Re: Dimension (IE3D)
Hi, Chest:
There are 2 problems in your finite ground model.
1. You put a polygon on z = 0 while you are still defining z = 0 as an infinite ground. By IE3D definition, the polygon becomes a slot on the ground.
2. You need to use differential port (+1, -1) between the feed line and the finite ground.
Attached is the corrected geometry. The result is almost identical to the one with infinite ground plane. For patch antennas, ground plane size does not affect the input impedance much. It is not true for some other types antennas. If the antenna has many 3D features, the ground plane size will be important. Ground plane size is also very important to slot antennas even they are low profile. The reason is that the field is not concentrated near the proximity of the main part of the antenna like a microstirp antenna.
Regards,