Method and apparatus for communicating with RFID devices coupled to a roll of flexible material

Abstract

A plurality of battery-operated transceivers encapsulated by lamination to form a sheet of independent transceivers is tested in a two piece fixture that forms an enclosure surrounding each in-sheet transceiver. Each enclosure has an antenna for transmitting a command signal to the transceiver at a known power level and for receiving a reply message from the transceiver containing a power level measurement made by the transceiver. Test methods using the fixture of the present invention are also described.Flexible radio frequency identification (RFID) devices are coupled to a roll of flexible material. Each RFID device coupled to the roll is advanced into a wireless communication region. An antenna in the region separately communicates with each of the RFID devices in a manner that isolates the communication from other REID devices counted to the roll outside the region.

1. A method of testing the RF communication operation of an RF transponder, comprising the steps of:
 providing a sheet characterized by first and second opposite faces and a thickness; 
 mounting on the sheet an RF transponder that includes a transponder RF antenna; 
 positioning a first RF shield so as to abut the first face of the sheet; 
 positioning a second RF shield so as to abut the second face of the sheet, the second RF shield being in the shape of a cup having a mouth abutting said second face, wherein the first and second RF shields are positioned so that the first and second RF shields together form a closed cavity which completely surrounds and encloses the transponder RF antenna except where the thickness of the sheet separates the first RF shield from the mouth of the second RF shield, wherein said thickness is sufficiently small so that the first and second RF shields prevent any RF signals within the cavity from radiating outside the cavity; 
 positioning a test fixture RF antenna within the cavity; 
 transmitting an RF signal from the test fixture antenna; 
 detecting a response by the transponder to the RF signal; and 
 subsequently removing the transponder from proximity to the first and second shields and the test fixture RF antenna, so that no shielding obstructs the transponder RF antenna from sending and receiving RF radiation at any angle. 
 
     
     
       2. A method according to  claim 1 , wherein the cavity encloses the entire RF transponder. 
     
     
       3. A method according to  claim 1 , wherein the sheet has no shielding mounted thereon that obstructs RF radiation from the transponder RF antenna. 
     
     
       4. A method according to  claim 1 , wherein:
 the first RF shield is in the shape of a cup having a mouth abutting the first face; and 
 the step of positioning the second RF shield further comprises aligning the mouth of the second shield with the mouth of the first shield. 
 
     
     
       5. A method according to  claim 1 , wherein the step of positioning the test fixture RF antenna within the cavity comprises:
 mounting the test fixture RF antenna to a surface of one of the two RF shields; 
 connecting an RF transmission line to the test fixture RF antenna; and 
 passing the transmission line through an opening in said one RF shield to extend outside the cavity. 
 
     
     
       6. A method according to  claim 1 , further comprising the step of:
 fabricating the sheet to include electrically conductive material adjacent the mouth of the second RF shield so as to improve RF shielding of the cavity. 
 
     
     
       7. A method according to  claim 1 , wherein the RF signal is transmitted at a predetermined wavelength, and wherein the RF shields are dimensioned to improve the gain of the cavity at that wavelength. 
     
     
       8. A method according to  claim 1 , wherein the RF signal is transmitted at a predetermined wavelength, and wherein the RF shields are dimensioned so that the cavity resonates at that wavelength. 
     
     
       9. A method of testing the RF communication operation of a plurality of RF transponders, comprising the steps of:
 providing a sheet characterized by first and second opposite faces and a thickness; 
 mounting on the sheet a plurality of RF transponders, wherein each transponder includes a transponder RF antenna; 
 positioning a first test fixture section having a first RF shield so that the first RF shield abuts the first face of the sheet; 
 positioning a second test fixture section so as to abut the second face of the sheet, wherein: 
 the second test fixture section includes a plurality of RF shields,
 each RF shield in the second test fixture section is in the shape of a cup having a mouth abutting said second face of the sheet, 
 the first and second test fixture sections so that each RF shield in the second test fixture section encircles a corresponding one of the transponder RF antennas so as to form, in combination with the first RF shield, a closed cavity that completely surrounds and encloses said corresponding transponder RF antenna except where the thickness of the sheet separates the first RF shield from the mouth of said RF shield in the second test fixture section, and 
 said thickness is sufficiently small so that the first and second RF shields prevent any RF signals within the cavity from radiating outside the cavity; 
 
 positioning within each cavity a corresponding test fixture RF antenna; 
 transmitting an RF signal from each test fixture antenna; 
 detecting a response by each at least one transponder to the RF signal transmitted by its corresponding test fixture antenna; and 
 subsequently removing each transponder from proximity to the first and second test fixture sections and the test fixture RF antennas, so that no shielding obstructs each transponder RF antenna from sending and receiving RF radiation at any angle. 
 
