RFID readers transmitting preambles denoting data rate and methods

• US 20050237162A1
• Filed: 07/13/2004
• Published: 10/27/2005
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Hyde, John D., Diorio, Christopher J.
• Granted Patent: US 7,973,643 B2
• Time in Patent Office: Days
• US Class Current: 340/10.510
• 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 7/10297 arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00

Abstract

RFID readers transmit data to query tags at one or more data rates. Before transmitting data, the RFID readers also transmit special preambles that inform of the data rate that will be used for transmitting the data. The preambles have a call aspect and a rate aspect. The rate aspect has a feature substantially determined from a rate selected for transmitting the data. The feature may encode the rate indirectly or explicitly. The call aspect may be implemented by call transitions that define a timing, whose duration is independent of the selected rate. The duration may be advantageously set according to an assumed state of the RFID tag bandwidth filter. Therefore an RFID tag may use the call aspect of the preamble to prepare itself for receiving data, and the rate aspect to determine its rate of transmission for setting its filter bandwidth accordingly.

Claims

1. An RFID reader capable of at least:

transmitting a preamble that includes a call aspect implemented by call transitions that define a timing whose duration is independent of a preset data rate, and a rate aspect having a feature substantially determined from the data rate; and

then transmitting data at the data rate.

2. The reader of claim 1, wherein

the reader is further capable of selecting the present data rate from a plurality of data rates.

3. The reader of claim 2, wherein

the reader further includes an interface detection module, and

the present data is selected according to an output of the module.

4. The reader of claim 2, wherein

the rates include at least of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

5. The reader of claim 2, wherein

the rates include at least two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

6. The reader of claim 2, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

7. The reader of claim 2, wherein

the rates take values in a continuous range between two endpoints.

8. The reader of claim 1, wherein

the preamble includes a call portion that implements the call aspect, and a rate portion that implements the rate aspect.

9. The reader of claim 8, wherein

the call portion occurs before the rate portion.

10. The reader of claim 1, wherein

the rate aspect is implemented by rate transitions having a timing corresponding to the rate.

11. The reader of claim 1, wherein

the rate aspect is implemented by rate transitions that replicate at least one data sample.

12. The reader of claim 1, wherein

the call transitions define at least one low pulse.

13. The reader of claim 12, wherein

the low pulse has a duration of one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

14. The reader of claim 12, wherein

the low pulse has a duration between a preset minimum and a preset maximum value.

15. The reader of claim 1, wherein

the call aspect includes a violation whose duration is independent of the rate.

16. The reader of claim 15, wherein

the call aspect also includes a low pulse whose duration is independent of the rate.

17. The reader of claim 1, wherein

the rate aspect is implemented by a violation having a duration corresponding to the preset rate.

18. The reader of claim 17, wherein

the duration is inversely proportional to the preset rate.

19. The reader of claim 17, wherein

the duration equals an integer multiple of a duration of a data sample.

20. The reader of claim 17, wherein

the preset rate is encoded in the duration.

21. An RFID reader comprising:

means for transmitting a preamble that includes a call aspect implemented by call transitions that define a timing whose duration is independent of a preset data rate, and a rate aspect having a feature substantially determined from the rate; and

means for transmitting data at the rate.

22. The reader of claim 21, wherein

the preamble includes a call portion that implements the call aspect, and a rate portion that implements the rate aspect.

23. The reader of claim 21, wherein

the rate aspect is implemented by rate transitions having a timing corresponding to the rate.

24. The reader of claim 21, wherein

the rate aspect is implemented by rate transitions that replicate at least one data sample.

25. The reader of claim 21, further comprising:

means for selecting the preset data rate from a plurality of data rates.

26. The reader of claim 25, further comprising:

means for detecting an interference, and

wherein the rate is selected according to the detected interference.

27. The reader of claim 25, wherein

the rates include at least two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

28. The reader of claim 25, wherein

the rates include at least two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

29. The reader of claim 25, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

30. The reader of claim 25, wherein

the rates take values in a continuous range between two endpoints.

31. A method for an RFID reader to transmit data at a data rate, comprising:

transmitting a preamble that includes a call aspect implemented by call transitions that define a timing whose duration is independent of the data rate, and a rate aspect having a feature substantially determined from the data rate; and

then transmitting data at the data rate.

32. The method of claim 31, further comprising:

selecting the data rate from a plurality of data rates.

33. The method of claim 32, further comprising:

detecting an interference, and wherein the rate is selected according to the detected interference.

34. The method of claim 32, wherein

the rates include at least two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

35. The method of claim 32, wherein

the rates include at least two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

36. The method of claim 32, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

37. The method of claim 32, wherein

the rates take values in a continuous range between two endpoints.

38. The method of claim 31, wherein

transmitting the preamble includes:

transmitting a call portion that includes the call transitions, and

transmitting a rate portion that implements the rate aspect.

39. The method of claim 38, wherein

the call portion is transmitted. before the rate portion.

40. The method of claim 31, wherein

the rate aspect is implemented by rate transitions having a timing corresponding to the rate.

41. The method of claim 31, wherein

the rate aspect is implemented by rate transitions that replicate at least one data sample.

42. The method of claim 31, wherein

the call transitions define at least one low pulse.

43. The method of claim 42, wherein

the low pulse has a duration of one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

44. The method of claim 42, wherein

the low pulse has a duration between a preset minimum and a preset maximum value.

45. The method of claim 31, wherein

the call aspect includes a violation whose duration is independent of the rate.

