Stacked microstrip patch configuration

Hi..I've design a stacked patch microstrip antenna..the lower patch (actually i used a meander line type structure) is coaxially fed and upper(parasitic) patch size is different from that of lower patch(meander)..resonant frequency of my lower patch is 1.3 GHz..When i use a stacked parasitic patch ,Bandwidth increases and the antenna is still resonating to 1.3GHz.. I think the resonant frequency of upper parasitic patch merge with the lower patch resonating frequency giving a wide impedance bandwidth
My question is "How to find out the resonant frequency of upper (parasitic) patch?" "How to prove that the resonant frequency of both patch merges with one another?"

Please anybody help..Its urgent..I ve to complete my project report so soon

Thanks :)