     
     
       10. A method according to  claim 9 , wherein the each cavity encloses the entire corresponding RF transponder. 
     
     
       11. A method according to  claim 9 , wherein:
 the first RF shield is in the shape of a plurality of cups so that each cup has a mouth abutting the first face of the sheet; and 
 the step of positioning the second RF shield further comprises aligning each mouth of the second shield with a corresponding mouth of the first shield. 
 
     
     
       12. A test fixture for testing the RF communication operation of an RF transponder which is mounted on a sheet which extends beyond the perimeter of the transponder, the RF transponder having an antenna for receiving RF signals, comprising:
 first and second RF shields, the second RF shield being in the shape of a cup having a mouth; 
 an alignment mechanism for positioning the first and second RF shields to abut opposite sides of the sheet so that the mouth encircles the transponder antenna and so that the combination of the first and second RF shields forms a closed cavity completely surrounding and enclosing the transponder antenna except where the sheet separates the two RF shields, wherein the distance by which the sheet separates the two RF shields is small enough to prevent any RF signals within the cavity from radiating outside the cavity; and 
 a test fixture RF antenna mounted within the cavity. 
 
     
     
       13. A test fixture according to  claim 12 , further comprising:
 a test fixture RF transmitter having an output connected to the test fixture RF antenna so that the RF antenna radiates RF signals to the transponder RF antenna; and 
 a test fixture RF receiver having an input connected to the test fixture RF antenna so that the RF receiver receives any responses transmitted by the RF transponder in response to said RF signals. 
 
     
     
       14. A test fixture according to  claim 12 , wherein the cavity encloses the entire transponder. 
     
     
       15. A test fixture according to  claim 12 , wherein:
 the first RF shield is in the shape of a cup having a mouth abutting the first face; and 
 the alignment mechanism aligns the mouth of the second shield with the mouth of the first shield. 
 
     
     
       16. A method according to  claim 12 , further comprising:
 an RF transmission line connected to the test fixture RF antenna; 
 wherein the transmission line extends through an opening in one of the RF shields so as to extend outside the cavity. 
 
     
     
       17. A test fixture according to  claim 12 , further comprising a test fixture RF transmitter for providing to the transponder antenna RF test signals having a predetermined wavelength, wherein the first and second RF shields are dimensioned to improve the gain of the cavity at that wavelength. 
     
     
       18. A test fixture according to  claim 12 , further comprising a test fixture RF transmitter for providing to the transponder antenna RF test signals having a predetermined wavelength, wherein the first and second RF shields are dimensioned so that the cavity resonates at that wavelength. 
     
     
       19. A test fixture for testing the RF communication operation of a plurality of RF transponders mounted on a sheet, each RF transponder having an RF antenna, comprising:
 a first test fixture section including a first RF shield; 
 a second test fixture section including a plurality of RF shields each of which is in the shape of a cup having a mouth; 
 an alignment mechanism for positioning the first and second test fixture sections to abut opposite sides of the sheet so that each RF shield in the second test fixture section encircles a corresponding one of the transponder antennas so as to form, in combination with the first RF shield, a closed cavity that completely surrounds and encloses said corresponding transponder RF antenna except where the sheet separates the first RF shield from the mouth of said RF shield in the second test fixture section, wherein the distance by which the sheet separates the first RF shield from each RF shield of the second test fixture section is small enough to prevent any RF signals within each cavity from radiating outside that cavity; and 
 a test fixture RF antenna mounted within each cavity. 
 
     
     
       20. A test fixture according to  claim 19 , wherein:
 the first RF shield is in the shape of a plurality of cups so that each cup has a mouth abutting the sheet; and 
 the alignment mechanism aligns each mouth of the second shield with a corresponding mouth of the first shield. 
 
     
     
       21. A method comprising the steps of:
 providing, to a material handling apparatus, a plurality of flexible radio frequency identification (RFID) devices coupled to a continuous roll of flexible material;   advancing to a first region a first RFID device while coupled to the roll of flexible material, the first RFID device comprising a dipole antenna coupled to an integrated circuit;   transmitting a first wireless interrogation signal to the first RFID device within the first region; and   receiving a first wireless reply signal from the first RFID device within the first region, wherein RF energy associated with wireless communication with the first RFID device is sufficiently isolated to the first region to prevent communication interference with a separate RFID device coupled to the roll of flexible material.   
     
     
       22. The method of claim 21, further comprising the steps of:
 advancing a second RFID device coupled to the roll of flexible material to a second region, wherein the second wireless interrogation signal is prevented from interfering with the first wireless interrogation signal; and   receiving a second wireless reply signal from the second RFID device within the second region, wherein RF energy associated with wireless communication with the second RFID device is sufficiently isolated to the second region to prevent communication interference with a separate RFID device coupled to the roll of flexible material, and wherein the second RFID device is in the second region while the first RFID device is simultaneously in the first region.   
     
