Array antenna system and algorithm applicable to RFID readers

• US 8,593,283 B2
• Filed: 01/30/2009
• Issued: 11/26/2013
• Est. Priority Date: 01/30/2008
• Status: Active Grant

• Current Assignee: Metrc, LLC
• Original Assignee: Mark H. Smith
• Inventors: Smith, Mark H.
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Labbees, Edny
• Application Number:
  US12/363,555
• Publication Number:
  US 20090195361A1
• Time in Patent Office: 1,761 Days
• Field of Search: 3405721-5729, 235375-385, 343/844, 343/893
• US Class Current: 340/572.7
• CPC Class Codes: G06K 7/10158 methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
• CPC Class Codes: G06K 7/10178 including auxiliary means for focusing, repeating or boosting the electromagnetic interrogation field comparable booster antennas integrated on the record carrier itself G06K19/07794
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10326 the antenna being of the very-near field type, e.g. capacitive
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• 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: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/245 provided with means for varying the polarisation polarising devices H01Q15/24; tracking by comparing linear polarisation compounds G01S3/146; reducing depolarisation effects H04B7/00; polarisation diversity H04B7/10
• CPC Class Codes: H01Q 3/00 Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system means for positioning H01Q1/125
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

Embodiments of the invention pertain to Radio Frequency Identification (RFID) method and system using an antenna array, an array controller, and control algorithms. Embodiments of the invention can induce strong radio-frequency (RF) excitation, for a given level of radiated RF power, at any point within an arbitrary inhomogeneous medium. For RFID applications, one typical inhomogeneous medium is an ensemble of cases on a pallet. Another typical medium is a warehouse environment having stored goods together with shelving and other material present. An embodiment of the invention is applicable to the process of reading battery-less, or “passive” RFID tags, which rely on incident RF electromagnetic fields established by RFID readers to power the electronic circuitry within the tags.

Claims

1. An antenna system, comprising:

an RF input port, wherein the RF input port is configured to receive an input RF signal, wherein the input RF signal is suitable for reading at least one RFID tag;

a plurality of antennas, wherein each antenna of the plurality of antennas is configured to produce an RF field in a volume of interest when an antenna input signal is inputted to the each antenna of the plurality of antennas, wherein one or more antenna of the plurality of antennas is configured to produce an RF field at any position in the volume of interest;

circuitry adapted to produce a corresponding plurality of antenna input signals from the input RF signal, wherein each of the antenna input signal of the plurality of antenna input signals is suitable for reading the at least one RFID tag, wherein when the plurality of antenna input signals is simultaneously inputted to the plurality of antennas a corresponding plurality of RF fields is simultaneously produced in the volume of interest;

a state controller, wherein the state controller changes a state of the plurality of antennas by altering the plurality of RF fields, wherein the state controller produces a first state during a first period of time and produces a second state during a second period of time, wherein the state controller alters the plurality of RF fields by altering one or more of the following;

a phase of a first at least one of the plurality of antenna input signals, wherein altering the phase of the first at least one of the plurality of antenna input signals is independent of altering a phase of any other of the plurality of antenna input signals,

a ratio of amplitudes of a first at least two of the plurality of antenna input signals,

a radiation pattern of a first at least one of the plurality of antennas, and

a polarization of a second at least one of the plurality of antennas.

2. The system according to claim 1, wherein the circuitry adapted to produce the plurality of antenna input signals comprises a power divider, wherein the input RF signal is inputted to the power divider and the plurality of antenna input signals are outputted from the power divider.

3. The system according to claim 1, wherein the state controller alters the plurality of RF fields by altering a phase of at least one of the plurality of antenna input signals.

4. The system according to claim 1, wherein the state controller alters the plurality of RF fields by altering a ratio of amplitudes of at least two of the plurality of antenna input signals.

5. The system according to claim 1, wherein the state controller alters the plurality of RF fields by altering a radiation pattern of at least one of the plurality of antennas.

6. The system according to claim 1, wherein the state controller alters the plurality of RF fields by altering a polarization of at least one of the plurality of antennas.

7. The system according to claim 1, further comprising:

an RFID reader, wherein the RFID reader is coupled to the RF input port and provides the input RF signal.

8. The system according to claim 1, further comprising:

an RF receiver, wherein the RF receiver receives a receive RF signal, wherein the receive RF signal is due to the plurality of the RF fields being incident on one or more of the at least one RFID tag.

