aperture coupling in ads

can anyone tell me how an aperture can be created in a substrate layer using ads.......so that a microstrip antenna can be fed by aperture coupling technique....plz

This is bit complicated for beginners.
Are you beginner or expert in Momentum modeling?

Added after 20 seconds:

I mean you need more guidance if beginner.

i just tried to use a layer called hole and made it a via in the substrate layer......and changed its property to be freespace by changing permitivity..........is this right or is there any other procedure........but am not getting any changes in results.....

Added after 1 minutes:

am not an expert but have designed many other multi-layered structures using ads

You can use any layer but must be properly set in the substrate definition.