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AssigneeCheckpoint Systems, Inc.
InventorsBen J. Wild, Upamanyu Madhow, Kannan Ramchandran, Artem Tkachenko
Estimating the term…
One or more readers transmit radio frequency (RF) beacons to be electronically reflected by tags. Data transmitted via modulated backscatter from radio frequency identification (RFID) tags is encoded so as to permit reliable demodulation of simultaneous transmissions from multiple tags. This includes the use of spreading sequences as in direct sequence spread spectrum, where the spreading sequences may be a function of the tag ID, or may be randomly chosen. Backscattered signals from multiple tags may be detected using well-known receiver techniques for code division multiple access (CDMA) systems. Readers may be equipped with transmit and/or receive antenna arrays. A receive antenna array permits a reader to estimate directions of arrival for received signals, as well as to enhance range by performing receive beamforming.
An RFID communication system comprising an RFID reader in communication with a plurality of RFID tags having an integrated circuit and a memory unit, the memory unit storing tag data representing the RFID tag identification, each RFID tag having a spreading sequence associated with the tag, the RFID tags responding to an RF signal from the RFID reader with a spread spectrum modulated backscatter signal including the tag data mixed with the spreading sequence, the RFID tag providing the spread spectrum modulated backscatter signal having a signal to noise ratio higher that a corresponding backscatter signal without the spreading sequence, the RFID reader receiving and correlating the spread spectrum modulated backscatter signal against expected spreading sequences to identify the corresponding RFID tag at a distance greater than for an RFID tag sending the corresponding backscatter signal without the spreading sequence.
A method for RFD communication, comprising:
A CDMA communication system comprising an RFID reader in communication with a plurality of RFID tags having an integrated circuit and a memory unit, the memory unit storing tag data representing the RFID tag identification, each RFID tag having a spreading sequence associated with the tag, the RFID tags responding to an RF signal from the RFID reader with a CDMA signal including the tag data mixed with the spreading sequence, the RFID tag providing the CDMA signal having a signal to noise ratio higher that a corresponding backscatter signal without the spreading sequence, the RFID reader receiving and correlating the CDMA signal against expected spreading sequences to identify the corresponding RFID tag at a distance greater than for an RFID tag sending the corresponding backscatter signal without the spreading sequence.
Dependencies are inferred from the claim text.