After my results with the ultrasonic sensor in Week 8 I started looking into alternatives with regard to longer range sensors. I was initially very curious about the FAB inventory Time-of-Flight sensors, but many mentioned that it only worked well indoors up to 2 meters.
There are some commercial long range LIDAR Rangefinders and even 360 degree scanners. However, the rangefinder is $150 and the scanning LIDAR is over $400 which not only put them beyond my price range, but put it far above what I would want to leave on a bike.
I remembered a few years back reading a Hackaday post about DIY Radars and adding it to the list of projects I never got around to. It turns out the post was written by a Engineer at MIT's' Lincoln Lab and he even taught and IAP course on Radar.
From the IAP course and his website, it seems reasonable to build a Frequency Modulated Continuous Wave (FMCW) rangefinding radar for under $400. As cool as this sounded, this seemed slightly beyond the scope of the class and still suffered from the price issue. But, in the Hackaday post, he referenced cheap X-Band radars availible on Ebay and $10 in quantity FMCW radars from a Swiss company.
I have ordered both some inexpensive FMCW Ebay modules ($3) as well as the K-LC1a FMCW and K-LC2 (Doppler) Radars from RFBeam which are both about $10 in quantity, $25 per if you need to order just a few. The RFBeams have not gotten FCC approval but can be imported for test and evaluation purposes.
In the mean time I've been reading the documentation and figuring out the best solution to process the incoming data. I will update this page as I get further along with experimenting with the modules.