Detection of multiple articles

US 5,726,630 A
Filed: 12/29/1995
Issued: 03/10/1998
Est. Priority Date: 11/18/1992
Status: Expired due to Term

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First Claim

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1. An identification system comprising:

an interrogator; and

a plurality of transponders;

the interrogator comprising;

transmitter means for transmitting an interrogation signal to a plurality of transponders,receiver means for receiving a respective plurality of response signals from the plurality of transponders, andmeans for identifying the plurality of transponders from the respective plurality of response signals,the interrogator being capable of disabling any of the plurality of transponders;

each of the plurality of transponders comprising;

receiving means, andtransmitting means,whereby, on receipt of the transmitted interrogation signal, the transponder transmits a response signal;

wherein the interrogator transmits at least two intermittent interrogation signals, with an interval between successive interrogation signals which is less than a minimum period within which transponders which have been disabled reset themselves automatically.

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Abstract

An identification system comprises an interrogator and a plurality of transponders. The interrogator includes a transmitter which transmits at least two independent interrogation signals to the transponders, and a receiver for receiving response signals from the transponders. The interrogator also includes processor means for identifying the transponders from data in the received response signals. Each transponder comprises receiving means, a code generator, and transmitter means connected to the code generator. On receipt of at least one of the transmitted interrogation signals the transponder transmits a response signal containing data which identifies it. The interrogation signals may be transmitted continuously or intermittently. In a preferred embodiment, the interrogation signals are relatively narrow bandwidth signals at different frequencies. The receiving means of each transponder has a relatively broad reception bandwidth so that the transponder is responsive to one or more of the interrogation signals.

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140 Claims

1. An identification system comprising:
- an interrogator; and
  
  a plurality of transponders;
  
  the interrogator comprising;
  
  transmitter means for transmitting an interrogation signal to a plurality of transponders,receiver means for receiving a respective plurality of response signals from the plurality of transponders, andmeans for identifying the plurality of transponders from the respective plurality of response signals,the interrogator being capable of disabling any of the plurality of transponders;
  
  each of the plurality of transponders comprising;
  
  receiving means, andtransmitting means,whereby, on receipt of the transmitted interrogation signal, the transponder transmits a response signal;
  
  wherein the interrogator transmits at least two intermittent interrogation signals, with an interval between successive interrogation signals which is less than a minimum period within which transponders which have been disabled reset themselves automatically.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
- - 2. An identification system according to claim 1, wherein:
    - the interrogation signals have respective different frequencies which are selected to fall within a reception bandwidth of the receiving means of the transponders.
  - 3. An identification system according to claim 2, wherein:
    - the interrogation signals are relatively narrow bandwidth signals; and
      
      the receiving means of each transponder has a relatively broad reception bandwidth within which the respective different frequencies of the interrogation signals fall;
      
      whereby the respective transponder is responsive to any one or more of the at least two intermittent interrogation signals.
  - 4. An identification system according to claim 3, wherein:
    - each of the interrogation signals is modulated with data, a data modulation bandwidth of each interrogation signal being less than a spacing between the respective different frequencies of the interrogation signals.
  - 5. An identification system according to any one of claim 1 to 4, wherein the transmitting means of the transponder comprises:
    - an antenna; and
      
      means for modulating the reflectivity of the antenna;
      
      the response signal of the transponder comprising at least one interrogation signal carrier modulated with data which identifies the transponder.
  - 6. An identification system according to any one of claim 1 to 4, wherein:
    - the transmitter means of the interrogator comprises at least two spaced apart transmitting antenna elements; and
      
      the receiver means comprises at least two spaced apart receiving antenna elements.
  - 7. An identification system according to any one of claim 1 to 4, wherein:
    - the transmitter means and the receiver means comprise at least two spaced apart antenna units, each of the at least two spaced apart antenna units comprising;
      
      a transmitting antenna element, andan adjacent receiving antenna element.
  - 8. An identification system according to claim 7, wherein:
    - each antenna element comprises a patch array designed to operate at a frequency between 800 MHz and 1 GHz.
  - 9. An identification system according to claim 7, wherein:
    - at least two of the respective transmitting and receiving antenna elements are polarized differently from one another.
  - 10. An identification system according to claim 7, wherein the transmitting means of the interrogator comprises:
    - a transmitting antenna element;
      
