RFID readers transmitting preambles denoting data rate and methods

• US 7,973,643 B2
• Filed: 07/13/2004
• Issued: 07/05/2011
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Hyde, John D., Diorio, Christopher J.
• Primary Examiner(s): Brown; Vernal U
• Application Number:
  US10/890,662
• Publication Number:
  US 20050237162A1
• Time in Patent Office: 2,548 Days
• Field of Search: 340/10.1, 340/825.72, 340/825.69, 340/10.4, 340/870.14, 340/870.19, 340/3.2
• US Class Current: 340/10.1
• 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 configured to transmit:

a first data transmitted at a first rate, and

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

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

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

2. The reader of claim 1, wherein

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

3. The reader of claim 1, wherein

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

4. The reader of claim 1, wherein

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

5. The reader of claim 1, wherein

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

sec and approximately 6.25 μ

sec.

6. The reader of claim 1, further configured to transmit:

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

a second preamble to the second data.

7. The reader of claim 6, 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.

8. The reader of claim 6, wherein

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

9. The reader of claim 6, wherein

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

10. The reader of claim 6, wherein

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

11. The reader of claim 6, wherein

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

12. The reader of claim 6, wherein the second preamble has plurality of low pulses of equal durations.

13. The reader of claim 6, further configured to transmit:

a third data at a third rate, and

a third preamble to the third data.

14. The reader of claim 6, 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.

15. The reader of claim 14, wherein

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

16. The reader of claim 14, 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.

17. The reader of claim 14, further configured to transmit:

a third data at a third rate, and

a third preamble to the third data.

18. An RFID reader configured to transmit:

a first data transmitted at a first rate, and

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

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

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

19. The reader of claim 18, wherein

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

20. The reader of claim 18, further configured to transmit:

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

a second preamble to the second data.

21. The reader of claim 20, 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.

22. The reader of claim 20, 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.

23. The reader of claim 20, further configured to transmit:

a third data at a third rate, and

a third preamble to the third data.

24. An RFID reader communicating with an RFID tag, the reader 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, wherein

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

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

means for transmitting the first data at the selected rate.

25. The reader of claim 24, wherein

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

26. The reader of claim 24, wherein

the first and the second rates have values in a continuous range between two endpoints, the endpoints including two of approximately 32 kbps, approximately 64 kbps, and approximately 128 kbps.

27. The reader of claim 24, wherein

the first and the second rates have values in a continuous range between two endpoints, the endpoints including two of approximately 40 kbps, approximately 80 kbps, and approximately 160 kbps.

28. The reader of claim 24, wherein

the first and the second rates have values in a continuous range between two endpoints, the endpoints including two of approximately 26.7 kbps, approximately 53.3 kbps, and approximately 106.7 kbps.

29. The reader of claim 24, wherein

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

30. An RFID reader communicating with an RFID tag, the reader 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, wherein

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

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

means for transmitting the first data at the selected rate.

31. The reader of claim 30, wherein

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

32. The reader of claim 30, further comprising:

means for transmitting a second data at a second rate different than the first rate, and

means for transmitting a second preamble to the second data.

33. The reader of claim 32, further comprising:

means for detecting interference, wherein

one of the first rate and the second rate is selected according to an output of the means for detecting interference.

34. The reader of claim 32, 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.

35. The reader of claim 32, further comprising:

means for transmitting a third data at a third rate, and

means for transmitting a third preamble to the third data.

36. A method for an RIFD reader communicating with an RIFD tag, comprising:

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

transmitting the first data at a first rate, wherein

a compliant one of the at least two low pulses has a duration according to the first rate, and

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

37. The method of claim 36, wherein

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

38. The method of claim 36, wherein

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

sec and approximately 6.25 μ

sec.

39. The method of claim 36, further comprising:

transmitting a second preamble to second data; and

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

40. The method of claim 39, further comprising:

detecting whether there is interference; and

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

41. The method of claim 39, wherein

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

42. The method of claim 39, wherein

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

43. The method of claim 39, wherein

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

44. The method of claim 39, wherein

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

45. The method of claim 39, further comprising:

transmitting a third preamble to the third data; and

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

46. The method of claim 39, 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.

47. The method of claim 46, further comprising:

transmitting a third preamble to the third data; and

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

48. A method for an RIFD reader communicating with an RIFD tag, comprising:

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

transmitting the first data at a first rate, wherein

a compliant one of the at least two low pulses has a duration according to the first rate, and

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

49. The method of claim 48, wherein

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

50. The method of claim 48, further comprising:

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

transmitting a second preamble to the second data.

51. The method of claim 50, wherein

detecting whether there is interference;

and

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

52. The method of claim 50, further comprising:

transmitting a third data at a third rate, and

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