Patent Document

TECHNICAL FIELD 
     The present invention relates to Radio Frequency Identification (RFID) inlays and RFID tags that are used in suspendable packages, articles, or products having only limited space available for the RFID inlay. 
     BACKGROUND OF THE INVENTION 
     RFID tags are small sized devices, typically in a label format, that can be applied to or incorporated into a product, device or even animal for the purpose of identification and tracking of the item in question using radio waves. Some RFID tags can be read from several meters away and beyond the line of sight of the reader. These capabilities make the use of RFID tags very interesting over optical bar codes in product logistics, even if the data contained in the RFID tags would be equal to the UPC (Universal Product Code), EAN (European Article Number) codes traditionally used in bar codes. EPC (Electronic Product Code) codes used globally in RFID tags make it possible to store more information in a standardized manner to the RFID tags than has been possible in case of basic optical bar codes. Thus, RFID tags are becoming increasingly popular in everyday product logistics in many commercial fields. 
     RFID is currently also used in Electronic Article Surveillance (EAS) systems. In such an application, RFID technology is used to detect the presence or absence of an object within the reading distance of a reading device. Articles in these RFID based EAS systems are detected by detecting an RFID tag or RFID inlay that is attached to an article or the package of an article. 
     An RFID tag typically comprises an RFID inlay and an overlay structure forming the RFID tag. The RFID inlay is an electrically fully functional RFID transponder device, that is, a device that works as a transmitter and responder. The main components of the transponder are an electronic integrated circuit and an antenna. An inlay further comprises a substrate and other optional layers to support the transponder. The overlay structure of an RFID tag forms further mechanical support for the inlay and it can be used for printing trademarks, brand names etc. Overlays can be e.g. laminated or molded on the inlay. A typical RFID inlay is flexible, and, depending on the overlay, the RFID tag can be flexible or rigid. RFID inlays are typically sold in reels or rolls comprising hundreds to thousands of inlays. Generally the RFID tags can be either active or passive depending on whether they include an internal energy source, or they are operated with the electro-magnetic field generated by the RFID reader device. 
     According to “A BASIC INTRODUCTION TO RFID TECHNOLOGY AND ITS USE IN THE SUPPLY CHAIN” (LARAN RFID, January 2004) RFID tags can operate on several frequencies. Four frequency ranges are generally defined as: (1) low frequency (LF); frequencies below 135 kHz, (2) high frequency (HF); frequencies around 13.56 MHz, (3) ultra high frequency (UHF); frequencies between 860 kHz and 960 kHz, and (4) microwave; frequencies around 2.54 MHz. RFID tags can be designed to operate near the reader device, or far from the reader device. In case tags are designed to work near the reader device, the tags are known as near field tags, and the energy transfer from the reader device to the RFID tag is mostly through the magnetic field generated by the RFID reader. Data transfer from the tag to the reader device in near field case is enabled by inductive coupling, where the RFID tag changes its impedance, and the alternating load is detected by the reader device. Sometimes the communication in the near field is known as near field communication (NFC). In case the tags are designed to work far away from the reader device, the tags are known as far field tags, and the energy transfer from the reader device to the tag is mainly through the electric field. Part of the RFID tag operates as an antenna, and the RFID device gets its energy from the electric field. In the far field case, data transfer from the tag to the reader device is enabled by field backscattering. The theoretical limit between the near field and the far field is proportional to λ/2π, where λ is the wavelength of the electromagnetic radiation generated by the reader device, equaling to c/f, where c is the speed of radiation (i.e. light) and f is the frequency. As a result, the limit between near and far fields for a HF RFID system would be 3.5 m and for an UHF RFID system the limit would be 5 cm. One can also define a transition zone between the near field and the far field. 
     In the near field tags, the strength of the inductive coupling between the RFID tag and the RFID reader is proportional to the area enclosed by the wiring of the RFID inlay. In the far field tags, the wiring of the RFID inlay performs as an antenna, and the length of the wiring must therefore be proportional to the wavelength λ. 
