background material meaning

Hello everybody,

Let assume that I have simple dipole antenna on the top of kind of substrate. All boundries are open unless from the top it is open "add space".

What does mean if I change the permittivity value in background material from "1" to the same value of the permittivity of substrate ?

Regards

it means that your medium around the antenna is not air any more. It is the material you have just defined :)