FR-4 Layers with AWR Microwave Simulation!!!!!

[Sara88]

I have a simulation problem with the defining the layers.

- I'm using FR-4 board.
-Operation freq. 850-900MHz.
-Return Loss at least -6dB
-Dipole Koch curve antenna.
-AWR Microwave 9.05

(1) i followed one of the examples and i followed it and i got my expected results from the graphs. (U can see the following output layers if there's any errors)

i used a top_air and bottom_air with thickness of 35mm. But my supervisor said how are you gonna build it like that.!!

(2) And in the following figure is my drawing of 3rd iteration of Koch curve dipole antenna,


(3) Finally i got these output graphs of S11


----

I asked Mr. Manju. and he said the top air should be 10 times the height of the antenna. But i'm not getting any good results.

- Layout


- Output Graphs


You can notice that i can't get to required return loss & freq.!

Any Suggestions!!!!!!!
Thanks