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.....