초록 ▼

Embodiments of the present invention include radio frequency identification location systems and methods. In one embodiment, RF signals are transmitted from one or more RFID readers, and in accordance therewith, backscattered signals are received from a tag to be located. A plurality of measured pos

Embodiments of the present invention include radio frequency identification location systems and methods. In one embodiment, RF signals are transmitted from one or more RFID readers, and in accordance therewith, backscattered signals are received from a tag to be located. A plurality of measured position parameters are used to determine a location of the tag. In one embodiment, one reader may transmit and three readers may receive signals to determine the position of a tag. In other embodiments, multiple readers may transmit and receive. In another embodiment, one reader may transmit from different positions to locate a tag. Embodiments of the invention may be used to track a moving tag. A reader's position may be determined using GPS, reference tags, or the reader may be positioned in a known location. A map may be provided to a user to display the location or movement of a tag or a corresponding item.

대표청구항 ▼

1. A method of locating radio frequency identification (RFID) tags using first, second, and third RFID readers, the method comprising: transmitting a single radio frequency (RF) signal at a particular time from the first RFID reader to a tag to be located;receiving, at each of the first, second, and

1. A method of locating radio frequency identification (RFID) tags using first, second, and third RFID readers, the method comprising: transmitting a single radio frequency (RF) signal at a particular time from the first RFID reader to a tag to be located;receiving, at each of the first, second, and third RFID readers, a signal backscattered off the tag from the single RF signal transmitted by the first RFID reader;extracting at least one measured position parameter from said signal backscattered off the tag and received at the first, second, and third RFID readers; anddetermining a location of the tag using the measured position parameters extracted from the signal backscattered off the tag from the single RF signal transmitted at the particular time from the first RFID reader, wherein all measured position parameters used in determining the location of the tag are extracted from said signal backscattered off the tag from said single transmission at said particular time from the first RFID reader. 2. The method of claim 1, wherein the first, second, and third RFID readers that receive the signal backscattered off the tag are at different locations. 3. The method of claim 2, wherein the first, second, and third RFID readers are synchronized to a same clock reference for measuring time, wherein time of arrival information based on the clock reference is used to calculate a distance to the tag. 4. The method of claim 1 further comprising storing a plurality of locations for the tag determined at a plurality of different times. 5. The method of claim 1, wherein the first RFID reader transmits a plurality of RF signals over a period of time to locate a moving tag. 6. The method of claim 4 further comprising determining a rate of movement of a moving tag based on the plurality of stored locations for the moving tag determined at the plurality of different times. 7. The method of claim 6 further comprising displaying a rate of movement of the moving tag to a user. 8. The method of claim 4 further comprising determining a direction of movement of a moving tag. 9. The method of claim 8 further comprising displaying the direction of movement of the moving tag to a user. 10. The method of claim 1 further comprising transmitting the measured position parameters corresponding to the signal backscattered off the tag from the single RF signal transmitted at the particular time from the first RFID reader and received by the first, second, and third RFID readers to a server, and determining the location of the tag on the server. 11. The method of claim 10 further comprising transmitting a location of each of the first, second, and third RFID readers to the server. 12. The method of claim 2, wherein the measured position parameters are derived from the single RF signal transmitted at the particular time from the first RFID reader and the signal backscattered from the tag received by the first, second, and third RFID readers. 13. The method of claim 1, wherein determining a location of the tag using the measured position parameters comprises: determining the location of the tag based on a measured position parameter resulting from the single RF signal transmitted at the particular time from the first RFID reader and the signal backscattered off the tag and received by the first, second, and third RFID readers. 14. The method of claim 1 further comprising receiving measured position parameters from the second and third RFID readers at the first RFID reader, and determining the location of the tag on the first RFID reader. 15. The method of claim 14 further comprising receiving locations of the second and third RFID readers at the first RFID reader. 16. The method of claim 1 further comprising storing locations corresponding to the first, second, and third RFID readers in at least one of the first, second, and third RFID readers or in a server. 17. The method of claim 1 further comprising determining one or more locations corresponding to at least one of the first, second, and third RFID readers using a global positioning system. 18. The method of claim 1, wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 19. The method of claim 18, wherein two or more different measured position parameters are extracted from the signal backscattered from the tag and used to determine the location of the tag. 20. The method of claim 1 further comprising determining raw location parameters for the tag to be located. 