Interference monitoring in an RFID system

• US 7,692,532 B2
• Filed: 07/29/2005
• Issued: 04/06/2010
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Quake Global, Inc.
• Original Assignee: Reva Systems Corp. (Quake Global, Inc.)
• Inventors: Fischer, Jeffrey H., Krishna, Pattabhiraman, Husak, David J.
• Primary Examiner(s): Zimmerman; Brian A
• Assistant Examiner(s): Nguyen; Nam V
• Application Number:
  US11/194,145
• Publication Number:
  US 20060022815A1
• Time in Patent Office: 1,712 Days
• Field of Search: 340/10.2, 340/10.31, 340/572, 340/825.69, 340/505, 340/539, 370/314, 708/250, 708/255, 455/41.2
• US Class Current: 340/10.2
• CPC Class Codes: G01S 5/02525 Gathering the radio frequency fingerprints
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G06K 17/0029 the arrangement being specially adapted for wireless interrogation of grouped or bundled articles tagged with wireless record carriers
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

A system and method for monitoring and characterizing various sources of RF interference within an RFID environment, and for adjusting the operational characteristics of an array of RFID readers within the system based on these interference characterizations. The system examines the received transmissions from readers in the network by controlling a calibration cycle or while they are operating as interrogators to determine interference parameters, and to verify the operation of the readers in the array. The system also examines outside sources of interference, and signal dependent interference. The interference characterization can also be estimated from a combination of calculations and co-monitoring.

Claims

1. A radio frequency identification (RFID) tag data acquisition system, comprising:

at least one RFID tag interrogator operative to transmit at least one first RF interrogation signal for interrogating RFID tags;

a plurality of RFID receivers, each of said plurality of RFID receivers including an RF receiver component and an RF monitoring component, said RF receiver component being operative to receive RF signals including said at least one first RF interrogation signal transmitted by said RFID tag interrogator, said RF monitoring component being operative to determine at least one characteristic associated with said RF signals received by said RF receiver component; and

a controller communicably coupled to said at least one RFID tag interrogator and said plurality of RFID receivers,

wherein said plurality of RFID receivers are operative to generate information indicative of said at least one characteristic, and to forward said information to said controller,

wherein said controller is operative to utilize said information in at least one of;

a) a determination of the operational status of said at least one RFID tag interrogator;

b) control of said at least one RFID tag interrogator;

c) control of said RF receiver component; and

d) control of said RF monitoring component,

wherein each RF receiver component is operative to receive RF signals on at least one frequency channel, and wherein each RF monitoring component is operative to monitor said at least one channel for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the at least one monitored channel,

wherein each RFID receiver is operative to generate information indicative of said at least one characteristic associated with the at least one external RF interference signal, and to forward said information to said controller, said controller being operative to utilize said information indicative of said characteristic associated with the external RF interference signal in at least one of the control of said RFID tag interrogator, the control of said RF receiver component, and the control of said RF monitoring component,

wherein each RF receiver component has a respective channel associated therewith, wherein each RF receiver component is operative to receive RF signals on said channel associated therewith, and wherein each RF monitoring component associated with the respective RF receiver component is operative to monitor said channel for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the monitored channel, and

wherein each RF monitoring component is operative, in response to monitoring at least one external RF interference signal on said channel associated therewith, to sample said at least one external RF interference signal at a predetermined sampling rate over a predetermined time interval, and wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one characteristic of the external RF interference signal sampled at the predetermined sampling rate over the predetermined time interval.

2. The system of claim 1 wherein said RF monitoring component is operative to determine at least one characteristic associated with said received first RF interrogation signal, the at least one characteristic including at least one first level associated with said received first RF interrogation signal.

3. The system of claim 2 wherein said first level associated with said received first RF interrogation signal corresponds to a first power level of the received first RF interrogation signal.

4. The system of claim 2 wherein said at least one first level associated with said received first RF interrogation signal corresponds to at least one first level of interference between said at least one RFID tag interrogator and said at least one RFID receiver.

5. The system of claim 4 wherein said RF monitoring component is operative to determine said first level of interference between said RFID tag interrogator and said RFID receiver by measuring a first power level of the received first RF interrogation signal.

6. The system of claim 4 wherein said controller is operative to utilize said information indicative of said first level of interference in the control of at least one of said RFID tag interrogator and said RF receiver component, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, said control of the RF receiver component including scheduling at least one RF signal reception by said RF receiver component, thereby reducing said first level of interference between said RFID tag interrogator and said RFID receiver.

