RFID antenna and methods

• US 20090009415A1
• Filed: 07/08/2008
• Published: 01/08/2009
• Est. Priority Date: 01/09/2006
• Status: Abandoned Application

• Current Assignee: Pulse Finland Oy (Yageo Corporation)
• Original Assignee: Pulse Finland Oy (Yageo Corporation)
• Inventors: Tanska, Mika, Koskiniemi, Kimmo
• Application Number:
  US12/217,789
• Publication Number:
  US 20090009415A1
• Time in Patent Office: Days
• US Class Current: 343/742
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• 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 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 7/08 Ferrite rod or like elongated core

Abstract

An antenna (200) of an RFID reader based on the magnetic field, especially intended for mobile stations. The main coil (220) of the antenna is inductively coupled to the feeding source, whereby the main coil becomes galvanically isolated from the source. For this purpose, the antenna structure includes an auxiliary coil (230) and a feed element (240) in addition to the main coil. The auxiliary coil is galvanically connected to the main coil, and there is a relatively strong inductive coupling (M) between the feed element and the auxiliary coil. The feed element is coupled directly to the AC source in the reader, in which case an alternating voltage is induced in the auxiliary coil, and an alternating current is generated in it and the main coil. The connection to the RFID tag in the object is provided with the magnetic field corresponding to that current. The reliability of the antenna improves in comparison to the known antennas, because the mechanical junctions that are susceptible to the deterioration of the contact are omitted.

Claims

1-7. -7. (canceled)

8. An antenna for use with an RFID system, comprising:

a primary coil coupled with an auxiliary coil, said primary coil and said auxiliary coil residing within the same plane; and

a feed element coupled to an alternating current source;

wherein inductive coupling between said auxiliary coil and said feed element isolate the primary coil galvanically from said alternating current source.

9. The antenna of claim 8, wherein said RFID system comprises a device comprising a substrate and an outer cover.

10. The antenna of claim 9, wherein said primary coil and said auxiliary coil reside on an inner surface of said outer cover of said device.

11. The antenna of claim 10, wherein the feed element is located on said substrate of said device below the auxiliary coil.

12. The antenna of claim 10, wherein the feed element is located on a surface of an inner casing of the device below the auxiliary coil, and connected to said substrate of the device by one or more contacts.

13. The antenna of claim 8, wherein a ferrite plate is located below the primary coil to shape at least a portion of the magnetic field of the antenna.

14. The antenna of claim 9, wherein the primary coil and the auxiliary coil comprise conductor patterns on an inner surface of said outer cover of said device.

15. The antenna of claim 14, wherein the respective planes of the auxiliary coil and the feed element are both substantially perpendicular to the plane of the primary coil.

16. The antenna of claim 8, wherein said auxiliary coil comprises a substantially rectangular coil comprising a predetermined length and width.

17. The antenna of claim 16, wherein said feed element comprises a substantially rectangular coil comprising substantially similar predetermined length and width as said auxiliary coil.

18. The antenna of claim 17, wherein said primary coil further comprises a substantially rectangular coil comprising a predetermined length and width, at least one of said length and width of said primary coil being larger than said respective predetermined length and width of said auxiliary coil.

19. A method of operating a radio frequency device, the device comprising a first substrate with a primary coil and a secondary coil disposed thereon, and a second substrate with a feed element and at least terminals from an alternating current source disposed thereon, the second substrate disposed substantially parallel and proximate to said first substrate, the method comprising:

providing current via said terminals;

inductively coupling said auxiliary coil and said feed element; and

based at least in part on said inductive coupling, isolating the primary coil from said alternating current source.

20. The method of claim 19, wherein said first substrate is disposed on an outer cover of said radio frequency device, and said second substrate is disposed on an internal casing of said radio frequency device.

21. The method of claim 20, wherein said act of providing current via said terminals comprises providing alternating current from said source for at least a period of time upon receipt of a signal from an entity external to said device.

22. The method of claim 20, wherein said act of isolating the primary coil from said alternating current source comprises isolating said primary coil galvanically.

23. An antenna of a radio frequency reader adapted for use inside of a device, the antenna comprising:

a main coil adapted to form a magnetic field; and

a coupling apparatus to connect the main coil to an alternating current source of the reader, said coupling apparatus comprising;

an auxiliary coil; and

a feed element;

wherein the auxiliary coil is galvanically coupled to the main coil and the feed element is arranged to be directly coupled to the source; and

wherein an inductive coupling is only between the auxiliary coil and the feed element to isolate the main coil galvanically from the source, said main coil and said auxiliary coil comprising conductor patterns on a surface of a single antenna substrate.

24. An antenna according to claim 23, wherein the antenna circuit board is fastened to an inner surface of an outer cover of said device.

25. An antenna according to claim 23, wherein the feed element is located on a main circuit board of said device below the auxiliary coil.

26. An antenna according to claim 23, wherein the feed element is located on a surface of an inner casing of the device below the auxiliary coil, and connected to a main circuit board of the device by one or more contacts.

27. An antenna according to claim 23, wherein a ferrite plate is located below the main coil to shape the magnetic field of the antenna.

28. An antenna according to claim 23, wherein the main coil and the auxiliary coil comprise conductor patterns on an inner surface of an outer cover of said device.

29. An antenna according to claim 23, wherein the planes of the auxiliary coil and the feed element are substantially perpendicular to the plane of the main coil.

30. An antenna of an RFID reader, the antenna comprising:

a main coil capable of forming a magnetic field and coupling means to connect the main coil to an alternating current source of the reader, said coupling means comprising an auxiliary coil and a feed element, the auxiliary coil being galvanically coupled to the main coil, and the feed element being arranged to be directly coupled to said source;

wherein an inductive coupling is formed only between the auxiliary coil and the feed element, so as to isolate the main coil galvanically from said source; and

wherein the main coil and the auxiliary coil comprise conductor patterns on a surface of the same substrate.