Problem with Rectangular patch antenna on silicon

I'm a begginer in using HFSS. I'm trying to design a rectangular patch antenna on silicon substrat. I don't know how much size must be the ground plane(my patch size is about 1mm^2)(for each ground plane size simulation, i obtained differenst results for S11). In simulation , an error message appears" [warning] Adaptive Passes did not converge based on specified criteria".

Does any one have an explanation, please help me

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

Thanks a lot, it works :) . Please have you any idea about the size of ground plane that i shoud make. I was working with ADS Momentum where there are no probleme of ground plane size .

The size of your ground plane depends on how large you are allowed to make your antenna. Typically, larger ground planes will result in less backward radiation and more stable and symmetrical radiation patterns. This means that you can obtain more directive antenna's if you increase your groundplane size. You'll see large fluctuations in the antenna's performance when the groundplane size becomes similar to the patch itself, however with some optimizing still good results can be obtained.