Method and apparatus for tracking items using dual frequency tags

• US 6,542,114 B1
• Filed: 04/24/2001
• Issued: 04/01/2003
• Est. Priority Date: 09/07/2000
• Status: Expired due to Term

• Current Assignee: Savi Technology Incorporated
• Original Assignee: Savi Technology Incorporated
• Inventors: Anderson, III, Arthur E., Brand, Timothy K., Cargonja, Nikola, Rajapakse, Ravindra U., Eagleson, James G.
• Primary Examiner(s): Tarca, Thomas H.
• Assistant Examiner(s): Andrea, Brian K
• Application Number:
  US09/841,780
• Time in Patent Office: 707 Days
• Field of Search: 340/988, 340/989, 340/991, 340/992, 340/993, 342/42, 342/44, 342/51, 342/357.07
• US Class Current: 342/357.25
• 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

Abstract

An apparatus (10, 240, 300) includes a signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) which transmits relatively low frequency signpost signals that are fundamentally magnetic in character, a beacon tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711) which receives the signpost signals and transmits radio frequency signals containing a signpost code (42, 93) from a received signpost signal, and a reader (13, 261, 319, 521-530) which receives the radio frequency signals. One of the signpost and tag is stationarily supported, and the other is mounted on a moveable item. Based on the signals received by the reader, the location of the item can determined with a high degree of accuracy.

Claims

1. An apparatus comprising a tag having circuitry which includes:

a receiver section operable to receive wireless signpost signals that each include a signpost code; and

a transmitter section operable to transmit wireless beacon signals which each include a beacon code associated with said tag, said transmitter section being responsive to receipt by said receiver section of a respective said signpost signal for including in at least one said beacon signal the signpost code from the received signpost signal;

wherein said wireless signpost signals are near field signals of primarily magnetic character, said receiver section being configured to receive said signpost signals of magnetic character.

2. An apparatus according to claim 1, wherein said transmitter section is operable to transmit said beacon signals over a distance substantially greater than a transmission range of said signpost signals.

3. An apparatus according to claim 1, wherein at least part of said signpost signal is subject to one of encryption and password protection.

4. An apparatus according to claim 1, wherein said signpost and beacon signals are transmitted at respective first and second frequencies which are substantially different.

5. An apparatus according to claim 4, wherein said second frequency is substantially higher than said first frequency.

6. An apparatus according to claim 5, wherein said second frequency is selected so that said beacon signal acts as a far field signal, said signpost signal having a roll-off which is several times larger than a roll-off of said beacon signal.

7. An apparatus according to claim 5, wherein said first frequency is approximately 132 KHz.

8. An apparatus according to claim 5, wherein said second frequency is one of approximately 433.92 MHz and approximately 915 MHz.

9. An apparatus according to claim 1, wherein said transmitter section is operable to transmit said beacon signals using a slotted aloha protocol.

10. An apparatus according to claim 1, wherein said signpost signals include an error control portion which is used by said receiver section of said tag to check for errors in each said signpost signal received by said receiver section.

11. An apparatus according to claim 1, wherein said transmitter section is operable to form said beacon signals by effecting modulation of a carrier signal using a Manchester encoded frequency shift keying (FSK) protocol.

12. An apparatus according to claim 1, wherein said signpost signals include amplitude modulation of a carrier signal with an amplitude shift keying (ASK) protocol.

13. An apparatus according to claim 1, wherein said tag further includes a housing having therein said receiver and transmitter sections, and a coupling section capable of physically coupling said housing to a mobile device.

14. An apparatus according to claim 1, wherein said tag includes a battery which powers said circuitry therein.

15. A method, comprising the steps of:

receiving in a receiver section of a tag wireless signpost signals that each include a signpost code, said wireless signpost signals being near field signals of primarily magnetic character; and

transmitting from a transmitter section of said tag wireless beacon signals which each include a beacon code associated with said tag, said transmitting step including the step of causing said transmitter section to be responsive to receipt by said receiver section of a respective said signpost signal for including in at least one said beacon signal the signpost code from the received signpost signal.

16. A method according to claim 15, wherein said transmitting step includes the step of transmitting said beacon signals over a distance substantially greater than a transmission range of said signpost signals.

17. A method according to claim 15, including the step of selecting first and second frequencies which are substantially different for said signpost and beacon signals, respectively.

18. A method according to claim 17, wherein said selecting step includes the step of selecting said second frequency to be substantially higher than said first frequency.

19. A method according to claim 18, wherein said selecting step includes the step of selecting said second frequency so that said beacon signal acts as a far field signal, said signpost signal having a roll-off which is several times larger than a roll-off of said beacon signal.

20. A method according to claim 18, wherein said selecting step includes the step of selecting said first frequency to be approximately 132 KHz.

21. A method according to claim 18, wherein said selecting step includes the step of selecting said second frequency to be one of approximately 433.92 MHz and approximately 915 MHz.

22. A method according to claim 15, including the step of providing an error control portion in each said signpost signal, and wherein said receiving step includes the step of causing said receiver section to use said error control portion of each said signpost signal received by said receiver section to check for errors in that signpost signal.

