Perfect E boundary HFSS

Hello

I m a new user of HFSS, I try to simulate an antenna

When I assign a perfect E boundary to the top face of my antenna and ground plane I get an S11=-16 dB that is correct but when I don't use it I get S11=-10 db..

Am I obliged to use this boundary? What does it change in my design? does it have any influence in radiation pattern?

Thank you for your help

yes you should apply pec boundary for metallic surfaces.

Does it change somthinhg in the radiation patern?

yes it should.

My antenna conductors are made with copper (PCB 2 layers)

In this case all the conductors faces must have perfect E boundary or just the upper and bottom faces?

It is better to have all faces assigned pec.

Is it the same thing, if I choose as material perfect conductor instead of copper?

no it is not the same. perfect condusctor usually doesn't take metallic losses into account.

To resume, for the design of a copper antenna, I choose copper as material I design the condcutors and after that I choose all faces and I assign perfect E boundary for better simulation

Is that right?

or you can assign material pec instead of copper. that would be faster. It is up to you.

But you have just said that it wasn't the same thing

using a metal takes into consideration losses. using pec instead is much faster. The results are not the same but are pretty close to each other.
Regards.

Thank you moh.haroun for your replies

you are welcome pal.