Method, system, and apparatus for remote data calibration of a RFID tag population

• US 7,145,482 B2
• Filed: 09/09/2005
• Issued: 12/05/2006
• Est. Priority Date: 02/12/2001
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Bandy, William R., Powell, Kevin J., Shanks, Wayne E., Arneson, Michael R.
• Primary Examiner(s): WAMSLEY, PATRICK G
• Application Number:
  US11/222,070
• Publication Number:
  US 20060077082A1
• Time in Patent Office: 452 Days
• Field of Search: 341/53, 340/10.2, 340/10.32, 340/572.1, 340/505, 340/573.4, 340/10.33, 340/825.52, 340/572.3, 340/572.7, 340/10.3, 340/572.2, 340/573.1, 340/825, 340/941, 705/28, 342/42, 235/375, 235/435, 714/703, 714/800, 455/259, 326/38, 326/81, 327/525, 257/476
• US Class Current: 341/53
• 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 19/0713 the arrangement including a power charge pump
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• 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 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10108 interrogating only those RFIDs that fulfill a predetermined requirement, e.g. selecting all RFIDs having the same speed and moving in a cloud like fashion, e.g. on the same train; interrogating only RFIDs having a certain predetermined temperature, e.g. in the same fridge, another possibility being the active ignoring of a group of tags that fulfill a predetermined requirement, equivalent to the Boolean NOT operation
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: G11C 5/142 Contactless power supplies, e.g. RF, induction, or IR
• CPC Class Codes: H04L 7/0331 with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock H04L7/0337 takes precedence

Abstract

A method, system, and apparatus for remotely calibrating data symbols received by a radio frequency identification (RFID) tag population are described. Tags are interrogated by a reader, which may be located in a network of readers. The reader transmits data symbols to the tags. Tags respond to the interrogations with symbols that each represent one or more bits of data. To calibrate the tags, the reader transmits a plurality of pulses of different lengths to the tag population. The tags receive the plurality of pulses. A characteristic of each pulse, such as a pulse length, is stored by the tags. The stored pulse lengths are used to define different data symbols that are subsequently received by the tags from the reader.

Claims

1. A method for defining data symbols in a radio frequency identification (RFID) tag device, comprising:

(a) receiving a first calibration signal;

(b) detecting a characteristic of the received first calibration signal; and

(c) storing the detected characteristic of the received first calibration signal as a stored first characteristic;

wherein a received data symbol is determined to be a first data value if a characteristic of the received data symbol has a first predetermined relationship with the stored first characteristic; and

wherein the received data symbol is determined to be a second data value if the characteristic of the received data symbol has a second predetermined relationship with the stored first characteristic.

2. The method of claim 1, wherein step (a) comprises:

(1) receiving the first calibration signal on a carrier signal.

3. The method of claim 2, wherein step (a) further comprises:

(2) storing charge from the received carrier signal in at least one capacitor to a direct current (DC) voltage, wherein the stored DC voltage is used to power the RFID tag device.

4. The method of claim 3, wherein step (2) comprises:

rectifying the carrier signal in a diode rectifier circuit.

5. The method of claim 4, wherein step (2) comprises:

rectifying the carrier signal in a diode rectifier circuit having a plurality of stages.

6. The method of claim 5, wherein said rectifying step comprises:

using the plurality of stages to cause the DC voltage to be greater than a received voltage of the carrier signal.

7. The method of claim 1, wherein the characteristic of the received first calibration signal is a frequency of the received first calibration signal.

8. The method of claim 1, wherein the characteristic of the received first calibration signal is an amplitude of the received first calibration signal.

9. The method of claim 1, wherein the characteristic of the received first calibration signal is a phase of the received first calibration signal.

10. The method of claim 1, wherein the characteristic of the received first calibration signal is a length of a pulse portion of the received first calibration signal.

11. The method of claim 1, wherein the characteristic of the received first calibration signal is a length of a cycle of the received first calibration signal.

