Radio-frequency identification (RFID) tag and system for determining locations of objects in a gaming environment

Abstract

A radio-frequency identification (RFID) tag includes an antenna with a relatively large number of turns and is de-tuned from an excitation frequency of an RFID reader. The RFID tag, when grouped with other similar RFID tags, uses resonant inductive coupling to channel the magnetic flux density field (B-field) through the group to power each of the tags in the group. As a result, the sensitivity is increased as compared to using an antenna having a smaller number of turns.

Claims

1. A radio frequency identification (RFID) tag, comprising: RFID tag electronic devices; An antenna assembly coupled to the RFID electronics is provided, wherein the antenna assembly includes an antenna having more than five turns and a capacitor, wherein the RFID tag has a resonant frequency derived from the antenna assembly, wherein the resonant frequency of the RFID tag is higher than an excitation frequency of a transmission generated by an RFID reader, wherein the RFID tag is one of a plurality of neighboring RFID tags in a group, wherein the group of RFID tags shapes a magnetic flux density field transmitted through the group of RFID tags generated by the RFID reader, wherein the group of RFID tags has a resonant frequency lower than the resonant frequency of each of the plurality of RFID tags individually considered due to resonant coupling, and wherein the transmission generated by the RFID reader powers the RFID tag electronics via the resonant coupling, and wherein the sensitivity of the RFID tag increases with the number of turns of the antenna.

2. The RFID tag as described in claim 1, further comprising: A circuit element connected in series between the antenna and the RFID tag electronics, wherein the circuit element includes at least one of a capacitor, an inductor and a resistor.

3. The RFID tag as requested in item 2, wherein the capacitor has a capacitance between 1.8 pF and 3.0 pF.

4. The RFID tag as requested in item 2, wherein the capacitor has a capacitance between 1.8 pF and 3.9 pF.

5. The RFID tag as requested in item 2, wherein the circuit element is a component of the antenna assembly.

6. The RFID tag as requested in item 1, wherein the capacitance of the antenna assembly originates from the self-capacitance of the antenna.

7. The RFID tag of claim 1, wherein the antenna assembly further includes a capacitor connected in parallel with the antenna.

8. The RFID tag as claimed in claim 7, wherein the capacitor connected in parallel with the antenna has a capacitance between 0.125 pF and 1.0 pF.

9. The RFID tag of claim 1, wherein the RFID electronics further includes a capacitor connected in parallel with the antenna.

10. The RFID tag as requested in item 1, wherein the antenna has between 6 and 19 turns.

11. The RFID tag as requested in item 1, wherein the antenna has between 20 and 34 turns.

12. The RFID tag as requested in item 1, wherein the antenna has 35 or more turns.

13. The RFID tag of claim 1, wherein a reading range between the RFID tag and the RFID reader increases with the increase of the number of turns of the antenna.

14. The RFID tag of claim 1, wherein the resonant frequency of one of the groups of the RFID tag is within 10% higher and 10% lower than the excitation frequency of the RFID reader.

15. A system for determining the position of an object in a game environment, the system comprising: A plurality of radio frequency identification (RFID) antennas are disposed at a plurality of locations on a game table; One or more RFID readers are coupled to the plurality of RFID antennas; The system comprises a plurality of RFID tags, wherein a given RFID tag includes: RFID tag electronics; and an antenna assembly coupled to the RFID electronics, wherein the antenna assembly includes an antenna having more than 5 turns and a capacitor, wherein the given RFID tag has a resonant frequency derived from the antenna assembly, wherein the resonant frequency of the given RFID tag is higher than an excitation frequency of a transmission generated by the one or more RFID readers, wherein the given RFID tag is one of the plurality of adjacent RFID tags in a group, wherein the group of RFID tags shapes a magnetic flux density field of the transmission through the group of RFID tags generated by the one or more RFID readers, wherein the group of RFID tags has a resonant frequency lower than the resonant frequency of each of the plurality of RFID tags individually considered due to resonant coupling, and wherein the transmission generated by the one or more RFID readers powers the RFID tag electronics via the resonant coupling, and wherein the sensitivity of the given RFID tag increases with the number of turns of the antenna.

16. The system of claim 15, wherein the given RFID tag further includes: A circuit element connected in series between the antenna and the RFID tag electronics, wherein the circuit element includes at least one of a capacitor, an inductor and a resistor.

17. The system of claim 15, wherein the capacitance of the antenna assembly is derived from the self-capacitance of the antenna of the given RFID tag.

18. The system of claim 15, wherein the antenna assembly further includes a capacitor connected in parallel with the antenna of the given RFID tag.

19. The system of claim 15, wherein the RFID electronics further includes a capacitor connected in parallel with the antenna of the given RFID tag.

20. The system of claim 15, wherein the antenna of the given RFID tag has 35 or more turns.

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