I wondered about that, too. There&#x27;s a worldwide ISM band at 5.725 to 5.875 GHz in which you can run radars.  But he says he&#x27;s sweeping from 5.2GHz to 6 GHz. That&#x27;s a lot of spectrum to be using. There&#x27;s lots of stuff in there, including satellite links and aeronautical radionavigation.<p>Here&#x27;s a similar project which is in the 5.8 to 6 GHz range.  With a little work, they could probably make it stay in the ISM band there. One big frustration of gigahertz RF work is that the test gear you need to see what&#x27;s happening costs far more than the project.  I tried to build a frequency-modulated LIDAR once, and ran into that.<p>[1] <a href="https:&#x2F;&#x2F;hackaday.io&#x2F;project&#x2F;1682-simple-low-cost-fmcw-radar" rel="nofollow">https:&#x2F;&#x2F;hackaday.io&#x2F;project&#x2F;1682-simple-low-cost-fmcw-radar</a>