Microstrip antenna for RFID device having both far-field and near-field functionality

• US 8,970,378 B2
• Filed: 09/12/2013
• Issued: 03/03/2015
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: University of Kansas
• Original Assignee: University of Kansas
• Inventors: Deavours, Daniel D., Sivakumar, Mutharasu
• Primary Examiner(s): Nguyen, Tai T
• Application Number:
  US14/025,188
• Publication Number:
  US 20140008447A1
• Time in Patent Office: 537 Days
• Field of Search: 340/572.1, 340/572.4, 340/572.7, 340/5.6, 340/10.51, 343/742, 343/746, 343/767, 343/850, 343/860
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/07773 Antenna details antennas for wireless devices, e.g. RFID tags, in general H01Q1/22
• CPC Class Codes: G06K 19/07775 the antenna being on-chip
• 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 9/045 with particular feeding means for circular polarisation H01Q9/0428
• CPC Class Codes: H01Q 9/0464 Annular ring patch
• CPC Class Codes: H01Q 9/06 Details

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 the 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 annular antenna (46c) design for application to the top of a metal cylinder around a stem.

Claims

1. A radio frequency transponder comprising:

an antenna providing electromagnetic coupling for far-field operation, and thereby acting as a far-field antenna;

a ground plane;

a dielectric substrate interposed between the ground plane and the antenna

an integrated circuit; and

a matching circuit coupling the antenna with the integrated circuit, the matching circuit including a circuit loop providing inductive coupling for near-field operation, and thereby acting as a near-field antenna.

2. The radio-frequency transponder as set forth in claim 1, wherein the antenna is a microstrip patch antenna.

3. The radio-frequency transponder as set forth in claim 1, wherein there are at least two antennas.

4. The radio-frequency transponder as set forth in claim 1, wherein there are at least two matching circuits.

5. The radio-frequency transponder as set forth in claim 1, wherein far-field operation involves frequencies approximately between ultra-high and microwave frequencies.

6. The radio-frequency transponder as set forth in claim 1, wherein near-field operation involves frequencies approximately between low and high frequencies.

7. The radio-frequency transponder as set forth in claim 1, wherein the antenna has a first impedance, and the integrated circuit has a second impedance, and the matching circuit transforms the first impedance of the antenna into the second impedance of the integrated circuit.

8. The radio-frequency transponder as set forth in claim 1, wherein the antenna is substantially annular in shape.

9. The radio-frequency transponder as set forth in claim 8, wherein the antenna is substantially polygonal in shape.

10. The radio-frequency transponder as set forth in claim 1, wherein the antenna has an inner edge and an outer edge, and the matching circuit is coupled with the inner edge of the antenna.

11. The radio-frequency transponder as set forth in claim 1, wherein the antenna has an inner edge and an outer edge, and the matching circuit is coupled with the outer edge of the antenna.

12. The radio-frequency transponder as set forth in claim 1, further including:

first and second feeds extending between the antenna and the matching circuit; and

a shorting stub extending between the first and second transmission lines.

13. A radio frequency identification transponder comprising:

a microstrip patch antenna providing electromagnetic coupling for far-field operation, and thereby acting as a far-field antenna;

a ground plane;

a dielectric substrate interposed between the ground plane and the antenna

an integrated circuit; and

a matching circuit coupling the microstrip patch antenna with the integrated circuit, the matching circuit including a circuit loop of sufficient size to provide inductive coupling for near-field operation, and thereby acting as a near-field antenna.

14. The radio-frequency identification transponder as set forth in claim 13, wherein there are at least two antennas and at least two matching circuits.

15. The radio-frequency identification transponder as set forth in claim 13, wherein far-field operation involves frequencies of approximately between 315 MHz and 5.8 GHz.

16. The radio-frequency identification transponder as set forth in claim 13, wherein near-field operation involves frequencies of approximately between 125 kHz and 13.56 MHz.

17. The radio-frequency identification transponder as set forth in claim 13, wherein the antenna has an inner edge and an outer edge, and the matching circuit is coupled with one of the inner and outer edges of the antenna.

18. A radio frequency identification transponder comprising:

a microstrip patch antenna providing electromagnetic coupling for far-field operation involving frequencies approximately between ultra-high and microwave frequencies, and thereby acting as a far-field antenna;

an integrated circuit;

a matching circuit coupling the microstrip patch antenna with the integrated circuit, the matching circuit including a circuit loop of sufficient size to provide inductive coupling for near-field operation involving frequencies approximately between low and high frequencies, and thereby acting as a near-field antenna;

a ground plane; and

a dielectric substrate interposed between the ground plane and the microstrip patch antenna, the integrated circuit, and the matching circuit.