21. The method of claim 20, wherein the raw location parameters represent the location of the tag as latitude and longitude, Cartesian coordinates, Polar coordinates, or as one or more vectors. 22. The method of claim 20 further comprising generating mapped position information from the raw location parameters. 23. The method of claim 1 further comprising associating a map image with the location of the tag and displaying the map image to a user. 24. The method of claim 1, wherein at least one of the first, second, and third RFID readers is embedded in a mobile device. 25. A method of locating radio frequency identification (RFID) tags, the method comprising: transmitting a radio frequency (RF) signal from an RFID reader at a first location;transmitting an RF signal from said RFID reader at a second location;transmitting an RF signal from said RFID reader at a third location, wherein the first, second, and third locations are different locations;receiving a signal backscattered off a tag from the RF signal transmitted from the RFID reader at each of the first, second, and third locations;extracting at least one measured position parameter from the signal backscattered off the tag and received by the RFID reader at each of the first, second, and third locations; andcalculating a location of the tag using the measured position parameters extracted from each signal backscattered off the tag. 26. The method of claim 25, wherein the RFID reader is a first RFID reader and the signal backscattered off the tag is a first signal backscattered off the tag, the method further comprising transmitting from at least a second and a third RFID reader from at least a fourth and a fifth location different from the first, second, and third locations, wherein receiving further comprises receiving at least a second and a third signal backscattered off the tag at the at least second and third RFID readers. 27. The method of claim 26, wherein the second and third RFID readers transmit RF signals from locations different from the first RFID reader and from each other. 28. The method of claim 25, wherein the RFID reader is a first RFID reader, the method further comprising transmitting from a second RFID reader, wherein the first RFID reader transmits an RF signal from a fourth location, wherein the second RFID reader transmits an RF signal from a fifth location and an RF signal from a sixth location. 29. The method of claim 25 further comprising transmitting from the RFID reader to a server the measured position parameters corresponding to the signals backscattered off the tag and received at each of the first, second, and third locations, and determining the location of the tag on the server. 30. The method of claim 29, wherein the RF signal transmitted from the RFID reader at each of the first, second, and third locations is transmitted at a single frequency. 31. The method of claim 25 further comprising receiving measured position parameters for the signals backscattered off the tag and received at each of the first, second, and third locations on the RFID reader, and determining the location of the tag on the RFID reader. 32. The method of claim 31 further comprising receiving each of the first, second, and third locations on the RFID reader. 33. The method of claim 25 further comprising storing one or more locations corresponding to the RFID reader. 34. The method of claim 25 further comprising determining one or more locations corresponding to the RFID reader using a global positioning system. 35. The method of claim 25, wherein the RF signal is transmitted and the signal backscattered from the tag is received by a same RFID reader. 36. The method of claim 25, wherein the RF signal is transmitted by an RFID reader different from an RFID reader that receives the signal backscattered from the tag. 37. The method of claim 25, wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 38. The method of claim 37, wherein two or more different measured position parameters are extracted from each signal backscattered from the tag and used to determine the location of the tag. 39. The method of claim 37, wherein the RFID reader transmits a plurality of RF signals from each of the first, second, and third locations and receives a plurality of corresponding signals backscattered off the tag at each location, and extracts measured position parameters from the signals backscattered off the tag at each location. 40. The method of claim 25 further comprising determining raw location parameters for the tag to be located. 41. The method of claim 40, wherein the raw location parameters represent the location of the tag as latitude and longitude, Cartesian coordinates, Polar coordinates, or as one or more vectors. 42. The method of claim 40 further comprising generating mapped position information from the raw location parameters. 43. The method of claim 25 further comprising associating a map image with the location of the tag and displaying the map image to a user. 44. The method of claim 25, wherein the RFID reader is embedded in a mobile device. 45. A method for locating radio frequency identification (RFID) tags using first, second, and third RFID readers, the method comprising: generating a location request;transmitting a single radio frequency (RF) signal at a particular time from the first RFID reader to a tag to be located;receiving, at each of the first, second, and third RFID readers, a signal backscattered off the tag from the single RF signal transmitted by the first RFID reader, wherein each of the first, second, and third RFID readers include a clock synchronized to a same clock reference for measuring time, wherein time of arrival information based on the clocks is used to calculate a distance to the tag;extracting at least one measured position parameter from the signal backscattered off the tag and received at the first, second, and third RFID readers; anddetermining a location of the tag using the measured position parameters extracted from the signal backscattered off the tag from the single RF signal transmitted at the particular time from the first RFID reader, wherein all measured position parameters used in determining the location of the tag are extracted from said signal backscattered off the tag from said single transmission at said particular time from the first RFID reader. 