RFID readers and systems initializing after antenna switch and methods

• US 7,920,046 B1
• Filed: 07/06/2007
• Issued: 04/05/2011
• Est. Priority Date: 07/21/2006
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Khwaja, Omar, Aiouaz, Ali, Dietrich, Paul
• Primary Examiner(s): Lee; Benjamin C
• Assistant Examiner(s): Mehravari; Peter C
• Application Number:
  US11/774,338
• Time in Patent Office: 1,369 Days
• Field of Search: 340 36- 363, 340 724- 727, 340/464, 340/310, 375132-137, 455101-103
• US Class Current: 340/3.63
• CPC Class Codes: G05B 15/02 electric

Abstract

RFID readers, reader systems, and methods are provided for processing RFID tags through interruptions for antenna change or other reasons. If the reason for the interruption is an antenna change, the reader restarts processing the tags initializing any operational parameters. If the reason is other than an antenna change, the reader determines whether the operation is to be continued or to be restarted upon power up and proceeds accordingly.

Claims

1. A method for an RFID reader system employing antenna switching, comprising:

causing a first signal for a first tag operation to be radiated through a first antenna;

turning off the first signal for a first reason, wherein the first tag operation includes a tag inventory operation;

determining whether the first reason is an antenna change from the first antenna to a second antenna;

if the first reason is the antenna change, causing a second signal to be radiated through the second antenna, for a second tag operation that does not continue the first tag operation, wherein the second tag operation includes restarting the tag inventory operation though the second antenna.

2. The method of claim 1, in which the first tag operation further includes a Tag Population Check (TPC) before starting the tag inventory operation.

3. The method of claim 2, in which the second tag operation further includes another TPC before restarting the tag inventory operation through the second antenna.

4. The method of claim 1, in which the second signal is radiated responsive to detecting that tags me present in the reader'"'"'s field of view.

5. The method of claim 1, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm.

6. The method of claim 5, in which the second signal dictates the initial Q parameter for restarting the tag inventory operation according to the Q-algorithm.

7. The method of claim 5, in which the second signal dictates a different Q parameter for restarting the tag inventory operation according to the Q-algorithm.

8. The method of claim 1, in which the antenna change from the first antenna to the second antenna includes:

selecting the second antenna to radiate the second signal from among a plurality of antennas associated with the RFID reader system based on one of;

a predefined algorithm, an order of available antennas, and by random selection, in which the selection is different depending on whether may tags are sensed through the first antenna.

9. The method of claim 8, in which selecting the second antenna is delayed until an operation for a specific tag is completed.

10. The method of claim 1, further comprising:

turning off the first signal for a second reason that is other than for an antenna change from the first antenna to the second antenna;

determining whether the first tag operation is to be continued due to the second reason;

if the first tag operation is not to be continued, causing a third signal to be radiated through the first antenna, for a third tag operation.

11. The method of claim 10, in which the second reason is a change from a first frequency to a second frequency for a Frequency Hopping Spread Spectrum (FHSS) operation of the reader system.

12. The method of claim 10, in which the second reason is a completion of the first tag operation, and the method further comprises:

restarting another tag operation when the third signal is radiated through the first antenna without repeating a portion of the first tag operation performed when the first signal is radiated.

13. The method of claim 10, further comprising continuing to inventory the tags when the third signal is radiated without repeating a portion of the tag inventory operation performed when the first signal is radiated.

14. The method of claim 13, further comprising:

performing a TPC before beginning the tag inventory operation when the first signal is radiated, in which the TPC is not repeated when the second signal is radiated.

15. The method of claim 13, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm;

and the second signal uses a Q parameter value determined by the reader when the first operation is interrupted.

16. The method of claim 13, further comprising:

if the tag inventory operation is completed about an expiration of a dwell period on a first frequency, combining a frequency change due to an FHSS operation and an antenna change from the first antenna to the second antenna.

17. The method of claim 16, in which combining the frequency change and the antenna change includes performing the antenna change earlier than a predefined time.

18. The method of claim 16, in which combining the frequency change and the antenna change includes performing the frequency change before the expiration of the dwell period.

19. The method of claim 16, further comprising:

if the second reason is the frequency change and the antenna change occurring at the same time, restarting the tag inventory operation when the third signal is radiated.

20. An RFID reader system employing antenna switching, the system comprising:

at least a first antenna and a second antenna;

a signal processing circuit coupled to the first and second antenna configured to;

cause a first signal for a first tag operation to be radiated through a first antenna;

turn off the first signal for a first reason, wherein the first tag operation includes a tag inventory operation;

determine whether the first reason is an antenna change from the first antenna to a second antenna;

if the first reason is the antenna change, cause a second signal to be radiated through the second antenna, for a second tag operation that does not continue the first tag operation, wherein the second tag operation includes restarting the tag inventory operation though the second antenna.

21. The RFID reader system of claim 20, in which the first tag operation further includes a Tag Population Check (TPC) before starting the tag inventory operation.

22. The RFID reader system of claim 20, in which the second tag operation further includes another TPC before restarting the tag inventory operation through the second antenna.