12. A system for defining data symbols in a radio frequency identification (RFID) tag device, comprising:

means for receiving a first calibration signal;

means for detecting a characteristic of the received first calibration signal; and

means for storing the detected characteristic of the received first calibration signal as a stored first characteristic;

means for determining a received data symbol to be a first data value if a characteristic of the received data symbol has a first predetermined relationship with the stored first characteristic, or to be a second data value if the characteristic of the received data symbol has a second predetermined relationship with the stored first characteristic.

13. The system of claim 12, wherein said means for receiving a first calibration signal comprises:

means for receiving the first calibration signal on a carrier signal.

14. The system of claim 13, wherein said means for receiving the first calibration signal on a carrier signal comprises:

at least one capacitor that stores charge from the received carrier signal to produce a direct current (DC) voltage, wherein the DC voltage is used to power the RFID tag device.

15. The system of claim 14, wherein said means for receiving the first calibration signal on a carrier signal further comprises:

a diode rectifier circuit that rectifies the carrier signal.

16. The system of claim 15, wherein said diode rectifier circuit has a plurality of stages.

17. The system of claim 16, wherein said plurality of stages cause the DC voltage to be greater than a received voltage of the carrier signal.

18. A method for communicating with radio frequency identification (RFID) tag devices, comprising:

(a) transmitting a calibration signal having a characteristic; and

(b) transmitting a data symbol;

wherein a RFID tag device that receives the calibration signal and the data symbol uses the characteristic to determine a data value of the data symbol.

19. The method of claim 18, wherein the characteristic of the calibration signal is a length of a pulse portion the calibration signal.

20. The method of claim 19, wherein the RFID tag device determines the data symbol to be a first data value if a length of a pulse portion of the data symbol is less than the length of the pulse portion of the calibration signal;

and

wherein the RFID tag device determines the data symbol to be a second data value if the length of the pulse portion of the data symbol is greater than the length of the pulse portion of the calibration signal.

21. The method of claim 18, wherein the RFID tag device determines the data symbol to be a first data value if a characteristic of the data symbol has a first predetermined relationship with the characteristic of the calibration signal;

and

wherein the RFID tag device determines the data symbol to be a second data value if the characteristic of the data symbol has a second predetermined relationship with the characteristic of the calibration signal.

22. The method of claim 18, wherein the characteristic of the calibration signal is a frequency of the calibration signal.

23. The method of claim 18, wherein the characteristic of the calibration signal is an amplitude of the calibration signal.

24. The method of claim 18, wherein the characteristic of the calibration signal is a phase of the calibration signal.

25. The method of claim 18, wherein the characteristic of the calibration signal is a length of a cycle of the calibration signal.

26. The method of claim 18, wherein step (a) comprises:

transmitting the calibration signal on a carrier signal.

27. A method for communicating with radio frequency identification (RFID) tag devices, comprising:

(a) transmitting a first calibration signal having a first characteristic;

(b) transmitting a second calibration signal having a second characteristic; and

(c) transmitting a data symbol;

wherein a RFID tag device that receives the first calibration signal, the second calibration signal, and the data symbol uses the first and second characteristics to determine a data value of the data symbol.

28. The method of claim 27, wherein the RFID tag device determines the data symbol to be a first data value if a characteristic of the data symbol has a first predetermined relationship with the first characteristic;

and

wherein the RFID tag device determines the data symbol to be a second data value if the characteristic of the data symbol has a second predetermined relationship with the first characteristic and has a third predetermined relationship with the second characteristic.

29. The method of claim 28, wherein the RFID tag device determines the data symbol to be a third data value if the characteristic of the data symbol has a fourth predetermined relationship with the second characteristic.

30. The method of claim 27, wherein the first characteristic is a length of a pulse portion the first calibration signal, and the second characteristic is a length of a pulse portion of the second calibration signal.

