Vibrational Radar Backscatter Communications

In this paper, we introduce a novel approach for backscatter communications using mmW automotive radar illumination of a vibrating transducer whose time-varying surface displacement is used to perform digital signaling. Radar backscat- ter communications, as exemplified by RFID tags, is typically limited to UHF frequencies due to the need for efficient transponder re-radiation of RF illumination. This has largely precluded backscatter communications at millimeter-wave (mmW) frequencies without the use of expensive retrodirective antenna arrays. This paper derives the effective communications channel model and optimum detector for M-ary vibrational radar backscatter communications (VRBC). Because of a wideband mmW radar's ability to separate transponders with high range and bearing resolution, the effective number of VRBC channels can scale without introducing mutual interference among transponders. Vibrational signal designs are presented with both simulation and real data experiments using a commercially-available low-power mmW radar and vibrational source. Essentially error-free data rates of 1 kbits/sec have been achieved in a laboratory setting.