7. The system of claim 1 wherein said at least one RFID tag interrogator is operative to transmit said at least one first RF interrogation signal on at least one first frequency channel, and wherein said RF receiver component is operative to receive said first RF interrogation signal on the same first channel upon which said first RF interrogation signal is transmitted by said RFID tag interrogator.

8. The system of claim 7 wherein said RF monitoring component is operative to determine at least one characteristic associated with said received first RF interrogation signal, said characteristic associated with the received first RF interrogation signal including a first level of interference between said RFID tag interrogator and said RFID receiver.

9. The system of claim 8 wherein said RF monitoring component is operative to estimate at least one characteristic associated with at least one second RF signal on at least one second frequency channel based on said first level of interference, said second channel being different from said first channel, said characteristic associated with the second RF signal on the second channel including an estimated second level of interference between said RFID tag interrogator and said RFID receiver.

10. The system of claim 7 wherein said RF receiver component is operative to receive at least one second RF signal on at least one second frequency channel, said second channel being different from said first channel, wherein said RF monitoring component is operative to determine at least one characteristic associated with said received second RF signal, and wherein said RFID receiver is operative to generate information indicative of said at least one characteristic associated with said received second RF signal, and to forward said information to the controller.

11. The system of claim 10 wherein said RF receiver component is operative to take wideband samples of said first RF interrogation signal received on said first channel and said second RF signal received on said second channel.

12. The system of claim 10 wherein said at least one characteristic associated with said received first RF interrogation signal includes at least one first level of said received first RF interrogation signal, and wherein said at least one characteristic associated with said received second RF signal includes at least one second level of said received second RF signal.

13. The system of claim 12 wherein said first level of said received first RF interrogation signal corresponds to a first level of interference between said RFID tag interrogator and said RFID receiver, and wherein said second level of said received second RF signal corresponds to a second level of interference between said RFID tag interrogator and said RFID receiver.

14. The system of claim 13 wherein said controller is operative to utilize said information indicative of said first level of interference and said information indicative of said second level of interference in the control of at least one of said RFID tag interrogator and said RF receiver component, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, said control of the RF receiver component including scheduling at least one RF signal reception by said RF receiver component, thereby reducing at least one of said first and second levels of interference between said RFID tag interrogator and said RFID receiver.

15. The system of claim 10 wherein said at least one second channel is adjacent to said at least one first channel upon which said RF interrogation signal is transmitted by said RFID tag interrogator.

16. The system of claim 15 wherein said at least one first channel and said at least one second channel adjacent thereto are within a specified frequency band.

17. The system of claim 15 wherein said at least one characteristic associated with said received first RF interrogation signal includes at least one first level of said received first RF interrogation signal, and wherein said at least one characteristic associated with said received second RF signal includes at least one second level of said received second RF signal.

18. The system of claim 17 wherein said first level of said received first RF interrogation signal corresponds to a first level of interference between said RFID tag interrogator and said RFID receiver, and wherein said second level of said received second RF signal corresponds to a second level of interference between said RFID tag interrogator and said RFID receiver.

19. The system of claim 15 wherein said at least one first channel comprises a plurality of first channels, wherein said at least one second channel comprises a plurality of second channels, and wherein each of the plurality of first channels is associated with at least one respective channel of the plurality of second channels.

20. The system of claim 19 wherein each association of a respective first channel with at least one respective channel of the plurality of second channels corresponds to a specified subband of frequencies.

21. The system of claim 20 wherein said at least one characteristic associated with said received first RF interrogation signal includes at least one first level of said first RF interrogation signal received on said respective first channel, and wherein said at least one characteristic associated with said received second RF signal includes at least one second level of said second RF signal received on said at least one respective channel of the plurality of second channels.

22. The system of claim 21 wherein said first level of said received first RF interrogation signal corresponds to a first level of interference between said RFID tag interrogator and said RFID receiver, and wherein said second level of said received second RF signal corresponds to a second level of interference between said RFID tag interrogator and said RFID receiver.

23. The system of claim 22 wherein said controller is operative to utilize said information indicative of said first level of interference and said information indicative of said second level of interference in the control of at least one of said RFID tag interrogator and said RF receiver component, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, said control of the RF receiver component including scheduling at least one RF signal reception by said RF receiver component, thereby reducing at least one of said first and second levels of interference between said RFID tag interrogator and said RFID receiver.

24. The system of claim 23 wherein said controller is operative to compare said information indicative of said second level of interference with a predetermined threshold level to determine whether said second interference level exceeds said predetermined threshold level.

25. The system of claim 24 wherein said predetermined threshold level is fixed.

26. The system of claim 24 wherein said predetermined threshold level is variable.

27. The system of claim 1 wherein each RF receiver component is operative to receive a respective RF signal on a respective frequency channel, and wherein each RF monitoring component is operative to determine at least one characteristic associated with the respective RF signal received by the RF receiver component on the respective frequency channel.

