I have tried to simulate a microstrip patch antenna. I got reasonable return loss and directivity. However, the simulated gain and radiation efficiency are not good. I think that the problem is from the way of modeling on the HFSS. I have attached the simulation file in the message. Can anyone tell me what is the problem of that model? Thanks.
But i've read once that adding a relatively high permitivity material above the patch (superstrate) would solve the problem, for my design it enhanced the gain but it reduced the bandwidth