Patch antenna substrate selecting criteria

[AmmarAli]

Hi
I'm working on designing a 2.4GHz antenna array for WiFi applications, I want to know what are the general criteria for selecting the substrate ?

Thanks a lot

 

[nesan]

choose FR4 is widley used by everyone

 

[Bob60]

Better without substrate.
Maximum of efficient.

 

[gujjulag]

If we don't use substrate, then how to suspend the patch in the air.