Thanks a lot.
I have another question, you know that when simulating antenna in HFSS, we need to set a radiation boundary(e.g. A air box enclosing the radiation objects). The lumped port set in the air box will contact the air on one side and contact the radiation object(e.g. TEM antenna) on the other.
Therefore there are reflections on both sides of the lumped port, then the S11 we get represents what, the reflection between the lumped port and the antenna, or the one between the lumped port and the air?
Looking forward to your reply!