HFSS Questions about S11 and Gain Pattern

[metrika]

Hello, I designed an antenna to work in 3.5 GHz and 5.8 Ghz and have few questions about the results.

For the S11, do you know why there is a point with low S11 around 7.25? And for the gain pattern created for 5.8 GHz why there is a low gain arround theta=0 ? More importantly how can I solve these issues? Thank you for any help.

 

[PlanarMetamaterials]

I assume this is a resonant patch-like antenna.

For the S11, do you know why there is a point with low S11 around 7.25?

It's probably some other resonant mode of the antenna. Have you investigate the radiation patterns/current patterns?

And for the gain pattern created for 5.8 GHz why there is a low gain arround theta=0 ?

Because that's how your antenna works. I can't say more without supporting information about the antenna's resonant modes.

More importantly how can I solve these issues?

Most likely through additional investigation.