46. The method of claim 45, wherein

the call aspect also includes a low pulse whose duration is independent of the rate.

47. The method of claim 31, wherein

the rate aspect is implemented by a violation having a duration corresponding to the rate.

48. The method of claim 47, wherein

the duration is inversely proportional to the rate.

49. The method of claim 47, wherein

the rate is encoded in the duration.

50. The method of claim 47, wherein

the duration equals an integer multiple of a duration of a data sample.

51. An RFID reader capable of transmitting:

first data, and

a first preamble to the first data, the first preamble including at least two low pulses of different durations.

52. The reader of claim 51, wherein

one of the low pulses has a duration that is approximately an integer multiple of the duration of the other low pulse.

53. The reader of claim 51, wherein

the first data is transmitted at a first rate,

a compliant one of the low pulses has a duration according to the first rate.

54. The reader of claim 53, wherein

the first preamble includes additional pulses having a duration similar to that of the compliant low pulse.

55. The reader of claim 53, wherein

a non-compliant one of the low pulses is transmitted before the compliant low pulse.

56. The reader of claim 53, wherein

a non-compliant one of the low pulses has a duration that is approximately an integer multiple of the duration of the compliant low pulse.

57. The reader of claim 53, wherein

a non-compliant one of the low pulses has a duration of one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

58. The reader of claim 53, wherein

a non-compliant one of the low pulses has a duration between a preset minimum and a preset maximum value.

59. The reader of claim 53, capable of transmitting further:

second data at a second rate different than the first rate, and

a second preamble to the second data.

60. The reader of claim 59, wherein

the reader further includes an interference detection module, and

one of the first rate and the second rate is selected according to an output of the module.

61. The reader of claim 59, wherein

the first and second rates are two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

62. The reader of claim 59, wherein

the first and second rates are two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

63. The reader of claim 59, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

64. The reader of claim 59, wherein

the second preamble includes low pulses all of which have durations according to the second rate.

65. The reader of claim 59, wherein

the second preamble has plurality of low pulses of equal durations.

66. The reader of claim 59, wherein

the second preamble has a low pulse of a duration substantially similar to a duration of a pulse of the first preamble.

67. The reader of claim 59, capable of transmitting further:

third data at a third rate, and

a third preamble to the third data.

68. The reader of claim 59, wherein

the second preamble includes at least two low pulses of different durations, and

a compliant one of the low pulses of the second preamble has a duration according to the second rate.

69. The reader of claim 68, wherein

the second preamble includes additional pulses having a duration similar to that of the compliant low pulse.

70. The reader of claim 68, wherein

a non-compliant one of the low pulses occurs before the compliant low pulse.

71. The reader of claim 68, wherein

a non-compliant one of the low pulses has a duration that is approximately an integer multiple of the duration of the compliant low pulse.

72. The reader of claim 68, capable of transmitting further:

third data at a third rate, and

a third preamble to the third data.

73. An RFID reader for transmitting to an RFID tag, comprising:

means for selecting one of a first rate and a second rate;

means for transmitting a first preamble to first data that includes at least two low pulses of different durations; and

means for transmitting the first data at the selected rate.

74. The reader of claim 73, wherein

the selecting means includes means for detecting whether there is interference.

75. The reader of claim 73, wherein

the first and second rates are two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

76. The reader of claim 73, wherein

the first and second rates are two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

77. The reader of claim 73, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

78. The reader of claim 73, wherein

a compliant one of the low pulses has a duration according to the selected rate.

79. The reader of claim 78, wherein

a non-compliant one of the low pulses is transmitted before the compliant low pulse.

80. The reader of claim 78, wherein

a non-compliant one of the low pulses has a duration of one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

81. The reader of claim 78, wherein

a non-compliant one of the low pulses has a duration between a preset minimum and a preset maximum value.

82. A method for an RFID reader to transmit to an RFID tag, comprising:

transmitting a first preamble to first data that includes at least two low pulses of different durations; and

transmitting the first data.

83. The method of claim 82, wherein

the first data is transmitted at a first rate,

a compliant one of the low pulses has a duration according to the first rate.

84. The method of claim 83, wherein

a non-compliant one of the low pulses is transmitted before the compliant low pulse.

85. The method of claim 83, wherein

a non-compliant one of the low pulses has a duration of one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

86. The method of claim 83, wherein

a non-compliant one of the low pulses has a duration between a preset minimum and a preset maximum value.

87. The method of claim 83, further comprising:

transmitting a second preamble to second data; and

transmitting the second data at a second rate different than the first rate.

88. The method of claim 87, further comprising:

detecting whether there is interference; and

selecting one of the first rate and the second rate depending on whether interference is detected.

89. The method of claim 87, wherein

the first and second rates are two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

90. The method of claim 87, wherein

the first and second rates are two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

91. The method of claim 87, wherein

the rates include at least two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

92. The method of claim 87, wherein

the second preamble has a low pulse of a duration substantially similar to a duration of a pulse of the first preamble.

93. The method of claim 87, further comprising:

transmitting a third preamble to third data; and

transmitting the third data at a third rate different than the first rate and the second rate.

94. The method of claim 87, wherein

the second preamble includes at least two low pulses of different durations, and

a compliant one of the low pulses of the second preamble has a duration according to the second rate.

95. The method of claim 94, further comprising:

transmitting a third preamble to third data; and

transmitting the third data at a third rate different than the first rate and the second rate.