outside of the interested wavelength range

Metal materials and SPP

The plane wave source can be closer to material interface a few meshs away.

But you can increase the PML distance to the material interface.

Please add a line monitor along the injection and see if there is any evanescent wave or SPP that has long tails to interact with PML.

Here is the original KB information moved to forum