     
       23. The method of claim 22, wherein the plurality of flexible RFID devices are coupled to the roll of flexible material in an array pattern comprising a plurality of rows and a plurality of columns. 
     
     
       24. The method of claim 21, further comprising the steps of:
 separating the first RFID device from the roll of flexible material; and   adhering the first RFID device to an article for tracking.   
     
     
       25. The method of claim 24, wherein the step of attaching the first RFID device to an article comprises attaching the RFID device to baggage for use as a baggage tag in a baggage handling system. 
     
     
       26. The method of claim 24, wherein the step of attaching the first RFID device to an article comprises adhering the RFID device to the article for use as a tracking label. 
     
     
       27. The method of claim 21, wherein the first RFID device further comprises a flexible polymer substrate upon which the dipole antenna and the integrated circuit are disposed. 
     
     
       28. The method of claim 21, wherein the step of advancing the first RFID device comprises aligning the first RFID device to a first location using guide marks formed on the flexible material. 
     
     
       29. The method of claim 28, wherein using guide marks includes optically aligning the guide marks to the location. 
     
     
       30. The method of claim 21, wherein the first wireless reply signal includes an indication of signal strength of the first wireless interrogation signal as determined by the first RFID device. 
     
     
       31. The method of claim 21, wherein the antenna comprises a printed conductive material. 
     
     
       32. The method of claim 27, wherein the flexible material is a polymer film comprising the polymer substrate of the RFID device. 
     
     
       33. A system comprising:
 a material handling apparatus:   a plurality of flexible RFID devices removably attached to a continuous roll of flexible material mounted on the material handling apparatus, each of the plurality of flexible RFID devices comprising a respective dipole antenna coupled to a respective integrated circuit and disposed on a respective flexible polymer substrate;   a first RFID device disposed in a first region, the first RFID device being removably attached to the continuous roll of flexible material, the first region configured to prevent a first adjacent RFID device of the plurality of flexible RFID devices from interfering with RF communication with the first RFID device in the first region; and   a first interrogation antenna disposed within the first region.   
     
     
       34. The system of claim 33, further comprising:
 a second region having disposed therein the first adjacent RFID device, the second region configured to prevent a second adjacent RFID device of the plurality of flexible RFID devices from interfering with RF communication with the second RFID device in the second region; and   a second interrogation antenna disposed within the second region.   
     
     
       35. The system of claim 34, wherein the plurality of flexible RFID devices removably attached to the continuous roll of flexible material is configured in an array pattern comprising a plurality of rows and a plurality of columns. 
     
     
       36. The system of claim 33, wherein each of the plurality of flexible RFID devices further comprises a respective battery coupled to the respective integrated circuit. 
     
     
       37. The system of claim 33, wherein the material handling apparatus includes a motor to align the first RFID device within the first region. 
     
     
       38. The system of claim 37, wherein the continuous roll of flexible material includes guide marks for use in aligning the first RFID device. 
     
     
       39. The system of claim 33, wherein the flexible material is a polymer film and each respective flexible polymer substrate of the plurality of respective RFID devices comprises a respective portion of the flexible material. 
     
     
       40. A system comprising:
 a material handling apparatus configured to receive a continuous roll of flexible material including a plurality of flexible RFID devices;   a motor to advance individual ones of the plurality of RFID devices separately into a first region; and   a first interrogation antenna disposed within the first region to communicate with the individual ones of the plurality of RFID devices while coupled to the roll, wherein RF signals are isolated to the first region to prevent confusion with other RFID devices coupled to the continuous roll.   
     
     
       41. The system of claim 40, further comprising a second interrogation antenna disposed within a second region, wherein RF signals are isolated to the second region to prevent confusion with other RFID devices coupled to the continuous roll. 
     
     
       42. The system of claim 41, wherein the motor and the material handling apparatus are configured to advance a first RFID device of the plurality of flexible RFID devices into the first region and to simultaneously advance a second RFID device of the plurality of flexible RFID devices into the second region. 
     
     
       43. The system of claim 42, wherein the plurality of flexible RFID devices is configured in an array pattern comprising a plurality of rows and a plurality of columns. 
     
     
       44. The system of claim 43, further comprising an array of enclosures, the array comprising a plurality of rows of enclosures and a plurality of columns of enclosures, each enclosure of the array having a respective antenna disposed therein and configured to isolate RF energy within each respective enclosure to prevent RF interference between enclosures. 
     