23. The RFID reader system of claim 20, in which the second signal is radiated responsive to detecting that tags are present in the reader'"'"'s field of view.

24. The RFID reader system of claim 20, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm.

25. The RFID reader system of claim 24, in which the second signal dictates the initial Q parameter for restarting the tag inventory operation according to the Q-algorithm.

26. The RFID reader system of claim 24, in which the second signal dictates a different Q parameter for restarting the tag inventory operation according to the Q-algorithm.

27. The RFID reader system of claim 20, in which the antenna change from the first antenna to the second antenna includes:

selecting the second antenna to radiate the second signal from among a plurality of antenna associated with the RFID reader system based on one of;

a predefined algorithm, an order of available antennas, and by random selection, in which the selection is different depending on whether may tags are sensed through the first antenna.

28. The RFID reader system of claim 27, in which selecting the second antenna is delayed until an operation for a specific tag is completed.

29. The RFID reader system of claim 20, in which the signal processing circuit is further configured to:

turn off the first signal for a second reason that is other than for an antenna change from the first antenna to the second antenna;

determine whether the first tag operation is to be continued due to the second reason;

if the first tag operation is not to be continued, cause a third signal to be radiated through the first antenna, for a third tag operation.

30. The RFID reader system of claim 29, in which the second reason is a change from a first frequency to a second frequency for a Frequency Hopping Spread Spectrum (FHSS) operation of the reader system.

31. The RFID reader system of claim 29, in which the second reason is a completion of the first tag operation, and the signal processing circuit is further configured to

restart another tag operation when the third signal is radiated through the first antenna without repeating a portion of the first tag operation performed when the first signal is radiated.

32. The RFID reader system of claim 29, in which the signal processing circuit is further configured to continue to inventory the tags when file third signal is radiated without repeating a portion of the tag inventory operation performed when the first signal is radiated.

33. The RFID reader system of claim 32, in which the signal processing circuit is further configured to:

perform a TPC before beginning the tag inventory operation when the first signal is radiated, in which the TPC is not repeated when the second signal is radiated.

34. The RFID reader system of claim 32, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm;

and the second signal uses a Q parameter value determined by the reader when the first operation is interrupted.

35. The RFID reader system of claim 32, in which the signal processing circuit is further configured to:

if the tag inventory operation is completed about an expiration of a dwell period on a first frequency, combine a frequency change due to an FHSS operation and an antenna change from the first antenna to the second antenna.

36. The RFID reader system of claim 35, in which combining the frequency change and the antenna change includes performing the antenna change earlier than a predefined time.

37. The RFID reader system of claim 35, in which combining the frequency change and the antenna change includes performing the frequency change before the expiration of the dwell period.

38. The RFID reader system of claim 35, in which the signal processing circuit is further configured to if the second reason is the frequency change and the antenna change occurring at the same time, restart the tag inventory operation when the third signal is radiated.

39. A Digital Signal Processing (DSP) chip for an RFID reader system coupled to at least a first antenna and a second antenna, the DSP chip comprising:

circuitry configured to;

cause a first signal for a first tag operation to be radiated though a first antenna;

turn off the first signal for a first reason, wherein the first tag operation includes a tag inventory operation;

determine whether the first reason is an antenna change from the first antenna to a second antenna;

if the first reason is the antenna change, cause a second signal to be radiated through the second antenna, for a second tag operation that does not continue the first tag operation, wherein the second tag operation includes restarting the tag inventory operation though the second antenna.

40. The DSP chip of claim 39, in which the first tag operation further includes a Tag Population Check (TPC) before starting the tag inventory operation.

41. The DSP chip of claim 40, in which the second tag operation further includes another TPC before restarting the tag inventory operation through the second antenna.

42. The DSP chip of claim 39, in which the second signal is radiated responsive to detecting that tags are present in the reader'"'"'s field of view.

43. The DSP chip of claim 39, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm.

44. The DSP chip of claim 43, in which the second signal dictates the initial Q parameter for restarting the tag inventory operation according to the Q-algorithm.

45. The DSP chip of claim 43, in which the second signal dictates a different Q parameter for restarting the tag inventory operation according to the Q-algorithm.

46. The DSP chip of claim 39, in which the antenna change from the first antenna to the second antenna includes:

selecting the second antenna to radiate the second signal from among a plurality of antennas associated with the DSP chip based on one of a predefined algorithm, an order of available antennas, and by random selection, in which the selection is different depending on whether may tags are sensed through the first antenna.

47. The DSP chip of claim 46, in which selecting the second antenna is delayed until an operation for a specific tag is completed.

48. The DSP chip of claim 39, in which the circuitry is further configured to:

turn off the first signal for a second reason that is other than for an antenna change from the first antenna to the second antenna;

determine whether the first tag operation is to be continued due to the second reason;

if the first tag operation is not to be continued, cause a third signal to be radiated through the first antenna, for a third tag operation.

49. The DSP chip of claim 48, in which the second reason is a change from a first frequency to a second frequency for a Frequency Hopping Spread Spectrum (FHSS) operation of the reader system.

