Abstract:
An inductive antenna device intervenes in communication between an RFID tag including an RFID chip and a tag antenna and an RFID access device for accessing the RFID tag. The inductive antenna device includes an access-device-side antenna that is electromagnetically coupled with the antenna of the RFID access device, and a tag-side antenna that is electromagnetically coupled with the tag antenna. The RFID chip and tag antenna in the RFID tag are in an electromagnetically shielded space. The inductive antenna device is attached to the RFID tag or the inductive antenna device is brought in a predetermined position to make communication possible between the RFID tag and RFID access device. An authorized access to the RFID tag is thereby permitted with easy operation with unlimited number of access times, and an illegal leak of the tag information is prevented with a low cost configuration.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to Application No. 2005-285160, filed on Sep. 29, 2005 in Japan. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an RFID (Radio Frequency IDentification) tag communications system including an RFID tag comprising an RFID chip and a tag antenna connected to the RFID chip. 
   2. Description of the Background Art 
   A system or a service using an RFID tag requires measures to protect itself against an illegal access of an unintended third person from reading or writing the tag information contained in the RFID tag or the like. Conventional RFID privacy protection technologies are described, for example, in Jun-ichi Kishigami, “All about Wireless IC Tags Directed to Ubiquitous Society—RFID Textbook” published by ASCII Corporation, Tokyo, Japan, pp. 165-184, 2005. This document describes three types of conventional RFID privacy protection technologies as briefly stated below. 
   One conventional RFID privacy protection technology is the Kill function. This technology disables an RFID tag to terminate its function once delivered to a consumer. 
   Another conventional RFID privacy protection technology is the internal re-encryption method. This technology makes an RFID tag equipped with the function of re-encrypting a public key cipher. An RFID tag is responsive to each delivery of a send request from an RFID reader to re-encrypt and send tag information such as tag identification (ID). 
   The remaining conventional RFID privacy protection technology is the Faraday cage. This technology prevents the illegal delivery of information such as tag identification from an RFID tag by covering the RFID tag with a material such as an aluminum foil that can shield radio waves. 
   The Kill function, however, suffers from problems in that the processing for disabling an RFID tag takes a long time, and the RFID tag, once disabled, cannot be used for services any more. 
   The internal re-encryption method needs to provide an RFID tag with means for encrypting tag information. The RFID tag then becomes more costly and the time per access becomes longer due to encryption or decryption. 
   For the Faraday cage, an RFID tag is required, every time to be accessed, to be taken out of and brought into its cover. This consumes time and cannot protect the RFID tag against an illegal access while it is out of the cover. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an RFID tag communications system with its security function improved. 
   It is a more particular object of the invention to provide an RFID tag communications system that may permit a normal access to an RFID tag with an easier operation without limiting access times. 
   It is another object of the invention to provide an RFID tag communications system which may prevent its tag information from illegally leaking with an inexpensive configuration. An RFID tag and an inductive antenna device for use in such a system are also provided. 
   In accordance with the present invention, an RFID (Radio Frequency IDentification) tag comprises: an RFID chip; a tag antenna connected to the RFID chip; an electromagnetic shield for forming a space including the RFID chip and the tag antenna into an electromagnetically shielded space; and a positional-relationship controller for providing a first positional relationship and a second positional relationship as a relative positional relationship between an inductive antenna device and the RFID tag, the inductive antenna device including an access-device-side antenna capable of being electromagnetically coupled with an antenna of an RFID access device, a tag-side antenna capable of being electromagnetically coupled with the tag antenna and a conductive line for electrically connecting the access-device-side antenna with the tag-side antenna, the first positional relationship making possible electromagnetic coupling between the tag antenna and the tag-side antenna staying in the electromagnetically shielded space with the access-device-side antenna positioning outside the electromagnetically shielded space, the second positional relationship making impossible electromagnetic coupling between the tag antenna and the tag-side antenna. 
   The present invention also provides an RFID tag communications system comprising: an RFID tag including an RFID chip and a tag antenna connected to the RFID chip; an RFID access device for activating wireless communication for accessing the RFID tag; and an inductive antenna device including an access-device-side antenna capable of being electromagnetically coupled with an antenna of the RFID access device, a tag-side antenna capable of being electromagnetically coupled with the tag antenna, and a conductive line for electrically connecting the access-device-side antenna and the tag-side antenna, the RFID tag comprising: an electromagnetic shield for forming a space including the RFID chip and the tag antenna into an electromagnetically shielded space; and a positional-relationship controller for providing a first positional relationship and a second positional relationship as a relative positional relationship between the inductive antenna device and the RFID tag, the first positional relationship making possible electromagnetic coupling between the tag antenna and the tag-side antenna staying in the electromagnetically shielded space with the access-device-side antenna positioning outside the electromagnetically shielded space, the second positional relationship making impossible electromagnetic coupling between the tag antenna and the tag-side antenna. 
