Apparatus for magnetically decoupling an RFID tag
First Claim
Patent Images
1. A radio frequency intelligent transponder comprising:
- an integrated circuit for storing data;
an inductor including a first coil electrically connected to a second coil;
a resonant capacitor electrically connected to the integrated circuit and at least one of the first and second coils, the resonant capacitor and the at least one connected coil having a first predetermined resonant frequency; and
a switch having a first position and a second position for selectively allowing a current to flow through the second coil, wherein when the switch is in the first position, exposure of the transponder to an external field at or near the first resonant frequency induces a voltage on the inductor and causes a first current to flow through the inductor in a first direction, thereby generating a near field and when the switch is in the second position, exposure of the transponder to an external field at or near the first resonant frequency induces a voltage on the inductor and causes a first current to flow through the first coil in a first direction, thereby generating a first near field and a second current to flow through the second coil in a second, opposite direction, thereby generating a second near field, wherein a sum of the first and second near fields approaches zero.
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Abstract
A resonant circuit tag includes an integrated circuit for storing data and an antenna circuit for generating a first local field and resonating at a first predetermined radio frequency. A second circuit including an inductive coil selectively generates a second local field such that a sum of the first and second local fields approaches zero. The second circuit thus allows the resonant tag to be selectively decoupled from its environment.
274 Citations
20 Claims
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1. A radio frequency intelligent transponder comprising:
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an integrated circuit for storing data;
an inductor including a first coil electrically connected to a second coil;
a resonant capacitor electrically connected to the integrated circuit and at least one of the first and second coils, the resonant capacitor and the at least one connected coil having a first predetermined resonant frequency; and
a switch having a first position and a second position for selectively allowing a current to flow through the second coil, wherein when the switch is in the first position, exposure of the transponder to an external field at or near the first resonant frequency induces a voltage on the inductor and causes a first current to flow through the inductor in a first direction, thereby generating a near field and when the switch is in the second position, exposure of the transponder to an external field at or near the first resonant frequency induces a voltage on the inductor and causes a first current to flow through the first coil in a first direction, thereby generating a first near field and a second current to flow through the second coil in a second, opposite direction, thereby generating a second near field, wherein a sum of the first and second near fields approaches zero. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A radio frequency intelligent transponder comprising:
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an integrated circuit for storing data;
an antenna circuit comprising a first coil and a resonant capacitor having a predetermined resonant frequency electrically connected to the integrated circuit for providing power to the integrated circuit and for transmitting the data stored in the integrated circuit to a device reader, wherein exposure of the transponder to an external field at a frequency near the predetermined resonant frequency causes a first current to flow through the first coil in a first direction, thereby producing a first near field which couples the transponder with its environment; and
means for selectively generating a second near field, wherein a sum of the first and second near fields approaches zero, for selectively decoupling the transponder from its environment. - View Dependent Claims (12, 13)
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14. An intelligent resonant tag comprising:
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an integrated circuit for storing data;
a first antenna circuit electrically connected to the integrated circuit, wherein exposure of the first antenna circuit to an electromagnetic field at a first predetermined radio frequency induces a voltage therein, which produces a current flowing in a first direction therethrough, thereby producing a first near field, the induced voltage also providing power to the integrated circuit such that the data stored therein is read therefrom and transmitted at a second predetermined radio frequency; and
means for generating a second near field which at least partially cancels the first near field generated by the first antenna circuit. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification