JP6159544B2 - RFID tag sensor and installation method of RFID tag sensor - Google Patents

Description

  The present invention relates to a technology for reading an RFID tag, and in particular, to an RFID tag sensor for reading an RFID tag attached to a plurality of articles stored in a shelf or the like by a reader installed on the shelf and an installation method thereof. It is related to effective technology.

  In order to understand and recognize the location and stock of items stored in racks, shelves, cabinets, etc. (hereinafter, these storage facilities may be simply referred to as “shelf”) A mechanism is used in which an RFID (Radio Frequency IDentification) tag is attached to an article and this is read by a reader.

  At this time, for example, by reading a RFID tag attached to a management object such as a book, various products, parts, or equipment stored in the shelf by a reader and an antenna or other sensor unit installed on the shelf board, etc. It is considered to grasp and recognize things. However, in a circularly polarized antenna or the like used for a normal reader, the output radio wave overflows inside and outside the shelf, so that it interferes with other shelves (readers) and the shelf cannot be specified, resulting in erroneous recognition. There is a case. In addition, when a metal device such as a communication device is housed in a shelf and is operating, noise may adversely affect the shelf.

  On the other hand, for example, in Japanese Patent Application Laid-Open No. 2011-82684 (Patent Document 1), the electromagnetic wave transmission sheet is attached to an end portion of the electromagnetic wave transmission sheet, and the electromagnetic waves are transmitted and received between the electromagnetic wave transmission sheet. An interface device, a signal reader that is electrically connected to the interface device, reads the predetermined signal sent from the interface device, accommodates the interface device and the signal reader, and is integrated with the end of the electromagnetic wave transmission sheet Describes a technology related to a communication device, which is provided with a storage box that is installed on a shelf, can be easily installed on a shelf, a table, etc., and enables efficient management of products with RFID tags. Yes.

  Japanese Patent Laid-Open No. 2008-78882 (Patent Document 2) discloses that the first leaky transmission line and the second leaky transmission line are connected to each other along the longitudinal direction on the surface of the shelf board forming each shelf of the bookcase. The first leaky transmission line is opened in parallel with the ends being terminated, the second leaky transmission line is short-circuited by a short-circuit member, and the first and second leaky transmission lines are cabled. The switch is connected to the wireless tag reader, and the wireless tag reader reads the first and second when reading the recorded data from the wireless tags attached to a large number of books on the bookshelf. A technique for efficiently performing wireless communication with a communication target such as a large number of wireless tags arranged in the vicinity by alternately using a leaky transmission path as an antenna is described.

JP 2011-82684 A JP 2008-78882 A

  In the technique as described in Patent Document 1, it is possible to read the RFID tag attached to the management object stored in the shelf by installing a communication device (electromagnetic wave transmission sheet) on the shelf board. However, the sensitivity is not so high because it has a structure that radiates electromagnetic waves on a flat surface. Therefore, RFID tags (or labels, tags, etc. including them) are placed on the shelf surface (electromagnetic wave transmission sheet surface) for the management objects to be stored. It is necessary to attach it so that it is opposite. For this reason, in a state in which the management object is stored in the shelf, the part to which the RFID tag (or a label or a tag including the tag) is attached may be in a position where it is difficult to see. In addition, for example, when members such as guide rails and holding parts are installed on the shelf to hold the stored items and the shelf surface is uneven, the installation itself becomes difficult.

  On the other hand, in the technique as described in Patent Document 2, a reader is set up relatively flexibly with respect to an existing shelf by disposing a cable-shaped leakage transmission path as an antenna on the surface of the shelf board. be able to. However, in order to reduce the sensitivity unevenness due to the distribution of the leaked electromagnetic wave, two or more leaky transmission paths having different distribution positions of the leaked electromagnetic wave are required, and a mechanism such as a switch for switching and using these is required. It may be difficult to install due to space constraints.

