System and method to identify multiple RFID tags
First Claim
Patent Images
1. An RFID system comprising:
- an RFID reader configured to issue a first RF command requesting that RF tags identify themselves, a subsequent second RF command, and timing information defining a plurality of timeslots; and
a plurality of RF tags in selective communication with the reader, the RF tags having respective IDs, respective tags being configured to randomly select a timeslot in which to reply to the first RF command, and to issue a first RF reply in response to the first RF command in the randomly selected timeslot, the first RF reply incompletely identifying the tag to the reader, the respective tags being further configured to issue a second RF reply in response to the second RF command to more completely identify the tag to the reader;
wherein the reader is configured to store data representing the timeslot in which an RF reply was received by the reader and wherein the second RF command indicates the timeslot for which a reply was received from a tag.
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Abstract
An RFID system comprises an RFID reader configured to issue an RF command requesting that RF tags identify themselves, and to issue timing information defining a plurality of timeslots; and a plurality of RF tags in selective communication with the reader, the RF tags having respective IDs, respective tags being configured to randomly select a timeslot in which to reply to the RF command, and to issue an RF reply in response to the RF command in the randomly selected timeslot, the RF reply including a frequency pattern to assist in identifying the tag but not the tag'"'"'s entire ID, different tags having different frequency patterns.
94 Citations
49 Claims
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1. An RFID system comprising:
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an RFID reader configured to issue a first RF command requesting that RF tags identify themselves, a subsequent second RF command, and timing information defining a plurality of timeslots; and a plurality of RF tags in selective communication with the reader, the RF tags having respective IDs, respective tags being configured to randomly select a timeslot in which to reply to the first RF command, and to issue a first RF reply in response to the first RF command in the randomly selected timeslot, the first RF reply incompletely identifying the tag to the reader, the respective tags being further configured to issue a second RF reply in response to the second RF command to more completely identify the tag to the reader; wherein the reader is configured to store data representing the timeslot in which an RF reply was received by the reader and wherein the second RF command indicates the timeslot for which a reply was received from a tag. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An RFID reader, for use with RF tags that have respective IDs, the RFID reader comprising:
circuitry configured to selectively provide a backscatter RF illumination field, to provide time synchronization information defining timeslots to RF tags, to issue a first RF command requesting that RF tags identify themselves, to store the identity of the timeslot where an RF reply was received by the reader from a tag, to determine if a collision occurred between RF replies, to issue a second RF command indicating the timeslot for which a reply was received from an RF tag and requesting that RF tags reply with their IDs, to receive and store IDs from RF tags, and to re-issue the first RF command response if it was determined that a collision occurred between RF replies. - View Dependent Claims (9, 10, 11)
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12. An RFID tag for use with a reader that is configured to issue timing signals defining timeslots, the RFID tag comprising:
circuitry configured to store an ID identifying the tag, to backscatter modulate an RF illumination field from a reader, to randomly select a timeslot in which to reply from a plurality of possible timeslots, to issue an RF reply in the selected timeslot, responsive to receiving a first RF command including a session identifier from the reader, the reply including a signal pattern, the signal pattern identifying the tag but not including the entire ID, the tag being further configured to issue a subsequent response to the reader including the tag'"'"'s ID in response to receiving a second RF command from the reader, the second RF command containing information corresponding to the selected timeslot to indicate that the tag has been found by the reader, and the circuitry being further configured to ignore further receptions of the first RF command which include the session identifier responsive to receiving a third RF command from the reader confirming that the tag'"'"'s ID has been received by the reader. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An RFID communications method comprising:
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providing an RF reader; providing a plurality of RF tags in selective communication with the reader, the RF tags having respective IDs; issuing, using the RF reader, an RF command requesting that the RF tags identify themselves; issuing, using the RF reader, timing information defining a plurality of timeslots; respective tags randomly selecting a timeslot in which to reply to the RF command; respective tags issuing an RF reply in response to the RF command, in the randomly selected timeslot, the RF reply including a frequency pattern to assist in identifying the tag but not the tag'"'"'s entire ID, different tags having different frequency patterns; storing, with the reader, the timeslot where an RF reply was received by the reader; and transmitting, with the reader, an RF message indicating the timeslot for which a reply was received from a tag. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A method of communicating with RF tags that have respective IDs, the method comprising:
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selectively providing a backscatter RF illumination field, including time synchronization information defining timeslots to RF tags; issuing a first RF command requesting that RF tags identify themselves; storing data identifying the timeslot where an RF reply was received from a tag; determining if a collision occurred between RF replies; issuing a second RF command indicating the timeslot for which a reply was received from an RF tag and requesting that RF tags reply with their IDs; receiving and storing IDs from RF tags; and re-issuing the first RF command response if it was determined that a collision occurred between RF replies received from tags. - View Dependent Claims (28, 29, 30, 31)
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32. A method of communicating with an RF reader that is configured to issue timing signals defining timeslots, the method comprising:
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storing an ID; backscatter modulating an RF illumination field from the reader; randomly selecting a timeslot in which to reply from a plurality of possible timeslots; issuing an RF reply in the selected timeslot, responsive to receiving a first RF command, including a session identifier, from the reader, the reply including a signal pattern, the signal pattern identifying the tag but not including the entire ID; issuing a response to the reader including the ID in response to receiving a subsequent second RF command from the reader that contains information corresponding to the selected timeslot; and ignoring further receptions of the first RF command which include the session identifier responsive to receiving a third RF command from the reader confirming that the ID has been received by the reader. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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40. A method of using an RFIT) reader, comprising:
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issuing a first RF command to an RF tag; selectively providing an RF illumination field including time synchronization pulses; monitoring for a reply during a period defined by a predetermined number of timeslots; receiving an RF reply, from a tag, including a signal pattern during the monitoring; issuing a second RF command indicating the timeslot during which a reply was received; receiving an RF reply including a tag'"'"'s ID in response to the second RF command; and issuing a third RF command in response to receiving an RF reply including a tag'"'"'s ID. - View Dependent Claims (41, 42, 43)
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44. An RFID system comprising:
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an RFID reader including means for issuing an RF command requesting that RF tags identify themselves, means for issuing timing information defining a plurality of timeslots, and means for monitoring a plurality of frequencies for a response; and a plurality of RF tags in selective communication with the reader, the RF tags having respective IDs, respective tags including means for randomly selecting a timeslot in which to reply to the RF command, means for randomly selecting a frequency on which to issue a reply to the RF command, and means for issuing an RF reply in response to the RF command in the randomly selected timeslot and using the randomly selected frequency, the RF reply including a frequency pattern that incompletely identifies the tag to the reader; wherein the reader includes means for storing data representing the timeslot and frequency in which an RF reply was received by the reader and is configured to transmit an RF message indicating the timeslot and frequency for which a reply was received from a tag. - View Dependent Claims (45, 46, 47, 48, 49)
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Specification