     Even if these wirings can be made to meander in the inlay, these physical principles determine size limits for the RFID inlays, e.g. the minimum size. 
     Typically RFID tags (or in some cases the RFID inlays) are attached to the articles or packages thereof. In case the article or package thereof is small in size, the RFID tag can take up a large portion of the article or package. Many of such articles are sold in stores, where they are placed for sale to a hanger. The mounting hole for the hanger also takes up some space of the package already with limited space available. Therefore, especially in case of small articles, it may be difficult to find space both for the mounting hole for the hanger and the RFID tag. 
     The hangers and respective hanger holes used in the art have been standardized for their dimensions. The frequently used versions include, for example, the so called “Euroslot”, “Inverted T”, “Osha” and “Oval” which will be described in more detail later. 
     SUMMARY OF THE INVENTION 
     Despite of a wide variety of different existing RFID tag solutions there still is a clear need for a solution that would facilitate improved capability to tag small sized suspendible items and to utilize the full potential of RFID tags including the possibilities to use RFID for EAS purposes. In order to improve the capability to tag small sized suspendible items, a product comprising a mounting hole or a perform for the mounting hole and a radio frequency identification transponder for wireless identification, said transponder comprising at least an integrated circuit and wiring, wherein the wiring of the transponder at least partly encircles the mounting hole, is disclosed. Furthermore, a method to produce such a product is disclosed. For the EAS purposes, a reader device configured to communicate with a radio frequency identification transponder of at least one product comprising a mounting hole wherein the reader device comprises an antenna configured to penetrate the mounting hole is disclosed. Furthermore, to facilitate a different reading distance or a different operating frequency for a suspended product and an unsuspended product, a method to change the operating frequency or the reading distance of a radio frequency identification transponder of at least one product comprising a mounting hole is, wherein the method comprises penetrating an electrically conductive object through the mounting hole, is disclosed. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the following examples, the embodiments of the invention will be described in more detail with reference to the appended drawings, in which 
         FIGS. 1   a ,  1   b ,  1   c , and  1   d  show schematically an RFID reader system and three RFID inlays, respectively, 
         FIGS. 2   a ,  2   b , and  2   c  show an article in a suspendible package with a Euroslot hanger hole, three suspendible packages in a hanger, and different types of hanger holes respectively, 
         FIGS. 3   a ,  3   b ,  3   c , and  3   d  show a suspendible package with a Euroslot hanger hole comprising an RFID inlay, a small suspendible package and an RFID inlay, a small suspendible package comprising an RFID inlay, and a smaller suspendible package comprising an RFID inlay, respectively, 
         FIGS. 4   a  and  4   b  show methods to produce a small suspendible package comprising an RFID inlay, 
         FIGS. 5   a ,  5   b ,  5   c , and  5   d  show RFID inlays of which wirings that encircle or partly encircle a mounting hole, 
         FIGS. 6   a ,  6   b ,  6   c ,  6   d , and  6   e  show an RFID device working in the stand-alone mode, the RFID device working in the extended mode, RFID devices working in the extended mode, an RFID reader system, and a handheld RFID reader system, respectively, 
         FIGS. 7   a ,  7   b ,  7   c , and  7   d  show a rear view, a side view, and a top view of a package comprising a seal and a rear view of a package comprising an RFID inlay, respectively 
         FIGS. 8   a ,  8   b ,  8   c ,  8   d ,  8   e , and  8   f  show a side view of a package comprising an RFID inlay, a side view of another package comprising an RFID inlay, front and top view of a package comprising an RFID inlay, front and top view of another package comprising an RFID inlay, and two perspective views of packages comprising an RFID inlay and inverted T type hanger holes, respectively, and 
