Mounting GPS ceramic patch antenna (Passive) on double sided PCB

I want to mount GPS ceramic patch (passive antenna) on a double sided PCB. Feed point will go through the PCB and will be soldered on bottom layer. Top layes will provide ground plane for the ceramic patch.

I found that ceramic patch is having two metal layers on both the sides. Top side metal layer is the patch to which feed point is connected. Bottom side metal layer is having the adhesive necessary to fix it on top layer of PCB.

Please help me understand what is the role of metal layer at the bottom of patch which is after mounting on PCB not connected to ground (simply floating).

Maybe that's capacitive coupling to the ground below, if the adhesive (and thus capacitance) is well defined?

Hi,

Isn′t there a datasheet, design note, manufacturer information?

Klaus