return loss question

can someone please look at the attached return loss graph and may be explain to me the behaviour. i was analysing an aperture coupled patch and i got this graph which to me seems it has two resonant frequencies. i wasn't intending to have dual polarisation since i have the ussual one feed. my design frequency was 2GHz. could this be normal?

Dear,
Sorry, In advance it seems that the question at hand have no enough info. to answer ACCURATELY. but I will try.

I first thought that there is a problem in your simulation setup, if you can add it
I can check it. may be will shed some light to the problem.
but after seen the graph and found that the two resonant are close to the design frequency, I think that there is a problem in the design values, normally when you design for large bandwidth antenna in microstrip, you make two resonant frequency near the design, and if there is an inaccuracy in these values -design- , I think to the best of the info provided that the design needs optimization.

please check this article that takes about the U-shaped slot, to get a wide bandwidth antenna, check figure 2 and see the two resonant frequency.
"http://www.mwrf.com/Articles/Index.cfm?Ad=1&ArticleID=10587 "
maybe this is will answer your question maybe not, that why I apologized in the first place. to be more of a help here add more info on the exact design and the simulation file.