         FIGS. 9   a ,  9   b ,  9   c ,  9   d , and  9   e  show three tamper-evident packages comprising RFID inlay, a tamper-evident or tamper proof RFID system, and a tamper-proof RFID system, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1   a  shows schematically a typical RFID system with an RFID reader. The RFID reader system comprises at least one RFID device  110 , an RFID reader device  120 , and a host computer  122 . The RFID device  110  may be an RFID tag, or it may be a product comprising an RFID tag or an inlay. In both cases, the RFID device comprises an RFID inlay  100 . The RFID reader device  120  comprises an antenna  121 . With the antenna  121  the RFID reader device  120  generates an RF field  123 . In response to the RF field  123 , the RFID device  110  scatters the RF field back to the antenna or modifies the inductive load seen by the reader device. In both cases the backscattered signal thus sent from the RFID device  110  can be read by the reader device  120 . The signal typically contains at least information indicative of the RFID device, e.g. an identity number of the RFID device  110  and possibly further product information related to the tagged item. The reader device  120  may be coupled to a host computer  122  to obtain other information regarding the RFID device of this particular identity number and/or to supply tag/product information to further remote systems. 
       FIGS. 1   b - 1   d  show some typical layouts for RFID inlays  100  used in the art. The RFID inlays comprise an integrated circuit (IC) chip  101 , wiring  103 , and a substrate  104 . The wiring comprises an impedance matching section  102  and an electromagnetic radiator section, either an antenna (typical for far field RFID) or a coil (typical for near field RFID). The substrate may be e.g. polyvinyl chloride (PVC), polyethylene terephthalate (PET), or paper. The wiring may be made of conductive material, such as copper, aluminum, silver, gold or a conductive ink comprising any of these metals or other conducting material. The chip  101  is bonded to the substrate such that input/output (I/O) pads of the chip  101  are connected to wiring  103 . Known bonding techniques include adhesive joining with either electrically conductive adhesive (isotropically conducting adhesive ICA, or anisotropically conducting adhesive, ACA), or a non-conductive adhesive, NCA. These adhesives can be supplied in film form, when the adhesives are known as ICF, ACF, or NCF, where the last letter stands for film. For these bonding techniques, the I/O pads of the chip  101  have to be bumped e.g. with gold bumps. In case of RFID inlays, the chips  101  are small, typically a square with the side length 0.5 mm. As discussed above, the size of wiring has to be relatively large. Typically the length of the UHF RFID antenna (wiring) has to be λ/4, which in typical UHF application (900 MHz) is about 8 cm. In addition to frequency, the permittivity of the substrate also affects the wavelength, and therefore the size of the antenna. As for the near field RFID inlays, the area enclosed by inlay wiring may be for example around 1 cm 2  and upwards for inductive coupling. It is also noted that the coupling depends on the number of wiring turns enclosing the area. In addition, antenna structures comprising properties of both far field and near field wirings have been used.  FIG. 1   b  shows an example of a far field RFID inlay, where the wiring  103  comprises an antenna, arranged to meander on the substrate  104 .  FIG. 1   c  shows a near field RFID inlay, where the wiring  103  forms a coil, wherein in the case of  FIG. 1   c  the coil has four turns.  FIG. 1   d  shows an RFID inlay of which structure comprises properties of both a typical far field inlay and a typical near field inlay. It should be noted that the  FIGS. 1   b - 1   d  are given here as examples only describing some possible RFID structures. Other structures are also possible and known to a person skilled in the art. 
     The RFID tag (or the RFID inlay) may be attached to the article or to the package of the article.  FIG. 2   a  shows, as an example, a front view of an article  200  in a package  201 . The package  201  is designed to be placed to hanger in a store. Thus, the package  201  may comprise a standardized mounting hole  202  for the hanger.  FIG. 2   b  is a side view of a typical hanger  203  in a store, wherein the hanger  203  contains packages  201 , and in this case three packages. A hanger is typically relatively long, thin, and rigid. Also, as depicted in  FIG. 2   b , the hanger may be perpendicular to a plane of a surface of the package.  FIG. 2   c  shows examples of some standardized mounting holes. The reference number  202   a  shows a Euroslot type hanger hole,  202   b  an Inverted T type hanger hole,  202   c  an Osha type hanger hole, and  202   d  an oval hanger hole. A special type of the oval hanger hole is the circular hanger hole, where the width w h  equals the heights h c  and h h . Moreover, depending on the roundness of the corners of the oval mounting hole, the hole can also be a square. Thus, the oval hole allows for more flexibility in the measures. Typical measures for these mounting holes are given in Table 1. The sizes are standardized in inches, and given in the table with the accuracy of two numbers. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Standard hanger holes and their measures. 
               
