substrate height of patch antenna

HAI ALL,

I have a doubt about substrate height of the patch antenna...
If we use substrate material as FR4(dielectric constant=4.4) ..and while calculating the antenna equations how can i take the "Height", if the pcb and the ground plane is separated with air gap ? Is the substrate height is "thickness of FR4" or "thickness of FR4+air gap"? and is there any change in dielectric constant ?

If the height is small relative to wave length, you can calculate an effective height for the layered dielectricum. e.g. H(eff) = H(FR4)/4.4 + H(airgap)

Thanks for your reply FvM.....