Problem with Ansoft Designer:Could you help me?

Hi, I've a problem with Ansoft Designer...
I've simulated the structure in attachment but instead of the expected capacitive behaviour it returns a S11 >1. Why?What's wrong?
Could anyone help me?
Thanks in adv.

Since there is no ground plane layer, you need to explicitly set the port reference. To do this, create a little rectangle on the plane below the port. Select an edge of this rectangle and then select the "Add Reference" option in the port options.

Hope this helps ...