             
          
           
               
                   
                 w h  (mm) 
                 h h  (mm) 
                 h c  (mm) 
               
               
                   
                   
               
             
          
           
               
                   
                 Euroslot 
                 32 
                 6.4 
                 13 
               
               
                   
                 Inverted T 
                 25-32 
                 4.8-32 
                 6.4-10 
               
               
                   
                 Osha 
                 13-37 
                  4.0-6.4 
                 6.4-10 
               
               
                   
                 Oval 
                 6.4-25  
                 6.4-13 
                 6.4-13 
               
               
                   
                   
               
             
          
         
       
     
       FIG. 3   a  shows a rear view of the package  201 . An RFID inlay  100  is attached to the (large) package. However, in case the package is small, as depicted in  FIG. 3   b , the RFID inlay  100  does not fit on the package  201 . According to an example embodiment of the invention, the suspendible package may be equipped with an RFID inlay in such a way that the mounting hole for the hanger is at least partly encircled by the wiring of the RFID inlay  100 . One embodiment of the invention is shown in  FIG. 3   c , where the package  201  and the inlay  100  comprise the same mounting hole  202 .  FIG. 3   d  shows another embodiment of the invention for packages  201  that do not fit the RFID inlay  100 . In such a case, the inlay may be partly attached to the package  201 , and the mounting hole may be made to the inlay  100  only. In both cases the mounting hole  202  extends through at least the RFID inlay  100 . As depicted in  FIGS. 3   b - 3   c , the cross-sectional area of the package  201  may be of the same order as the area of the RFID inlay  100 . Moreover, as shown in  FIG. 3   d , the RFID inlay may be larger than the package, or, as will be shown later, the package may be larger than the RFID inlay. Thus the mounting hole  202  may be arranged to extend through the package  201  and the RFID inlay  100 . The size of an RFID transponder can vary a lot and depends e.g. on the operating distance of the RFID transponder. The far field RFID transponders have typically a size ranging from e.g. 1.5×7 cm to about 15×15 cm. The near field RFID transponders may be smaller. 
     It should be noted that the arrangement of the RFID inlay or tag into a small sized package according to this invention is not limited by the purpose of the use of the RFID. The RFID inlay or tag can be used for normal EPC coding and logistics but according to some advantageous embodiments of the invention also for EAS purposes. The use of the invention for EAS purposes is described in more detail later in this text. 
       FIGS. 4   a  and  4   b  show two examples of ways to produce a package according to an example embodiment. In  FIG. 4   a , an ordinary, unpunched, RFID inlay  100  is attached to the unpunched package  201  during the manufacturing of the package. At a later stage of the package manufacturing process, both the RFID inlay and the package are punched to form the mounting hole  202 . In this case, the mounting hole  202  is arranged to the RFID inlay  100  and the package  201  at essentially the same time. Alternatively, in case the RFID inlay cannot be attached during the manufacturing of the package, an RFID inlay (or RFID tag) may be punched to form a punched RFID inlay  101  shown in  FIG. 4   b . Thereafter the punched RFID inlay may be attached to the package containing the mounting hole  202 . In case the RFID inlay can be attached to the package already during the package manufacturing process, punching both the inlay  100  and the package  201  provides a more economical way to produce the package avoiding, for example, the need to separately line up the holes in the package and the RFID inlay. In addition to punching, other methods known in the art, such as various cutting methods may be used to produce the mounting hole. Moreover, only a preform for the mounting hole can be made, such that the mounting hole is opened by penetrating an object through the preform. A preform may be made e.g. by perforating or partly cutting the edge of the area defining the mounting hole. The inlay can be attached to the rear side of the package, as depicted in  FIG. 3   c , or it can be attached to the front of the package. Moreover, it is possible to laminate the RFID inlay  100  between the front and rear surfaces of the package whereas the RFID inlay remains invisible from the outside of the package. It is noted that some products, e.g. various types of cards, are not sold in a package. In these cases an RFID inlay can be attached directly to the product. Moreover, it is noted, that the package itself is an example of a product that is not further packaged. It is further noted that a package, an article, and a product that comprises an RFID inlay is an RFID device. 