      at least first and second transmitters for generating interrogation signals at respective different frequencies; and
      
      switch means for switching the outputs of the transmitters alternately to the transmitting antenna element.
  - 11. An identification system according to any one of claims 1 to 4, wherein:
    - the transmitter means and the receiver means of the interrogator are mounted on or adjacent to a structure which defines an interrogation zone through which the transponders to be identified may be passed.
  - 12. An identification system according to claim 11, wherein:
    - the transmitter means and the receiver means of the interrogator are supported by a frame defining a passage through which a conveyance containing articles to which respective transponders are attached can pass.
  - 13. An identification system according to any one of claims 1 to 4, wherein:
    - the at least two interrogation signals have respective different frequencies which are selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 14. An identification system according to any one of claims 1 to 4, further comprising:
    - processor means for recording data received from each identified transponder, and for relating the received data to stored data corresponding to the received data.
  - 15. An identification system according to claim 14, wherein:
    - the processor means stores at least one of price data and identification data of articles to which different transponders are attached, and relates the identification codes of identified transponders thereto.
  - 16. An identification system according to claim 15, further comprising:
    - display means for generating a display in which descriptions of the articles to which respective transponders are attached are associated with price data.
  - 17. An identification system according to claim 16, further comprising:
    - printer means for generating a printout of the display.

18. A method of identifying a plurality of transponders, comprising:
- transmitting an interrogation signal to the transponders, each transponder receiving the interrogation and transmitting a response signal in response;
  
  receiving the response signals from the transponders;
  
  identifying a particular transponder from the response signals; and
  
  disabling the particular transponder;
  
  wherein at least two intermittent interrogation signals are transmitted, with an interval between successive interrogation signals which is less than a minimum period within which transponders which have been disabled reset themselves automatically.
- View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
- - 19. A method according to claim 18, further comprising:
    - selecting the respective different frequencies of the at least two interrogation signals to fall within the reception bandwidth of the transponders.
  - 20. A method according to claim 19, wherein:
    - the at least two interrogation signals have a relatively narrow bandwidth and the transponders have a relatively broad reception bandwidth within which the respective different frequencies of the at least two interrogation signals fall.
  - 21. A method according to claim 20, wherein:
    - each interrogation signal is modulated with data, the data modulation bandwidth of each interrogation signal being less than the spacing between the respective different frequencies of the interrogation signals.
  - 22. A method according to any one of claims 18 to 21, wherein:
    - the response signal from a transponder comprises one or more interrogation signal carriers modulated with data which identifies the transponder.
  - 23. A method according to any one of claims 18 to 21, further comprising:
    - switching between the at least two interrogation signals.
  - 24. A method according to any one of claims 18 to 21, further comprising:
    - selecting the at least two interrogation signals to have respective different frequencies so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 25. A method according to any one of claims 18 to 21, further comprising:
    - recording data received from each identified transponder; and
      
      relating the received data to stored data corresponding to the received data.
  - 26. A method according to claim 25, further comprising:
    - storing at least one of price data and identification data of articles to which different transponders are attached; and
      
      relating thereto the identification codes of identified transponders.
  - 27. A method according to claim 26, further comprising:
    - displaying descriptions of the articles to which respective transponders are attached; and
      
      associating the articles with the price data.
  - 28. A method according to claim 27, further comprising:
    - printing a printout of the display.

29. An identification system comprising:
- an interrogator; and
  
  a plurality of transponders;
  
  the interrogator comprising;
  
  transmitter means for transmitting an interrogation signal to the transponders,receiver means for receiving response signals from the transponders, andmeans for identifying the transponders from the response signals;
  
  each of the plurality of transponders comprising;
  
  receiving means, andtransmitting means,whereby, on receipt of the transmitted interrogation signal, the transponder transmits a response signal;
  