   The present invention also provides an inductive antenna device intervening in communication between an RFID tag including an RFID chip and a tag antenna connected to the RFID chip and an RFID access device for activating wireless communication for accessing the RFID tag, comprising: an access-device-side antenna capable of being electromagnetically coupled with an antenna of the RFID access device; a tag-side antenna capable of being electromagnetically coupled with the tag antenna; and a conductive line for electrically connecting the access-device-side antenna and the tag-side antenna, a first positional relationship and a second positional relationship being provided as a relative positional relationship of the inductive antenna device to the RFID tag, the first positional relationship making possible electromagnetic coupling between the tag antenna and the tag-side antenna staying in an electromagnetically shielded space provided in the RFID tag with the access-device-side antenna positioning outside the electromagnetically shielded space, the second positional relationship making impossible electromagnetic coupling between the tag antenna and the tag-side antenna. 
   In accordance with the present invention, the RFID tag has an RFID chip and a tag antenna built in an electromagnetically shielded space, and the RFID chip in the electromagnetically shielded space may be accessed using an inductive antenna device that is detachable from, or movable relative to, the RFID tag, thereby permitting an authorized access to the RFID tag with an easy operation with unlimited number of access times, and preventing an illegal leak of the tag information with a low cost configuration. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  illustrates the schematic configuration of the RFID tag communications system in accordance with an illustrative embodiment of the present invention; 
       FIG. 2  is a front view of the insertion slot shape of the RFID tag of the illustrative embodiment shown in  FIG. 1 ; 
       FIG. 3  illustrates a communication path, when the label inductive antenna device is used, in the RFID tag communications system of the illustrative embodiment; 
       FIG. 4  illustrates the communication path, when the management inductive antenna device is used, in the RFID tag communications system of the illustrative embodiment; 
       FIG. 5  illustrates, similarly to  FIG. 1 , the schematic configuration of the RFID tag communications system in accordance with an alternative embodiment of the invention; and 
       FIGS. 6A and 6B  illustrate the schematic configuration of the RFID tag communications system in accordance with another alternative embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to the accompanying drawings, a description will be given below of an RFID (Radio Frequency IDentification) tag communications system in accordance with an illustrative embodiment of the present invention. The illustrative embodiment is directed to an RFID tag communications system applied to a sales management system of commercial products although the present invention is not limited thereto. 
   With reference to  FIG. 1 , which illustrates the schematic configuration of the RFID tag communications system of the illustrative embodiment, the RFID tag communications system  1  mainly includes an RFID tag  10 , an RFID reader and writer  20 , a label inductive antenna device  30 , and a management inductive antenna device  40 . 
   The RFID tag  10  may be used when attached to a commercial product. The RFID tag  10  is, for example, of a card-like shape which is generally rectangular in its plan view. The RFID tag  10  has its one end, preferably its shorter end portion, an insertion slot  11  formed which may accept a mating card portion  31  or  41  of a label inductive antenna device  30  or management inductive antenna device  40 , respectively, as will be described below. The mating card portions  31  and  41  are thinner than the RFID tag  10  in order to be received by the latter. 
   With reference to  FIG. 2 , for example, the insertion slot  11  has, like a keyhole for receiving a physical key, projections or depressions specific to the relevant RFID tag  10  in its cross section. Correspondingly, the mating card portions  31  and  41  of the label inductive antenna device  30  and management inductive antenna device  40 , respectively, have projections or depressions formed in the cross-sectional outer shape or contour for mating with the relevant RFID tag  10 . The mating card portion  41  of the management inductive antenna device  40  may has its cross-sectional outer shape formed so as to be received commonly by the insertion slot  11  of many RFID tags  10  like a master key. 
   Continuously following the above-described insertion slot  11 , a receptacle space  12  to be mated is formed into the body of the RFID tag  10 . The space  12  to be mated is adapted to receive the entire mating card portion  31  or  41  in its engageable condition. The RFID tag  10  includes therein an RFID chip  13  made of semiconductor and carrying an electronics device for storing tag information, and an antenna  14 , referred to as a tag antenna, interconnected to the RFID chip  13 , which are sealed with a sealant  15  such as resin. 