       FIG. 5   a  shows another type of an RFID inlay, designed for a suspendible product (cf.  FIG. 1   c ). In this case the wiring  103  of the RFID inlay  100  encircles the mounting hole  202  for the hanger. The center of the mounting hole is marked by the reference number  205 . This may be the case, when the wiring of the RFID device forms a coil, i.e. in near field RFID devices. In some other cases, the wiring  103  of the RFID device may only partly encircle the mounting hole. This was the case in  FIGS. 3   c  and  4 , and shown in more detail in  FIG. 5   b . As the wiring  103  of the RFID device does not form a coil, it only partly encircles the mounting hole. In this case, the angle of view of the wiring α, as seen from the center  205  of the mounting hole  202 , is less than 360 degrees.  FIG. 5   c  shows an alternative wiring, where the angle of view α of the wiring is 180 degrees, and  FIG. 5   d  shows still another example, where the angle of view is slightly less than 180 degrees. Possibly more space is saved, when the angle of view α is increased. 
     In many cases the hanger  203  is made of some metal or other electrically conductive material. In these cases the performance of the RFID device is altered when an electrically conductive object is penetrated through the mounting hole. As an example, for one case, in which the maximum reading range of the RFID device not penetrated by a metallic hanger is at 990 MHz, experiments show that the maximum reading range is obtained with the frequency 820 MHz, when the RFID device is penetrated by a metallic hanger. In addition to reading distance and operating frequency, the presence of the metallic hanger affects the radiation pattern of the RFID device. I.e. an electrically conductive object electro-magnetically couples to the wiring of RFID device, and forms a part of the antenna of the RFID device. Therefore, an RFID device having an essentially two-dimensional wiring in its inlay, may be specifically designed to operate also with an extended, possible three-dimensional, antenna, i.e. when an electrically conductive object is located such that the wiring of the device at least partly encircles the electrically conductive object. 
     Such an RFID device may have two operating modes: a stand-alone mode and an extended mode. In the stand-alone mode, the wiring of the inlay comprises the antenna of the RFID device, while in the extended mode the antenna is extended with an electrically conductive object. The extended mode is enabled e.g. when the RFID device is located such that its wiring partly encircles an electrically conductive object. For example, the extended mode may be enabled, when a package with an RFID inlay, of which wiring is arranged such that the wiring of the RFID inlay at least partly encircles the mounting hole, is inserted to a hanger in a store. The difference between these operating modes is the different operating frequency and different reading distance and possibly also different orientation sensitivity/radiation pattern. In particular, the electrically conductive object can form an antenna extension, which enables a longer reading distance for the RFID device in the extended mode, than in the stand-alone mode. In order to enable the extended mode, the wiring of the RFID device should at least partly encircle a mounting hole for the electrically conductive object. The angle of view of the wiring α, as seen from the center of the mounting hole may be preferably more than approximately 90 degrees. 
     In case the package comprises a preform for the mounting hole, the wiring of the RFID transponder can be arranged such that part of the wiring is located in or on the preform, while other parts of the wiring partly encircle the preform. Opening the mounting hole by removing the preform with an object by penetrating the object through the mounting hole, could alter the RF properties of the RFID transponder, since modifying the antenna section of the wiring also modifies the RF properties of the transponder. Therefore, the transponder may have different RF properties, e.g. operating frequency, reading distance, or radiation pattern, depending on whether the preform has been removed or not, and whether there is an electrically conductive object in the mounting hole or not. 
