Method and apparatus for multiple frequency RFID tag architecture

• US 7,248,165 B2
• Filed: 09/09/2004
• Issued: 07/24/2007
• Est. Priority Date: 09/09/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gurney, David P., Collins, Timothy J., Kuffner, Stephen L., Rachwalski, Richard S.
• Primary Examiner(s): Pham; Toan N.
• Application Number:
  US10/937,208
• Publication Number:
  US 20050052283A1
• Time in Patent Office: 1,048 Days
• Field of Search: 340/572.1, 340/572.7, 340/10.1, 343/853, 343/725, 343/893
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies

Abstract

The present invention provides a multi-band, multi-mode RFID tag that uses a single antenna structure and integrated circuit to provide asset location information at any stage of a supply chain. The unified tag design operates at multiple frequencies (or bands) using the antenna structure, for example, 125 kHz, 13.56 MHz, 915 MHz, and 2.45 GHz, and preferably operates electrostatically (at lower frequencies) and electromagnetically (ay higher frequencies). An on-chip frequency monitor in the integrated circuit automatically determines which frequency is present and derives a local clock for the tag'"'"'s integrated circuit, which can vary in accordance with the frequency or which can be constant. Alternatively, a phase locked loop circuit can be used to derive a local clock signal modulated into the interrogation signal. On-chip matching and power extraction circuits derive power for the tag from the interrogation signal, which is preferably passive. Additionally, a receiver can receive data from the interrogation signal.

Claims

1. An antenna structure for a RFID tag interrogatable by at least one reader, comprising:

a first antenna portion, comprising first and second electrostatic elements, that is responsive to an electrostatic interrogation signal at at least one first frequency; and

a second antenna portion, comprising first and second electromagnetic elements, that is responsive to a far-field electromagnetic signal at at least one second frequency,

wherein the first electrostatic element comprises a first non-resonant plate and the first electromagnetic element, and the second electrostatic element comprises a second non-resonant plate and the second electromagnetic element.

2. The antenna of claim 1, wherein the first antenna portion is responsive to the electrostatic interrogation signal at at least two frequencies.

3. The antenna of claim 1, wherein the second antenna portion is responsive to the far-field electromagnetic interrogation signal at at least two frequencies.

4. The antenna of claim 3, wherein the second antenna portion is slotted to be responsive to the far-field electromagnetic interrogation signal at at least two frequencies.

5. The antenna of claim 1, wherein the first antenna portion is made from a material of a first conductivity, and wherein the second antenna portion is made from a material of a second conductivity.

6. The antenna of claim 5, wherein the first conductivity is lower than the second conductivity.

7. The antenna of claim 1, wherein the second antenna portion is directly connected to circuitry on the tag.

8. The antenna of claim 7, wherein the second antenna portion electrically intervenes between the first antenna portion and the circuitry on the tag.

9. The antenna of claim 1, wherein both the first antenna portion and the second antenna portion are directly connected to circuitry on the tag.

10. The antenna of claim 1, wherein the first and second antenna portions are formed on a single substrate.

11. The tag of claim 1, wherein the circuitry comprises a frequency detecting circuit capable of determining the frequency of the at least one first frequency and the at least one second frequency.

12. The tag of claim 11, wherein the frequency detecting circuit further comprises a clock generating circuit for generating a local clock for the tag.

13. The tag of claim 12, wherein the local clock varies in accordance with the determined frequency.

14. The tag of claim 12, wherein the local clock is independent of the determined frequency.

15. The tag of claim 1, wherein the circuitry comprises a phase locked loop circuit for deriving a local clock signal carried with either interrogation signal.

16. The tag of claim 1, wherein the circuitry comprises at least one power extraction circuit for deriving power for the tag from either interrogation signal.

17. The tag of claim 1, wherein the circuitry further comprises a receiver for accepting data from the reader.

18. A RFID tag interrogatable by at least one reader, comprising:

an antenna structure on a substrate, comprising

a first antenna portion, comprising first and second electrostatic elements, that is responsive to an electrostatic interrogation signal at at least one first frequency; and

a second antenna portion, comprising first and second electromagnetic elements, that is responsive to a far-field electromagnetic signal at at least one second frequency,

wherein the first electrostatic element comprises a first non-resonant plate and the first electromagnetic element, and the second electrostatic element comprises a second non-resonant plate and the second electromagnetic element; and

an integrated circuit mounted to the substrate and coupled to the antenna for providing data from the tag to the reader in response to either the electrostatic or far-field electromagnetic interrogation.

19. The tag of claim 18, wherein either or both of the electrostatic and electromagnetic antenna portions are responsive to their interrogation signals at at least two frequencies.

20. The tag of claim 18, wherein the electrostatic antenna portion is made from a material of a first conductivity, and wherein the electromagnetic antenna portion is made from a material of a second conductivity, and wherein the first conductivity is lower than the second conductivity.

21. The tag of claim 18, wherein the electromagnetic antenna portion is directly connected to the integrated circuit on the tag.

22. The tag of claim 21, wherein the electromagnetic antenna portion electrically intervenes between the electrostatic antenna portion and the integrated circuit on the tag.

23. The tag of claim 18, wherein the integrated circuit comprises a frequency detecting circuit capable of determining the frequency of the at least one first frequency and the at least one second frequency.

24. The tag of claim 23, wherein the frequency detecting circuit further comprises a clock generating circuit for generating a local clock for the tag.

25. The tag of claim 18, wherein the integrated circuit comprises a phase locked loop circuit for deriving a local clock signal carried with either interrogation signal.

26. The tag of claim 18, wherein the integrated circuitry comprises at least one power extraction circuit for deriving power for the tag from either interrogation signal.

27. The tag of claim 18, wherein the integrated circuit further comprises a receiver for accepting data from the reader.