Ultra high frequency radio frequency identification tag

• US 20050134506A1
• Filed: 12/23/2003
• Published: 06/23/2005
• Est. Priority Date: 12/23/2003
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Egbert, William C.
• Granted Patent: US 6,999,028 B2
• Time in Patent Office: Days
• US Class Current: 343/700.MS
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 9/265 Open ring dipoles; Circular dipoles

Abstract

An antenna design for radio frequency identification (“RFID”) tags. More particularly, the present invention relates to design for RFID tags particularly operating in the ultra high frequency (“UHF”) operating band.

Claims

1. An ultra high frequency (“

UHF”

) radio frequency identification (“

RFID”

) tag, comprising;

a) a dielectric substrate;

b) an antenna attached to the dielectric substrate, wherein the antenna comprises;

i) a first antenna element, wherein the first antenna element comprises a first conductor and a second conductor, wherein each conductor has a first end and a second end opposite the first end, wherein the first antenna element is selected to provide a desired operating frequency range of the antenna; and

ii) a second antenna element, wherein the second antenna element comprises a first portion and a second portion, wherein the first portion is attached to the second end of the first conductor and the second portion is attached to the second end of the second conductor, and wherein the second antenna element is selected to provide a desired impedance value of the antenna; and

c) an integrated circuit attached to the first end of the first conductor and the first end of the second conductor.

2. The UHF RFID tag of claim 1, wherein the integrated circuit has a first impedance value, and wherein the antenna has a second impedance value, and wherein the magnitude of the real component of the second impedance value is substantially similar to the magnitude of the real component of the first impedance value, and the magnitude of the imaginary component of the second impedance value is substantially similar to the magnitude of the imaginary component of the first impedance value, and wherein the phase of the imaginary component of the first impedance value and the phase of the imaginary component of the second impedance value are opposite.

3. The UHF RFID tag of claim 2, wherein the first impedance value has a first real component value and a first imaginary component value, wherein the second impedance value has a second real component value and a second imaginary component value, wherein the first real component value is equal to the second real component value and wherein the magnitude of the imaginary component of the second impedance value is equal to the magnitude of the imaginary component of the imaginary component of the first impedance value, and wherein the phase of the imaginary component or the first impedance value and the phase of the imaginary component of the second impedance value are opposite.

4. The UHF RFID tag of claim 2, wherein the first portion of the antenna has a first real component value and a first imaginary component value and the second portion of the antenna has a second real component value and a second imaginary component value, and wherein the second portion of the antenna is selected to provide a second real component value and second imaginary component value which assist in balancing the first real component value and the first imaginary component value to provide the second impedance value of the antenna substantially similar to the first impedance value of the integrated circuit.

5. The UHF RFID tag of claim 4, wherein the first portion of the antenna has a first real component value and a first imaginary component value and the second portion of the antenna has a second real component value and a second imaginary component value, and wherein the second portion of the antenna is selected to provide a second real component value and second imaginary component value which assist in balancing the first real component value and the first imaginary component value to provide the second impedance value of the antenna equal to the first impedance value of the integrated circuit.

6. The UHF RFID tag of claim 1, wherein the first portion of the second antenna element and the second portion of the second antenna element are in the shape of closed loops.

7. The UHF RFID tag of claim 1, wherein the first portion of the second antenna element and the second portion of the second antenna element are in the shape of polygons.

8. The UHF RFID tag of claim 1, wherein the first portion of the second antenna element is dissimilar in shape to the second portion of the second antenna element.

9. The UHF RFID tag of claim 1, wherein the first portion of the second antenna element is similar in shape to the second portion of the second antenna element.

10. The UHF RFID tag of claim 1, wherein the first portion of the second antenna element is different in size than the second portion of the second antenna element.

11. The UHF RFID tag of claim 1, wherein the first conductor and second conductor include meanders.

12. The UHF RFID tag of claim 1, wherein the first conductor and second conductor are made from a wire, patterned conductive foils, or printed conductive traces.