  wherein the interrogator transmitter transmits a plurality of simultanteous interrogation signals at a plurality of frequencies, each transponder transmiting a response signal on receipt of at least one of whichever of the interrogation signals, and the interrogator identifying response signals from the same transponder which are transmitted at some or all of the frequencies.
- View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
- - 30. An identification system according to claim 29, wherein:
    - the transmitter means transmits the plurality of interrogation signals continuously.
  - 31. An identification system according to claim 29 or claim 30, wherein:
    - the interrogation signals have respective different frequencies which are selected to fall within the reception bandwidth of the receiving means of the transponders.
  - 32. An identification system according to claim 31, wherein:
    - the interrogation signals are relatively narrow bandwidth signals; and
      
      the receiving means of each transponder have a relatively broad reception bandwidth within which the respective different frequencies of the interrogation signals fall;
      
      whereby the transponder is responsive to at least one of the interrogation signals.
  - 33. An identification system according to claim 32, wherein:
    - each interrogation signal is modulated with data, the data modulation bandwidth of each interrogation signal being less than the spacing between the respective different frequencies of the interrogation signals.
  - 34. An identification system according to any one of claims 29 to 32, wherein the transmitting means of the transponder comprises:
    - an antenna; and
      
      means for modulating the reflectivity of the antenna;
      
      whereby the response signal of the transponder comprises one or more interrogation signal carriers modulated with data which identifies the transponder.
  - 35. An identification system according to any one of claims 29 to 32, wherein:
    - the transmitter means and the receiver means comprise at least two spaced apart antenna units, each antenna unit comprising a transmitting antenna element and an adjacent receiving antenna element.
  - 36. An identification system according to any one of claims 29 to 32, wherein:
    - the interrogation signals have respective different frequencies which are selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 37. An identification system according to any one of claims 29 to 32, wherein:
    - the transmitter means and the receiver means of the interrogator are mounted on or adjacent to a structure which defines an interrogation zone through which the transponders to be identified may be passed.
  - 38. An identification system according to claim 37, wherein:
    - the transmitter means and the receiver means of the interrogator are supported by a frame defining a passage through which a conveyance containing articles to which respective transponders are attached can pass.
  - 39. An identification system according to any one of claims 29 to 32, wherein:
    - the transmitter means of the interrogator comprises at least two spaced apart transmitting antenna elements; and
      
      the receiver means comprises at least two spaced apart receiving antenna elements.
  - 40. An identification system according to claim 39, wherein:
    - each antenna element comprises a patch array designed to operate at a frequency between 800 MHz and 1 GHz.
  - 41. An identification system according to claim 39, wherein:
    - at least two of the respective transmitting and receiving antenna elements are polarized differently from one another.
  - 42. An identification system according to claim 39, wherein:
    - the receiver means distinguishes response signals from transponders in response to interrogation signals transmitted at the respective different frequencies of the at least first and second transmitters.
  - 43. An identification system according to claim 42, further comprising:
    - processor means to detect duplicate transponder response signals transmitted on two or more of the respective different frequencies.
  - 44. An identification system according to claim 42, further comprising:
    - processor means for disregarding transponder response signals transmitted on two or more of the respective different frequencies.
  - 45. An identification system according to any one of claims 29 to 32, further comprising:
    - processor means for recording data received from each identified transponder, and for relating the received data to stored data corresponding to the received data.
  - 46. An identification system according to claim 45, wherein:
    - the processor means stores at least one of price data and identification data of articles to which different transponders are attached, and relates the identification codes of identified transponders thereto.
  - 47. An identification system according to claim 46, further comprising:
    - display means for generating a display in which descriptions of the articles to which respective transponders are attached are associated with price data.
  - 48. An identification system according to claim 47, further comprising:
    - printer means for generating a printout of the display.

