Detection of multiple articles

• US 5,519,381 A
• Filed: 11/18/1993
• Issued: 05/21/1996
• Est. Priority Date: 11/18/1992
• Status: Expired due to Term

• Current Assignee: ZIH Corp. (Zebra Technologies Corporation)
• Sponsoring Entity: British Technology Group Ltd.
• Inventors: Van Zyl, Clinton A., Marsh, Michael J. C., Oosthuizen, Marthinus J. R., Van Schalkwyk, Andries C., Lenarcik, Andrzej
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Wu, Daniel J.
• Time in USPTO: 915 Days
• Field of Search: 340/825.54, 340/825.35, 340/825.73, 340/568, 340/572, 340/571, 340/505, 340/539, 340/870.31, 340/870.01, 342/44
• US Class Current: 340/10.2
• CPC Class Codes: A47F 9/048 : automatically
• CPC Class Codes: G01S 13/24 : using frequency agility of carrier wave
• CPC Class Codes: G01S 13/758 : using a signal generator powered by the interrogation signal
• CPC Class Codes: G01S 13/87 : Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G06K 17/0022 : arrangements or provisious for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• 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 7/10059 : transponder driven
• CPC Class Codes: G06K 7/10336 : the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10346 : the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G07C 9/00111 : the pass performing a presence indicating function, e.g. identification tag or transponder identification by using radar means G01S13/02, G01S13/74; detecting presence by using magnetic or electric fields produced or modified by objects in general G01V3/08, G01V3/165; means for indicating the location of accidentally buried persons A63B29/02
• CPC Class Codes: G07G 1/0036 : Checkout procedures
• CPC Class Codes: G07G 1/0054 : with control of supplementary check-parameters, e.g. weight or number of articles
• CPC Class Codes: G07G 3/003 : Anti-theft control theft alarms G08B13/00
• CPC Class Codes: G07G 3/006 : False operation
• CPC Class Codes: G08B 13/2422 : using acoustic or microwave tags
• CPC Class Codes: G08B 13/246 : Check out systems combined with EAS, e.g. price information stored on EAS tag anti-theft systems in point of sale systems G07G3/003
• CPC Class Codes: G08B 13/2471 : Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2474 : Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: G08B 13/2485 : Simultaneous detection of multiple EAS tags
• CPC Class Codes: G08B 13/2488 : Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver
• CPC Class Codes: H01Q 1/2216 : used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/065 : Patch antenna array

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.

Claims

1. An identification system comprising an interrogator and a plurality of transponders, wherein:

the interrogator comprises transmitter means for transmitting at least two independent interrogation signals to the transponders simultaneously, each independent interrogation signal being adapted to independently activate any one or more transponders receiving said signal, receiver means for receiving response signals from the transponders in response to any one or more of the independent interrogation signals transmitted by said transmitter means, and processor means for identifying the transponders from data in the response signals; and

each transponder comprises receiving means, a code generator, and transmitting means connected to the code generator, so that on receipt of any one or more of the independent interrogation signals transmitted by said transmitter means the transponder transmits a response signal containing data which identifies the transponder.

2. An identification system according to claim 1 wherein the at least two interrogation signals have respective different frequencies which are selected to fall within the reception bandwidth of the receiving means of the transponders.

3. An identification system according to claim 2 wherein the at least two interrogation signals are relatively narrow bandwidth signals, the receiving means of each transponder having a relatively broad reception bandwidth within which the respective different frequencies of the at least two interrogation signals fall.

4. An identification system according to claim 3 wherein each interrogation signal is modulated with data, the 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 claim 2 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.

6. An identification system according to claim 1 wherein the transmitting means of the transponder comprises an antenna and means for modulating the signals received on the antenna, so that the response signal of the transponder comprises at least one interrogation signal carriers modulated with the data which identifies the transponder.

7. An identification system according to claim 1 wherein the transmitter means of the interrogator comprises at least two spaced apart transmitting antennas and the receiver means comprises at least two spaced apart receiving antennas.

8. An identification system according to claim 7 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.

9. An identification system according to claim 8 wherein each antenna element comprises a patch array designed to operate at a frequency between 800 MHz and 1 GHz.

