Modulated backscatter wireless communication system having an extended range

摘要

A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (10) (e.g., a ceiling node) and one or more remote nodes (20-40) (e.g., ESL tags). The central node (10) transmits a downlink radio signal (16) which is reflectively modulated at a remote node (20) to produce a modulated reflected radio signal (17). At the remote node (20), a precise-frequency subcarrier signal (26,27) is modulated (24) with an uplink information signal (25) to produce a modulated signal which is used to produce (22) the modulated reflected radio signal (17). At the central node, the modulated reflected radio signal is received (12), detected and narrowband filtered (13,19) to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal (25), with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.