       FIG. 6   a  shows a rear and a side view of an RFID device  201 , the device being an article in a package  201  comprising an RFID inlay  100 . The device  201  of  FIG. 6   a  operates in the stand-alone mode.  FIG. 6   b  shows the RFID device of  FIG. 6   a  operating in the extended mode, where the extended mode is enabled by an electrically conductive object  203 , which has been penetrated through the mounting hole  202  of the RFID device  201 . The operating frequency of the RFID device may also be modified as the hanger  203  is penetrated through the mounting hole  202 . As depicted in  FIG. 6   c , it is also possible that the electrically conductive object  203  works as an antenna extension for several suspendible RFID packages  201 . 
     As discussed, the RF properties of the RFID devices that can operate in the stand-alone mode and in the extended mode may be different in different operating modes. This property can be used to configure RFID reader devices to read only RFID tags that are operating in the extended mode or only devices that are operating in the stand-alone mode. Furthermore, the reader devices can be designed to read RFID tags both in the stand-alone mode and in the extended mode. This also enables a designer to design RFID systems with different reading distances for RFID devices in the stand-alone mode and RFID devices in the extended mode, e.g. for objects that are not hanging from a metallic hanger and objects that are hanging. Depending on the design, either of these reading distances can be longer than the other, or the reading distances can be equal. Accordingly, when relying on the standard reading frequencies it is possible to design the RFID tag in a manner that reading is not possible while the suspendible item is suspended in a hanger but only after the item is removed from the hanger. Or, if required by the end application, also vice versa: the RFID tag is unreadable until it is suspended in a hanger. 
     One further example is to design an RFID reader device such that the electrically conductive object that is partly encircled by the wiring of the RFID device is a part of the RFID reader device, e.g. an antenna of the reader device. This example is depicted in  FIG. 6   d . In the figure, an electrically conductive object, denoted by “ 121 / 203 ”, can work both as the hanger  203  for the packages  201  and as the antenna  121  of the reader device  120 . As previously, the reader device  120  may be connected to a host computer  122 . When the RFID device  201  so designed has a short reading distance, the reader device  120  can be use to make online inventory of the hanging articles. The RFID reader device  120  simply counts the number of packages  201  seen by the reader device  120 . It is noted that even if the hanger  203  is used as the antenna  121  of the reader device  120 , the hanger  203  also couples to the wirings of the packages  201 . Therefore, the packages  201 , as RFID devices, are operating in the extended mode.  FIG. 6   e  shows another embodiment of an RFID system. This system comprises a handheld RFID reader device  600 . The handheld reader device  600  has an electric contact point  601  that provides the reader device  600  with a position for an external reader antenna  602 . In the left part of the figure, the electric contact point  601  of the reader device  600  is not in contact with an external antenna  602 . The reader device may thus be used to read e.g. RFID tags in the stand-alone mode or in the extended mode. Furthermore, the reader device itself may operate in two modes: the internal mode, when the device is not coupled to an external antenna  602 , and an external mode, when an external antenna  602  is coupled to the RFID reader. The internal mode operation is illustrated in the left part of  FIG. 6   e , while the external mode operation is illustrated in the right part of the figure. The external mode for the reader is enabled, when the electric contact point  601  forms an electrical contact with an external antenna  602 , e.g. a conductive hanger  203 . The hanger  203  may thus also work as the external antenna  602 , and therefore the number “ 602 / 203 ” is used in the figure. In this way, online inventory can also be made with a handheld RFID reader device  600 . 
