CST MWS modeling FSS with semi-infinite substate

Hi,
I'm using CST MWS 2009 to simulate FSS with semi-infinite glass substrate (n=1.56). How to set up the surrounding space? Any suggestion is grateful!
Zhang

Hi dear zhang
could you find how simulate your structure on the semi-infinite glass substrate?

Dear hosseincomm,
I have one idea about the semi-infinite substrate which isn't verified yet. Suppose you define a material with a height h, such as glass, below your FSS, and define the surrounding background materials's outer distance as zero, then you let your port Zmin shift into the glass. As a result, your Zmin Port lies in substrate. I'm not sure the influence of the two distance, the one is distance between FSS and Port, the other is between Port and the outer interface of substrate, on the simulation.

I think simulating a semi-infinite substrate that is different from the background (eg vacuum) is trivial since CST automatically recognizes what you want to do. Just set up a finite thickness of the substrate beneath your structure, eg going down to Zmin. In the x and y direction use the unit cell boundary conditions and in z direction use the open (Floquet) boundary conditions. I've checked this by comparing with analytical results for plane waves and it gave correct results, so it should also work in the FSS case (though I'm slightly suspicious about how the Floquet open BCs are implemented...). Also, CST doesn't allow you to use dispersive or lossy substrates which adds to the above suspicion... If the open boundaries are properly implemented (eg using a PML), this should not be the case.
Does anyone else have some experience with semi-infinite substrates in CST?

Thank you very much for your reply ~:)

Do you have any experience in semi-infinite substrate simulations? Do you know of any other way to do it?