inverted f antenna design

Hi guys!

I am designing an antenna for zigbee applications.
I am looking at antennas from different makers and simulating them just to have a basis for my design.
I think i have a problem with my setup in HFSS. I do not get the published results. I mean it is not even close.

Could you please review my setup and give comments or advice on how to implement this?

Thanks a lot!

ps. I attached my HFSS file and the reference antenna from TI
pps. HFSS file extension cannot be attached? why? just curious...

i dont have hfss at the moment but:

1.What kind of port are you using?(if its a wave port did you made it at the right dimentions? matched?)
2.what kind of boundary conditions are you using?
3. did you left enough space between the structure and the boundary conditions?