9. The system according to claim 8, wherein the RF receiver comprises the plurality of antennas.

10. The system according to claim 8, wherein the received receive RF signal is outputted from the RF input port.

11. The system according to claim 7, further comprising:

an RF receiver, wherein the RF receiver receives a receive RF signal, wherein the receive RF signal is due to the plurality of the RF fields being incident on one or more of the at least one RFID tag.

12. The system according to claim 11, wherein the received receive RF signal is outputted from the RF input port to the RFID reader.

13. The system according to claim 8, wherein the RF receiver comprises a second plurality of antennas.

14. The system according to claim 13, further comprising:

a second state controller, wherein the second state controller changes a receive state of the second plurality of antennas by altering one or more of the following;

a phase of a first at least one of a plurality of received receive RF signals as received by the second plurality of antennas,

a ratio of amplitudes of at least two of the plurality of received receive RF signals,

a radiation pattern of at least one of the second plurality of antennas, and

a polarization of one or more of the second plurality of antennas.

15. The system according to claim 14, wherein the second state controller produces a first receive state during the first period of time and produces a second receive state during the second period of time.

16. The system according to claim 7, further comprising:

one or more RFID tags located in a far-field region of the plurality of antennas.

17. The system according to claim 16, wherein the far-field region is greater than or equal to

18. The system according to claim 7, further comprising:

one or more RFID tags located in a radiating near field of the plurality of antennas.

19. The system according to claim 18, wherein the radiating near field is in the range

20. The system according to claim 7, further comprising:

one or more RFID tags located greater than or equal to 3λ

away from the plurality of antennas, where λ

is the wavelength of the plurality of RF fields.

21. The system according to claim 7, further comprising:

one or more RFID tags located closer than 3λ

away from the antenna array, where λ

is the wavelength of the plurality of RF fields.

22. The system according to claim 3, wherein the state controller alters the phase of the at least one of the plurality of antenna input signals via a corresponding at least one phase shifters, wherein each of the at least one phase shifters receives a corresponding antenna input signal of the at least one plurality of antenna input signals and outputs the corresponding antenna input signal with altered phase to the corresponding antenna of the plurality of antennas.

23. The system according to claim 1, wherein each antenna of the plurality of antennas is within

24. The system according to claim 1, wherein each antenna of the plurality of antennas is in a range of

25. The system according to claim 1, wherein each antenna of the plurality of antennas is greater than λ

away from a closest neighbor antenna of the plurality of antennas, where λ

is the wavelength of the plurality of RF fields.

26. The system according to claim 5, wherein altering the radiation pattern of the at least one of the plurality of antennas comprises altering a beam shape of the at least one of the plurality of antennas.

27. The system according to claim 5, wherein altering the radiation pattern of the at least one of the plurality of antennas comprises altering a beam pointing angle of the at least one of the plurality of antennas.

28. The system according to claim 1, wherein at least two of the same antennas from the plurality of antennas produce one of the plurality of RF fields in the first state and the second state.

29. The system according to claim 1, wherein the plurality of antennas comprises at least four antennas.

46. The system according to claim 3, wherein altering the phase of at least one of the plurality of antenna input signals is achieved by at least one variable time-delay.

47. The system according to claim 1, wherein altering the plurality of RF fields comprises using control elements controlled by analog voltages that are generated by analog oscillator circuits.

59. The antenna system according to claim 1, wherein in at least the first state or the second state the plurality of RF fields produced in the volume of interest, when incident upon one of the at least one RFID tag, results in the one of the at least one RFID tag producing a receive RF signal having a higher intensity than a second receive RF signal produced by an RF field produced in the volume of interest, when the input RF signal is inputted to any one of the plurality of antennas, is incident upon the one of the at least one RFID tag.

61. The system according to claim 1, wherein for at least one location in the volume of interest each antenna of the plurality of antennas is configured to produce an RF field at the at least one location in the volume of interest.

62. The system according to claim 1, wherein each antenna of the plurality of antennas is configured to produce an RF field at any position in the volume of interest.

