Making of Dual Band antenna

Hello,
Can any one tell me how to make dual band rectangular Patch antenna for(2.45 Ghz and 5.Ghz or 2.45 Ghz or 3.2 Ghz) and i know we make some slot on patch but how to calculate its dimensions and shape?I want very easy and Simple design for Dual band as possible as it is...
thank you

Hello Chirag, yes by making slot in the patch you can get dual band characteristic but as I know there is no set formula for these slots. You just have to optimize its length and width to get the best performance.

Atcually i have designed at 2.45 ghz frequency now by introduving slot i get one fre. @ 2.45 ghz and second at 4.2Ghz but i want second frequency at 3.2 Ghz..
now how to reduce second frequency?
thank you for reply

Try to change the position of the slot in such a way that first freuqency should not be disturbed and you can work on the length and width of the slot also.