how to calculate radius of circular patch antenna?

Hello all,
I know following formula
fr= Knm * C / 2* pi* ae* sqrt(er)
My question is if I want to fabricate antenna for 2.4 GHz then I'll get ae using above formula. But how to get actual patch radius a? Plz reply.

see balanis book chp "Microstrip[ Antennas". There is an example for that also

Send me resonant frequency. I'll let u know actual patch radius.

Added after 2 minutes:

Actually there is no such formula to determine actual radius. We have to solve for different values of a and chk out value of ae with calculated one. then we can decide a if match found. I have written program in MATLAB which is helpful to calculate a.

hiii can you please send me the matlab code for the circular patch . urgent! plz..........