46. The method of claim 45, wherein the clock reference to which the clocks of the first, second, and third RFID readers are synchronized is located on a server. 47. The method of claim 45, wherein the first, second, and third RFID readers that receive the signal backscattered off the tag are at different locations. 48. The method of claim 45, wherein locations of the first, second, and third RFID readers are stored on the first RFID reader and transmitted to a server. 49. The method of claim 48, wherein locations of the first, second, and third RFID readers are stored on the server. 50. The method of claim 45, wherein each of the first, second, and third RFID readers transmits RF signals from one or more known locations. 51. The method of claim 45 wherein at least one of the first, second, and third RFID readers includes a global positioning system for determining the location of the at least one RFID reader. 52. The method of claim 45, wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 53. The method of claim 45 further comprising displaying a map to a user specifying the location of the tag. 54. A system for locating radio frequency identification (RFID) tags, the system comprising: a plurality of tags for backscattering radio frequency (RF) signals;a computer system including location software for determining a location of a tag;an RFID reader comprising an RFID transmitter, an RFID receiver, and a communication unit for communicating with a server, wherein the RFID reader transmits an RF signal at a first location, a second location, and a third location, wherein the first, second, and third locations are different locations, and the RFID reader receives a signal backscattered off the tag from the RF signal transmitted from the RFID reader at each of the first, second, and third locations, wherein the RFID reader transmits to the server at least one measured position parameter corresponding to the signal backscattered off the tag and received by the RFID reader at the first, second, and third locations, and wherein the measured position parameters are used by the location software on the server to calculate the location of the tag. 55. The system of claim 54 further comprising a plurality of RFID readers, wherein each of the plurality of RFID readers comprises an RFID transmitter, an RFID receiver, and a communication unit for communicating with a server, wherein the plurality of RFID readers transmits a plurality of RF signals at each of a plurality of different locations, and wherein the plurality of RFID readers receives a plurality of signals backscattered off the tag from the plurality of RF signals transmitted from the plurality of RFID readers at each of the plurality of different locations. 56. The system of claim 55, wherein the plurality of RFID readers transmits RF signals from locations different from the RFID reader. 57. The system of claim 54, wherein the RFID reader is a first RFID reader, the system further comprising a second RFID reader, wherein the second RFID reader transmits an RF signal from a fourth location and an RF signal from a fifth location. 58. The system of claim 54, wherein the RFID reader further comprises a global positioning system for determining a location of the RFID reader. 59. The system of claim 54, wherein the measured position parameters comprise at least one of a power of the signal backscattered off the tag, an angle of arrival of the signal backscattered off the tag, a time difference of arrival of the signal backscattered off the tag, and a phase of the signal backscattered off the tag. 60. The system of claim 54 further comprising a display, wherein a user enters an item to be located, and the system displays a map to the user showing the location of the item. 61. A device for locating radio frequency identification (RFID) tags, the device comprising: a radio frequency (RF) signal transmitter for transmitting RF signals to a tag;a backscattering receiver for receiving signals backscattered off the tag;a position parameter measurement unit for extracting measured position parameters from each signal backscattered off the tag and received by the backscattering receiver; anda communication unit for establishing a data communication link between the device and an external system, wherein measured position parameters obtained from signals backscattered off the tag and received by the backscattering receiver at first, second, and third locations of the device are used to determine a location of the tag, wherein the signals backscattered off the tag correspond to RF signals transmitted by the RF signal transmitter at the first, second, and third locations, wherein the first, second, and third locations are different locations. 62. The device of claim 61 further comprising a global positioning system for determining a location of the device. 63. The device of claim 61, wherein the external system comprises one or more additional devices for locating RFID tags. 64. The device of claim 63 further comprising location software, wherein measured position parameters from the one or more additional devices are received by the device, and the location software determines the location of the tag. 65. The device of claim 61, wherein the external system comprises a server, wherein measured position parameters are transmitted to the server, and wherein the server determines the location of the tag. 66. The device of claim 61 further comprising mapping software for displaying a map to a user showing the location of the tag. 67. The device of claim 61, wherein the device is a cellular phone. 