31. The method of claim 30, wherein the RFID tag device determines the data symbol to be a first data value if a length of a pulse portion of the data symbol is less than the length of the pulse portion of the first calibration signal;

wherein the RFID tag device determines the data symbol to be a second data value if the length of the pulse portion of the data symbol is greater than the length of the pulse portion of the first calibration signal and less than a length of the pulse portion of the second calibration signal; and

wherein the RFID tag device determines the data symbol to be a third data value if the length of the pulse portion of the data symbol is greater than the length of the pulse portion of the second calibration signal.

32. The method of claim 27, wherein the first characteristic is a frequency of the first calibration signal, and the second characteristic is a frequency of the second calibration signal.

33. The method of claim 27, wherein the first characteristic is an amplitude of the first calibration signal, and the second characteristic is an amplitude of the second calibration signal.

34. The method of claim 27, wherein the first characteristic is a phase of the first calibration signal, and the second characteristic is a phase of the second calibration signal.

35. The method of claim 27, wherein the first characteristic is a length of a cycle of the first calibration signal, and the second characteristic is a length of a cycle of the second calibration signal.

36. The method of claim 27, wherein step (a) comprises transmitting the first calibration signal on a carrier signal;

and

wherein step (b) comprises transmitting the second calibration signal on the carrier signal.

37. A radio frequency identification (RFID) reader, comprising:

a transmitter; and

an antenna coupled to an output of said transmitter;

wherein said transmitter is capable of outputting a calibration signal for transmission by said antenna, wherein said calibration signal has a characteristic,

wherein said transmitter is capable of outputting a data symbol for transmission by said antenna;

wherein a RFID tag device that receives said calibration signal and said data symbol uses said characteristic to determine a data value of said data symbol.

38. The RFID reader of claim 37, wherein said calibration signal is transmitted on a carrier signal.

39. The RFID reader of claim 38, wherein the RFID tag device determines said data symbol to be a first data value if a length of a pulse portion of said data symbol is less than said length of said pulse portion of said calibration signal;

and

wherein the RFID tag device determines said data symbol to be a second data value if said length of said pulse portion of said data symbol is greater than said length of said pulse portion of said calibration signal.

40. The RFID reader of claim 37, wherein the RFID tag device determines said data symbol to be a first data value if a characteristic of said data symbol has a first predetermined relationship with said characteristic of said calibration signal;

and

wherein the RFID tag device determines said data symbol to be a second data value if said characteristic of said data symbol has a second predetermined relationship with said characteristic of said calibration signal.

41. The RFID reader of claim 37, wherein said characteristic of said calibration signal is a frequency of said calibration signal.

42. The RFID reader of claim 37, wherein said characteristic of said calibration signal is an amplitude of said calibration signal.

43. The RFID reader of claim 37, wherein said characteristic of said calibration signal is a phase of said calibration signal.

44. The RFID reader of claim 37, wherein said characteristic of said calibration signal is a length of a pulse portion said calibration signal.

45. The RFID reader of claim 37, wherein said characteristic of said calibration signal is a length of a cycle of said calibration signal.

46. A radio frequency identification (RFID) reader, comprising:

a transmitter; and

an antenna coupled to an output of said transmitter;

wherein said transmitter is capable of outputting first and second calibration signals for transmission by said antenna, wherein said first calibration signal has a first characteristic and said second calibration signal has a second characteristic;

wherein said transmitter is capable of outputting a data symbol for transmission by said antenna;

wherein a RFID tag device that receives said first calibration signal said second calibration signal, and said data symbol uses said first and second characteristics to determine a data value of said data symbol.

47. The RFID reader of claim 46, wherein the RFID tag device determines said data symbol to be a first data value if a characteristic of said data symbol has a first predetermined relationship with said first characteristic;

and

wherein the RFID tag device determines said data symbol to be a second data value if said characteristic of said data symbol has a second predetermined relationship with said first characteristic and has a third predetermined relationship with said second characteristic.

