MICROSTRIP ANTENNA FOR RFID DEVICE

• US 20070164868A1
• Filed: 12/13/2006
• Published: 07/19/2007
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: University of Kansas
• Original Assignee: University of Kansas
• Inventors: Sivakumar, Mutharasu, DEAVOURS, Daniel
• Granted Patent: US 7,750,813 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• 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 1/22 by structural association with other equipment or articles
• 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 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• 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 1/48 Earthing means; Earth screens; Counterpoises
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 5/35 using two or more simultaneously fed points
• CPC Class Codes: H01Q 5/40 Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H01Q 9/0442 with particular tuning means
• CPC Class Codes: H01Q 9/28 Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines waveguide horns or mouths H01Q13/00; slot antennas H01Q13/00
• CPC Class Codes: H01Q 9/30 with feed to end of elongated active element, e.g. unipole H01Q9/44 takes precedence
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface

Abstract

Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near/field-far/field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annual antenna (46c) design for application to the top of a metal cylinder around a stem.

Claims

1. A radio frequency identification transponder comprising:

a microstrip patch antenna;

a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed; and

a matching circuit coupling the first and second feeds with an integrated circuit.

2. The radio frequency identification transponder as set forth in claim 1, wherein the first feed and the second feed are each located an approximately equal distance from and on opposite sides of an approximately center of the non-radiating edge.

3. The radio frequency identification transponder as set forth in claim 1, wherein the first feed and the second feeds each consist of one or more microstrip transmission lines.

4. The radio frequency identification transponder as set forth in claim 1, wherein the matching circuit includes a first transmission line coupled with the first feed and a second transmission line coupled with the second feed, with the first and second transmission lines being substantially symmetrical.

5. The radio frequency identification transponder as set forth in claim 4, wherein the first transmission line and the second transmission line are coupled with the integrated circuit.

6. The radio frequency identification transponder as set forth in claim 1, wherein the matching circuit consists of a first transmission line coupled with the first feed and a second transmission line coupled with the second feed, with the first and second transmission lines being substantially symmetrical.

7. The radio frequency identification transponder as set forth in claim 1, wherein the matching circuit includes a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds.

8. In a radio frequency identification transponder for physical association with an object and for storing and communicating data regarding the object, the radio frequency identification transponder having a microstrip patch antenna and an integrated circuit, the improvement comprising:

a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed; and

a matching circuit coupling the first and second feeds with an integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds.

9. The radio frequency identification transponder as set forth in claim 8, wherein the first feed and the second feed are each located an approximately equal distance from and on opposite sides of an approximately center of the non-radiating edge.

10. The radio frequency identification transponder as set forth in claim 8, wherein the first feed and the second feeds each consist of one or more microstrip transmission lines.

11. The radio frequency identification transponder as set forth in claim 8, wherein the matching circuit consists of a first transmission line coupled with the first feed and a second transmission line coupled with the second feed, with the first and second transmission lines being substantially symmetrical.

12. A radio frequency identification transponder comprising:

a first patch antenna and a second patch antenna;

an integrated circuit having a first pair of terminals and a second pair of terminals; and

a first matching circuit for coupling the first patch antenna to the first pair of terminals, wherein the first matching circuit resonates at a first frequency; and

a second matching circuit for coupling the second patch antenna to the second pair of terminals, wherein the second matching circuit resonates at a second frequency.

13. The radio frequency identification transponder as set forth in claim 12, further including, for each patch antenna, first and second balanced feeds and a shorting stub coupling the balanced feeds.

14. The radio frequency identification transponder as set forth in claim 12, wherein the first patch antenna is a microstrip patch antenna operable above a ground plane separated by a substrate, and the second patch antenna is operable with the substrate in free space.

15. The radio frequency identification transponder as set forth in claim 12, wherein the first frequency is approximately identical to the second frequency.

16. In a radio frequency identification transponder for physical association with an object and for storing and communicating data regarding the object, the improvement comprising:

a first patch antenna and a second patch antenna;

an integrated circuit having a first pair of terminals and a second pair of terminals;

a first matching circuit for coupling the first patch antenna to the first pair of terminals, wherein the first matching circuit resonates at a first frequency; and

a second matching circuit for coupling the second patch antenna to the second pair of terminals, wherein the second matching circuit resonates at a second frequency.

17. The radio frequency identification transponder as set forth in claim 16, further including, for reach patch antenna, first and second balanced feeds and a shorting stub coupling the balanced feeds.

18. The radio frequency identification transponder as set forth in claim 16, wherein the first patch antenna is a microstrip patch antenna operable above a ground plane separated by a substrate, and the second patch antenna is operable with the substrate in free space.

19. The radio frequency identification transponder as set forth in claim 16, wherein the first frequency is approximately identical to the second frequency.

20. A radio frequency identification transponder comprising:

a microstrip patch antenna providing electromagnetic coupling for far-field operation;

an integrated circuit; and

a matching circuit coupling the microstrip patch antenna with the integrated circuit includes a circuit loop that is sufficiently large to provide inductive coupling for near-field operation.

21. In a radio frequency identification transponder for physical association with an object for storing data regarding the object, the radio frequency identification transponder having a microstrip patch antenna, an integrated circuit, and a matching circuit coupling the microstrip patch antenna with the integrated circuit, the improvement comprising:

the matching circuit including a circuit loop which also functions as a near-field antenna.