49. An interrogator for identifying a plurality of transponders, the interrogator comprising:
- transmitter means for transmitting an interrogation signal to the transponders;
  
  receiver means for receiving response signals from the transponders; and
  
  means for identifying transponders from the response signals;
  
  wherein the interrogator transmitter transmits a plurality of simultaneous interrogation signals at a respective plurality of frequencies, and the interrogator identifies a plurality of respectively distinguishable response signals from the same transponder which are transmitted at some or all of the frequencies.
- View Dependent Claims (50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63)
- - 50. An interrogator according to claim 49, further comprising:
    - processor means for detecting duplicate transponder response signals transmitted on two or more of the respective different frequencies.
  - 51. An interrogator according to claim 49, further comprising:
    - processor means for disregarding transponder response signals transmitted on two or more of the respective different frequencies.
  - 52. An interrogator according to claim 49, wherein:
    - the transmitter means of the interrogator transmits the plurality of interrogation signals continuously.
  - 53. An interrogator according to claim 49 or claim 52, wherein:
    - the transmitter means and the receiver means comprise at least two spaced apart antenna units, each antenna unit comprising;
      
      a transmitting antenna element, andan adjacent receiving antenna element.
  - 54. An interrogator according to claim 49 or claim 52, wherein:
    - the interrogation signals have respective different frequencies which are selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 55. An interrogator according to claim 49 or claim 52, wherein the transmitter means of the interrogator comprises:
    - at least two spaced apart transmitting antenna elements; and
      
      the receiver means comprises at least two spaced apart receiving antenna elements.
  - 56. An interrogator according to claim 55, wherein each antenna element comprises:
    - a patch array designed to operate at a frequency between 800 MHz and 1 GHz.
  - 57. An interrogator according to claim 55, wherein:
    - at least two of the respective transmitting and receiving antenna elements are polarized differently from one another.
  - 58. An interrogator according to claim 55, wherein:
    - the receiver means distinguishes response signals from transponders transmitted at the respective different frequencies of the at least first and second transmitters.
  - 59. An interrogator according to claim 49 or claim 52, wherein:
    - the transmitter means and the receiver means of the interrogator are mounted on or adjacent to a structure which defines an interrogation zone.
  - 60. An interrogator according to claim 59, wherein:
    - the transmitter means and the receiver means of the interrogation are supported by a frame defining a passage through which a conveyance containing articles can pass.
  - 61. An interrogator according to claims 49 or claim 52, wherein:
    - the interrogation signals have respective different frequencies.
  - 62. An interrogator according to claim 61, wherein:
    - the interrogation signals are relatively narrow bandwidth signals.
  - 63. An interrogator according to claim 62, wherein:
    - each interrogation signal is modulated with data, the data modulation bandwidth of each interrogation signal being less than the spacing between the respective different frequencies of the interrogation signals.

64. An interrogator for identifying a plurality of transponders, comprising:
- transmitter means for transmitting an interrogation signal to the transponders;
  
  receiver means for receiving response signals from the transponders; and
  
  means for identifying the transponders from the response signals;
  
  the interrogator being capable of disabling any transponder; and
  
  the interrogator transmitter transmiting at least two intermittent interrogation signals, with an interval between successive interrogation signals which is less than a minimum period within which transponders which have been disabled reset themselves automatically.
- View Dependent Claims (65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75)
- - 65. An interrogator according to claim 64, wherein:
    - the transmitter means and the receiver means comprise at least two spaced apart antenna units, each antenna unit comprising a transmitting antenna element and an adjacent receiving antenna element.
  - 66. An interrogator according to claim 64, wherein the transmitting means of the interrogator comprises:
    - a transmitting antenna element;
      
      at least first and second transmitters for generating interrogation signals at respective different frequencies; and
      
      switch means for switching the outputs of the transmitters alternately to the transmitting antenna element.
  - 67. An interrogator according to claim 64, wherein:
    - the at least two interrogation signals have respective different frequencies which are selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 68. An interrogator according to claim 64, wherein:
    - the transmitter means of the interrogator comprises at least two spaced apart transmitting antenna elements; and
      
      the receiver means comprises at least two spaced apart receiving antenna elements.
  - 69. An interrogator according to claim 68, wherein:
    - each antenna element comprises a patch array designed to operate at a frequency between 800 MHz and 1 GHz.
  - 70. An interrogator according to claim 68, wherein:
    - at least two of the respective transmitting and receiving antenna elements are polarized differently from one another.
  - 71. An interrogator according to claim 64, wherein:
    - the transmitter means and the receiver means of the interrogator are mounted on or adjacent to a structure which defines an interrogation zone.
  - 72. An interrogator according to claim 71, wherein:
    - the transmitter means and the receiver means of the interrogator are supported by a frame defining a passage through which a conveyance containing articles can pass.
  - 73. An interrogator according to claim 64, wherein:
    - the at least two interrogation signals have respective different frequencies.
  - 74. An interrogator according to claim 73, wherein:
    - the at least two interrogation signals are relatively narrow bandwidth signals.
  - 75. An interrogator according to claim 74, wherein:
    - each interrogation signal is modulated with data, a data modulation bandwidth of each interrogation signal being less than a spacing between the respective different frequencies of the interrogation signals.