48. The RFID reader of claim 47, wherein the RFID tag device determines said data symbol to be a third data value if said characteristic of said data symbol has a fourth predetermined relationship-with said second characteristic.

49. The RFID reader of claim 46, wherein said first characteristic is a phase of said first calibration signal, and said second characteristic is a phase of said second calibration signal.

50. The RFID reader of claim 49, wherein the RFID tag device determines said data symbol to be a first data value if a length of a pulse portion of said data symbol is less than said length of said pulse portion of said first calibration signal;

wherein the RFID tag device determines said data symbol to be a second data value if said length of said pulse portion of said data symbol is greater than said length of said pulse portion of said first calibration signal and less than a length of said pulse portion of said second calibration signal; and

wherein the RFID tag device determines said data symbol to be a third data value if said length of said pulse portion of said data symbol is greater than said length of said pulse portion of said second calibration signal.

51. The RFID reader of claim 46, wherein said first characteristic is a frequency of said first calibration signal, and said second characteristic is a frequency of said second calibration signal.

52. The RFID reader of claim 46, wherein said first characteristic is an amplitude of said first calibration signal, and said second characteristic is an amplitude of said second calibration signal.

53. The RFID reader of claim 46, wherein said first characteristic is a length of a pulse portion said first calibration signal, and said second characteristic is a length of a pulse portion of said second calibration signal.

54. The RFID reader of claim 46, wherein said first characteristic is a length of a cycle of said first calibration signal, and said second characteristic is a length of a cycle of said second calibration signal.

55. The RFID reader of claim 46, wherein said first calibration signal is transmitted on a carrier signal and said second calibration signal is transmitted on said carrier signal.

56. A radio frequency identification (RFID) communications system, comprising:

a RFID reader that includes a transmitter and an antenna coupled to an output of said transmitter; and

a RFID tag device;

wherein said transmitter is capable of outputting a calibration signal for transmission by said antenna, wherein said calibration signal has a characteristic,

wherein said transmitter is capable of outputting a data symbol for transmission by said antenna;

wherein said RFID tag device is configured to receive said calibration signal and said data symbol, and is configured to use said characteristic to determine a data value of said data symbol.

57. The system of claim 56, wherein said antenna transmits the first calibration signal on a carrier signal.

58. The system of claim 57, wherein said RFID tag device comprises:

at least one capacitor that stores charge from the received carrier signal to produce a direct current (DC) voltage, wherein the DC voltage is used to power the RFID tag device.

59. The system of claim 58, wherein said RFID tag device further comprises:

a diode rectifier circuit that rectifies the carrier signal.

60. The system of claim 59, wherein said diode rectifier circuit has a plurality of stages.

61. The system of claim 60, wherein said plurality of stages cause the DC voltage to be greater than a received voltage of the carrier signal.

62. A radio frequency identification (RFID) communications system, comprising:

a RFID reader that includes a transmitter and an antenna coupled to an output of said transmitter; and

a RFID tag device;

wherein said transmitter is capable of outputting first and second calibration signals for transmission by said antenna, wherein said first calibration signal has a first characteristic and said second calibration signal has a second characteristic,

wherein said transmitter is capable of outputting a data symbol for transmission by said antenna;

wherein said RFID tag device is configured to receive said first calibration signal, said second calibration signal, and said data symbol, and is configured to use said first and second characteristics to determine a data value of said data symbol.

63. The system of claim 62, wherein said antenna transmits the first and second calibration signals on a carrier signal.

64. The system of claim 63, wherein said RFID tag device comprises:

at least one capacitor that stores charge from the received carrier signal to produce a direct current (DC) voltage, wherein the DC voltage is used to power the RFID tag device.

65. The system of claim 64, wherein said RFID tag device further comprises:

a diode rectifier circuit that rectifies the carrier signal.

66. The system of claim 65, wherein said diode rectifier circuit has a plurality of stages.

67. The system of claim 66, wherein said plurality of stages cause the DC voltage to be greater than a received voltage of the carrier signal.