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

I built and extended this for a college project years ago: https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/index.htm 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)).