Particularly with software-defined-radio, it has become feasible for electronics enthusiasts and engineering students to build their own radar.
Here are a few projects.
6 GHz singleboard FMCW radar, 100 meter range with Github
MIT OpenCourseware coffee can radar
8 GHz radar for UAV: PCBs and software with report
6 GHz radar Gerber files and Matlab
Raspberry Pi-based radar for measuring vehicle measurement: description, parts list, software
Schematics, PCB, software for another FMCW radar
HF imaging radar using Red Pitaya
University coffee can radar 2011
First coffee can radar from 2006
Breathing and heartbeat detection radar
Python code for correcting FMCW non-linearity effects
Coffee can radar: forward model and estimation code (including SAR)