65. The system according to claim 1, further comprising:

one or more auxiliary receive antennas, wherein the one or more auxiliary receive antennas sense a far field electromagnetic field intensity of the plurality of RF fields in real time, wherein a magnitude of transmitted power from the plurality of antennas is adjusted in real time based on the far-field electromagnetic field intensity sensed by the one or more auxiliary receive antennas.

66. The method according to claim 1, further comprising:

positioning one or more auxiliary receive antennas in the volume of interest,

sensing a far-field electromagnetic field intensity of the plurality of RF fields in real time via the one or more auxiliary receive antennas,

adjusting a magnitude of transmitted power from the plurality of antennas in real time based on the far-field electromagnetic field intensity sensed by the one or more auxiliary receive antennas.

30. A method of reading one or more RFID tags, comprising:

positioning one or more RFID tags in a volume of interest;

positioning a plurality of antennas, wherein each antenna of the plurality of antennas is configured to produce an RF field in the volume of interest when an antenna input signal is inputted to the each antenna of the plurality of antennas, wherein one or more antenna of the plurality of antennas is configured to produce an RF field at any position in the volume of interest;

receiving an input RF signal, wherein the input RF signal is suitable for reading at least one of the one or more RFID tags;

producing a corresponding plurality of antenna input signals from the received input RF signal, each of the plurality of antenna input signals suitable for reading the at least one of the one or more RFID tags;

inputting each of the plurality of antenna input signals into a corresponding antenna of the plurality of antennas while the plurality of antennas is in a first state during a first period of time, such that a corresponding first plurality of RF fields is simultaneously produced in the volume of interest from the plurality of antennas;

receiving a first receive RF signal, wherein the first receive RF signal is due to the first plurality of RF fields produced during the first period of time being incident on the at least one of the one or more RFID tags;

processing the first receive RF signal to determine whether the at least one of the one or more RFID tags is present in the volume of interest;

inputting each of the plurality of antenna input signals into the corresponding antenna of the plurality of antennas while the plurality of antennas is in a second state during a second period of time, such that a corresponding second plurality of RF fields is simultaneously produced in the volume of interest from the plurality of antennas, wherein the second plurality of RF fields produced in the region of interest is altered compared with the first plurality of RF fields produced in the volume of interest;

receiving a second receive RF signal, wherein the second receive RF signal is due to the plurality of RF fields produced during the second period of time being incident on the at least one of the one or more RFID tags;

processing the second receive RF signal to determine whether the at least one of the one or more RFID tags is present in the volume of interest, wherein the second plurality of RF fields produced in the volume of interest is altered as compared to the first plurality of RF fields produced in the volume of interest via one or more of the following;

altering a phase of a first at least one of the plurality of antenna input signals, wherein altering the phase of the first at least one of the plurality of antenna input signals is independent of altering a phase of any other of the plurality of antenna input signals,

altering a ratio of amplitudes of a first at least two of the plurality of antenna input signals,

altering a radiation pattern of a first at least one of the plurality of antennas, and

altering a polarization of a second at least one of the plurality of antennas.

31. The method according to claim 30, wherein the second plurality of RF fields produced in the volume of interest is altered as compared to the first plurality of RF fields produced in the volume of interest by altering a phase of at least one of the plurality of antenna input signals.

32. The method according to claim 30, wherein the second plurality of RF fields produced in the volume of interest is altered as compared to the first plurality of RF fields produced in the volume of interest by altering a ratio of amplitudes of at least two of the plurality of antenna input signals.

33. The method according to claim 30, wherein the second plurality of RF fields produced in the volume of interest is altered as compared to the first plurality of RF fields produced in the volume of interest by altering a radiation pattern of at least one of the plurality of antennas.

34. The method according to claim 30, wherein the second plurality of RF fields produced in the volume of interest is altered as compared to the first plurality of RF fields produced in the volume of interest by altering a polarization of at least one of the plurality of antennas.

35. The method according to claim 30, further comprising:

a) inputting each of the plurality of antenna input signals into the corresponding antenna of the plurality of antennas while the plurality of antennas are in at least one additional state during at least one additional period of time, such that a corresponding at least one additional plurality of RF fields are simultaneously produced in the volume of interest from the plurality of antennas;

b) receiving at least one additional receive RF signal, wherein the at least one additional receive RF signal is due to the at least one additional plurality of RF fields produced during the at least one additional period of time being incident on the at least one of the one or more RFID tags, wherein each of the at least one additional plurality of RF fields produced in the volume of interest is altered as compared with the first plurality of RF fields, is altered as compared with the second plurality of RF fields, and is altered as compared with each of the other at least one additional plurality of RF fields produced in the volume of interest; and

c) processing the at least one additional receive RF signal to determine whether the at least one of the one or more RFID tags is present in the volume of interest.

