RFID material tracking method and apparatus

• US 7,042,358 B2
• Filed: 08/28/2002
• Issued: 05/09/2006
• Est. Priority Date: 08/09/1999
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Moore, Scott E.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): NGUYEN, NAM V
• Application Number:
  US10/229,475
• Publication Number:
  US 20030001725A1
• Time in Patent Office: 1,350 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.3, 340/572.4, 340/572.5, 340/10.1, 340/10.3, 340/539, 340/514, 235/385, 235/438, 235/491, 455/423, 455/67.4
• US Class Current: 340/572.1
• CPC Class Codes: G06K 17/00 Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00

Abstract

A method and apparatus for tracking items automatically is described. A passive RFID (Radio Frequency IDentification) tag is used with a material tracking system capable of real-time pinpoint location and identification of thousands of items in production and storage areas. Passive RFID tags are attached to the item to be tracked, remote sensing antennas are placed at each remote location to be monitored, interrogators with several antenna inputs are connected to the sensing antennas to multiplex the antenna signals, and a host computer communicates with the interrogators to determine item locations to an exacting measure.

Claims

1. A method of self-testing an RFID identification system, comprising:

polling an identification tag location with a sensing antenna;

detecting if a voltage is present in the sensing antenna from a tag at the polled tag location;

waiting a predetermined time for a voltage to become present in the sensing antenna if no voltage is present in the sensing antenna;

determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna;

turning an antenna carrier of the sensing antenna off if there is no tag data present in the sensing antenna;

turning the antenna carrier back on after it is turned off, such that the antenna carrier cycles off and back, to repower the tag at the tag location; and

issuing an alert if after the predetermined time has elapsed that there is no voltage present in the sensing antenna.

2. The method of self-testing an RF identification system as described in claim 1, and further comprising:

querying an identification tag database to determine if an antenna should be present at a location if no voltage is present at the polling location.

3. The method of claim 1, wherein the method further includes determining whether a current iteration, for determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna, is above a limit for the number of iterations.

4. The method of claim 1, wherein the method further includes setting tag information data to indicate no tag if no tag information data is present at the sensing antenna for a number of iterations above a limit for the number of iterations for determining if tag information data is present at the sensing antenna.

5. The method of claim 1, wherein the method further includes sending tag information data to a host after determining if tag information data is present at the sensing antenna.

6. The method of claim 1, wherein the method further includes storing tag information data after determining if tag information data is present at the sensing antenna.

7. The method of claim 1, wherein determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna includes waiting two power cycles to determine whether a signal representing the tag information data is present.

8. The method of claim 1, wherein determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna includes waiting about 50 milliseconds to determine whether a signal representing the tag information data is present.

9. The method of claim 1, wherein scanning for a tag using the sensing antenna has a scan time of about 0.1 seconds for self-testing the identification tag location if no tag is sensed.

10. A method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

turning on one of the antennas to poll a specific tag location;

determining whether a voltage due to an excited tag is present at the active antenna;

waiting a predetermined time to detect a voltage in the active antenna if no voltage is present in the active antenna;

reading tag data from the tag associated with the active antenna if there is a voltage;

turning the active antenna off if after the predetermined time there is no voltage present in the active antenna;

turning the antenna back on, such that the antenna cycles off and back on, to repower the tag at the tag location; and

repeating the determining through the reading until a voltage is detected in the active antenna or until a certain second predetermined time has elapsed.

11. The method of claim 10, and further comprising:

sequentially activating each of the plurality of antennas to read tag information for all tag locations.

12. The method of claim 10, wherein turning on one of the antennas to poll a specific tag location includes driving one of the antennas with a square wave drive signal operating at 125 kHZ.

13. The method of claim 10, wherein repeating the determining through the reading until a voltage is detected in the active antenna or until a certain second predetermined time has elapsed includes determining whether a current iteration for determining whether a voltage due to an excited tag is present is above a limit for the number of iterations.

14. The method of claim 10, wherein the method further includes setting tag data to indicate no tag if no voltage due to an excited tag is present at the active antenna for a number of iterations above a limit for the number of iterations for determining if voltage due to an excited tag is present at the active antenna.