10. An identification system according to claim 7 wherein at least two of the respective transmitting and receiving antennas are polarized differently from one another.

11. An identification system according to claim 7 wherein the transmitter means and the receiver means of the interrogator are mounted in proximity 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 claim 1 further comprising another processor means for recording data received from each identified transponder and for relating the received data to stored data corresponding to the received data.

14. An identification system according to claim 13 wherein said processor means stores price or identification data of articles to which different transponders are attached, and relates the identification codes of identified transponders thereto.

15. An identification system according to claim 14 including display means for generating a display in which descriptions of the articles to which respective transponders are attached are associated with price data.

16. An identification system according to claim 15 including printer means for generating a printout of the display.

17. An identification system comprising an interrogator and a plurality of transponders, wherein:

the interrogator comprises transmitter means for transmitting at least two independent interrogation signals to the transponders, receiver means for receiving response signals from the transponders responsive to at least one of the interrogation signals transmitted by said transmitter means, and processor means for identifying the transponders from data in the response signals;

each transponder comprises receiving means, a code generator, and transmitting means connected to the code generator, so that on receipt of at least one of the interrogation signals transmitted by said transmitter means the transponder transmits a response signal containing data which identifies the transponder; and

the transmitter means of the interrogator transmits the at least 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.

18. An identification system comprising an interrogator and a plurality of transponders, wherein:

the interrogator comprises transmitter means for transmitting at least two independent interrogation signals to the transponders, receiver means for receiving response signals from the transponders responsive to at least one of the interrogation signals transmitted by said transmitter means, and processor means for identifying the transponders from data in the response signals;

the transmitting means of the interrogator comprises a transmitting antenna, at least first and second transmitters for generating interrogation signals at respective different frequencies, and switch means for switching the outputs of the transmitters alternatively to the transmitting antenna;

the receiver means and the processor means of the interrogator distinguish response signals from transponders in response to interrogation signals transmitted at the respective different frequencies of the at least first and second transmitters;

each transponder comprises receiving means, a code generator, and transmitting means connected to the code generator, so that on receipt of at least one of the interrogation signals transmitted by said transmitter means the transponder transmits a response signal containing data which identifies the transponder; and

the processor means detects duplicate transponder response signals transmitted on two or more of the respective different frequencies and disregards them.

19. An identification system comprising an interrogator and a plurality of transponders, wherein:

the interrogator comprises transmitter means for transmitting an interrogation signal and an inhibiting signal having respective different frequencies to the transponders, receiver means for receiving response signals from the transponders responsive to the interrogation signal transmitted by said transmitter means, and processor means for identifying the transponders from data in the response signals; and

each transponder comprises receiving means for receiving the interrogation signal and the inhibiting signal transmitted by said transmitter means, a code generator, and transmitting means connected to the code generator,

the respective different frequencies of the interrogation signal and the inhibiting signal being selected to fall within the reception bandwidth of the receiving means of the transponder,

the transponder being adapted to transmit a response signal containing data which identifies the transponder on receipt of the interrogation signal, to be disabled by a turn-off instruction in the interrogation signal on successful identification of the transponder, and to remain disabled while it continues to receive the inhibiting signal.

20. An identification system according to claim 19 wherein the interrogation signal is a relatively directional signal, and the inhibiting signal is a relatively widely dispersed signal.

21. An identification system according to claim 20 wherein the inhibiting signal has a beam width which is at least 5 times greater than that of the interrogating signal.

22. An identification system according to claim 19 wherein the interrogation signal is a relatively high power signal and the inhibiting signal is a relatively low power signal.

23. An identification system according to claim 19 wherein the turn-off instruction to the transponder is transmitted in both the interrogation signal and the inhibiting signal.

24. An interrogator for identifying at least one transponder of a plurality of transponders, the interrogator comprising:

transmitter means for simultaneously transmitting at least two independent interrogation signals to the transponders, each independent interrogation signal being adapted to independently activate any one or more transponders receiving said signal;

receiver means for receiving at least one response signal from any of the transponders in response to any one or more of the independent interrogation signals transmitted by said transmitter means, each response signal including data identifying a respective transponder; and

processor means for identifying the respective transponder from data contained in the at least one response signal.

