Open-ended two-strip meander line antenna, RFID tag using the antenna, and antenna impedance matching method thereof

• US 20070023525A1
• Filed: 07/27/2006
• Published: 02/01/2007
• Est. Priority Date: 07/27/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Choi, Gil-Young, Pyo, Cheol-Sig, Choi, Won-Kyu, Son, Hae-Won
• Granted Patent: US 8,009,118 B2
• Time in Patent Office: Days
• US Class Current: 235/454
• 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 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• 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

Abstract

An open-ended two-strip meander line antenna, an RFID tag using the same and an antenna impedance matching method thereof are provided. The antenna includes: a radiating strip line for deciding a resonant frequency of the antenna; and a feeding strip line for providing a radio frequency (RF) signal to an element connected to the antenna, wherein ends of the radiating strip line and the feeding strip line are open.

Claims

1. An antenna comprising:

a radiating strip line for deciding a resonant frequency of the antenna; and

a feeding strip line for providing a radio frequency (RF) signal to an element connected to the antenna,

wherein ends of the radiating strip line and the feeding strip line are open.

2. The antenna as recited in claim 1, wherein the feeding strip line includes a terminal for accessing to the element connected to the antenna.

3. The antenna as recited in claim 2, wherein the radiating strip line and the feeding strip line are disposed at different sides of a substrate.

4. The antenna as recited in claim 3, wherein the length of the feeding strip line is shorter than the length of the radiating strip line.

5. The antenna as recited in claim 4, wherein an input impedance is controlled using a characteristic that an impedance of the radiating strip line is shown at the terminal of the feeding strip line by being transformed to a predetermined impedance step-up ratio through an electromagnetic coupling of the radiating strip line and the feeding strip line.

6. The antenna as recited in claim 5, wherein the input impedance is controlled based on a characteristic that a real number part of an admittance of the antenna varies according to the impedance step-up ratio.

7. The antenna as recited in claim 6, wherein the input impedance is controlled based on a characteristic that the real number part of the admittance of the antenna is reduced as the impedance step-up ratio increases.

8. The antenna as recited in claim 6, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio varies according to a length ratio of the radiating strip line to the feeding strip line.

9. The antenna as recited in claim 8, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio increases as the length ratio of the radiating strip line to the feeding strip line increases.

10. The antenna as recited in claim 8, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio varies according to a width ratio of the radiating strip line to the feeding strip line.

11. The antenna as recited in claim 10, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio increase as the width ratio of the radiating strip line to the feeding strip line is reduced.

12. The antenna as recited in claim 4, wherein the input impedance is controlled based on a characteristic that a real number part of an admittance of the antenna varies according to a real number part of an impedance of the radiating strip line.

13. The antenna as recited in claim 12, wherein the input impedance is controlled based on a characteristic that a real number of the antenna admittance is reduced as the real number part of the impedance of the radiating strip line increases.

14. The antenna as recited in claim 4, wherein the input impedance is controlled based on a characteristic that an imaginary number of the antenna admittance varies according to a characteristic impedance of a transmission line formed by the radiating strip line and the feeding strip line.

15. The antenna as recited in claim 14, wherein the input impedance is controlled based on a characteristic that an imaginary number part of the antenna admittance increases as the characteristic impedance of the transmission line is reduced.

16. The antenna as recited in claim 14, wherein the input impedance is controlled based on a characteristic that a characteristic impedance of the transmission line varies according to line widths of the radiating strip line and the feeding strip line.

17. The antenna as recited in claim 14, wherein an input impedance is controlled based on a characteristic that a characteristic impedance varies according to a thickness and a dielectric constant of the substrate.

18. The antenna as recited in claim 4, wherein an input impedance is controlled based on a characteristic that an imaginary number part of the antenna impedance varies according to a length of a transmission line formed by the radiating strip line and the feeding strip line.

19. The antenna as recited in claim 18, wherein the length of the transmission line is the length of the feeding strip line.

20. The antenna as recited in claim 18, wherein the length of the transmission line is controlled to make the imaginary number part of the antenna impedance to be an inductive reactance.

21. The antenna as recited in claim 18, wherein a value of multiplying the length of the transmission line and the propagation constant of the transmission line is greater than (n+½

)*n, and smaller than (n+1)*n, where n is an integer greater than 0.

22. The antenna as recited in claim 4, wherein the radiating strip line and the feeding strip line have a meander structure.

23. The antenna as recited in claim 4, wherein the radiating strip line and the feeding strip line have a dipole structure.

24. The antenna as recited in claim 4, wherein an input impedance is controlled based on a characteristic that the antenna impedance varies according to relative locations of the radiating strip line and the feeding strip line.

25. A radio frequency identification (RFID) tag, comprising:

an antenna for receiving an RF signal transmitted from an RFID reader;

a RF front-end for rectifying and detecting the RF signal; and

a signal processing unit connected to the RF front-end, wherein the antenna includes;

a radiating strip line for deciding a resonant frequency of the antenna; and

a feeding strip line for providing a radio frequency (RF) signal to an element connected to the antenna, wherein ends of the radiating strip line and the feeding strip line are oped.