  Accordingly, an object of the present invention is to reduce the sensitivity unevenness without emitting a strong radiated electromagnetic wave, and can be installed flexibly and with a simple configuration on a shelf board of an existing shelf without requiring a space. To provide a tag sensor and an RFID tag sensor installation method.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

  An RFID tag sensor according to a representative embodiment of the present invention is connected to a reader device that wirelessly communicates with an RFID tag and reads the contents thereof, and transmits the electromagnetic wave output from the reader device when the electromagnetic wave output from the reader device is transmitted. An RFID tag sensor comprising a balanced transmission line that outputs a leaked electromagnetic wave for performing the balanced transmission line, wherein the balanced transmission line is formed in a ribbon shape by an insulating material with a pair of balanced transmission lines arranged at predetermined intervals. A termination resistor substantially equivalent to the characteristic impedance of the balanced transmission line is connected to the termination part of the transmission line, and is folded in a state where the nodes of the intensity distribution of the leaked electromagnetic wave in the balanced transmission line do not overlap. .

  The present invention can also be applied to a method for installing the RFID tag sensor as described above.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  That is, according to a typical embodiment of the present invention, sensitivity unevenness is reduced without emitting strong radiated electromagnetic waves, and a flexible and simple configuration is not required for a shelf of an existing shelf. It is possible to install an RFID tag sensor on the device.

It is the figure which showed the outline | summary about the structural example of the RFID tag sensor which is one embodiment of this invention. (A) (b) is the figure which showed the outline | summary about the example at the time of installing the RFID tag sensor and reader in one embodiment of this invention on a shelf board. It is the figure which showed the outline | summary about the example of the state which accommodated the management thing in the shelf which installed the RFID tag sensor and reader in one embodiment of this invention. It is the figure which showed the outline | summary about the example at the time of comprising the RFID tag sensor in one embodiment of this invention in the sheet form. It is the figure which showed the outline | summary about the example of the structure which reads an RFID tag using a balanced transmission line in a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted. In the following, in order to make the features of the present invention easier to understand, the description will be made in comparison with the prior art.

  There is a transmission line (cable) as means for efficiently transmitting electromagnetic waves from one end to the other, and there are a balanced transmission line and an unbalanced transmission line. The unbalanced transmission line is surrounded by insulation so that the outer conductor of the cable shields the central conductor as represented by the coaxial cable, and blocks unwanted electromagnetic waves that try to enter the inside from the outside of the cable, It has a role of preventing internal signal electromagnetic waves from leaking to the outside.

  On the other hand, a balanced transmission line has no outer conductor like a coaxial cable, and two central conductors are arranged in parallel through insulation, and a flat ribbon-like ribbon feeder, a parallel feeder, and two parallel conductors are mutually connected. There are intertwined twisted pair cables. Unlike the coaxial cable, these two conductors are not shielded, so most of the electromagnetic energy is transmitted in the cable extension direction (x direction), but also in the direction orthogonal to the x direction (z direction). Some electromagnetic waves leak or penetrate (hereinafter referred to as “leakage electromagnetic waves”).

  In the present embodiment, leakage electromagnetic waves leaking from a balanced transmission line connected to an RFID tag reader / writer (hereinafter sometimes simply referred to as “reader”) are used on the balanced transmission line along the cable. A configuration is adopted in which communication is performed with a plurality of arranged RFID tags to read them. That is, a balanced transmission line such as a ribbon feeder is used as an RFID tag sensor. Thereby, it is possible to perform communication by weak proximity leakage electromagnetic waves distributed along the cable line without emitting strong radiated electromagnetic waves.

  FIG. 5 is a diagram showing an outline of an example of a configuration for reading an RFID tag using a balanced transmission line in the prior art. Here, as shown in the upper drawing, the balanced transmission path 21 in the ribbon feeder 20 ′ is connected to the reader 10, and the RFID tag 30 (actually, the RFID tag 30 exists in the vicinity of the ribbon feeder 20 ′ or the like. The data is read by communicating with a leaked electromagnetic wave with a label or a bill including the label.

