RADIO FREQUENCY IDENTIFICATION SYSTEM WITH IMPROVED ACCURACY AND DETECTION EFFICIENCY IN PRESENCE OF CLUTTER
First Claim
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1. A passive backscatter radio frequency identification (RFID) tag, comprising:
- a non-dipole antenna;
a switch connected to the non-dipole antenna; and
at least one circuit having a predetermined impedance,the switch adapted to switch an electrical connection between the non-dipole antenna and the at least one circuit such that the RFID tag emits a predetermined pattern of signals when illuminated by an RFID interrogator, the pattern of signals corresponding to a device signature of the RFID tag.
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Abstract
A technique that improves performance of passive backscatter RFID tags such as mitigation of read error in presence of clutter, provide enhanced range, speed up anti-collision reading, provide increased throughput etc. The technique utilizes amplitude and phase modulation at the tag and a compensation algorithm at the RFID reader without inflicting significant changes in the RFID chip and therefore has minimum cost impact. Modifications can be primarily in the antenna design and passive circuitry around it, printable by a single step process.
18 Citations
24 Claims
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1. A passive backscatter radio frequency identification (RFID) tag, comprising:
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a non-dipole antenna; a switch connected to the non-dipole antenna; and at least one circuit having a predetermined impedance, the switch adapted to switch an electrical connection between the non-dipole antenna and the at least one circuit such that the RFID tag emits a predetermined pattern of signals when illuminated by an RFID interrogator, the pattern of signals corresponding to a device signature of the RFID tag. - View Dependent Claims (2, 3, 4, 5, 6, 14)
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7. A passive backscatter radio frequency identification (RFID) tag, comprising:
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an antenna; an electrical switch; a first circuit element having a first impedance; a second circuit element having a second impedance; and the switch adapted to switch from an electrical connection between the antenna and the first circuit element to an electrical connection between the antenna and the second circuit element when the RFID tag is illuminated by an RFID interrogator such that the RFID tag emits a predetermined pattern of signals when illuminated by an RFID interrogator, the pattern of signals corresponding to a device signature of the RFID tag. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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15. A method of impedance modulation of a passive backscatter radio frequency identification (RFID) tag, the method comprising:
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receiving a wireless input signal into an antenna of an RFID tag, the antenna operatively connected to a switch; switching the switch between a first circuit having a first impedance and a second circuit having a second impedance such that an output signal from the antenna is modulated both in a predetermined amplitude and a predetermined phase, the modulation in both the predetermined amplitude and the predetermined phase corresponding to a device signature of the RFID tag; and emitting the output signal from the RFID tag. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A machine-implemented method of discerning a radio frequency identification (RFID) tag among non-RFID tag clutter, the method comprising:
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receiving a wireless signal into an antenna, the wireless signal including an emitted signal from an RFID tag and clutter; estimating an amplitude and phase of the signal in two or more distinct states; estimating an amplitude and phase of the clutter; and subtracting the clutter from the received signal. - View Dependent Claims (23, 24)
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Specification