22. A radio frequency identification transponder comprising:

a first layer including a substrate and a ground plane;

a second layer including

first and second microstrip patch antennas, with each patch antenna extending toward a different side of the second layer,

an integrated circuit, and

first and second matching circuits coupling the first and second microstrip patch antennas, respectively, to the integrated circuit.

23. The radio frequency identification transponder as set forth in claim 22, wherein the first microstrip patch antenna extends toward a first side of the second layer, and the second microstrip patch antenna extends toward an opposite second side of the second layer, so as to achieve directional diversity.

24. The radio frequency identification transponder as set forth in claim 22, further including a third layer including a superstrate protecting the second layer from an adverse condition of an operating environment.

25. The radio frequency identification transponder as set forth in claim 24, wherein the superstrate of the third layer has a higher dielectric than the substrate of the first layer.

26. The radio frequency identification transponder as set forth in claim 25, wherein the dielectric of the superstrate is less than 10.

27. The radio frequency identification transponder as set forth in claim 25, wherein the dielectric of the superstrate is equal to or less than 6.

28. The radio frequency identification transponder as set forth in claim 24, wherein the adverse condition is a physical impact.

29. The radio frequency identification transponder as set forth in claim 24, wherein the adverse condition is a high temperature.

30. The radio frequency identification transponder as set forth in claim 22, wherein the first and second layers are flexible so as to conform to a curved shape when applied thereto.

31. In a radio frequency identification transponder for physical association with an object and for storing and communicating data regarding the object, the radio frequency identification transponder having an integrated circuit, the improvement comprising:

a first layer including a substrate and a ground plane;

a second layer including

first and second microstrip patch antennas, with each patch antenna extending toward a different side of the second layer,

an integrated circuit, and

first and second matching circuits coupling the first and second microstrip patch antennas, respectively, to the integrated circuit; and

a third layer including a superstrate for protecting the second layer from an adverse condition of an operating environment.

32. The radio frequency identification transponder as set forth in claim 31, wherein the first microstrip patch antenna extends toward a first side of the second layer, and the second microstrip patch antenna extends toward an opposite second side of the second layer, so as to achieve directional diversity.

33. The radio frequency identification transponder as set forth in claim 31, wherein the superstrate of the third layer has a higher dielectric than the substrate of the first layer.

34. The radio frequency identification transponder as set forth in claim 33, wherein the dielectric of the superstrate is less than 10.

35. The radio frequency identification transponder as set forth in claim 33, wherein the dielectric of the superstrate is equal to or less than 6.

36. The radio frequency identification transponder as set forth in claim 31, wherein the adverse condition is a physical impact.

37. The radio frequency identification transponder as set forth in claim 31, wherein the adverse condition is a high temperature.

38. The radio frequency identification transponder as set forth in claim 31, wherein the first, second, and third layers are flexible so as to conform to a curved shape when applied thereto.

39. A radio frequency identification transponder comprising:

a microstrip patch antenna having an annular shape with an inner edge and an outer edge;

an integrated circuit;

a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed; and

a matching circuit coupling the first and second feeds with an integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds.

40. The radio frequency identification transponder as set forth in claim 39, wherein the matching circuit is coupled with the inner edge of the microstrip patch antenna.

41. The radio frequency identification transponder as set forth in claim 39, wherein the matching circuit is coupled with the outer edge of the microstrip patch antenna.

42. The radio frequency identification transponder as set forth in claim 39, wherein the microstrip patch antenna has annular polygonal shape.

43. The radio frequency identification transponder as set forth in claim 42, further including one or more slots manufactured into the annular polygonal shape.

44. In a radio frequency identification transponder for physical association with a cylindrical object having a stem and for storing and communicating data regarding the object, the radio frequency identification transponder having a microstrip patch antenna and an integrated circuit, the improvement comprising:

the microstrip patch antenna having an annular shape with an inner edge and an outer edge;

a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed; and

a matching circuit coupling the first and second feeds with the integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds, wherein the matching circuit is coupled with the inner edge of the microstrip patch antenna.

45. The radio frequency identification transponder as set forth in claim 44, wherein the matching circuit is coupled with the outer edge of the microstrip patch antenna.

46. The radio frequency identification transponder as set forth in claim 44, wherein the microstrip patch antenna has a annular polygonal shape.

47. The radio frequency identification transponder as set forth in claim 46, further including one or more slots manufactured into the annular polygonal shape.

48. In a radio frequency identification transponder for physical association with a cylindrical object having a stem and for storing and communicating data regarding the object, the radio frequency identification transponder having a microstrip patch antenna and an integrated circuit, the improvement comprising:

the microstrip patch antenna having an annular shape with an inner edge and an outer edge;

a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed; and

a matching circuit coupling the first and second feeds with the integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds,

wherein the matching circuit is coupled with the outer edge of the microstrip patch antenna.

49. The radio frequency identification transponder as set forth in claim 48, wherein the matching circuit is coupled with the outer edge of the microstrip patch antenna.

50. The radio frequency identification transponder as set forth in claim 48, wherein the microstrip patch antenna has an annular polygonal shape.

51. The radio frequency identification transponder as set forth in claim 50, further including one or more slots manufactured into the annular polygonal shape.