Very low efficiency patch antenna

[Salving]

Hello everybody, need help with next problem.
I'm designing patch antenna, freq - 2.6 GHz, using cst mws. The substrate is FR4. The problem is low efficiency i get, about 30%. I thought it was due to losses in substrate, but when i changed tg delta to zero, the efficiency stayed the same. Can anybody tell me how to solve this issue?

 

[flanello]

Can you provide more information of your antenna? For example the size or the height an perhaps a picture with your antenna feed.

 

[Salving]

I tried aperture-coupled, coax, microstrip line feeds and various heights of substrate but i couldn't get high efficiency.

 

[flanello]

Is the ground plane large enough?
You can also try to increase the mesh or use the adaptive sweeps.
And what do you mean with efficiency? The efficiency only of the antenna or the total efficiency of the antenna and the matching? E.g. what is your gain and your S11?

 

[Salving]

Is the ground plane large enough?
You can also try to increase the mesh or use the adaptive sweeps.
And what do you mean with efficiency? The efficiency only of the antenna or the total efficiency of the antenna and the matching? E.g. what is your gain and your S11?

No, matching losses arу not taken into account. Gain is about 2.5 dBi and return losses are very small(about -25 dB). But i get good efficiency with rogers substrate, but bandwidth is 1.45% so i'm no longer interested in patches for my frequency