50. The DSP chip of claim 48, in which the second reason is a completion of the first tag operation, and the circuitry is further configured to restart another tag operation when the third signal is radiated through the first antenna without repeating a portion of the first tag operation performed when the first signal is radiated.

51. The DSP chip of claim 48, in which the circuitry is further configured to:

continue to inventory the tags when the third signal is radiated without repeating a portion of the tag inventory operation performed when the first signal is radiated.

52. The DSP chip of claim 51, in which the circuitry is further configured to:

perform a TPC before beginning the tag inventory operation when the first signal is radiated, in which the TPC is not repeated when the second signal is radiated.

53. The DSP chip of claim 51, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm;

and the second signal uses a Q parameter value determined by the reader when the first operation is interrupted.

54. The DSP chip of claim 51, in which the circuitry is further configured to:

if the tag inventory operation is completed about an expiration of a dwell period on a first frequency, combine a frequency change due to an FHSS operation and an antenna change from the first antenna to the second antenna.

55. The DSP chip of claim 54, in which combining the frequency change and the antenna change includes performing the antenna change earlier than a predefined time.

56. The DSP chip of claim 54, in which combining the frequency change and the antenna change includes performing the frequency change before the expiration of the dwell period.

57. The DSP chip of claim 54, in which the circuitry is further configured to:

if the second reason is the frequency change and the antenna change occurring at the same time, restart the tag inventory operation when the third signal is radiated.

58. A non-transitory machine-readable storage medium with instructions encoded thereon for operating an RFID reader system coupled to at least a first antenna, the instructions such that, if executed by a machine that is reading them result in operations comprising:

causing a first signal for a first tag operation to be radiated through a first antenna;

turning off the first signal for a first reason, wherein the first tag operation includes a tag inventory operation;

determining whether the first reason is an antenna change from the first antenna to a second antenna;

if the first reason is the antenna change, causing a second signal to be radiated through the second antenna, for a second tag operation that does not continue the first tag operation, wherein the second tag operation includes restarting the tag inventory operation though the second antenna.

59. The non-transitory medium of claim 58, in which the first tag operation further includes a Tag Population Check (TPC) before starting the tag inventory operation.

60. The non-transitory medium of claim 59, which the second tag operation further includes another TPC before restarting the tag inventory operation through the second antenna.

61. The non-transitory medium of claim 58, in which the second signal is radiated responsive to detecting that tags are present in the reader'"'"'s field of view.

62. The non-transitory medium of claim 58, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm.

63. The non-transitory medium of claim 62, in which the second signal dictates the initial Q parameter for restarting the tag inventory operation according to the Q-algorithm.

64. The non-transitory medium of claim 62, in which the second signal dictates a different Q parameter for restarting the tag inventory operation according to the Q-algorithm.

65. The non-transitory medium of claim 58, in which the antenna change from the first antenna to the second antenna includes:

selecting the second antenna to radiate the second signal from among a plurality of antennas associated with the RFID reader system based on one of;

a predefined algorithm, an order of available antennas, and by random selection, in which the selection is different depending on whether any tags are sensed through the first antenna.

66. The non-transitory medium of claim 65, in which selecting the second antenna is delayed until an operation for a specific tag is completed.

67. The non-transitory medium of claim 58, the operations further comprising:

turning off the first signal for a second reason that is other than for an antenna change from the first antenna to the second antenna;

determining whether the first tag operation is to be continued due to the second reason;

if the first tag operation is not to be continued, causing a third signal to be radiated through the first antenna, for a third tag operation.

68. The non-transitory medium of claim 67, in which the second reason is a change from a first frequency to a second frequency for a Frequency Hopping Spread Spectrum (FHSS) operation of the reader system.

69. The non-transitory medium of claim 67, in which the second reason is a completion of the first tag operation, and the operations further comprise:

restarting another tag operation when the third signal is radiated through the first antenna without repeating a portion of the first tag operation performed when the first signal is radiated.

70. The non-transitory medium of claim 67, in which the operations further comprise:

continuing to inventory the tags when the third signal is radiated without repeating a portion of the tag inventory operation performed when the first signal is radiated.

71. The non-transitory medium of claim 70, the operations further comprising:

performing a TPC before beginning the tag inventory operation when the first signal is radiated, in which the TPC is not repeated when the second signal is radiated.

72. The non-transitory medium of claim 70, in which the first signal dictates an initial Q parameter for performing the tag inventory operation according to a Q-algorithm;

and the second signal uses a Q parameter value determined by the reader when the first operation is interrupted.

73. The non-transitory medium of claim 70, the operations further comprising:

if the tag inventory operation is completed about an expiration of a dwell period on a first frequency, combining a frequency change due to an FHSS operation and an antenna change from the first antenna to the second antenna.

74. The non-transitory medium of claim 73, in which combining the frequency change and the antenna change includes performing the antenna change earlier than a predefined time.

75. The non-transitory medium of claim 73, in which combining the frequency change and the antenna change includes performing the frequency change before the expiration of the dwell period.

76. The non-transitory medium of claim 73, the operations further comprising:

if the second reason is the frequency change and the antenna change occurring at the same time, restarting the tag inventory operation when the third signal is radiated.