23. An apparatus comprising:

a tag having circuitry which includes a receiver section and a transmitter section, said receiver section being operable to receive wireless signpost signals that each include a signpost code, and said transmitter section being operable to transmit wireless beacon signals which each include a beacon code associated with said tag, said transmitter section being responsive to receipt by said receiver section of a respective said signpost signal for including in at least one said beacon signal the signpost code from the received signpost signal;

a signpost which is physically separate from said tag and which transmits said signpost signals to said tag; and

a reader which is physically separate from said signpost and said tag, and which receives said beacon signals;

wherein said signpost is configured to transmit said wireless signpost signals as near field signals of primarily magnetic character, and said receiver section is configured to receive said signpost signals of magnetic character.

24. An apparatus according to claim 23, wherein said transmitter section is operable to transmit said beacon signals over a distance substantially greater than a transmission range of said signpost signals.

25. An apparatus according to claim 23,

including a mobile device having one of said tag and said signpost thereon; and

wherein the other of said tag and said signpost is stationarily supported near a path of travel of said mobile device, said tag being respectively within and outside a transmission range of said signpost signals from said signpost when said mobile device is at respective different locations along said path of travel.

26. An apparatus according to claim 25, wherein said tag is on said mobile device and said signpost is stationarily supported.

27. An apparatus according to claim 25, wherein said signpost is on said mobile device and said tag is stationarily supported.

28. An apparatus according to claim 25, including a control section which is coupled to said reader, and which is responsive to information in said beacon signals received from said tag through said reader for determining a location of said mobile device.

29. An apparatus according to claim 28,

wherein said mobile device is configured to be operated by a human operator;

and

including a portable device which can receive a wireless signal containing operator instructions from said control section, and which has a section that can provide an operator perceptible presentation of said operator instructions.

30. An apparatus according to claim 29, wherein said portable device is operable to receive input information identifying an operator and identifying said mobile device, and to forward said input information to said control section, including transmission by said portable device of a wireless signal containing said input information.

31. An apparatus according to claim 23, including a mobile device, and an item removably supported on said mobile device, said item having said tag disposed thereon, and said signpost being stationarily supported near a path of travel of said mobile device so that said tag passes through a transmission range of said signpost signals from said signpost as said mobile device travels past said signpost with said item thereon.

32. An apparatus according to claim 31, including a further item removably supported on said mobile device, and a further tag supported on said further item at a location so that said further tag is within a transmission range of said signpost signals from said signpost, said further tag having circuitry that includes a receiver section and a transmitter section, said receiver section of said further tag being operable to receive wireless signpost signals that each include a signpost code, and said transmitter section of said further tag being operable to transmit wireless beacon signals which each include a unique beacon code associated with said further tag, said transmitter section of said further tag being responsive to receipt by said receiver section thereof of a respective said signpost signal for including in at least one said beacon signal thereof the signpost code from the received signpost signal.

33. A method comprising the steps of:

transmitting signpost signals from a signpost, said signpost signals each including a signpost code and being a near field signal of primarily magnetic character;

receiving said signpost signals in a receiver section of circuitry of a tag which is physically separate from said signpost;

transmitting from a transmitter section of said circuitry of said tag wireless beacon signals which each include a beacon code associated with said tag, said transmitting step including the step of causing said transmitter section to be responsive to receipt by said receiver section of a respective said signpost signal for including in at least one said beacon signal the signpost code from the received signpost signal;

receiving said beacons signals in a reader which is physically separate from said signpost and said tag.

34. A method according to claim 33, wherein said transmitting step includes the step of transmitting said beacon signals over a distance substantially greater than a transmission range of said signpost signals.

35. A method according to claim 33, including the steps of:

supporting one of said tag and said signpost on a mobile device; and

stationarily supporting the other of said tag and said signpost near a path of travel of said mobile device in a manner so that said tag is respectively within and outside a transmission range of said signpost signals from said signpost when said mobile device is at respective different locations along said path of travel.

36. A method according to claim 35, wherein said supporting steps are carried out so that said tag is on said mobile device and said signpost is stationarily supported.

37. A method according to claim 35, wherein said supporting steps are carried out so that said signpost is on said mobile device and said tag is stationarily supported.

38. A method according to claim 35, including the step of causing a control section which is coupled to said reader to be responsive to information in said beacon signals received from said tag through said reader for determining a location of said mobile device.

39. A method according to claim 38, including the steps of:

effecting operation of said mobile device by a human operator;

receiving in a portable device a wireless signal containing operator instructions from said control section; and

providing on a section of said portable device an operator perceptible presentation of said operator instructions.

40. A method according to claim 39, including the steps of:

inputting into said portable device input information identifying an operator and identifying said mobile device; and

forwarding said input information to said control section, including the step of transmitting a wireless signal containing said input information.

41. A method according to claim 33, including the steps of:

removably supporting on a mobile device an item which has said tag disposed thereon; and

stationarily supporting said signpost near a path of travel of said mobile device in a manner so that said tag passes through a transmission range of said signpost signals from said signpost as said mobile device travels past said signpost with said item thereon.

42. A method according to claim 41, including the steps of:

removably supporting on said mobile device a further item having a further tag supported thereon at a location within a transmission range of said signpost signals from said signpost;

receiving said signpost signals in a receiver section of circuitry of said further tag;

transmitting from a transmitter section of said circuitry of said further tag wireless beacon signals which each include a beacon code associated with said further tag, said transmitter section of said further tag being responsive to receipt by said receiver section thereof of a respective said signpost signal for including in at least one said beacon signal of said further tag the signpost code from the received signpost signal; and

receiving said beacons signals from said further tag in said reader.