Radar is kind of fun to get into, though 2 Ghz isn&#x27;t a very good frequency for (through-wall) imaging. <a href="http:&#x2F;&#x2F;ocw.mit.edu&#x2F;resources&#x2F;res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011&#x2F;" rel="nofollow">http:&#x2F;&#x2F;ocw.mit.edu&#x2F;resources&#x2F;res-ll-003-build-a-small-radar-...</a> has some SAR demos, and if you follow to Dr. Charvat&#x27;s website you can see he made a 10 Ghz system that images through concrete walls very well.