   The RFID tag  10  has its entire surface member  16  functioning as electromagnetically shielding the tag antenna  14  from communicating with outside. The electromagnetic shielding, which is depicted with shaded in the figures, may be achieved by, for example, metal plating, applying an electromagnetic shield seal or adhesive sheet, or fabricating at least one of the one or more layers, not limited to an exposed layer, which form the surface of the tag  10  with an electromagnetic shield material. 
   The tag antenna  14  is disposed in such a position in the RFID tag  10  that the tag antenna  14  establishes an electromagnetic coupling with a tag-side inductive antenna  35  or  45 , described below, in the mating card portion  31  or  41 , when inserted into the RFID tag  10 , of the label inductive antenna device  30  or management inductive antenna device  40 , respectively.  FIG. 1  shows the tag antenna  14  as being in parallel with the tag-side inductive antenna  35  or  45  in the lateral direction in the figure. The position of the tag antenna  14  is, however, not limited to what is illustrated. Any position is applicable that establishes an electromagnetic coupling between the both antennas. The tag antenna  14  may be positioned so that, for example, the tag antenna  14  and tag-side inductive antenna  35  or  45  are overlapped with each other in the direction normal to the plane of  FIG. 1 . 
   The RFID tag reader and writer  20  has its function capable of transmitting and receiving, via its own antenna  21 , an enquiry and a response electromagnetic wave or signal to and from the RFID tag  10  having its communication condition consistent with the reader and writer  20  to access the RFID tag  10 . In the illustrative embodiment, the RFID tag reader and writer  20  accesses the RFID tag  10 , more accurately the RFID chip  13 , via the label inductive antenna device  30  or management inductive antenna device  40 . The RFID tag reader and writer  20  sends, for example, the tag information read out from the RFID tag  10  to a higher-level device (for example, an information processing unit such as a personal computer) for commercial product management. 
   The label inductive antenna device  30  and management inductive antenna device  40  have the function of relaying the communication between the RFID tag  10  and RFID tag reader and writer  20 . Either of the label inductive antenna device  30  and management inductive antenna device  40  may alternatively operate at one time. 
   The label inductive antenna device  30  is used, for example, before a commercial product to which the RFID tag  10  is attached is sold for the first time. The label inductive antenna device  30  includes the mating card portion  31  and a label portion  32 . The mating card portion  31  may engage with the receptacle space  12  to be mated in the RFID tag  10 , as described above. The label portion  32  is disposed outside the RFID tag  10  even when the mating card portion  31  is engaged with or inserted into the space  12  to be mated in the RFID tag  10 . The label portion  32  maybe used as, for example, indicating various information, such as a trade name or price, on a commercial product or have an information seal attached thereto. 
   The label inductive antenna device  30  includes as components for the relay function, a reader and writer-side inductive antenna  33 , an electrically conductive line  34 , and the tag-side inductive antenna  35 , which are interconnected as illustrated. The reader and writer-side inductive antenna  33  and tag-side inductive antenna  35  are both loop antennas. The reader and writer-side inductive antenna  33  and tag-side inductive antenna  35  are connected via the conductive line  34  to each other to form a loop current path in its entirety. The reader and writer-side inductive antenna  33  is provided in the label portion  32  so as to allow the antenna  33  to establish an electromagnetic coupling with its outside. When, for example, the label portion  32  is fabricated to have two flexible sheets laminated with each other, the antenna  33  intervenes between the two flexible sheets. 
   The tag-side inductive antenna  35  resides inside the mating card portion  31  in such a way that the antenna  35  may establish an electromagnetic coupling with its outside. When, for example, the mating card portion  31  is fabricated with resin, the resin seals the tag-side inductive antenna  35  there inside. The conductive line  34  electrically connects the reader and writer-side inductive antenna  33  to the tag-side inductive antenna  35 , as described above. The conductive line  34  extends inside the label portion  32  and mating card portion  31 . 
   The management inductive antenna device  40  may be used, for example, after a commercial product to which the RFID tag  10  is attached is sold for the first time. The management inductive antenna device  40  is almost the same in structure as the label inductive antenna device  30  except that a non-mating card portion  42  replaces the label portion  32  of the label inductive antenna device  30 . The non-mating card portion  42  has a reader and writer-side inductive antenna  43  built therein. The non-mating card portion  42  is exposed outside even when the mating card portion  41  is engaged with the space  12  to be mated in the RFID tag  10 . The non-mating card portion  42  may be formed with, for example, the same resin as used in the mating card portion  41 . 
   The operation of the RFID tag communications system of the illustrative embodiment will be described below. The label inductive antenna device  30 , when engaged with the RFID tag  10 , is handled together before the RFID tag  10  is attached to a commercial product, or after the RFID tag  10  is attached to a commercial product before sold. 