15. The method of claim 10, wherein the method further includes sending tag data to a host after determining whether a voltage due to an excited tag is present at the active antenna.

16. The method of claim 10, wherein the method further includes storing tag data after determining whether a voltage due to an excited tag is present at the active antenna.

17. The method of claim 10, wherein waiting a predetermined time to detect a voltage in the active antenna includes waiting two power cycles to determine whether a signal representing the tag data is present.

18. The method of claim 10, wherein waiting a predetermined time to detect a voltage in the active antenna includes waiting about 50 milliseconds to determine whether a signal representing the tag data is present.

19. The method of claim 10, wherein scanning for a tag using one of the antennas to poll a specific tag location has a scan time of about 0.1 seconds for testing the system for identifying goods at the specific tag location if no tag is sensed.

20. A method of self-testing an REID identification system, comprising:

accessing an antenna map of a plurality of antennas to determine which antennas in the antenna map are active, the antenna map having an address for each antenna;

selecting an active antenna;

activating the selected antenna;

determining if the selected antenna has an antenna voltage that exceeds a predetermined lower limit; and

obtaining tag data for a tag associated with the selected antenna.

21. The method of claim 20, wherein accessing an antenna map to determine which antennas on the antenna map are active includes skipping the self-testing with antennas indicated as inactive on the antenna map.

22. The method of claim 20, wherein activating the selected antenna includes driving the selected antenna with a square wave drive signal operating at 125 kHZ.

23. The method of claim 20, wherein the method further includes alerting a host or a local alarm on determining that the selected antenna has an antenna voltage less than the predetermined lower limit.

24. The method of claim 20, wherein obtaining tag data for a tag associated with the selected antenna includes waiting a predetermined time for tag data to be read.

25. The method of claim 24, wherein waiting a predetermined time for tag data to be read includes waiting two power cycles.

26. The method of claim 24, wherein waiting a predetermined time for tag data to be read includes waiting about 50 milliseconds.

27. The method of claim 20, wherein obtaining tag data for a tag associated with the selected antenna includes:

determining if tag data is detected by the selected antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations; and

if tag data is detected by the selected antenna, storing the tag data.

28. The method of claim 27, wherein obtaining tag data for a tag associated with the selected antenna further includes setting the tag data to no tag if tag data is not detected and the current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations.

29. The method of claim 20, wherein the method further includes sending tag data to a host after obtaining tag data for a tag associated with the selected antenna.

30. The method of claim 20, wherein the method further includes storing tag data after obtaining tag data for a tag associated with the selected antenna.

31. The method of claim 20, wherein scanning for the tag associated with the selected antenna has a scan time of about 0.1 seconds for self-testing a location of the tag if no tag is sensed.

32. A method of self-testing an RFID identification system, comprising:

accessing an antenna map to determine which antennas in the antenna map are active;

selecting an active antenna;

activating the selected antenna;

determining if the selected antenna has an antenna voltage that exceeds a predetermined lower limit; and

obtaining tag data for a tag associated with the selected antenna, wherein obtaining tag data for a tag associated with the selected antenna includes;

determining if tag data is detected by the selected antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations; and

if tag data is detected by the selected antenna, storing the tag data, wherein obtaining tag data for a tag associated with the selected antenna further includes incrementing the iteration count and cycling a driver for the selected antenna off and then on if tag data is not detected and the current iteration count for determining if tag data is detected by the selected antenna is below a limit for the number of iterations.

33. A method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

accessing an antenna map of the plurality of sensing antennas to determine which sensing antennas of the plurality of sensing antennas are active, the antenna map having an address for each sensing antenna;

selecting an active sensing antenna to poll a specific tag location;

driving the selected sensing antenna;

determining if the selected sensing antenna has an antenna voltage that exceeds a predetermined lower limit;

obtaining tag data for a tag at a specific tag location associated with the selected sensing antenna; and

selecting a second sensing antenna of the plurality of sensing antennas from the antenna map to determine if the second sensing antenna has an antenna voltage that exceeds a predetermined lower limit and to obtain tag data for a second tag at a specific second tag location associated with the selected second sensing antenna, wherein the second sensing antenna is indicated as active on the antenna map.