76. A method of identifying a plurality of transponders, comprising:
- transmitting an interrogation signal to the plurality of transponders, each of the plurality of transponders receiving the interrogation signal and transmitting a signal in response;
  
  receiving the response signals from the transponders; and
  
  identifying transponders from the response signals;
  
  wherein a plurality of simultanteous interrogation signals at a plurality of frequencies are transmitted, a response signal is transmitted by each transmitter on receipt of at least one of whichever of the interrogation signals, and response signals from the same transponder which are transmitted at some or all of the frequencies are identified.
- View Dependent Claims (77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88)
- - 77. A method according to claim 76, further comprising:
    - detecting duplicate transponder response signals transmitted on at least two of the respective different frequencies.
  - 78. A method according to claim 76, further comprising:
    - disregarding transponder response signals transmitted on at least two of the respective different frequencies.
  - 79. A method according to claim 76, wherein:
    - a plurality of interrogation signals are transmitted continuously.
  - 80. A method according to claim 76 or claim 79, wherein:
    - the response signal of a transponder comprises at least one interrogation signal carrier modulated with data which identifies the transponder.
  - 81. A method according to claim 76 or claim 79, further comprising:
    - selecting the interrogation signals to have respective different frequencies so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 82. A method according to claim 79, wherein:
    - respective different frequencies of the interrogation signals are selected to fall within the reception bandwidth of the transponders.
  - 83. A method according to claim 82, wherein:
    - the interrogation signals have relatively narrow bandwidth; and
      
      the transponders have a relatively broad reception bandwidth within which the respective different frequencies of the interrogation signals fall.
  - 84. A method according to claim 83, wherein:
    - each interrogation signal is modulated with data, the data modulation bandwidth of each interrogation signal being less than a spacing between respective different frequencies of the interrogation signals.
  - 85. A method according to claim 76 or claim 79, further comprising:
    - recording data received from each identified transponder; and
      
      relating the received data to stored data corresponding to the received data.
  - 86. A method according to claim 85, further comprising:
    - storing at least one of price data and identification data of articles to which different transponders are attached; and
      
      relating thereto the identification codes of identified transponders.
  - 87. A method according to claim 86, further comprising:
    - displaying descriptions of the articles to which respective transponders are attached; and
      
      associating the articles with price data.
  - 88. A method according to claim 87, further comprising:
    - printing a printout of the display.

89. A method of identifying a plurality of transponders, comprising:
- transmitting an interrogation signal to the plurality of transponders, each of the plurality of transponders receiving the interrogation signal; and
  
  disabling any one of the plurality of transponders;
  
  whereby the interrogation signal and an inhibiting signal are transmitted; and
  
  a disabled transponder remains disabled while the disabled transponder continues receiving the inhibiting signal.
- View Dependent Claims (90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103)
- - 90. A method according to claim 89, wherein:
    - the interrogation signal and the inhibiting signal have relatively narrow bandwidth; and
      
      the transponders have a relatively broad reception bandwidth within which the respective different frequencies of the interrogation signal and the inhibiting signal fall.
  - 91. A method according to claim 90, further comprising:
    - modulating the interrogation signal with data, the data modulation bandwidth of the interrogation signal being less than a spacing between the respective different frequencies of the interrogation signal and the inhibiting signal.
  - 92. A method according to claim 89, wherein:
    - the interrogation signal is relatively directional; and
      
      the inhibiting signal is relatively widely dispersed.
  - 93. A method according to claim 89, wherein:
    - a width of the inhibiting signal is at least 5 times greater than a width of the interrogating signal.
  - 94. A method according to any one of claims 89 to 93, wherein:
    - the interrogation signal is relatively high power; and
      