   For example, once a manufacturer delivers the commercial product to a distributor, a person responsible attaches to the commercial product the RFID tag  10  having the label inductive antenna device  30  engaged. 
   The person responsible operates a higher-level device for commercial product management, not shown, to activate the RFID reader and writer  20 . The RFID reader and writer  20  then reads the tag identification (ID) contained on the RFID chip  13  in the RFID tag  10 , writes appropriate information on the RFID chip  13 , and stores various information associated with the tag identification in a database for commercial product management in the relevant higher-level device, not specifically shown. 
   As shown in  FIG. 3 , a communication path  71  will be exemplified when accessing to the RFID tag  10 . The RFID reader and writer  20  emits an enquiry electromagnetic wave, such as a magnetic flux wave, from its antenna  21 . 
   The enquiry electromagnetic wave cannot reach the tag antenna  14  residing in the electromagnetically shielded space nor the tag-side inductive antenna  35  that is made located in the electromagnetically shielded space by receiving the card portion  31  therein, but is captured by the reader and writer-side inductive antenna  33  outside the electromagnetically shielded space. The capture causes a current to be induced in the reader and writer-side inductive antenna  33 . The current then flows on the loop current path formed by the reader and writer-side inductive antenna  33 , conductive line  34 , and tag-side inductive antenna  35 . The current flowing through the tag-side inductive antenna  35  may cause a magnetic flux wave to emit which corresponds to the enquiry electromagnetic wave as described above. Because the tag-side inductive antenna  35  is also disposed inside the electromagnetically shielded space, the magnetic flux wave may reach the tag antenna  14 , thereby establishing an electromagnetic coupling between the tag-side inductive antenna  35  and tag antenna  14 . 
   When the enquiry electromagnetic wave instructs the reading of information from the RFID chip  13 , the RFID chip  13  reads out the information and outputs it. When the enquiry electromagnetic wave instructs the writing of information into the RFID chip  13 , the RFID chip  13  stores given information and produces a write response. The output from the RFID chip  13  changes the electromagnetic coupling state, or magnetic flux, between the tag-side inductive antenna  35  and tag antenna  14 . The change is returned back on a response wave over the path in the reverse direction of the enquiry electromagnetic wave described above to the RFID reader and writer  20 . 
   When changing, e.g. in position, a commercial product to which attached is the RFID tag  10  having the label inductive antenna device  30  engaged, an access from the RFID reader and writer  20  is used to update the database of the higher-level device or the like. 
   When a customer buys the commercial product and the sales procedure necessary for transaction is completed, the salesperson removes the label inductive antenna device  30  from the RFID tag  10  and passes to the customer the commercial product having the RFID tag  10  remaining alone. Alternatively, the salesperson passes to the customer the commercial product and the RFID tag  10  with the label inductive antenna device  30  removed therefrom. 
   The RFID reader and writer  20  cannot access the RFID tag  10  with the label inductive antenna device  30  removed therefrom because the electromagnetic shielding function prevents the enquiry electromagnetic wave from reaching the tag antenna  14 . If a specific label inductive antenna device  30 , which does not mate with the RFID tag  10 , is tried to be inserted into the RFID tag  10 , it would not be engaged with the RFID tag  10 . A person who has a specific label inductive antenna device  30  not mating with the RFID tag  10  could not make the RFID tag  10  effectively accessible. 
   Suppose now, for example, that the RFID tag  10  is attached to a commercial product such as a brand-name article that may be frequently bought and sold even after used, and that the commercial product attached to the RFID tag  10  is brought in a right store dealing with used articles. 
   In this case, the management inductive antenna device  40  is attached to the commercial product by engaging the card portion  41  with the RFID tag  10 , and then the RFID reader and writer  20 , which may differ from one used by the distributor, accesses the RFID tag  10 . Also in this case, the RFID reader and writer  20  may access the RFID chip  13  on a communication path almost the same as the communication path  71  shown in  FIG. 4  as in the label inductive antenna device  30  described above. For example, the RFID chip  13  including commercial product information or the like may determine whether or not the used product is the normal brand-name product. 
   As described above, according to the illustrative embodiment, the RFID reader and writer  20  that is not attached to the label inductive antenna device  30  or management inductive antenna device  40  may not access the RFID tag  10  due to the electromagnetic shielding function. The RFID tag  10  thus has higher security in tag information. 
