how to realize a perfectE plane!

while simulating,I set a horizontal stripline connected with a vertical perfectE plane at the end of the stripeline. I have thought that I could make a big ground plane conected with other ground plane to take place the perfectE.but the result is very terrible.I have no idea of how to realize the perfectE I have assumed.Who can help me,thanks very much!

Hallo
Before assigning the perfect E plane be sure that the electric field will be tangential to that plane otherwise u could have trouble..