Magic Mirrors: Active Frequency-Selective Surface Beacons for Synchronization, Communication, and Identification in Biomedical Radar

Radar systems are often considered as pure obser-vation platforms, gathering data on unaware or non-cooperative targets. The options for a target wishing to transmit information back to an observing radar sensor are limited, complex, and often require clock synchronisation. This work presents the design and analysis of a series of active frequency-selective surface (AFSS) based beacons that can modulate their reflectivity in a controllable manner. Using this modulation with an on-off-keying (OOK) scheme and a communications protocol based on reversals and Barker codes, it is shown how these beacons may be located by a radar, and how information may be encoded and transmitted from beacon to radar without the need for clock synchronization. Several practical applications are explored, including identifying individuals and enabling clock synchronization between channel-separated radars.