When the electromagnetic wave output from the reader 10 is input to the power receiving end of the ribbon feeder 20 ′, the electromagnetic wave reaches the end of the ribbon feeder 20 ′ through the balanced transmission path 21. The sensitivity of communication with the RFID tag 30 at a position (distance from the reader 10) x on the cable differs depending on whether the resistor 23 (Z _L ) is present. This is because the communication sensitivity is proportional to the strength (amplitude) of the standing wave generated by the interference between the traveling wave of the electromagnetic wave and the reflected wave of the return.

The strength (amplitude) of the standing wave, that is, the distribution of the communication sensitivity theoretically has a shape as shown in the lower part of FIG. For example, when the cable end is open (Z _L ≈∞) or shorted (Z _L ≈0), the distribution of the standing wave intensity (the distribution of the standing wave of Z _L ≠ Z _{0 in} the figure) is maximum. Periodic distribution is performed so that the value points and the minimum value appear for each half wavelength of the wavelength λ of the electromagnetic wave output from the reader 10. Such distribution has a region where high sensitivity can be obtained from the viewpoint of reading / detection of the RFID tag 30 (near the abdomen of the standing wave (the point where the intensity is maximum)), but the sensitivity is below the sensitivity limit of the reader 10. In the region (near the node of the standing wave (the point where the intensity is the minimum)), a null point (K ₀ in the figure) where the RFID tag 30 cannot be detected is generated, resulting in sensitivity unevenness. .

As a method for eliminating such a null point K ₀ , the resistance value of the terminating resistor 23 (Z _L ) is made the same as the characteristic impedance value (Z ₀ ) of the ribbon feeder 20 ′ (balanced transmission line 21). Theoretically, it is conceivable that the reflected wave is eliminated, that is, only the traveling wave is generated without generating the standing wave. Thereby, theoretically, the intensity (amplitude) can be kept the same (the sensitivity distribution is constant) at any position on the cable (distribution of traveling wave amplitude of Z _L = Z _{0 in} the figure). However, in reality, the standing wave does not disappear, for example, the value of Z ₀ changes due to the influence of the surrounding environment such as the routing of the ribbon feeder 20 ′ and the material of the object placed nearby. As a result, there arises a problem that the null point K ₀ tends to appear.

Therefore, in the RFID tag sensors according to an embodiment of the present invention, with respect to the balanced transmission line, such as one of the ribbon feeder, resistance value generally connect termination resistors Z _0, this starting point of the balanced transmission line And the end point is shifted in advance by approximately λ / 4. This suppresses the generation of standing waves, and even if a standing wave is generated, the phase of the standing waves is shifted between the forward path and the return path of the folded balanced transmission line, and the abdomen and the node are In other words, at a point at an arbitrary distance from the reader, a point where the forward path part and the return path part of the balanced transmission line both become null points (K ₀ ) (null points K ₀ overlap) Can not be.

  Further, in order to facilitate such folding, a mark serving as a mark is displayed at every position of λ / 2 from the starting point of the balanced transmission line. Thereby, when the balanced transmission line is folded and installed, the difference between the phases of the standing wave in the forward path portion and the backward path portion can be easily provided by preventing the marks from overlapping.

FIG. 1 is a diagram showing an outline of a configuration example of an RFID tag sensor according to an embodiment of the present invention. In the present embodiment, as shown in the upper diagram, one balanced transmission line such as a ribbon feeder or the like (a pair of balanced transmission lines 21 is resin with a constant interval W ₁₎ with respect to the reader 10 as in the example of FIG. The balanced transmission path 21 in the RFID tag sensor 20 made of an insulating material such as a ribbon is connected. Further, a termination resistor 23 (Z _L ) is connected to the end of the ribbon feeder, and the resistance value thereof is substantially the same as the characteristic impedance value (Z ₀ ). As described above, since the value of Z ₀ can vary depending on the surrounding environment where the balanced transmission line is installed, it is not necessary to strictly satisfy Z _L = Z ₀ . As described above, when Z _L = Z ₀ , the sensitivity distribution is constant (straight line).