   Also according to the illustrative embodiment, limited, specific label inductive antenna devices  30  can mate with the RFID tag  10 . Specifically, label inductive antenna devices  30  not mating therewith may not be installed into the RFID tag  10 . The RFID reader and writer  20  may access the RFID tag  10  only when the label inductive antenna device  30  normal or appropriate therefor is attached to the RFID tag  10 . This also attains higher security in tag information of the RFID tag  10 . 
   Further according to the illustrative embodiment, the security function described above may eliminate a troublesome procedure such as the disabling of the RFID tag  10  when a product carrying the tag is sold in order to prevent the tag information from being monitored. 
   Still further according to the illustrative embodiment, the transmitting and receiving processings themselves of the RFID tag  10  and RFID reader and writer  20  may not specifically be tailored with its security taken into account. The security function thus does not prolong the access time. 
   Even after the label inductive antenna device  30  mating with the RFID tag  10  is gone after the commercial product sold or the like, the management inductive antenna device  40  is available so that the tag information may be retrieved from the RFID tag  10  as necessary. 
   The coupling between the RFID tag  10  and label inductive antenna device  30  or management inductive antenna device  40  is attained electromagnetically and not mechanically. That permits resin or the like to hermetically seal the electronics components included in the RFID tag  10  and in the label inductive antenna device  30  or management inductive antenna device  40 . Therefore, a water droplet, moisture or any other environmental factor does not deteriorate the electronics components. 
   With reference to further figures, a description will now be given of an RFID tag communications system in accordance with an alternative embodiment of the present invention.  FIG. 5  illustrates the schematic configuration of the RFID tag communications system of an alternative embodiment. In  FIG. 5 , like elements or components are designated with the identical reference numerals. 
   In  FIG. 5 , an RFID tag communications system  2  of the alternative embodiment mainly includes the RFID tag  10 , RFID reader and writer  20 , and a plurality (three in the example of  FIG. 5 ) of inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3 . 
   The RFID tag  10  of the alternative embodiment includes a different number of RFID chips and tag antennas from the RFID tag of the illustrative embodiment shown in and described with reference to  FIG. 1 . Specifically, the RFID tag  10  of the alternative embodiment includes a plurality of RFID chips  13 - 1 ,  13 - 2  and  13 - 3 , and a plurality of tag antennas  14 - 1 ,  14 - 2  and  14 - 3  respectively connected to the RFID chips  13 - 1 ,  13 - 2  and  13 - 3 , the plurality being three in the example shown in  FIG. 5 . 
   The plurality of tag antennas  14 - 1 ,  14 - 2  and  14 - 3  are disposed in different positions such that each of the tag antennas may establish the electromagnetic coupling with corresponding one of the tag-side inductive antennas  55 - 1 ,  55 - 2  and  55 - 3 , which are differently positioned as will be described below. It is to be noted that the RFID chips  13 - 1 ,  13 - 2  and  13 - 3  may-be in the vicinity of or spaced apart from the corresponding tag antennas  14 - 1 ,  14 - 2  and  14 - 3 . Although  FIG. 5  shows the plurality of tag antennas  14 - 1 ,  14 - 2  and  14 - 3  disposed in parallel in the vertical direction in the figure, the positions of the tag antennas are not limited to the specific arrangement. For example, different tag antennas may be provided on the upper, right and lower sides of the space  12  to be mated. The tag antennas  14 - 1 ,  14 - 2  and  14 - 3  may be electromagnetically shielded from each other. 
   In the alternative embodiment, it is intended that each of the RFID chips  13 - 1 ,  13 - 2  and  13 - 3  stores different tag information. 
   The RFID reader and writer  20  of the alternative embodiment may be the same as in the illustrative embodiment except that the RFID reader and writer  20  of the alternative embodiment functions as dealing with simultaneous access to, e.g. reading of, the plurality of RFID chips  13 - 1 ,  13 - 2  and  13 - 3 . Namely, the RFID reader and writer  20  of the alternative embodiment may have an anti-collision function. 
   Each of the inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  may be the same as the management inductive antenna device  40  of the illustrative embodiment shown in  FIG. 1 . The inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  have mating card portions  51 - 1 ,  51 - 2  and  51 - 3  and non-mating card portions  52 - 1 ,  52 - 2  and  52 - 3 , respectively. Each of the inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  includes therein the reader and writer-side inductive antenna, conductive line, and tag-side inductive antenna, which may respectively be the same as the elements  43 ,  44  and  45  shown in  FIG. 1 . Note that for convenient description of the plurality of inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3 ,  FIG. 5  shows the inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  as being smaller than the space  12  to be engaged in the RFID tag  10 . In the same manner as described for the management inductive antenna device  40  of the embodiment shown in  FIG. 1 , the inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  are sized so that their mating card portions  51 - 1 ,  51 - 2  and  51 - 3  can engage with the space  12  to be mated in the RFID tag  10 . 