36. The method according to claim 35, further comprising:

repeating a, b, and c until a criterion is met.

37. The method according to claim 35, wherein the criterion is all of the one or more RFID tags in the volume of interest are present.

38. The method according to claim 37, wherein the criterion is all of the states of at least one additional state have been utilized.

39. The method according to claim 37, wherein the criterion is a certain time period has passed.

40. The method according to claim 37, wherein the criterion is a termination signal is received.

41. The method according to claim 30, wherein receiving the first receive RF signal and receiving the second receive RF signal is accomplished via an RF receiver.

42. The method according to claim 41, wherein the RF receiver comprises the plurality of antennas.

43. The method according to claim 41, wherein the RF receiver comprises a second plurality of antennas.

44. The method according to claim 30, wherein receiving the input RF signal comprises receiving the input RF signal from an RFID reader.

45. The method according to claim 44, further comprising:

inputting the first receive RF signal to the RFID reader; and

inputting the second receive RF signal to the RFID reader.

48. The method according to claim 35, wherein the first state, second state, and the at least one additional state are ordered to place states having a statistically higher probability of successfully reading tags earlier in the ordering.

49. The method according to claim 35, wherein the first state, second state, and the at least one additional state are ordered to place array states for which RFID tags have been successfully read earlier in the ordering.

50. The method according to claim 48, wherein the probability of successfully reading tags applies to a specific ensemble of tags in a fixed configuration.

51. The method according to claim 49, wherein the RFID tags that have been successfully read comprise a specific ensemble of tags in a fixed configuration.

52. The method according to claim 50, wherein the probability of successfully reading tags applies to a category of ensembles.

53. The method according to claim 51, wherein the proven history of successfully reading tags applies to a category of ensembles.

54. The method according to claim 35, wherein one or more electronic control elements are used to alter the plurality of RF fields produced in the volume of interest in order to change the plurality of antennas from one of:

the first state, the second state, and the at least one additional state, to another of;

the first state, the second state, and the at least one additional state, wherein digital commands are provided to the electronic control elements to alter the plurality of RF fields produced in the volume of interest, wherein the first state, the second state, and the at least one additional state include all possible states, wherein possible states correspond to possible combinations of digital commands that can be provided to the electronic control elements.

55. The method according to claim 54, wherein one or more electronic control elements are used to alter the plurality of RF fields produced in the volume of interest in order to change the plurality of antennas from one of:

the first state, the second state, and the at least one additional state, to another of;

the first state, the second state, and the at least one additional state, wherein digital commands are provided to the electronic control elements to alter the plurality of RF fields produced in the volume of interest, wherein the first state, the second state, and the at least one additional state are ordered so that all possible permutations of the N most-significant bits of the digital commands are cycled through first, where N is an integer.

56. The method according to claim 45, wherein data from the RFID reader and/or a controller of the RFID reader is monitored to detect reports of newly identified tags, wherein an interval between successive new tag identifications is calculated from detections, and wherein the state of the plurality of antennas is changed when the interval between new tag identifications is longer than a specified threshold.

57. The method according to claim 45, wherein transmissions of the RFID reader are monitored and processed, and wherein signal features from the transmissions such as burst durations, signal gaps, and frequency hops are used to ascertain the status of the reader with respect to the reader'"'"'s read cycles.

58. The method according to claim 57, wherein the signal features are utilized to time state transitions so as to avoid corruption of individual read cycles.

60. The method according to claim 30, wherein at least the first receive RF signal or the second receive RF signal has a higher intensity than a third receive RF signal due to an RF field produced in the volume of interest being incident on the at least one of the one or more RFID tags, wherein the RF field is produced upon inputting the input RF signal to any one of the plurality of antennas.

63. The method according to claim 30, wherein for at least one location in the volume of interest each antenna of the plurality of antennas is configured to produce an RF field at the at least one location in the volume of interest.

64. The method according to claim 30, wherein each antenna of the plurality of antennas is configured to produce an RF field at any position in the volume of interest.