28. The system of claim 27 wherein the respective channels upon which said RF receiver components receive the respective RF signals are within a specified frequency band.

29. The system of claim 27 wherein said at least one characteristic includes at least one power level of the respective RF signal received by the RF receiver component on the respective channel.

30. The system of claim 29 wherein the RF monitoring components are operative to normalize the power levels of the respective RF signals received by the RF receiver components on the respective channels.

31. The system of claim 1 wherein each RF receiver component is operative to receive RF signals on an associated plurality of frequency channels, and wherein each RF monitoring component is operative to determine at least one characteristic associated with the RF signals received by the RF receiver component on the plurality of channels associated therewith.

32. The system of claim 31 wherein each plurality of channels associated with a respective RF receiver component is within a specified subband of frequencies.

33. The system of claim 31 wherein the at least one characteristic includes at least one power level of the RF signals received by the RF receiver component on the plurality of channels associated therewith.

34. The system of claim 33 wherein the at least one characteristic includes an aggregate of the power levels of the RF signals received by the RF receiver components on the pluralities of channels associated therewith.

35. The system of claim 33 wherein the RF monitoring components are operative to normalize the power levels of the RF signals received by the RF receiver components on the pluralities of channels associated therewith.

36. The system of claim 1 wherein each RF receiver component is operative to receive RF signals on an associated plurality of frequency channels, and wherein each RF monitoring component is operative to determine at least one characteristic associated with at least one RF signal received by at least a respective one of the RF receiver components on the plurality of channels associated therewith.

37. The system of claim 36 wherein said at least one characteristic associated with said at least one RF signal received by at least a respective one of the RF receiver components includes at least one level of interference between said at least one RFID tag interrogator and said plurality of RFID receivers.

38. The system of claim 37 wherein said controller is operative to utilize said information indicative of said level of interference in the control of said at least one RFID tag interrogator and in the control of the respective RF receiver components, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, said control of the RF receiver components including scheduling at least one RF signal reception by at least one of said RF receiver components, thereby reducing said level of interference between said RFID tag interrogator and said plurality of RFID receivers.

39. The system of claim 1 wherein said RFID tag interrogator is operative to transmit said first RF interrogation signal on at least one first frequency channel, wherein each RF receiver component is operative to receive said first RF interrogation signal on the same first channel upon which said first RF interrogation signal is transmitted by said RFID tag interrogator, and wherein each RF monitoring component is operative to determine at least one characteristic associated with the first RF interrogation signal received by a respective RF receiver component on the first channel.

40. The system of claim 39 wherein said at least one characteristic includes at least one first power level of said first RF interrogation signal received by the respective RF receiver component on the first channel.

41. The system of claim 40 wherein said controller is operative to generate at least one first power profile corresponding to said RFID tag interrogator based on a plurality of first power levels of the received first RF interrogation signal.

42. The system of claim 41 wherein said controller is operative to utilize said at least one first power profile as a baseline power profile of said RFID tag interrogator in the determination of the operational status of said RFID tag interrogator.

43. The system of claim 41 wherein said RFID tag interrogator is operative to transmit at least one second RF interrogation signal on said first channel, wherein each RF receiver component is operative to receive said second RF interrogation signal on said first channel, and wherein each RF monitoring component is operative to determine at least one characteristic associated with said received second RF interrogation signal including at least one second power level of the second RF interrogation signal received by a respective RF receiver component on the first channel.

44. The system of claim 43 wherein said controller is operative to generate at least one second power profile corresponding to said RFID tag interrogator based on a plurality of second power levels of the second RF interrogation signal, and to compare characteristics of the at least one second power profile with characteristics of the at least one first power profile in the determination of the operational status of said RFID tag interrogator.

45. The system of claim 1 wherein said RFID tag interrogator is operative to transmit a plurality of first RF interrogation signals on a plurality of first frequency channels, respectively, wherein each RF receiver component is operative to receive at least two of the first RF interrogation signals on at least two associated first channels, said at least two associated first channels being within a respective subband of frequencies, and wherein each RF monitoring component is operative to determine at least one characteristic associated with the at least two first RF interrogation signals received by a respective RF receiver component on the at least two associated first channels.

46. The system of claim 45 wherein said at least one characteristic includes at least one first power level of said at least two first RF interrogation signals received by the respective RF receiver component on the at least two associated first channels.

47. The system of claim 46 wherein said controller is operative to generate a plurality of power profiles corresponding to said RFID tag interrogator, each power profile being generated by the controller based on said first power levels of at least two first RF interrogation signals received by a respective RF receiver component on at least two associated first channels.

