For the mmWave Human Detection Sensor Kit, what is the radiation pattern for the antenna relative to the enclosure? i.e. what direction should the box be facing to best detect motion?
Here mmWave Human Detection Sensor Kit | Seeed Studio Wiki it says " 1. The network function of the XIAO ESP32C3 requires the use of an antenna. If you want to install a Grove module, try not to change the position of the antenna. The antenna is placed on the back of the baseboard by default, which ensures a good signal and does not interfere with the radar work."
Apologies if I was unclear. I am referring to the 24GHz mmWave antenna, not the 2.4GHz wifi antenna.
Hi there DougLife and Welcome,
If you watch that NON academy award worthy Install video recorded in hyper speed on the wiki.
He (the subject’s back) he waves at the three Holes in the front of the unit.
More Seriously though 
check out the User manual Section 4.
The only issue is if you install a Grove connecting sensor inside that you make sure the RADAR board is Higher (1mm) and that 2 to 5mm space behind the cover with the holes.
4. Antenna and housing layout requirements
PCBA: Need to keep the radar patch height ≥ 1mm higher than other devices
Housing structure: need to keep the radar antenna surface and the housing surface
have 2 - 5mm distance
Housing detection surface: non-metallic housing, need to be straight to avoid bending
surface, affect the performance of the whole sweep surface area Performance
As you know the WIFI antenna is on the back so mounting is important.
the actual antenna’s are on the top of the PCB.
Look over section 2 for a “working Principle” and why the position of this thing is key to good and reliable data from it. IMO
HTH
GL 
PJ
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