What does the padding do?

[Farhana]

Hello,

Can anyone please suggest why do we need to put the extra padding around the simulation region? Is it only for calculating field values at those points outside the bounding box of my objects?

I am simulating an antenna. If I only need the reflection coefficient, then is it necessary to have an extended padding? Can I put a very small padding, e.g. 1mm, which is much smaller than the default lambda/8 padding size for broadband setup? Will it be an issue if the grid contains the antenna only, i.e. such a small padding around the antenna?

Thanks.

[sayimgokyar]

@farhana
Hi Farhana,
It is safe to put extra padding to avoid errors due to boundary conditions. Especially for antenna simulations, you should avoid fictitious reflections from the open boundary conditions (absorbing boundary conditions, ABC, or perfectly matched layer, PML).
However, if you have a directive antenna, you can decrease the extra padding layers in the directions with lower radiation, and also you may use less PML layers in these directions as well. For the main beam direction, you should definitely use extra padding and high number of PMLs. These are my two cents for you. I hope these may help.
Best, Sayim