48. The system of claim 47 wherein said controller is operative to compare characteristics of respective ones of the plurality of power profiles in the determination of the operational status of said RFID tag interrogator.

49. The system of claim 1 wherein the respective channels associated with the RF receiver components are within a specified frequency band.

50. The system of claim 1 wherein the RF monitoring components are operative to monitor the channels associated with the corresponding RF receiver components simultaneously.

51. The system of claim 1 wherein said at least one characteristic associated with said at least one external RF interference signal includes at least one power level of the external RF interference signal.

52. The system of claim 51 wherein the RF monitoring components are operative to normalize the power levels of said external RF interference signals on the respective channels associated therewith.

53. The system of claim 1 wherein the predetermined sampling rate is greater than or equal to a Nyquist sampling rate.

54. The system of claim 1 wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one time domain characteristic of the external RF interference signal sampled by the RF monitoring component on the channel associated therewith.

55. The system of claim 1 wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one frequency domain characteristic of the external RF interference signal sampled by the respective RF monitoring component.

56. The system of claim 1 wherein said controller is operative to utilize said information indicative of the at least one characteristic of the external RF interference signal in the control of said RFID tag interrogator and in the control of at least one of the RF receiver components, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, and said control of at least one of said RF receiver components including scheduling at least one RF signal reception by the at least one RF receiver component.

57. The system of claim 1 wherein each RF receiver component is operative to receive RF signals on an associated plurality of channels, and wherein each RF monitoring component is operative to monitor the associated plurality of channels for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the plurality of channels associated therewith.

58. The system of claim 57 wherein the plurality of channels associated with each RF receiver component is within a specified subband of frequencies.

59. The system of claim 1 wherein each RF receiver component is operative to receive RF signals on an associated plurality of channels over a predetermined time interval, the RF receiver components receiving said RF signals on said channels associated with the corresponding RF receiver components at staggered time intervals, and wherein each RF monitoring component is operative to monitor said associated plurality of channels for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the plurality of channels associated therewith.

60. The system of claim 1 wherein said controller is operative to store at least one value of at least one frequency of transmission of said RFID tag interrogator, and to determine an identity of said RFID tag interrogator transmitting the first RF interrogation signal using said at least one stored value of transmission frequency.

61. The system of claim 60 wherein said controller is operative to determine the identity of said RFID tag interrogator transmitting the first RF interrogation signal using time causality relationships.

62. The system of claim 60 wherein said first RF interrogation signal has an identifying signal included therein, and wherein said controller is operative to determine the identity of said RFID tag interrogator transmitting the first RF interrogation signal by detecting the identifying signal included in said first RF interrogation signal.

63. The system of claim 1 wherein the at least one RFID receiver includes an RF transmitter component operative to transmit at least one second RF signal, and wherein the RFID tag interrogator includes an RF receiver component operative to receive said at least one second RF signal.

64. The system of claim 63 wherein the RFID tag interrogator includes an RF monitoring component, wherein the RF monitoring component included in the RFID receiver is operative to determine at least one power level associated with said first RF interrogation signal, and wherein the RF monitoring component included in the RFID tag interrogator is operative to determine at least one power level associated with said second RF signal.

65. The system of claim 64 wherein said RFID receiver and said RFID tag interrogator are operative to generate information indicative of said at least one power level of said received first and second RF signals, respectively, and to forward said information to said controller.

66. The system of claim 65 wherein said controller is operative to compare the power level of said received first RF interrogation signal with the power level of said received second RF signal in the determination of the operational status of said RFID tag interrogator.

67. A radio frequency identification (RFID) tag data acquisition system, comprising:

at least one RFID tag interrogator operative to transmit at least one first RF interrogation signal for interrogating RFID tags;

a plurality of RFID receivers, each of said plurality of RFID receivers including an RF receiver component and an RF monitoring component, said RF receiver component being operative to receive RF signals including said at least one first RF interrogation signal transmitted by said RFID tag interrogator, said RF monitoring component being operative to determine at least one characteristic associated with said RF signals received by said RF receiver component; and

a controller communicably coupled to said at least one RFID tag interrogator and said plurality of RFID receivers,

wherein said plurality of RFID receivers are operative to generate information indicative of said at least one characteristic, and to forward said information to said controller,

wherein said controller is operative to utilize said information in at least one of;

a) a determination of the operational status of said at least one RFID tag interrogator;

b) control of said at least one RFID tag interrogator;

