I built and extended this for a college project years ago: https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar...

It's not a bad place to start. And cheap if you want to build your own too (some third party even sells the "cantennas" so you don't have to fiddle with tuning that part (which is kind of infeasible without a network analyzer anyway)).

Thanks Jach

A good place to start would be the paper's references.

I went to the website and casually looked down. There was a "see also" section. Browsed through those and remembered Prof Dina Katabi demonstrating this concept before Prez Obama in the White House, few years ago.

Will go through references too :)

I come at this entirely from the ML side, not the hardware one, so that stuff is a mystery to me :-)