I was pretty surprised, until I realized that regular radar works essentially the same way. Usually you use two antenna spaced some known distance apart so you

I was pretty surprised, until I realized that regular radar works essentially the same way. Usually you use two antenna spaced some known distance apart so you can use Doppler to distinguish moving from stationary objects. The surprising thing is that it works so well. I guess I'll need to build a Faraday cage around my house now...