34. The method of claim 33, wherein accessing an antenna map to determine which sensing antennas on the antenna map are active includes skipping the testing of sensing antennas indicated as inactive on the antenna map.

35. The method of claim 33, wherein driving the selected sensing antenna includes driving the selected sensing antenna with a square wave drive signal operating at 125 kHZ.

36. The method of claim 33, wherein the method further includes alerting a host or a local alarm on determining that the selected sensing antenna has an antenna voltage less than the predetermined lower limit.

37. The method of claim 33, wherein obtaining tag data for a tag associated with the selected sensing antenna includes waiting a predetermined time for tag data to be read.

38. The method of claim 37, wherein waiting a predetermined time for tag data to be read includes waiting two power cycles.

39. The method of claim 37, wherein waiting a predetermined time for tag data to be read includes waiting about 50 milliseconds.

40. The method of claim 33, wherein obtaining tag data for a tag associated with the selected sensing antenna includes:

determining if tag data is detected by the selected sensing antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected sensing antenna is above a limit for the number of iterations; and

if tag data is detected by the selected sensing antenna, storing the tag data.

41. The method of claim 40, wherein obtaining tag data for a tag associated with the selected sensing antenna further includes setting the tag data to no tag if tag data is not detected and the current iteration count for determining if tag data is detected by the selected sensing antenna is above a limit for the number of iterations.

42. The method of claim 33, wherein the method further includes sending tag data to a host after obtaining tag data for a tag associated with the selected sensing antenna.

43. The method of claim 33, wherein the method further includes storing tag data after obtaining tag data for a tag associated with the selected sensing antenna.

44. The method of claim 33, wherein scanning for the tag associated with the selected sensing antenna has a scan time of about 0.1 seconds for testing the system for identifying goods at the specific tag location if no tag is sensed.

45. A method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

accessing an antenna map to determine which sensing antennas of the plurality of sensing antennas are active;

selecting an active sensing antenna to poll a specific tag location;

driving the selected sensing antenna;

determining if the selected sensing antenna has an antenna voltage that exceeds a predetermined lower limit;

obtaining tag data for a tag at a specific tag location associated with the selected sensing antenna; and

selecting a second sensing antenna of the plurality of sensing antennas from the antenna map to determine if the second sensing antenna has an antenna voltage that exceeds a predetermined lower limit and to obtain tag data for a second tag at a specific second tag location associated with the selected second sensing antenna, wherein the second sensing antenna is indicated as active on the antenna map, wherein obtaining tag data for a tag associated with the selected sensing antenna includes;

determining if tag data is detected by the selected sensing antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected sensing antenna is above a limit for the number of iterations; and

if tag data is detected by the selected sensing antenna, storing the tag data, wherein obtaining tag data for a tag associated with the selected sensing antenna further includes incrementing the iteration count and cycling a driver for the selected sensing antenna off and then on if tag data is not detected and the current iteration count for determining if tag data is detected by the selected sensing antenna is below a limit for the number of iterations.

46. A computer-readable medium having computer-executable instructions for performing a method of self-testing an RFID identification system, the method comprising:

polling an identification tag location with a sensing antenna;

detecting if a voltage is present in the sensing antenna from a tag at the polled tag location;

waiting a predetermined time for a voltage to become present in the sensing antenna if no voltage is present in the sensing antenna;

determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna;

turning an antenna carrier of the sensing antenna off if there is no tag data present in the sensing antenna;

turning the antenna carrier back on after it is turned off, such that the antenna carrier cycles off and back on, to repower the tag at the tag location; and

issuing an alert if after the predetermined time has elapsed that there is no voltage present in the sensing antenna.

47. The computer-readable medium of claim 46, wherein the method further includes querying an identification tag database to determine if an antenna should be present at a location if no voltage is present at the polling location.

48. The computer-readable medium of claim 46, wherein the method further includes determining whether a current iteration, for determining if tag information data is present at the sensing antenna if a voltage is present in the sensing antenna, is above a limit for the number of iterations.

49. The computer-readable medium of claim 46, wherein the method further includes setting tag information data to indicate no tag if no tag information data is present at the sensing antenna for a number of iterations above a limit for the number of iterations for determining if tag information data is present at the sensing antenna.

