Distributed RFID antenna array utilizing circular polarized helical antennas

• US 20060208080A1
• Filed: 05/04/2006
• Published: 09/21/2006
• Est. Priority Date: 11/05/2004
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: GOLIATH Solutions LLC (Osa Acquisition, LLC)
• Inventors: Hardman, Gordon E., Overhultz, Gary L., Mead, Robert W.
• Granted Patent: US 7,614,556 B2
• Time in Patent Office: Days
• US Class Current: 235/451
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil

Abstract

In accordance with the teachings described herein, RFID systems are provided that include a distributed RFID antenna array utilizing one or more circular polarized helical antennas. A plurality of RFID tags may be used, with each RFID tag including a linear polarized antenna for communicating RFID tag signals. One or more receiver antennas may be used for receiving the RFID tag signals from the RFID tags. An RFID tag signal reader may be used to process RFID tag signals received by the receiver antennas. In one example, the receiver antennas may include a circular polarized helical antenna element. One or more transmitter antennas may be used for transmitting an RF signal to the plurality of RFID tags, the transmitter antennas including a circular polarized helical antenna element. A transmitter may be used to generate the RF signal for transmission by the transmitter antennas. In one example, the RFID tag signal reader and the transmitter may be included in a single reader/transmitter unit.

Claims

1. A radio frequency identification (RFID) system, comprising:

at least one RFID tag that communicates an RFID tag signal via a linear polarized antenna;

at least one receiver antenna for receiving the RFID tag signals, the receiver antenna including a circular polarized helical antenna element; and

an RFID tag signal reader coupled to the at least one receiver antenna that processes the RFID tag signals.

2. The system of claim 1, further comprising:

at least one transmitter antenna for transmitting an RF signal to the RFID tag, the transmitter antenna including a circular polarized helical antenna element; and

a transmitter coupled to the at least one transmitter antenna that generates the RF signal;

wherein the RFID tag communicates the RFID tag signal in response to receiving the RF signal from the transmitter antenna.

3. The system of claim 1, wherein the receiver antenna is a single turn helix antenna.

4. The system of claim 2, wherein the transmitter antenna is a single turn quadrafilar helix antenna.

5. The system of claim 2, wherein the RF signal transmitted by the transmitter antenna includes a carrier wave that is modulated by the RFID tag to generate the RFID tag signal.

6. The system of claim 3, wherein the receiver antenna includes:

a dielectric core; and

an antenna element having a single radiating arm that extends in a spiral pattern around the dielectric core.

7. The system of claim 6, wherein the receiver antenna further includes an antenna backplane that adds directivity to a circular polarized radiation pattern of the antenna element.

8. The system of claim 6, wherein the receiver antenna further includes an amplifier circuit coupled to the antenna element.

9. The system of claim 3, wherein the receiver antenna includes:

a dielectric structure; and

an antenna element having a single radiating arm that is attached to the dielectric structure using one or more support structures.

10. The system of claim 9, wherein the receiver antenna further includes an antenna backplane that adds directivity to a circular polarized radiation pattern of the antenna element.

11. The system of claim 9, wherein the receiver antenna further includes an amplifier circuit coupled to the antenna element.

12. The system of claim 4, wherein the transmitter antenna includes:

a dielectric core; and

an antenna element attached to the dielectric core, the antenna element including four radiating arms that extend in a helical pattern from a common junction.

13. The system of claim 12, wherein the four radiating arms are formed from two antenna wires that are bonded at the common junction.

14. The system of claim 12, wherein the transmitter antenna further includes an antenna backplane that adds directivity to a circular polarized radiation pattern of the antenna element.

15. The system of claim 12, wherein the transmitter antenna further includes an amplifier circuit coupled to the antenna element.

16. The system of claim 2, wherein the transmitter and the RFID tag signal reader are included in a single reader/transmitter unit.

17. The system of claim 5, wherein the linear polarized antenna includes:

a first antenna element;

a second antenna element; and

a switching circuit for selectively coupling the first antenna element with the second antenna element;

when coupled together by the switching circuit, the first and second antenna elements forming a single antenna element that reflects the RF signal transmitted by the transmitter antenna; and

when not coupled together by the switching circuit, the first and second antenna elements absorbing at least a portion of the RF signal transmitted by the transmitter antenna.

18. The system of claim 1, wherein the RFID tag signal reader processes the RFID tag signals to determine an identification associated with the RFID tag and encoded in the RFID tag signal.

19. The system of claim 1, wherein the RFID tag signal reader processes the RFID tag signals to determine a location of the RFID tags.

20. The system of claim 1, wherein the RFID tag signal reader processes the RFID tag signals to determine an amount of time that the RFID tags are present within a facility.

21. A distributed radio frequency identification (RFID) antenna array system, comprising:

at least one transmitter antenna for transmitting RF signals, the transmitter antenna including a circular polarized helical antenna element;

at least one RFID tag that includes a linear polarized antenna for receiving the RF signals and for transmitting RFID tag signals, the RFID tag signals being transmitted by the at least one RFID tag in response to receiving the RF signals;

a plurality of receiver antennas for receiving the RFID tag signals from the at least one RFID tag; and

a reader/transmitter unit coupled to the at least one transmitter antenna and the plurality of receiver antennas, the reader/transmitter unit generating the RF signals for transmission by the at least one transmitter antenna and processing the RFID tag signals received by the plurality of receiver antennas.

22. The system of claim 21, wherein the RF signals transmitted by the transmitter antenna include carrier waves that are modulated by the at least one RFID tag to generate the RFID tag signals.

23. The system of claim 21, wherein the transmitter antenna includes a single turn quadrifiler helix antenna.

24. The system of claim 22, wherein the linear polarized antenna in the at least one RFID tag includes:

a first antenna element;

a second antenna element; and

a switching circuit for selectively coupling the first antenna element with the second antenna element;

when couple together by the switching circuit, the first and second antenna elements forming a single antenna element that reflects the RF signals transmitted by the transmitter antenna;

when not coupled together by the switching circuit, the first and second antenna elements absorbing at least a portion of the RF signals transmitted by the transmitter antenna.

25. A distributed radio frequency identification (RFID) antenna array system, comprising:

at least one transmitter antenna for transmitting RF signals, the transmitter antenna including a circular polarized helical antenna element;

a plurality of RFID tags, each RFID tag including a linear polarized antenna for receiving the RF signals and for transmitting RFID tag signals, the RFID tag signals being transmitted by the RFID tags in response to receiving the RF signals;

a plurality of receiver antennas for receiving the RFID tag signals from the RFID tags; and

means for generating the RF signals for transmission by the at least one transmitter antenna; and

means for processing the RFID tag signals received by the plurality of receiver antennas.

26. The system of claim 25, wherein at least one of the plurality of RFID tags is a switched backscatter RFID tag.

27. The system of claim 26, wherein the switched backscatter RFID tag comprises:

a first antenna segment;

a second antenna segment;

means for coupling the first antenna segment to the second antenna segment to reflect the RF signals; and

means for decoupling the first antenna segment from the second antenna segment to absorb the RF signals.