non-symmetrical Radiation pattern of a square patch antenna

Hi to everyone

I have a question that troubles me a lot and would be grateful if I could get a little help.

I've designed a simple square patch antenna at 60GHz in CST (attached), frequency domain.
The problem that I face is that I can't get the maximum gain at broadside. maximum is tilted by 30 degrees.
I changed dimensions of the patch, substrate but no change.

Does anybody have a clue about what's going on?

Thanks
Yannis

Hi gouzou,

Based on the image you posted, the patch is microstrip fed, and therefore is not physically symmetric. Why would you expect the pattern to be exactly symmetric?

You can probably mitigate most of this by increasing the size of the dielectric and ground plane. Another possibility is that you are exciting more than one mode (since the patch is square). Is there a reason its square? If not, consider making it rectangular.