How to setup the airbox in HFSS for patch antenna with finite ground plane?

Hi

If you have a patch antenna with finite ground plane. How to setup the airbox correct?

I have used minimum

/4 as a distance to my antenna structure.
But lets say you have an antenna with a very small ground-plane and you still need the

/4 as minimum distance. Then there is a gap between the antenna and radiation box.
Should this be filled with a radiation plane?

Hope this make sense

Thank you

"But lets say you have an antenna with a very small ground-plane and you still need the /4 as minimum distance. Then there is a gap between the antenna and radiation box. "


I don't see how you make a gap here. If you antenna is smaller, then your airbox/rad boundary) is smaller too -> less memory needed ;)

you do not really need a space between the bottom of your ground plane and the bottom face of the radiation box -

on the edges of the ground plane, you should definitely put the lambda/4 distance to the side faces of your radiation boundary. Well, not up to lambda / 4. For your patch antenna there might be radiation to the sides of the ground plane. Kinda like a parachute shape.

OK, but then you do not have radiation boundary around your structure. Will that not give an error in your results?

you will, but the radiation boundary is useless on the face underneath the ground plane. Am I answering your question wrongly?

You have several options and can use either radiation boundaries or a PML. Both have advantages.

The latest guidance from Ansoft is to use a PML and the set up differs slightly when the object touches the boundary vs. when it does not. Read the on-line help sections and if you need additional help call one of their application engineers.