RFID reader
First Claim
1. An RFID tag reader, the reader comprising:
- a resonant circuit;
an electromagnetic (EM) field generator for driving said resonant circuit to generate an electromagnetic (EM) field for modulation by a tag, said modulation comprising load modulation of said EM field by said tag;
a detector system responsive to fluctuations in strength of said EM field at said reader;
a negative feedback system responsive to said detector system to provide a control signal to control said EM field generator to reduce said detected fluctuations in strength of said EM field generated by said resonant circuit, wherein said negative feedback system operates on a per-cycle basis; and
a demodulator responsive to said control signal to demodulate said EM field modulation by said tag,the reader further comprising a signal generator configured to drive said EM field generator, wherein said EM field generator has a power supply, and wherein said signal generator drives said EM field generator such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the tag reader further comprising a demand signal output circuit to provide a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein said demodulator is configured to interpret said demand signal to thereby demodulate said EM field modulation by said tag.
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Accused Products
Abstract
Embodiments of the invention relate to the field of RFID (radio frequency identification). Some particularly preferred embodiments relate to a high-Q, so-called “full duplex” (FDX) RFID Reader. An RFID tag reader, the reader comprising: an electromagnetic (em) field generator for generating an electromagnetic (em) field for modulation by said tag, said modulation comprising modulated load of said em field by said tag; a detector system responsive to fluctuations in strength of said em field at said reader; a negative feedback system responsive to said detector system to provide a control signal for said em field generator for controlling said em field generator to reduce said detected fluctuations; and a demodulator responsive to said control of said em field to demodulate said em field modulation by said tag.
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Citations
22 Claims
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1. An RFID tag reader, the reader comprising:
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a resonant circuit; an electromagnetic (EM) field generator for driving said resonant circuit to generate an electromagnetic (EM) field for modulation by a tag, said modulation comprising load modulation of said EM field by said tag; a detector system responsive to fluctuations in strength of said EM field at said reader; a negative feedback system responsive to said detector system to provide a control signal to control said EM field generator to reduce said detected fluctuations in strength of said EM field generated by said resonant circuit, wherein said negative feedback system operates on a per-cycle basis; and a demodulator responsive to said control signal to demodulate said EM field modulation by said tag, the reader further comprising a signal generator configured to drive said EM field generator, wherein said EM field generator has a power supply, and wherein said signal generator drives said EM field generator such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the tag reader further comprising a demand signal output circuit to provide a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein said demodulator is configured to interpret said demand signal to thereby demodulate said EM field modulation by said tag. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An RFID system including a transponder and a reader for the transponder, wherein the reader is configured to use negative feedback to increase the stability of the amplitude of a resonance in a resonant circuit of the reader in the presence of a modulating transponder, the RFID system comprising an electromagnetic (EM) field generator for driving said resonant circuit to generate an electromagnetic (EM) field for modulation by said transponder, wherein a level of drive to be input into the resonance of the resonant circuit is measured to demodulate said transponder modulation, wherein said negative feedback operates on a per-cycle basis,
the reader further comprising a signal generator configured to drive said EM field generator, wherein said EM field generator has a power supply, and wherein said signal generator drives said EM field generator such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the reader further comprising a demand signal output circuit to provide a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein the reader is configured to interpret said demand signal to thereby demodulate said EM field modulation by said transponder.
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21. A method of remotely interrogating a transponder, the method comprising:
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generating, using a resonant circuit, an electromagnetic (EM) field for modulation by said transponder, said modulation comprising modulated load of said EM field by said transponder; detecting fluctuations in said EM field caused by said modulation; applying negative feedback to said EM field generating to compensate said detected fluctuations; and detecting said applied negative feedback to demodulate said modulation of said EM field by said transponder, wherein said negative feedback operates on a per-cycle basis, the method further comprising generating a signal to drive said EM field generating, wherein said EM field generating uses a power supply, and wherein said signal drives said EM field generating such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the method further comprising providing a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generating, and wherein said demodulation interprets said demand signal to thereby demodulate said EM field modulation by said transponder.
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22. Apparatus for remotely interrogating a transponder, the apparatus comprising:
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an EM field generator comprising a resonant circuit for generating an electromagnetic (EM) field for modulation by said transponder, said modulation comprising load absorption of said EM field by said transponder; means for detecting fluctuations in said EM field caused by said modulation; means for applying negative feedback to a driver of the resonant circuit to compensate said detected fluctuations; and means for detecting said applied negative feedback to demodulate said modulation of said EM field by said transponder, wherein said means for applying negative feedback operates on a per-cycle basis, the apparatus further comprising a signal generator configured to drive said EM field generator, wherein said EM field generator has a power supply, and wherein said signal generator drives said EM field generator such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the apparatus further comprising a demand signal output circuit to provide a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein the system is configured to interpret said demand signal to thereby demodulate said EM field modulation by said transponder.
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Specification