I need guidance regarding using a millimeter wave sensor for human detection.
Do you mean an off the shelf commercial product like the ones from Aqara and Tuya? If so, see the community FAQ.
As always, the purpose of this forum is for people using the Samsung SmartThings ™ Home automation platform to help others with ideas and troubleshooting, so all of the questions and answers are assumed to be in that context.
FAQ: Best mmWave Sensor to Use with ST? (human presence sensor/occupancy sensor)
If you are trying to build your own device to work with SmartThings, we’ll need a few more details. 
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