      the inhibiting signal is relatively low power.
  - 95. A method according to any one of claims 89 to 93, further comprising:
    - transmitting a turn-off instruction in both the interrogation signal and the inhibiting signal.
  - 96. A method according to any one of claims 89 to 93, further comprising:
    - selecting respective different frequencies of the interrogation signal and the inhibiting signal to fall within the reception bandwidth of the transponders.
  - 97. A method according to any one of claims 89 to 93, wherein:
    - the response signal of a transponder comprises a interrogation signal carrier modulated with data which identifies the transponder.
  - 98. A method according to any one of claims 89 to 93, further comprising:
    - selecting the interrogation signal and the inhibiting signal to have respective different frequencies so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 99. A method according to any one of claims 89 to 93, further comprising:
    - disregarding transponder response signals transmitted on the frequency of the inhibiting beam.
  - 100. A method according to any one of claims 89 to 93, further comprising:
    - recording data received from each identified transponder; and
      
      relating the received data to stored data corresponding to the received data.
  - 101. A method according to claim 100, further comprising:
    - storing at least one of price data and identification data of articles to which different transponders are attached; and
      
      relating thereto the identification codes of identified transponders.
  - 102. A method according to claim 101, further comprising:
    - displaying descriptions of the articles to which respective transponders are attached; and
      
      associating the articles with the price data.
  - 103. A method according to claim 102, further comprising:
    - printing a printout of the display.

104. A transponder comprising:
- receiving means for receiving an interrogation signal;
  
  a code generator; and
  
  transmitting means connected to the code generator, the transponder transmitting a response signal which identifies the transponder on receipt of the interrogation signal, and being disabled by an instruction in the interrogation signal;
  
  the transponder receiving the interrogation signal and an inhibiting signal; and
  
  a disabled transponder remaining disabled while the disabled transponder continues receiving the inhibiting signal.
- View Dependent Claims (105)
- - 105. A transponder according to claim 104, wherein the transmitting means of the transponder comprises:
    - an antenna; and
      
      means for modulating reflectivity of the antenna;
      
      whereby the response signal of the transponder comprises an interrogation signal carrier modulated with data which identifies the transponder.

106. An identification system comprising:
- a plurality of transponders, each transponder comprising receiving means, a code generator, and transmitting means connected to the code generator, wherein in each transponder the transmitting means transmits a response signal containing data from the code generator which identifies the transponder in response to whichever of two independent interrogation signals the receiving means of the transponder receives; and
  
  an interrogator comprising transmitter means for transmitting two independent interrogation signals to the transponders wherein each independent interrogation signal being adapted to independently activate any one or more of the transponders, receiver means for receiving the response signals from the transponders, and processor means for identifying the transponders from data in the response signals.
- View Dependent Claims (107, 108, 109)
- - 107. A system as in claim 106, wherein the transmitter means of the interrogator transmits the two independent interrogation signals simultaneously.
  - 108. A system as in claim 106, wherein the transmitter means of the interrogator transmits the two interrogation signals intermittently, with an interval between successive interrogation signals which is less than a minimum period within which transponders which have been disabled by a disable instruction in an interrogation signal reset themselves automatically.
  - 109. A system as in claim 106, wherein the two interrogation signals have respective different frequencies which fall within the reception bandwidth of the transponders.

110. A method for identifying one of a plurality of transponders, the method comprising:
- transmitting two independent interrogation signals to the transponders, each independent interrogation signal being adapted to independently activate any one or more of the transponders;
  
  activating one of the transponders in response to whichever of the two independent interrogation signals the one transponder receives, such that the one transponder transmits a response signal containing code data which identifies the transponder and at least some signal energy from whichever of the two independent interrogation signals the one transponder receives;
  
  receiving the response signal from the one transponder; and
  
  identifying the one transponder from the code data in the response signal.
- View Dependent Claims (111, 112, 113, 114)
- - 111. A method as in claim 110, wherein the step of transmitting two independent interrogation signals comprises simultaneously transmitting the two independent interrogation signals.
  - 112. A method as in claim 110, wherein the step of transmitting two independent interrogation signals comprises transmitting the two independent interrogation signals intermittently, with an interval between successive interrogation signals which is less than a minimum period within which transponders remain disabled responsive to a disable instruction before an automatic reset.
  - 113. A method as in claim 110, wherein the two independent interrogation signals have respective different frequencies which fall within a reception bandwidth of the transponders.
  - 114. A method as in claim 113, wherein the frequencies of the two independent interrogation signals are such that electric fields of the two transmitted independent interrogation signals have no overlapping nulls in an area encompassing the transponders.