c) control of said RF receiver component; and

d) control of said RF monitoring component,

wherein each RF receiver component is operative to receive RF signals on at least one frequency channel, and wherein each RF monitoring component is operative to monitor said at least one channel for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the at least one monitored channel,

wherein each RFID receiver is operative to generate information indicative of said at least one characteristic associated with the at least one external RF interference signal, and to forward said information to said controller, said controller being operative to utilize said information indicative of said characteristic associated with the external RF interference signal in at least one of the control of said RFID tag interrogator, the control of said RF receiver component, and the control of said RF monitoring component,

wherein each RF receiver component is operative to receive RF signals on an associated plurality of channels, and wherein each RF monitoring component is operative to monitor the associated plurality of channels for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the plurality of channels associated therewith, and

wherein each RF monitoring component is operative, in response to monitoring at least one external RF interference signal on at least one of the plurality of channels associated with the respective RF receiver component, to sample said at least one external RF interference signal at a predetermined sampling rate over a predetermined time interval, and wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one characteristic of the external RF interference signal sampled at the predetermined sampling rate over the predetermined time interval.

68. The system of claim 67 wherein the predetermined sampling rate is greater than or equal to a Nyquist sampling rate.

69. The system of claim 67 wherein said information indicative of said at least one characteristic of the external RF interference signal samples includes time domain signal sample information, and wherein said controller is operative to transform said time domain information to frequency domain information.

70. The system of claim 67 wherein said controller is operative to utilize said information indicative of the at least one characteristic of the external RF interference signal in the control of said RFID tag interrogator and in the control of at least one of the RF receiver components, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, said control of at least one of the RF receiver components including scheduling at least one RF signal reception by the at least one RF receiver component.

71. A radio frequency identification (RFID) tag data acquisition system, comprising:

at least one RFID tag interrogator operative to transmit at least one first RF interrogation signal for interrogating RFID tags;

a plurality of RFID receivers, each of said plurality of RFID receivers including an RF receiver component and an RF monitoring component, said RF receiver component being operative to receive RF signals including said at least one first RF interrogation signal transmitted by said RFID tag interrogator, said RF monitoring component being operative to determine at least one characteristic associated with said RF signals received by said RF receiver component; and

a controller communicably coupled to said at least one RFID tag interrogator and said plurality of RFID receivers,

wherein said plurality of RFID receivers are operative to generate information indicative of said at least one characteristic, and to forward said information to said controller,

wherein said controller is operative to utilize said information in at least one of;

a) a determination of the operational status of said at least one RFID tag interrogator;

b) control of said at least one RFID tag interrogator;

c) control of said RF receiver component; and

d) control of said RF monitoring component,

wherein each RF receiver component is operative to receive RF signals on at least one frequency channel, and wherein each RF monitoring component is operative to monitor said at least one channel for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the at least one monitored channel,

wherein each RFID receiver is operative to generate information indicative of said at least one characteristic associated with the at least one external RF interference signal, and to forward said information to said controller, said controller being operative to utilize said information indicative of said characteristic associated with the external RF interference signal in at least one of the control of said RFID tag interrogator, the control of said RF receiver component, and the control of said RF monitoring component,

wherein each RF receiver component is operative to receive RF signals on an associated plurality of channels over a predetermined time interval, the RF receiver components receiving said RF signals on said channels associated with the corresponding RF receiver components at staggered time intervals, and wherein each RF monitoring component is operative to monitor said associated plurality of channels for at least one external RF interference signal, and to determine at least one characteristic associated with said at least one external RF interference signal on the plurality of channels associated therewith, and

wherein each RF monitoring component is operative, in response to monitoring at least one external RF interference signal on said plurality of channels, to sample said at least one external RF interference signal at a predetermined sampling rate over the predetermined time interval, and wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one characteristic of the external RF interference signal sampled at the predetermined sampling rate over the predetermined time interval.

72. The system of claim 71 wherein the predetermined sampling rate is greater than or equal to a Nyquist sampling rate.

73. The system of claim 71 wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one time domain characteristic of the external RF interference signal sampled by the RF monitoring component on the respective plurality of channels.

74. The system of claim 71 wherein said information forwarded to the controller by each RFID receiver includes information indicative of at least one frequency domain characteristic of the external RF interference signal sampled by the RF monitoring component on the respective plurality of channels.

75. The system of claim 71 wherein said controller is operative to utilize said information indicative of the at least one characteristic of the external RF interference signal in the control of said RFID tag interrogator and in the control of at least one of the RF receiver components, said control of the RFID tag interrogator including scheduling at least one RF signal transmission by said RFID tag interrogator, and said control of at least one of said RF receiver components including scheduling at least one RF signal reception by the at least one RF receiver component.