     The package or the mounting hole may have various shapes.  FIGS. 7   a - 7   c  show another type of a suspendible package, where the mounting hole is arranged by using a hook.  FIG. 7   a  shows the rear view of the package  201 . The package has been sealed with a seal  700 , and the lower part of the seal is shown in the rear view. The mounting hole  202  is arranged to the package by arranging a hook  710  in the top of the package. The hook  710  thus at least partly encircles the mounting hole  202 . In this case the mounting hole is arranged for a round hanger, and the round mounting hole is a special case of the oval mounting hole, as discussed in the context of  FIG. 2   c .  FIG. 7   b  shows the side view of the package, where thickness of the seal  700  is exaggerated.  FIG. 7   c  shows the top view of the package, in which the upper part of the seal is visible. In this kind of package, the RFID device may be integrated into the seal, e.g. the seal may comprise the RFID inlay. As an example, the rear view of the package of  FIG. 7   a , in which the seal comprises an RFID inlay is shown in  FIG. 7   d . In this configuration, the angle of view a of the RFID device wiring, as seen from the centre of the mounting hole  202 , becomes almost 180 degrees. Therefore, the package  201  is an RFID device that can be operated in the two modes: the stand-alone mode, where the RFID inlay is not coupled to an electrically conductive object, and in the extended mode, which is enabled by penetrating an electrically conductive object through the mounting hole  202 . 
     For some other package shapes, the RFID inlays are not necessarily arranged perpendicular to the hanger. Some examples of possible arrangements are shown in  FIGS. 8   a  and  8   b . The figures show a side view of packages  201  comprising an RFID inlay  100 . In the figures, the RFID inlay  100  is arranged to the rear side of the package  201 , and the plane of the rear side is not perpendicular to the direction  800  of the hanger. The plane of RFID inlay thus forms an angle β less than 90 degrees with the direction of the hanger, as depicted in the figures. It is noted that the extended mode can be enabled even for RFID inlays having an angle β equal to 0 degrees with respect to the direction of the electrically conductive object.  FIGS. 8   c  and  8   d  show examples, where the inlay is curved and arranged on top of a package. In this case all the tangent planes of the curved plane formed by the inlay comprise the direction on the electrically conductive object, making the angle β equal to 0. In these examples, the planar RFID inlay is also curved to increase the angle of view α. In case of  FIG. 8   c , the RFID inlay is arranged underneath the mounting hole and the angle of view is less than 180 degrees. In contrast, in  FIG. 8   d  the RFID inlay is arranged above the mounting hole and the angle of view is greater than 180 degrees. It is also noted that the mounting hole  202  of  FIG. 8   c  has a slightly different form than the mounting hole previously presented. Moreover, in  FIG. 8   d , the mounting hole for the hanger is formed by attaching the ends of the RFID inlay  100  to the package  201 , and the space in between these objects form the mounting hole  202 . 
     The suspendible RFID package may also be arranged such that the angle β between the tangent plane of the RFID inlay and the electrically conductive object is greater than zero, and the inlay is curved.  FIG. 8   e  illustrates a package  201  that has a concave surface, onto which an RFID inlay  100  (or a tag comprising the inlay) has been attached.  FIG. 8   f  illustrates a convex surface comprising the inlay. 
     One further advantage of the dual-mode RFID operation is that it can be used to achieve a tamper-evident or a tamper-proof RFID package.  FIGS. 9   a - 9   c  show tamper-evident RFID packages  201 . They are characterized in that a perforation  901  is arranged into the package such that the perforation  901  overlaps the wiring  103  of the RFID inlay  100 . Furthermore, the perforation is arranged from the mounting hole to an edge of the package. It is noted that the perforation  901  may not alter the RF properties of the RFID inlay, and therefore, the wiring  103  may not be punched in the perforation process. Preferably, the perforations  901  are arranged to the package  201  before the inlay  100  is attached to the package  201 . Also preferably, the mounting hole  202  for the hanger is punched to the perforated package  201  after the RFID inlay  100  has been attached to it.  FIG. 9   a  shows an example of a tamper-evident RFID device, where a perforation  901  has been arranged to overlap the wiring  103 . The package is not symmetric, because the angle of view is less than 360 degrees, the perforation  901  may overlap the wiring  103 , and the gap in the wiring (not shown, on top of the mounting hole) is on the symmetry axis. Another perforation could be arranged to make the package symmetric, if desired e.g. for a symmetric appearance. When the package breaks through the perforation  901 , the RF properties of the inlay  101  may be detuned.  FIG. 9   b  shows another tamper-evident RFID device of which wiring has an angle of view α of 360 degrees. In this case the perforation  901  can be arranged to the symmetry axis. It is noted, that the perforation  901  need not to be on the symmetry axis. In this case, breaking the inlay through the perforation  901  also breaks the RFID device  201 , as the inductive coil breaks, and power supply of the RFID device breaks. As depicted in  FIG. 9   c , a perforation  901  may also be arranged to overlap the impedance matching section  102  of the chip  101 . Breaking this type of package results also in the breaking of the RFID device, not just detuning its RF properties as was the case with the device shown in  FIG. 9   a.    
