I need hfss file of short backfire antenna designed to operate on 2.4 ghz.....

i need an hfss file of short backfire antenna that operates at 2.4Ghz....as i have made one in hfss but the dip comes on 2.8Ghz and i want it to be at 2.4Ghz....as i have tried alot but of no use...so plz help if anyone has short backfire antenna's hfss design in which dip comes at 2.4Ghz...than kindly share it...