50. The computer-readable medium of claim 46, wherein the method further includes sending tag information data to a host after determining if tag information data is present at the sensing antenna.

51. The computer-readable medium of claim 46, wherein the method further includes storing tag information data after determining if tag information data is present at the sensing antenna.

52. A computer-readable medium having computer-executable instructions for performing a method of self-testing an RFID identification system, the method comprising:

accessing an antenna map of a plurality of antennas to determine which antennas on the antenna map are active, the antenna map having an address for each antenna;

selecting an active antenna;

activating the selected antenna;

determining if the selected antenna has an antenna voltage that exceeds a predetermined lower limit; and

obtaining tag data for a tag associated with the selected antenna.

53. The computer-readable medium of claim 52, wherein accessing an antenna map to determine which antennas on the antenna map are active includes skipping the self-testing with antennas indicated as inactive on the antenna map.

54. The computer-readable medium of claim 52, wherein activating the selected antenna includes driving the selected antenna with a square wave drive signal operating at 125 kHZ.

55. The computer-readable medium of claim 52, wherein the method further includes alerting a host or a local alarm on determining that the selected antenna has an antenna voltage less than the predetermined lower limit.

56. The computer-readable medium of claim 52, wherein obtaining tag data for a tag associated with the selected antenna includes waiting a predetermined time for tag data to be read.

57. The computer-readable medium of claim 52, wherein obtaining tag data for a tag associated with the selected antenna includes:

determining if tag data is detected by the selected antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations; and

if tag data is detected by the selected antenna, storing the tag data.

58. The computer-readable medium of claim 57, wherein obtaining tag data for a tag associated with the selected antenna further includes setting the tag data to no tag if tag data is not detected and the current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations.

59. The computer-readable medium of claim 52, wherein the method further includes sending tag data to a host after obtaining tag data for a tag associated with the selected antenna.

60. The computer-readable medium of claim 52, wherein the method further includes storing tag data after obtaining tag data for a tag associated with the selected antenna.

61. A computer-readable medium having computer-executable instructions for performing a method of self-testing an RFID identification system, the method comprising:

accessing an antenna map to determine which antennas on the antenna map are active;

selecting an active antenna;

activating the selected antenna;

determining if the selected antenna has an antenna voltage that exceeds a predetermined lower limit; and

obtaining tag data for a tag associated with the selected antenna, wherein obtaining tag data for a tag associated with the selected antenna includes;

determining if tag data is detected by the selected antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected antenna is above a limit for the number of iterations; and

if tag data is detected by the selected antenna, storing the tag data, wherein obtaining tag data for a tag associated with the selected antenna further includes incrementing the iteration count and cycling a driver for the selected antenna off and then on if tag data is not detected and the current iteration count for determining if tag data is detected by the selected antenna is below a limit for the number of iterations.

62. A computer-readable medium having computer-executable instructions for performing a method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

turning on one of the antennas to poll a specific tag location;

determining whether a voltage due to an excited tag is present at the active antenna;

waiting a predetermined time to detect a voltage in the active antenna if no voltage is present in the active antenna;

reading tag data from the tag associated with the active antenna if there is a voltage;

turning the active antenna off if after the predetermined time there is no voltage present in the active antenna;

turning the antenna back on, such that the antenna cycles off and back on, to repower the tag at the tag location; and

repeating the determining through the reading until a voltage is detected in the active antenna or until a certain second predetermined time has elapsed.

63. The computer-readable medium of claim 62, the method further including sequentially activating each of the plurality of antennas to read tag information for all tag locations.

64. The computer-readable medium of claim 62, wherein turning on one of the antennas to poll a specific tag location includes driving one of the antennas with a square wave drive signal operating at 125 kHZ.

65. The computer-readable medium of claim 62, wherein repeating the determining through the reading until a voltage is detected in the active antenna or until a certain second predetermined time has elapsed includes determining whether a current iteration for determining whether a voltage due to an excited tag is present is above a limit for the number of iterations.

66. The computer-readable medium of claim 62, wherein the method further includes setting tag data to indicate no tag if no voltage due to an excited tag is present at the active antenna for a number of iterations above a limit for the number of iterations for determining if voltage due to an excited tag is present at the active antenna.

