AWR1642BOOST: Enclosure for AWR1642

Hello,

I am wondering what materials will allow the 76-GHz-77GHz waves from the AWR1642 to pass with minimal reflection/attenuation. We were thinking of using either polycarbonate or polypropylene. I know car bumpers are usually made of polypropylene but I would prefer polycarbonate because it is readily available and extremely tough. Also, what thickness should we be using? Our goal is for the enclosure to not interfere with the radar.

Thanks,

Ethan