       FIG. 9   d  shows a hanger  203  designed to be used with tamper-evident RFID packages. One end of the hanger  203  is attached to a wall  903  and a locking mechanism  902  is arranged in the other end of the hanger  203 . The locking mechanism  902  makes it impossible to take away a package  201  from the hanger  203  without either breaking the package  201  or opening the locking mechanism  902 . If a package  201  is taken from the hanger  203  by force, the package  201  will be ripped off through the perforation(s)  901 . This breaks the RFID package  201 , which helps to identify stolen products. 
     The embodiment shown in the  FIG. 9   d  can also be used for tamper-proof RFID packages. Namely, an RFID reader device can be arranged to detect the number of packages  201  suspending from the hanger  203 . If the locking mechanism  902  is locked, a package  201  may not be taken from the hanger  203  without ripping it off. If someone removes the package  201  from the hanger  203  by ripping it off, the RFID transponder arranged around the hanger hole will become destroyed or detuned. This will deactivate the RFID transponder, which could be detected by the reader device. This detection can be made e.g. by using RFID reader polling for the items on regular basis. The polling would be engaged, for example when the locking mechanism is locked, and the initial number of the packages  201  in the hanger  203  could be read by the RFID reader device. Polling would then compare the number of packages in the hanger to the previously known number of packages  201  in the hanger  203 . Opening the locking mechanism would suspend the polling procedure, since this corresponds to the normal buying process, where the seller opens the locking mechanism  902  and hands the package to the customer. Essentially the reading distance of the reader device must extend at least the size of the hanger  203 . This embodiment does not necessarily need the perforated packages of  FIGS. 9   a - 9   c , since in case the wiring of the transponder encircles the mounting hole, ripping the package from the hanger will destroy the transponder unit. Moreover, in case the angle of view is large, it may be extremely hard to rip the package from the hanger without destroying or detuning the transponder. 
     Another embodiment of a tamper-proof RFID system is depicted in  FIG. 9   e . In the figure, the hanger  203 , arranged for tamper-evident packages  201 , with the locking mechanism  902 , also works as the antenna  121  of an RFID reader device  120 . Due to the locking mechanism, a package can be taken from the hanger  203  only by force, if the locking mechanism  902  is locked. If a tamper-evident package  201  is taken from the hanger  203  by force, the package  201  will be ripped off through the perforation(s)  901  and the RFID inlay  100  will not function. In this case, the RFID reader device  120  detects one package fewer in the hanger  203 . The host computer  122  may react to this event by raising an alarm or calling a security guard. As discussed in the context of  FIGS. 9   d  and  9   e , the hanger  203  may or may not be part of the reader device  120 . In both cases, the reading distance of the reader device  120  must extend at least the size of the hanger  203 . 
     It is also noted that this type of tamper-proof RFID system needs not tamper-evident RFID packages. In case the RFID inlay is located such that the angle of view is somewhat less that 180 degrees, as in case of  FIGS. 7-8 , taking a package  201  by force from the hanger  203  does not break the wiring of the RFID inlay. However, if the reading distance of the RFID reader device  120  is relatively short (especially for a device operating in the stand-alone mode), the RFID reader  120  still detects the decreasing number of products in the hanger  203 , and may raise an alarm if the locking mechanism  902  is locked. 
     The foregoing descriptions of the preferred embodiments of the invention have been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Technology Category: 3