13. The UHF RFID tag of claim 1, wherein the first antenna element is made from a different conductive material than the second antenna element.

14. The UHF RFID tag of claim 1, wherein the dielectric substrate includes a dielectric constant ε

≦

10*ε

₀ between 850 MHz and 960 MHz, wherein ε

₀ is the permittivity of free space (ε

₀=8.85×

10<sup>−

12</sup> C²/N.m²).

15. The UHF RFID tag of claim 1, wherein the dielectric substrate includes a first side and a second side opposite the first side, wherein the antenna is attached to the first side and the integrated chip is attached to the second side.

16. The UHF RFID tag of claim 1, wherein the distance between the first portion of the second antenna element and the first conductor is different from the distance between the second portion of the second antenna element and the second conductor.

17. The UHF RFID tag of claim 1, wherein the length of the first conductor is different than the length of the second conductor.

18. A method of manufacturing an ultra high frequency (“

UHF”

) radio frequency identification (“

RFID”

) tag, comprising the steps of;

a) providing a dielectric substrate;

b) selecting an antenna comprised of a first antenna element and a second antenna element, wherein the first antenna element is selected to provide a desired operating frequency range of the antenna, wherein the second antenna element is selected to provide a desired impedance value, wherein the first antenna element comprises a first conductor and a second conductor, wherein each conductor has a first end and a second end opposite the first end, and wherein the second antenna element comprises a first portion and a second portion; and

c) attaching the antenna to the dielectric substrate such that the first portion of the second antenna element is attached to the second end of the first conductor and the second portion of the second antenna element is attached to the second end of the second conductor; and

d) attaching an integrated circuit to the first end of the first conductor and the first end of the second conductor.

19. The method of claim 18, wherein the integrated circuit has a first impedance value, and wherein the antenna has a second impedance value, and wherein the magnitude of the real component of the second impedance value is substantially similar to the magnitude of the real component of the first impedance value, and the magnitude of the imaginary component of the second impedance value is substantially similar to the magnitude of the imaginary component of the first impedance value, and wherein the phase of the imaginary component of the first impedance value and phase of the imaginary component of the second impedance value are opposite.

20. The method of claim 19, wherein the first impedance value has a first real component value and a first imaginary component value, wherein the second impedance value has a second real component value and a second imaginary component value, wherein the first real component value is equal to the second real component value and wherein the magnitude of the imaginary component of the second impedance value is equal to the magnitude of the imaginary component the first impedance value, and wherein the phase of the imaginary component of the first impedance value and the phase of the imaginary component of the second impedance value are opposite.

21. The method of claim 19, wherein the first portion of the antenna has a first real component value and a first imaginary component value and the second portion of the antenna has a second real component value and a second imaginary component value, and wherein the second portion of the antenna is selected to provide a second real component value and second imaginary component value which assist in balancing the first real component value and the first imaginary component value to provide the second impedance value of the antenna substantially similar to the first impedance value of the integrated circuit.

22. The method of claim 21, wherein first portion of the antenna has a first real component value and a first imaginary component value and the second portion of the antenna has a second real component value and a second imaginary component value, and wherein the second portion of the antenna is selected to provide a second real component value and second imaginary component value which assist in balancing the first real component value and the first imaginary component value to provide the second impedance value of the antenna equal to the first impedance value of the integrated circuit.

23. The method of claim 18, wherein the first portion of the second antenna element and the second portion of the second antenna element are in the shape of closed loops.

24. The method of claim 18, wherein the first portion of the second antenna element and the second portion of the second antenna element are in the shape of polygons.

25. The method of claim 18, wherein the first portion of the second antenna element is dissimilar in shape to the second portion of the second antenna element.

26. The method of claim 18, wherein the first portion of the second antenna element is similar in shape to the second portion of the second antenna element.

27. The method of claim 18, wherein the first portion of the second antenna element is different in size than the second portion of the second antenna element.