Trying a video on the iPad for the first time, so sorry if the camera is a bit clumsy. I think it's actually a little bulky and awkward compared to using a phone.
Here the voltage on the varactor is held constant, without any modulation, so the output frequency isn't being modulated.
The only thing that comes out from the mixer is the frequency offset of the Doppler-shifted RF reflected back from a target that is moving. In this mode, spatial mapping or rangefinding is impossible, but measuring a target's speed, like a police radar, is possible.
A stationary target produces no signal, no matter how close it is or what its radar cross-section is like. Much like the Tyrannosaurus that eats Gennaro in Jurassic Park, it can only "see" movement.
And I just realised there's a typo in the title.