26. The RFID tag as recited in claim 25, wherein the feeding strip line includes a terminal for accessing the element connected to the antenna.

27. The RFID tag as recited in claim 26, wherein the radiating strip line and the feeding strip line are disposed at different sides of a substrate, and the length of the feeding strip line is shorter than the length of the radiating strip line.

28. The RFID tag as recited in claim 27, wherein an input impedance is controlled based on a characteristic that an impedance of the radiating strip line is shown at the terminal of the feeding strip line by being transformed to a predetermined impedance step-up ratio through an electromagnetic coupling of the radiating strip line and the feeding strip line.

29. The RFID tag as recited in claim 28, wherein the input impedance is controlled based on a characteristic that a real number part of an admittance of the antenna varies according to the impedance step-up ratio.

30. The RFID tag as recited in claim 29, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio varies according to a length ratio of the radiating strip line to the feeding strip line.

31. The RFID tag as recited in claim 29, wherein the input impedance is controlled based on a characteristic that the impedance step-up ratio varies according to a width ratio of the radiating strip line to the feeding strip line.

32. The RFID tag as recited in claim 27, wherein the input impedance is controlled based on a characteristic that a real number part of an admittance of the antenna varies according to a real number part of an impedance of the radiating strip line.

33. The RFID tag as recited in claim 27, wherein the input impedance is controlled based on a characteristic that an imaginary number of the antenna admittance varies according to a characteristic impedance of a transmission line formed by the radiating strip line and the feeding strip line.

34. The RFID tag as recited in claim 27, wherein the input impedance is controlled based on a characteristic that a characteristic impedance of the transmission line varies according to line widths of the radiating strip line and the feeding strip line.

35. The RFID tag as recited in claim 26, wherein an input impedance is controlled based on a characteristic that a characteristic impedance varies according to a thickness and a dielectric constant of the substrate.

36. The RFID tag as recited in claim 27, wherein an input impedance is controlled based on a characteristic that an imaginary number part of the antenna impedance varies according to a length of a transmission line formed by the radiating strip line and the feeding strip line.

37. The RFID tag as recited in claim 36, wherein the length of the transmission line is the length of the feeding strip line.

38. The RFID tag as recited in claim 36, wherein the length of the transmission line is controlled to make the imaginary number part of the antenna impedance an inductive reactance.

39. The RFID tag as recited in claim 27, wherein the radiating strip line and the feeding strip line have a meander structure.

40. The RFID tag as recited in claim 27, wherein the antenna is resonated at an RF signal frequency transmitted from the RFID reader, and is conjugate-matched at the front-end.

41. The RFID tag as recited in claim 27, wherein the substrate is one of glass, ceramic, teflon, epoxy, and FR-4.

42. The RFID tag as recited in claim 27, wherein the substrate is an organic material.

43. The RFID tag as recited in claim 27, wherein the conductive material used for the radiating strip line and the feeding strip line is one selected from the group consisting of copper, copper alloy, aluminum, and conductive ink.

44. The RFID tag as recited in claim 27, wherein the radiating strip line and the feeding strip line are manufactured with different conductive materials.

45. The RFID tag as recited in claim 27, wherein the radiating strip line and the feeding strip line are manufactured through one of etching, depositing and printing.

46. The RFID tag as recited in claim 27, wherein the radiating strip line and the feeding strip line are manufactured using different methods.

47. An antenna impedance matching method for an open-ended strip line antenna, the antenna impedance matching method comprising the step of:

matching an impedance based on a characteristic that an impedance of the radiating strip line is shown at the terminal of the feeding strip line by being transformed to a predetermined impedance step-up ratio through an electromagnetic coupling of the radiating strip line and the feeding strip line,

wherein the open-ended strip line antenna includes having a radiating strip line for deciding a resonant frequency of the antenna, and a feeding strip line for providing an RF signal to an element connected through a terminal, where the feeding strip line and the radiating strip line are disposed at both sides of a substrate and are electromagnetically coupled with each other.

48. The antenna impedance matching method as recited in claim 47, wherein the impedance matching is performed based on a characteristic that a real number part of an admittance of the antenna varies according to the impedance step-up ratio.

49. The antenna impedance matching method as recited in claim 48, wherein the impedance matching is performed based on a characteristic that the impedance step-up ratio varies according to a length ratio and a width ratio of the radiating strip line to the feeding strip line.

50. The antenna impedance matching method as recited in claim 48, wherein the impedance matching is performed based on a characteristic that a real number part of an admittance of the antenna varies according to a real number part of an impedance of the radiating strip line.

51. The antenna impedance matching method as recited in claim 47, wherein the impedance matching is performed based on a characteristic that an imaginary number of the antenna admittance varies according to a characteristic impedance of a transmission line formed by the radiating strip line and the feeding strip line.

52. The antenna impedance matching method as recited in claim 51, wherein the impedance matching is performed based on a characteristic that a characteristic impedance of the transmission line varies according to line widths of the radiating strip line and the feeding strip line.

53. The antenna impedance matching method as recited in claim 51, wherein the impedance matching is performed based on a characteristic that an imaginary number part of the antenna impedance varies according to a length of a transmission line formed by the radiating strip line and the feeding strip line.