The difference from the example of FIG. 5 is that a balanced transmission line such as a ribbon feeder is used by folding it back near the center. At this time, the start point and the end point of the ribbon feeder are folded back in a state shifted by, for example, Δ ₁ = λ / 4. Thus, even if a standing wave is generated, the distribution of the standing wave intensity in the cable outward path (outward sensitivity curve in the lower diagram of FIG. 5) and the distribution in the cable return path (in FIG. 5). A phase difference is provided to the return path sensitivity curve in the lower diagram so that the abdomen and the node complement each other. That is, at the point of an arbitrary distance x from the reader 10, the higher one of the standing wave intensity (sensitivity at the reader 10) can be used in the cable forward path and the cable return path (sensor sensitivity in the lower diagram of FIG. 5). ), It is possible to avoid that both sensitivities are null points (K ₀ ).

Further, in order to facilitate such folding, a half-wave mark 22 (indicated by ▲ in the figure), which serves as a mark, is displayed by printing, sticker, or the like at each position approximately Δ ₂ = λ / 2 from the starting point of the ribbon feeder. . Accordingly, when the ribbon feeder is folded and installed to form the RFID tag sensor 20, the difference between the standing wave phases of the cable forward path and the cable return path can be easily provided by preventing the half-wave mark 22 from overlapping. Can do. The position of the half-wave mark 22 is the frequency of the electromagnetic wave for reading output from the reader 10 (for example, in air, λ = about 31 cm in the 900 MHz band, λ = about 12 cm in the 2.45 GHz band), Since it depends on a shortening rate (for example, about 60% in the case of a normal insulating resin) proportional to the reciprocal of the square root of the relative dielectric constant of the dielectric forming the ribbon feeder, it is half for each standing wave node pattern. A plurality of patterns may be displayed by changing the shape or color of the mark of the wavelength mark 22.

When the ribbon feeder or the like is folded and used, the balanced transmission path 21 of the cable forward path and the cable return path is folded back with a certain distance between them. That is, as shown in the upper part of FIG. 1, if the distance between the pair of balanced transmission line 21 in the ribbon feeder was W _1, the total width of the balanced transmission line 21 of the two pairs at the time of folding back the ribbon feeder When W ₂ , it is desirable to fold back in a separated state so that W ₂ is about three times W ₁ . If the folded cable return path and the cable return path are too close to each other, the balanced transmission paths 21 interfere with each other and the characteristics change. On the other hand, if they are too far from each other, a space is required for installation. another will not be able to complement the intensity of the standing wave in the, because that will be affected by the null point K _0.

  FIG. 2 is a diagram showing an outline of an example when the RFID tag sensor 20 and the reader 10 are installed on a shelf board. FIG. 2A shows a state where the entire RFID tag sensor 20 is attached to the shelf plate 41 in a state where the RFID tag sensor 20 is folded back on the front thickness portion (the thickness portion of the shelf plate 41). Here, a cable such as a ribbon feeder constituting the RFID tag sensor 20 is cut to an appropriate length according to the width of the shelf board 41, and an appropriate termination resistor 23 (not shown) is attached and used. The reader 10 can be attached to, for example, a shelf side plate 42 as shown in the figure. In this state, as will be described in detail later, for example, an RFID tag 30 (or a label or a tag including the RFID tag 30) attached to a management object (not shown) stored on the shelf board 41 with a string or the like is an RFID tag sensor. By being in a state of being overlaid on 20, this can be read by the reader 10.

  FIG. 2B shows an example where the thickness of the shelf board 41 is thin. In this case, the folded portion of the RFID tag sensor 20 is attached to, for example, the upper surface (or lower surface) side of the shelf board 41. By adopting the shape, the same effect can be obtained. In addition, the shelf board 41 in FIG. 2 (a) (b) may have a metal surface.