   The inductive antenna devices  50 - 1 ,  50 - 2  and  50 - 3  are selectively arranged so as to access and mate with the respective RFID chips  13 - 1 ,  13 - 2  and  13 - 3  provided in the RFID tag  10 . Specifically, differences are provided in position and number of a set of the reader and writer-side inductive antennas, conductive lines, and tag-side inductive antennas between the inductive antenna devices  50 - 1 ,  50 - 2 , and  50 - 3 . 
   The inductive antenna device  50 - 1  includes one set of reader and writer-side inductive antenna  53 - 1 , conductive line  54 - 1 , and tag-side inductive antenna  55 - 1 . This set is positioned so that the inductive antenna device  50 - 1  may access the RFID chip  13 - 1  in the RFID tag  10 , when engaged with the latter. The inductive antenna device  50 - 2  includes one set of reader and writer-side inductive antenna  53 - 2 , conductive line  54 - 2 , and tag-side inductive antenna  55 - 2 . This set is positioned so that inductive antenna device  50 - 2  may access the RFID chip  13 - 2  in the RFID tag  10 , when engaged with the latter. The inductive antenna device  50 - 3  includes two sets of reader and writer-side inductive antennas  53 - 31  and  53 - 32 , conductive lines  54 - 31  and  54 - 32 , and tag-side inductive antennas  55 - 31  and  55 - 32 . The one set ( 53 - 31 ,  54 - 31  and  55 - 31 ) is positioned so that it may access the corresponding one RFID chip  13 - 1  in the RFID tag  10 . The other set ( 53 - 32 ,  54 - 32 , and  55 - 32 ) is positioned so that it may access the corresponding other RFID chip  13 - 3  in the RFID tag  10 . 
   The reader and writer-side inductive antenna may be positioned differently from that shown in  FIG. 5  while the tag-side inductive antenna may be positioned the same as in  FIG. 5 . This also allows an access to intended one of the RFID chips in the RFID tag  10 . In the inductive antenna device  50 - 3 , the two reader and writer-side inductive antennas  53 - 31  and  53 - 32  may be incorporated with each other. 
   Also in the alternative embodiment, the RFID reader and writer  20  cannot access the RFID tag  10  when having none of the label inductive antenna devices  50 - 1 ,  50 - 2 , and  50 - 3  engaged because the electromagnetic shielding function prevents the enquiry electromagnetic wave from reaching the tag antenna. Specifically, the third party cannot make access to the RFID tag  10  unless mounting any of the label inductive antenna devices  50 - 1 ,  50 - 2 , and  50 - 3 , even using the RFID reader and writer  20 . 
   When a normal or authorized user wishes to access the RFID chip  13 - 2  in the RFID tag  10 , he or she inserts or engages the inductive antenna device  50 - 2  into the RFID tag  10  and activates the RFID reader and writer  20 . In this case, the communication path is formed by two electromagnetic couplings between the antennas: the first electromagnetic coupling between the antenna  21  of the RFID reader and writer  20  and the reader and writer-side inductive antenna  53 - 2  of the inductive antenna device  50 - 2 ; and the second electromagnetic coupling between the tag-side inductive antenna  55 - 2  of the inductive antenna device  50 - 2  and the tag antenna  14 - 2 . The RFID reader and writer  20  may thus access the RFID chip  13 - 2 . 
   No electromagnetic coupling is established between the tag-side inductive antenna  55 - 2  of the inductive antenna device  50 - 2  and the tag antenna  14 - 1  or  14 - 3  because of the electromagnetic shielding function provided and the position of the tag antennas  14 - 1  and  14 - 3  in the RFID tag  10 . With the inductive antenna device  50 - 2  being attached to the RFID tag  10 , therefore, the RFID reader and writer  20  cannot access the RFID chip  13 - 1  or  13 - 3 . 
   Likewise, when the normal or appropriate user attaches the inductive antenna device  50 - 1  to the RFID tag  10  and performs the access operation, he or she may access only the RFID chip  13 - 1 . When the normal user attaches the inductive antenna device  50 - 3  to the RFID tag  10  and performs the access operation, he or she may access the RFID chips  13 - 1  and  13 - 3  at the same time. 
   The alternative embodiment may provide the same advantages as the illustrative embodiment shown in and described with reference to  FIG. 1 , and further provide the following advantages. 
