Few months ago I posted the following video from MIT Lincoln lab where drones were used to detect peoples cellphones in search and rescue scenarios.
I was testing my FMCW RADAR and I was receiving pretty good signal even when my transmit antenna was disconnected. Operating frequency of my radar is 2-2.5GHz so usually when I am testing my radar I turn off all the ISM band stuff in my home including my WiFi router. When I processed the recorded data in Matlab I found that it was my neighbors wifi router and knowing the layout of his house I could tell where the router was placed in the the house.
So I wondering if the same technique can be used to locate people trapped in buildings in a search and rescue scenario since most people keep their phone wifi on all the time when they are at home or office. ISM band RADARs are cheap to make and can be easily mounted on drones. Just a thought, your input will be appreciated.
Edit:
I forgot to mention the most important part. You can do a SAR sweep with radar using a drone and overlay that over the existing map and see where the signal is coming from.
Here the RADAR is operating in active mode and transmitting and receiving at the same time. Radar is on the ground.
So, we use the radar to listen we can locate the source.