Multichannel Backscatter Communication and Ranging for Distributed Sensing With an FMCW Radar

This paper considers the adaptation of frequency modulated continuous wave (FMCW) radars for sensor data exfiltration in addition to their primary use in area surveillance. In particular, the application of wideband RF backscatter from semi-passive RF sensor nodes for simultaneous ranging and wireless telemetry uplink to an FMCW radar is examined. We present an upper bound on data communication rates for baseband-coded binary backscatter modulation given a particular sensor node density and radar parameters, as well as a method for line coding to mitigate stationary clutter. Proof-of-principle measurements using a brass-board S-band radar with center frequency of 2.45 GHz and 40-MHz bandwidth show the simultaneous ranging and demodulation of two sensor nodes at ranges of 15 and 33 m in a cluttered indoor environment. In this demonstration, a signaling rate of 10 kbit/s per sensor with a bit error rate below the measurable threshold of 4×10^-3 is achieved.