67. The computer-readable medium of claim 62, wherein the method further includes sending tag data to a host after determining whether a voltage due to an excited tag is present at the active antenna.

68. The computer-readable medium of claim 62, wherein the method further includes storing tag data after determining whether a voltage due to an excited tag is present at the active antenna.

69. A computer-readable medium having computer-executable instructions for performing a method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

accessing an antenna map of the plurality of sensing antennas to determine which sensing antennas of the plurality of sensing antennas are active, the antenna map having an address for each sensing antenna;

selecting an active sensing antenna to poll a specific tag location;

driving the selected sensing antenna;

determining if the selected sensing antenna has an antenna voltage that exceeds a predetermined lower limit;

obtaining tag data for a tag at a specific tag location associated with the selected sensing antenna; and

selecting a second sensing antenna of the plurality of sensing antennas from the antenna map to determine if the second sensing antenna has an antenna voltage that exceeds a predetermined lower limit and to obtain tag data for a second tag at a specific second tag location associated with the selected second sensing antenna, wherein the second sensing antenna is indicated as active on the antenna map.

70. The computer-readable medium of claim 69, wherein accessing an antenna map to determine which sensing antennas on the antenna map are active includes skipping the testing of sensing antennas indicated as inactive on the antenna map.

71. The computer-readable medium of claim 69, wherein driving the selected sensing antenna includes driving the selected sensing antenna with a square wave drive signal operating at 125 kHZ.

72. The computer-readable medium of claim 69, wherein the method further includes alerting a host or a local alarm on determining that the selected sensing antenna has an antenna voltage less than the predetermined lower limit.

73. The computer-readable medium of claim 69, wherein obtaining tag data for a tag associated with the selected sensing antenna includes waiting a predetermined time for tag data to be read.

74. The computer-readable medium of claim 69, wherein obtaining tag data for a tag associated with the selected sensing antenna includes:

determining if tag data is detected by the selected sensing antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected sensing antenna is above a limit for the number of iterations; and

if tag data is detected by the selected sensing antenna, storing the tag data.

75. The computer-readable medium of claim 74, wherein obtaining tag data for a tag associated with the selected sensing antenna further includes setting the tag data to no tag if tag data is not detected and the current iteration count for determining if tag data is detected after determining whether a voltage due to an excited tag is present at the active antenna by the selected sensing antenna is above a limit for the number of iterations.

76. The computer-readable medium of claim 69, wherein the method further includes sending tag data to a host after obtaining tag data for a tag associated with the selected sensing antenna.

77. The computer-readable medium of claim 69, wherein the method further includes storing tag data after obtaining tag data for a tag associated with the selected sensing antenna.

78. A computer-readable medium having computer-executable instructions for performing a method of testing a system for identifying goods, the system having an interrogator with a plurality of antenna inputs, a plurality of identification tags, and a plurality of sensing antennas each operatively connected to the interrogator, the sensing antennas in close proximity to the tag locations, the method comprising:

accessing an antenna map to determine which sensing antennas of the plurality of sensing antennas are active;

selecting an active sensing antenna to poll a specific tag location;

driving the selected sensing antenna;

determining if the selected sensing antenna has an antenna voltage that exceeds a predetermined lower limit;

obtaining tag data for a tag at a specific tag location associated with the selected sensing antenna; and

selecting a second sensing antenna of the plurality of sensing antennas from the antenna map to determine if the second sensing antenna has an antenna voltage that exceeds a predetermined lower limit and to obtain tag data for a second tag at a specific second tag location associated with the selected second sensing antenna, wherein the second sensing antenna is indicated as active on the antenna map, wherein obtaining tag data for a tag associated with the selected sensing antenna includes;

determining if tag data is detected by the selected sensing antenna;

if tag data is not detected, determining whether a current iteration count for determining if tag data is detected by the selected sensing antenna is above a limit for the number of iterations; and

if tag data is detected by the selected sensing antenna, storing the tag data, wherein obtaining tag data for a tag associated with the selected sensing antenna further includes incrementing the iteration count and cycling a driver for the selected sensing antenna off and then on if tag data is not detected and the current iteration count for determining if tag data is detected by the selected sensing antenna is below a limit for the number of iterations.