115. An identification system comprising:
- an interrogator; and
  
  a plurality of transponders;
  
  the interrogator comprising;
  
  transmitter means for transmitting an interrogation signal to the transponders,receiver means for receiving response signals from the transponders, andmeans for identifying the transponders from the response signals;
  
  each of the plurality of transponders comprising;
  
  receiving means responsive to a disabling instruction from the interrogator;
  
  the interrogator transmiting the interrogation signal and an inhibiting signal; and
  
  a disabled transponder remains disabled while the disabled transponder continues receiving the inhibiting signal.
- View Dependent Claims (116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129)
- - 116. An identification system according to claim 115, wherein:
    - the interrogation signal and the inhibiting signal are relatively narrow bandwidth signals; and
      
      the receiving means of each transponder has a relatively broad reception bandwidth within which the respective different frequencies of the interrogation signal and the inhibiting signal fall.
  - 117. An identification system according to claim 116, wherein:
    - the interrogation signal is modulated with data, the data modulation bandwidth of the interrogation signal being less than a spacing between respective different frequencies of the interrogation signal and the inhibiting signal.
  - 118. An identification system according to claim 115, wherein:
    - the interrogation signal is a relatively directional signal; and
      
      the inhibiting signal is a relatively widely dispersed signal.
  - 119. An identification system according to claim 118, wherein:
    - the inhibiting signal has a beam width which is at least 5 times greater than that of the interrogating signal.
  - 120. An identification system according to any one of claims 115 to 119, wherein:
    - the interrogation signal is a relatively high power signal; and
      
      the inhibiting signal is a relatively low power signal.
  - 121. An identification system according to any one of claims 115 to 119, wherein:
    - a turn-off instruction to the transponder is transmitted in both the interrogation signal and the inhibiting signal.
  - 122. An identification system according to any one of claims 115 to 119, wherein:
    - the interrogation signal and the inhibiting signal have respective different frequencies which are selected to fall within the reception bandwidth of the receiving means of the transponders.
  - 123. An identification system according to any one of claims 115 to 119, wherein the transmitting means of the transponder comprises:
    - an antenna; and
      
      means for modulating the reflectivity of the antenna;
      
      whereby the response signal of the transponder comprises the interrogation signal carrier modulated with data which identifies the transponder.
  - 124. An identification system according to any one of claims 115 to 119, wherein:
    - the interrogator detects transponder response signals transmitted on a frequency of the inhibiting beam and disregards such transponder response signals.
  - 125. An identification system according to any one of claims 115 to 119, further comprising:
    - processor means for recording data received from each identified transponder, and for relating the received data to stored data corresponding to the received data.
  - 126. An identification system according to claim 125, wherein:
    - the processor means stores at least one of price data and identification data of articles to which different transponders are attached, and to relate the identification codes of identified transponders thereto.
  - 127. An identification system according to any one of claims 115 to 119, wherein:
    - the interrogation signal and the inhibiting signal have respective different frequencies selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 128. An identification system according to claim 127, further comprising:
    - display means for generating a display in which descriptions of the articles to which respective transponders are attached are associated with price data.
  - 129. An identification system according to claim 128, further comprising:
    - printer means for generating a printout of the display.

