ie3d software to design microstrip patch antenna

hi everyone...
how should i dig circular hole in the ground plane in ie3d software..i have make real part of the ground plane =0 and then dig a circular hole in d grnd substrate bt this is creating problem at the time of simulation as because the grnd plane is also acting as a dielectric substrate..so,how sud i simulate ..i am working in ie3d 10 version...PLS HELP..NEED URGENTLY..