   The provision of the plurality of RFID chips in the RFID tag allows tag information to be stored in appropriate RFID chips in dependent upon the kind or level of information. Even in the case of storing a series of tag information, a large amount of information may be stored in dependent upon the plurality of RFID chips. 
   A plurality of inductive antenna devices are provided correspondingly to combinations of the RFID chips so as to allow different combinations of the RFID chips accessible in one access operation to be prepared. For example, if a chief and his or her staff have inductive antenna devices different from each other, then different RFID chips are accessible in dependent upon the chief and staff. The alternative embodiment may thus control the access operation more finely. 
   Further with reference to the figures, a description will now be given of an RFID tag communications system of another alternative embodiment of the present invention. In the illustrative embodiments described above, the inductive antenna device is detachable from the RFID tag. In the other alternative embodiment, the inductive antenna device is mounted movable on the RFID tag. 
     FIGS. 6A and 6B  illustrate the schematic configuration of the RFID tag communications system of the instant alternative embodiment. Like elements are designated with the same reference numerals. In  FIGS. 6A and 6B , an RFID tag communications system  3  of the alternative embodiment generally includes the RFID tag  10 , RFID reader and writer  20 , and an inductive antenna device  60 . 
   The RFID tag  10  of the instant alternative embodiment is also, for example, generally of a card-like rectangular shape. Unlike the RFID tag in the embodiments described above, the RFID tag  10  of the present embodiment does not include an insertion slot and a space corresponding to the slot  11  and space  12  to be engaged, respectively, into which the inductive antenna device is inserted. The RFID tag  10  of the instant alternative embodiment has an opening  17  formed therein. Except for the area of the opening  17 , the electromagnetic shielding function attained by the surface member  16  applied by processing an electromagnetic shielding material prevents communication from being established between the inside of the RFID tag  10  and an outside device. The opening  17  may be electromagnetic, and may be covered with a resin or the like, for example. It is needless to say that the RFID tag  10  of the instant alternative embodiment includes therein the RFID chip  13  and tag antenna  14 . 
   The inductive antenna device  60  of the instant embodiment includes a reader and writer-side inductive antenna  63 , a conductive line  64  and a tag-side inductive antenna  65 , as well as a shifting device  66 . The reader and writer-side inductive antenna  63 , conductive line  64 , and tag-side inductive antenna  65  are provided in the RFID tag  10  such that they may move between the opposite end positions in link with the shifting device  66  manipulated. The reader and writer-side inductive antenna  63 , conductive line  64 , and tag-side inductive antenna  65  may all be sealed in a resin body, which is adapted to be movable as a unit. Alternatively, the tag-side inductive antenna  65  may be designed movable alone. The movement may be reciprocal, rotational or pivotal. 
   The reader and writer-side inductive antenna  63 , conductive line  64 , and tag-side inductive antenna  65  may be designed so as not to stop at the opposite end positions of the movement and not a position on the way between the opposite end positions by means of, e.g. the elastic force of a spring or a stopper, not-shown. 
   At both the opposite end positions, the tag-side inductive antenna  65  resides in a space where the electromagnetic shielding function is effected. The opposite end positions are selected so that when the tag-side inductive antenna  65  is at the one end position, the electromagnetic coupling is possible between the tag-side inductive antenna  65  and tag antenna  14 , and when the tag-side inductive antenna  65  is at the other end position, the electromagnetic coupling is impossible between the tag-side inductive antenna  65  and tag antenna  14 . 
   The reader and writer-side inductive antenna  63  takes, when positioned in the opening  17 , at least the one end position. 
   The shifting device  66  may be, for example, a simple knob or the like, or may include a plurality of members for converting a rotational motion to a linear motion. In this way, the user may handle the shifting device  66  to move the reader and writer-side inductive antenna  63 , conductive line  64 , and tag-side inductive antenna  65  between the opposite end positions. 
   With reference to  FIG. 6B , the user may manipulate the shifting device  66  to bring the inductive antenna device  60  at the other end position when he or she does not wish unnecessary communication with the RFID tag  10 . Under that situation, if the RFID reader and writer  20  performs the access operation, its antenna  21  and the reader and writer site antenna  63  of the inductive antenna device  60  may establish the electromagnetic coupling therebetween, but the inductive antenna device  60  staying at the other end position prevents the electromagnetic coupling between the tag-side antenna  65  and tag antenna  14 , thereby preventing the communication between the RFID reader and writer  20  and RFID tag  10 . 
