Here's some info I ran across on the Internet while researching police radar one day. There have been several posts (a couple recent ones too) about police radar. It's interesting reading. Or maybe I'm just entertained too easily.
http://home.earthlink.net/~bootou/3si/RADAR.pdf
PS - I up'd the file but didn't test. Please let me know if it is corrupt/incomplete. It is case sensitive apparently.