130. An interrogator for identifying a plurality of transponders, the interrogator comprising:
- transmitter means for transmitting an interrogation signal to the plurality of transponders, wherein, transponders which identified themselves from the interrogation signal are capable of being disabled by an instruction in the interrogation signal;
  
  receiver means for receiving response signals from the plurality of transponders; and
  
  means for identifying the plurality of transponders from the response signals;
  
  the interrogator transmitting the interrogation signal and an inhibiting signal, wherein a disabled transponder remains disabled while the disabled transponder continued receiving the inhibiting signal.
- View Dependent Claims (131, 132, 133, 134, 135, 136, 137, 138, 139, 140)
- - 131. An interrogator according to claim 130, wherein:
    - the interrogation signal and the inhibiting signal are relatively narrow bandwidth signals.
  - 132. An interrogator according to claim 131, wherein:
    - the interrogation signal is modulated with data, the data modulation bandwidth of the interrogation signal being less than a spacing between the respective different frequencies of the interrogation signal and the inhibiting signal.
  - 133. An interrogator according to claim 130, wherein:
    - the interrogation signal is a relatively directional signal; and
      
      the inhibiting signal is a relatively widely dispersed signal.
  - 134. An interrogator according to claim 133, wherein:
    - the inhibiting signal has a beam width which is at least 5 times greater than that of the interrogating signal.
  - 135. An interrogator according to any one of claims 130 to 134, wherein:
    - the interrogation signal is a relatively high power signal; and
      
      the inhibiting signal is a relatively low power signal.
  - 136. An interrogator according to any one of the claims 130 to 134, wherein:
    - a turn-off instruction is transmitted in both the interrogation signal and the inhibiting signal.
  - 137. An interrogator according to any one of claims 130 to 134, wherein:
    - the interrogation signal and the inhibiting signal have respective different frequencies.
  - 138. An interrogator according to any one of claims 130 to 134, wherein:
    - the interrogation signal and the inhibiting signal have respective different frequencies which are selected so that there are no overlapping nulls in the electric fields of the interrogation signals within a predetermined distance of the transmitter means of the interrogator.
  - 139. An interrogator according to any one of claims 130 to 134, wherein:
    - the interrogator detects transponder response signals transmitted on a frequency of the inhibiting beam and disregards such transponder response signals.
  - 140. An interrogator according to any one of claims 130 to 134, wherein:
    - the interrogator is a hand-held type interrogator.

Specification

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Litigation Data

Current Assignee
Zebra Technologies Corporation
Original Assignee
British Technology Group Ltd.
Inventors
Van Zyl, Clinton Aiden, Van Schalkwyk, Andries Christoffel, Oosthuizen, Marthinus Jacobus Rudolph, Marsh, Michael John Camille, Lenarcik, Andrzej
Primary Examiner(s)
Hofsass, Jeffery
Assistant Examiner(s)
Lee, Benjamin C.

Application Number

US08/580,913
Time in Patent Office

802 Days
Field of Search

340/572, 340/825.54, 340/508, 340/568, 235/435, 235/436, 235/383, 235/375, 235/325
US Class Current

340/10.2
CPC Class Codes

A47F 9/048   automatically

G01S 13/24   using frequency agility of ...

G01S 13/758   using a signal generator po...

G01S 13/87   Combinations of radar syste...

G06K 17/0022   arrangements or provisious ...

G06K 7/0008   General problems related to...

G06K 7/10059   transponder driven

G06K 7/10336   the antenna being of the ne...

G06K 7/10346   the antenna being of the fa...

G07C 9/28   the pass enabling tracking ...

G07G 1/0036   Checkout procedures

G07G 1/0054   with control of supplementa...

G07G 3/003   Anti-theft control theft al...

G07G 3/006   False operation

G08B 13/2422   using acoustic or microwave...

G08B 13/246   Check out systems combined ...

G08B 13/2471   Antenna signal processing b...

G08B 13/2474   Antenna or antenna activato...

G08B 13/2485   Simultaneous detection of m...

G08B 13/2488   Timing issues, e.g. synchro...

H01Q 1/2216 : used in interrogator/reader...

H01Q 21/065 : Patch antenna array

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Detection of multiple articles

First Claim

4 Assignments

Litigations

0 Petitions

Accused Products

Abstract

283 Citations

140 Claims

Specification

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Detection of multiple articles

First Claim

4 Assignments

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Subscription Required

Litigations

0 Petitions

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Accused Products

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Abstract

283 Citations

140 Claims

Specification

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Use Cases

Quick Links

Others