   With reference to  FIG. 6A , when the user wishes the communication with the RFID tag  10 , he or she may handle the shifting device  66  to position the inductive antenna device  60  at the one end position. If the RFID reader and writer  20  performs the access operation here, then its antenna  21  and the reader and writer-side antenna  63  of the inductive antenna device  60  located in the opening  17  may establish the electromagnetic coupling therebetween, and also the inductive antenna device  60  at the one end position may establish the electromagnetic coupling between the tag-side-antenna  65  and tag antenna  14 , thereby establishing the communication path  71  to allow communication between the RFID reader and writer  20  and RFID tag  10 . 
   In this way, according to the instant alternative embodiment, when the inductive antenna device  60  is at the other end position, the RFID reader and writer  20  cannot access the RFID tag  10  due to the electromagnetic shielding function. The shifting device  66 , using a key or the like, would increase the security of the tag-information of the RFID tag  10 . 
   Further, according to the instant embodiment, the security function described above may eliminate the disabling of the RFID tag  10 , e.g. when selling a produce carrying the RFID tag  10  for preventing the tag information from leaking or the like. 
   Still further, according to the instant embodiment, the transmitting and receiving functions per se of the RFID tag  10  and RFID reader and writer  20  may not specifically be tailored for security. The security function thus does not prolong the access time. 
   The coupling between the RFID tag  10  and inductive antenna device  60  is electromagnetic and not mechanical via a physical connector. There is thus no metallic components such as a mechanical connector which would be deteriorated by a water droplet, moisture or any other environmental factor. 
   According to the instant alternative embodiment, the inductive antenna device  60  may not be detached from the RFID tag  10 , thereby avoiding the situation where the RFID tag  10  cannot be accessed when the loss of the inductive antenna device would have been lost. 
   Further, according to the instant embodiment, the user may easily determine whether or not the RFID chip is accessible by e.g. observing the position of, or touching, the shifting device  66 . 
   Although the various embodiments have described above, there may be additional modifications, as will be described below. Although the embodiments described above use the card-like RFID tags, the invention is not limited to the card-like RFID tag but may be directed to an enclosure-like or a tubular shape. The inductive antenna device may be any shape corresponding to such an RFID tag shape. 
   The fitting method of the RFID tag with the inductive antenna device is not limited to what is described with reference to the illustrative embodiments. For example, the RFID tag may be adapted to include a slide cover so that the RFID tag, when its slide cover is shifted, may engage with the corresponding portion of the inductive antenna device. 
   Although the illustrative embodiments described above use the RFID tag having the single space  12  to be engaged, the RFID tag may include a plurality of spaces to be engaged. As a variant of the alternative embodiment shown in  FIG. 5 , for example, the spaces to be engaged may be provided correspondingly to the accessible RFID chips. 
   Although the alternative embodiment described with reference to  FIGS. 6A and 6B  uses the RFID tag having the solo RFID chip built therein, the technical idea of that embodiment may also be applied to the RFID tag having a plurality of RFID chips built in. In this case, an inductive antenna may be provided that is common to the plurality of RFID chips, or individual inductive antenna devices may be provided that mate with respective RFID chips. In the latter case, individual shifting devices may also be provided that mate with respective RFID chips, or a single shifting device may be provided that establishes the relationship between the RFID chips and inductive antenna devices which is described in respect of the embodiment shown in  FIG. 5 . 
   Although the alternative embodiment described with reference to  FIGS. 6A and 6B  employs the movable inductive antenna device, the inductive antenna device may not be movable but the RFID chip and tag antenna may be movable. Further, the inductive antenna device, RFID chip, or tag antenna may not be movable, but the electromagnetic shielding element may be movable, thereby establishing or interrupting the electromagnetic coupling between the tag-side inductive antenna and tag antenna. 
   Although the embodiments described above employ the RFID chip having a memory device that is readable and writable, a memory device in the RFID chip may be of the read-only type. Likewise, the RFID reader and writer may be replaced with an RFID reader or an RFID writer. They may be referred in generic to as an RFID access device. 
   In the illustrative embodiments, the state in which the label inductive antenna device  30  and RFID tag  10  are controlled in position where they may be electromagnetically coupled is sometimes referred to one positional relationship. The state in which the label inductive antenna device  30  and RFID tag  10  cannot be electromagnetically coupled is sometimes referred to as the other positional relationship. In the other positional relationship, the label inductive antenna device  30  and RFID tag  10  may be controlled to a specific position so far as they cannot be electromagnetically coupled. 
   The entire disclosure of Japanese patent application No. 2005-285160 filed on Sep. 29, 2005, including the specification, claims, accompanying drawings and abstract of the disclosure is incorporated herein by reference in its entirety. 
   While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.