MPA for 1.8GHz to 2.45GHz

Hi all.

I'm designing a MPA to operate btw 1.8 to 2.45Ghz. I wanna use stacked structure with slots along with coax feed. Pls provide some ideas for designing it. I need formula to calculate dimensions of slots. help me

I'm a B.E student doing project on patch antenna.. Experts pls help. I can design a single band MPA but how to create dual resonance. Is everything trial n error process or is there any standard procedure in creating slots?