25. An interrogator according to claim 24, wherein the at least two interrogation signals have respective different frequencies which fall within the reception bandwidth of the transponders.

26. An interrogator according to claim 25, wherein the at least two interrogation signals are relatively narrow bandwidth signals, each transponder having a relatively broad reception bandwidth within which the respective different frequencies of the at least two interrogation signals fall.

27. An interrogator according to claim 26, wherein each interrogation signal is modulated with data, the data modulation bandwidth of each interrogation signal being less than a spacing between the respective different frequencies of the interrogation signals.

28. An interrogator according to claim 25, 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.

29. An interrogator according to claim 24, wherein:

the transmitter means comprises at least two spaced apart transmitting antennas, and the receiver means comprises at least two spaced apart receiving antennas.

30. An interrogator according to claim 29, 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.

31. An interrogator according to claim 30, wherein each antenna element comprises a patch array designed to operate at a frequency between 800 MHz and 1 GHz.

32. An interrogator according to claim 29, wherein at least two of the respective transmitting and receiving antennas are polarized differently from one another.

33. An interrogator according to claim 29, wherein the transmitter means and the receiver means are mounted in proximity to an interrogation zone through which the transponders to be identified may pass.

34. An interrogator according to claim 33, wherein the transmitter means and the receiver means are supported by a frame defining a passage through which a conveyance containing articles to which respective transponders are attached can pass.

35. An interrogator according to claim 24, further comprising another processor means for recording data received from each identified transponder and for relating the received data to stored data corresponding to the received data.

36. An interrogator according to claim 35, wherein said another processor means stores price or identification data of articles to which different transponders are attached, and relates the identification codes of identified transponders thereto.

37. An interrogator according to claim 36, including display means for generating a display in which descriptions of the articles to which respective transponders are attached are associated with price data.

38. An interrogator according to claim 37, including printer means for generating a printout of the display.

39. An interrogator for identifying at least one transponder of a plurality of transponders, the interrogator comprising:

transmitter means for transmitting at least two independent interrogation signals to the plurality of transponders;

receiver means for receiving at least one response signal from any of the transponders in response to any one or more of the independent interrogation signals transmitted by said transmitter means, each response signal including data identifying a respective transponder; and

processor means for identifying the respective transponder from data contained in the at least one response signal,

wherein the transmitter means transmits the at least 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.

40. An interrogator for identifying at least one transponder of a plurality of transponders, the interrogator comprising:

transmitter means for transmitting at least two independent interrogation signals to the plurality of transponders, wherein the transmitter means comprises a transmitting antenna, at least first and second transmitters for generating interrogation signals at respective different frequencies, and switch means for switching the outputs of the transmitters alternatively to the transmitting antenna;

receiver means for receiving at least one response signal from any of the transponders in response to any one or more of the independent interrogation signals transmitted by said transmitter means, each response signal including data identifying a respective transponder; and

processor means for identifying the respective transponder from data contained in the at least one response signal, wherein;

the receiver means and the processor means distinguish response signals from transponders in response to interrogation signals transmitted at the respective different frequencies of the at least first and second transmitters, and

the processor means detects duplicate transponder response signals transmitted on two or more of the respective different frequencies to disregard them.

41. An identification system comprising an interrogator and a plurality of transponders, wherein:

the interrogator comprises transmitter means for transmitting at least two independent interrogation signals to the transponders simultaneously at respective different interrogation frequencies, receiver means for receiving response signals from the transponders in response to any one or more of the interrogation signals transmitted by said transmitter means, and processor means for identifying the transponders from data in the response signals; and

each transponder comprises receiving means, a code generator, and transmitting means connected to the code generator, so that on receipt of any one or more of the independent interrogation signals transmitted by said transmitter means the transponder transmits a response signal containing data which identifies the transponder, said response signal being on one or more of the respective different interrogation frequencies depending on which one or more of the independent interrogation signals are received by the transponder.