HFSS Simulation of restangular patch help needed

What is wrong in my simulation of patch?
Gain is too low.
The operating frequency of my design is 820 Mhz.
Help me please///
Here my patch..

Hi

First of all I can not simulate your design. There seem to be a problem with your port.
Second I would increase your Air_box in the +Z direction this would properly change the result.

Regards

I simulate design without problem.
I change size of airbox but it is not enough.Gain change from 0.02 to 0.28.And here my changing design

Hi

I have simulated your design and i seems to have very low gain.
I do not think you have specified it in dB.

hi
pls convert your file to.sm3 and check it in cst and see u far field usually HFSS have problem for lower frequency simulation if u simulate in CST i think u receive more than 1 dB

No it is does not help. And I increase frequency to 2.75 Ghz. And gain does't change. Frequencies of resonance are 0.82 and 2.75 Ghz.