     
       45. The system of claim 40, further comprising an alignment mechanism to align the RFID devices within the first region. 
     
     
       46. The system of claim 45, wherein the alignment mechanism includes an optical receiver. 
     
     
       47. A method comprising:
 providing a system containing a plurality of flexible radio frequency identification (RFID) labels coupled to a continuous sheet of flexible material, each of the plurality of flexible RFID labels comprising a respective antenna coupled to a respective integrated circuit disposed on a respective, flexible polymer film;   advancing a first RFID label of the plurality of RFID labels to a wireless communication region of the system;   transmitting a first wireless signal to the first RFID label while the first RFID label is in the wireless communication region of the system and is coupled to the sheet, the first wireless signal being effectively isolated to the wireless communication region of the system to prevent interference by a separate RFID label external to the wireless communication region and coupled to the continuous sheet; and   attaching the first RFID label to an article for tracking in accordance with an article tracking process.   
     
     
       48. The method of claim 47, wherein the continuous sheet of flexible material is in the form of a roll. 
     
     
       49. The method of claim 47, further comprising wirelessly testing the first RFID label while the first RFID label is in the wireless communication region of the system. 
     
     
       50. The method of claim 49, further comprising receiving a first wireless reply signal from the first RFID label and evaluating the first reply signal to determine that the first RFID label passes a test. 
     
     
       51. The method of claim 49, wherein testing comprises near-field testing. 
     
     
       52. The method of claim 49, further comprising wirelessly testing at least one other RFID label of the plurality of RFID labels while the first RFID label is being tested. 
     
     
       53. The method of claim 47, further comprising:
 advancing the first RFID label out of the wireless communication region of the system while advancing a second RFID label of the plurality of RFID labels into the wireless communication region of the system; and   transmitting a second wireless signal to the second RFID label while the second RFID label is in the wireless communication region of the system.   
     
     
       54. The method of claim 53, wherein the continuous sheet of flexible material is in the form of a roll. 
     
     
       55. The method of claim 53, further comprising wirelessly testing a third RFID label of the plurality of RFID labels while the second RFID label is in the wireless communication region of the system. 
     
     
       56. The method of claim 47, wherein advancing the first RFID label comprises aligning the first RFID label to a first location using guide marks. 
     
     
       57. The method of claim 47, wherein the respective polymer film of each of the plurality of flexible RFID labels comprises a respective portion of the flexible material. 
     
     
       58. A method comprising:
 providing an apparatus with a continuous sheet of flexible material including a plurality of flexible RFID devices;   advancing an RFID device of the plurality of RFID devices into a wireless communication region of the apparatus while the RFID device is coupled to the continuous sheet of flexible material;   wirelessly communicating, via an interrogation antenna, with the RFID device in the wireless communication region in a manner that prevents communication between the antenna and an adjacent RFID device external to the region and coupled to the continuous sheet of flexible material; and   attaching the RFID device to a respective article for tracking in accordance with an article tracking process.   
     
     
       59. The method of claim 58, wherein the continuous sheet of flexible material includes flexible RFID devices in an array pattern comprising a plurality of rows and a plurality of columns. 
     
     
       60. The method of claim 58, wherein the continuous sheet of flexible material is in the form of a roll. 
     
     
       61. The method of claim 58, wherein advancing the RFID device comprises aligning the RFID device to a first location using guide marks. 
     
     
       62. The method of claim 58, wherein communicating includes near-field communication. 
     
     
       63. The method of claim 58, wherein communicating includes near-field testing of the RFID device. 
     
     
       64. The method of claim 58, wherein the RFID device comprises a first flexible layer attached directly to a second flexible layer. 
     
     
       65. The method of claim 64, wherein the first flexible layer comprises a portion of the flexible material. 
     
     
       66. The method of claim 64, wherein the RFID device comprises a dipole antenna. 
     
     
       67. The method of claim 64, wherein a thickness along a contour of the RFID device is less than a thickness through an integrated circuit region of the RFID device. 
     
     
       68. The method of claim 58, wherein the RFID device includes a battery. 
     
     
       69. A system comprising:
 a first reel;   a second reel;   an interrogator antenna configured to transmit RF signals having a wavelength;   two plates separated by a distance of less than the wavelength;   a roll of flexible material extending from the first reel, between the two plates, to the second reel, wherein the roll comprises a plurality of RFID devices; and   a motor to align a first RFID device of the plurality of RFID devices between the two plates, wherein the RF signals from the antenna are isolated from an adjacent RFID device of the plurality of RFID devices.   
     
     
       70. The system of claim 69, further comprising a computer and a first interrogator coupled to the antenna and configured to generate the RF signals and to analyze a reply signal from the first RFID device to determine if the first RFID device fails a test. 
     
     
       71. The system of claim 69, wherein the first RFID device comprises a dipole antenna. 
     
     
       72. The system of claim 71, wherein the roll comprises polymer film 86 which the dipole antenna is disposed. 
     
     
       73. The system of claim 69, wherein the first RFID device is attached directly to the adjacent RFID device.