Hi ing_2012,
The issue seems to be described by the warning you're getting. The simulation is not converged, so the solution will be invalid.
Under the Analysis menu on the left, select the simulation setup (image of a magnifying glass) by double clicking it. Under Adaptive Solutions, set maximum number of passes to at least 20, and maximum delta S to 0.01. You can also set up a seed mesh (assign mesh operation) to the antenna substrate to do less passes.
Good Luck