radiation boundary problem

in desighning stacked patch anteena

1. substrate with patch
then on top of this another substrate(air)
t hen again a substrate with patch.....



but when i assignes radiation boundary using box which i made of dimension from 1st substrate to above the top patch and assigned radiation boundary hfss gives error that the first patch perfectly electric boundary and radiation boundary overlap......

whats the reason and how to remove it.....plzzzz help urgent...?

help me yaar..long time i posted it

Better to post your file here so that we can know your problem better.