68. The device of claim 61, wherein the device is a personal digital assistant. 69. The device of claim 61, wherein the device is a portable computer. 70. A method of determining a position using radio frequency identification tags, the method comprising: transmitting three or more RF signals from an RFID reader, and in accordance therewith, receiving three or more backscattered signals from three or more reference tags with known positions;extracting at least one measured position parameter from each of the three or more backscattered signals;accessing the positions of the three or more reference tags; anddetermining a location of the RFID reader using the plurality of measured position parameters. 71. The method of claim 70, wherein the position of at least one reference tag is stored on the at least one tag. 72. The method of claim 70 further comprising: storing one or more locations corresponding to one or more reference tags;receiving one or more tag IDs in one or more backscattered signals; andretrieving the stored location of one or more reference tags using the tag IDs. 73. The method of claim 70, wherein accessing the positions of the three or more reference tags comprises accessing a server on which the positions of the three or more references tags are stored. 74. The method of claim 70, wherein accessing the positions of the three or more reference tags comprises retrieving the positions of the three or more references tags stored in the RFID reader. 75. The method of claim 70, wherein accessing the positions of the reference tags comprises extracting the position of each particular reference tag from the backscattered signal received from the particular reference tag. 76. The method of claim 70, wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 77. The method of claim 70 further comprising transmitting from the RFID reader to a server the measured position parameters extracted from the backscattered signals received from the reference tags, wherein determining the location of the RFID reader comprises determining the location of the RFID reader by the server using the measured position parameters. 78. The method of claim 70, wherein determining the location of the RFID reader comprises: determining a relative location of the RFID reader relative to the known positions of the reference tags using the measured position parameters extracted from the reference tags; anddetermining the positions of the RFID tag using the positions of the RFID reader relative to the known positions of the reference tags and the known positions of the reference tags. 79. The method of claim 70 further comprising: transmitting three or more RF signals from the RFID reader to a tag at an unknown location, and in accordance therewith, receiving three or more backscattered signals from the tag at the unknown location;extracting at least one measured position parameter from each of the three or more backscattered signal received from the tag at the unknown location; anddetermining a location of the tag at the unknown location using the measured position parameters extracted from the backscattered signals received from the tag at the unknown location and said determined location of the RFID reader. 80. The method of claim 79 further comprising transmitting from the RFID reader to a server the measured position parameters extracted from the backscattered signals received from the reference tags and the measured position parameters extracted from the backscattered signals received from the tag at the unknown location, wherein determining the location of the tag at the unknown location comprises determining the location of the tag at the unknown location by the server using the measured position parameters extracted from the backscattered signals received from (i) the reference tags and (ii) the tag at the unknown location. 81. A method of determining location using first, second, third, and fourth radio frequency identification (RFID) readers, the method comprising: receiving an input from a user specifying an item to be located, the item being associated with a tag;determining an identification of the tag;transmitting a single radio frequency (RF) signal at a particular time from the first RFID reader to the tag;receiving at each of the second, third and fourth RFID readers a signal backscattered off the tag from the single RF signal transmitted by the first RFID reader;extracting at least one measured position parameter from the signal backscattered off the tag and received at the second, third, and fourth RFID readers; anddetermining a location of the tag using the measured position parameters extracted from the signal backscattered off the tag from the single RF signal transmitted at the particular time from the first RFID reader, wherein all measured position parameters used in determining the location of the tag are extracted from said signal backscattered off the tag from said single transmission at said particular time from the first RFID reader. 82. The method of claim 81 further comprising calculating raw location parameters that specify the location of the tag. 83. The method of claim 81 further comprising generating mapped position information and displaying the mapped position information to the user. 84. The method of claim 81 further comprising displaying the location of the item to the user on a map. 85. The method of claim 81 further comprising navigating the user to the item. 86. The method of claim 81, wherein the user input is received at a mobile device. 87. The method of claim 81, wherein the user input is received at a kiosk.