Help on HFSS simulation for horn antenna.

Hi all,
I am a beginner,and the first time to simulate antenna.I met a problem,indicated Warning - Boundary 'Rad1', Boundary 'WavePort1' : Boundaries overlap. Attached as bellow.
Anybody can help me?
Thank you in advanced.

Your boundaries overlap and the port will take precedence. The problem should run just fine. The warning is just that, suggesting you look at the overlap in case it resulted from an error.

I expect that your port is somewhere in the middle of RAD1 boundary.

(I didn't open your model to make sure this is the problem. Look the boundaries over to see if they are as you intended and try to solve the model.)

I used HFSS 9.0 simulate.and attached the document FYI.And the above attached file can be opened with Winrar.

You can look at the Attachment file. This's an example of horn-simulation.