Help for Planar antenna for microwave imaging system

I design planar antenna for microwave imaging system 8mmX10.6mm by using HFSS software and I got result for loss gain which should be less than -10 for 3-11GHZ .

This pic shows conductor which has pink color and slot with white color

and this shows wave port with yellow color

here the result which should lesdd than -10

Any one can help to impove this design to cover 3-11 GHZ with loss gain less than -10