  FIG. 3 is a diagram showing an outline of an example of a state in which management objects are stored in a shelf on which the RFID tag sensor 20 and the reader 10 are installed. Each shelf board 41 is provided with the RFID tag sensor 20 on the front thickness part (or the front thickness part and the upper surface or lower surface of the shelf board 41) in the shape shown in the example of FIG. The reader 10 is attached to the side plate 42 of the shelf.

  On each shelf board 41, on the upper stage, for example, a management object 51 on a flat plate equivalent to a metal plate such as a component made of a printed board has a concave cross section (not shown) provided on the shelf board 41. These holding parts are stored in a state where they can be slid left and right on the shelf 41 along guide rails provided in the left and right directions on the shelf 41. Has been. Here, the RFID tag 30 (or a label or a tag including the RFID tag 30) is attached to each managed object 51 by a string or the like on the front side, and the RFID tag 30 is placed on the RFID tag sensor 20. It is in a state.

  In the lower stage, other management objects 52 such as equipment and boxes are stored. Also in these cases, the RFID tag 30 is attached on the RFID tag sensor 20 directly or with a string or the like on the front side. When the RFID tag 30 is attached in this way, each RFID tag 30 (or a label or a tag including the RFID tag 30 or the like) even if the managed objects 51 and 52 are stored in the shelf. It is also easy to confirm visually.

  As described above, since the RFID tag sensor 20 is installed in a folded state, the sensitivity unevenness is suppressed so that a null point is not generated due to the distance from the reader 10, so that each of the management objects 51 and 52 is a shelf. Each RFID tag 30 can be collectively read by the reader 10 at any position in the left-right direction on the plate 41 (that is, at any distance from the reader 10).

  In the above-described example, the RFID tag sensor 20 is configured such that a balanced transmission line such as a ribbon feeder is installed in a state in which the end portion of the balanced transmission path 21 is shifted by λ / 4 from the starting point. It is also possible to configure the whole as a single sheet in a folded state.

  FIG. 4 is a diagram showing an outline of an example in which the RFID tag sensor 20 is configured in a sheet shape. As shown in the figure, the balanced transmission line 21 is not limited to one diffraction as shown in FIG. 1, but is arranged so that the half-wave mark 22 of each folded portion does not overlap (for example, balanced transmission). The folding point in the vicinity of the end of the path 21 is shifted by approximately λ / 4, or the terminal portion is shifted from the starting point by approximately λ / 4), and is integrally formed into a sheet shape by resin, cloth, film, or the like. As a result, it is possible to realize a wide reading area while suppressing sensitivity unevenness so that a null point does not occur. Moreover, when the surface of the shelf board 41 is flat with few irregularities, installation is also easy.

As described above, according to the RFID tag sensor 20 according to an embodiment of the present invention, the RFID tags 30 are collectively recognized within a reachable range by weakly leaking electromagnetic waves using a balanced transmission line such as a ribbon feeder. It becomes possible to do. At this time, with respect to one of the ribbon feeder, resistance value generally connects the terminating resistor 23 of Z _0, which, the shape folded back in a state that generally shifted by lambda / 4 the start and end points of the balanced transmission line To do. As a result, generation of standing waves is suppressed, and even if standing waves are generated, the phase of the standing waves is shifted between the forward path portion and the return path portion of the balanced transmission line, and the null point K ₀ is overlapped. Can not be.

  Further, in order to facilitate such folding, a half-wave mark 22 serving as a mark is displayed approximately every λ / 2 from the starting point of the balanced transmission line. Thus, when the balanced transmission line is folded and installed, the half-wave mark 22 is prevented from overlapping so that a difference can be easily made in the phase of the standing wave in the forward path portion and the backward path portion. In addition, since the RFID tag sensor 20 is configured using a balanced transmission line such as a ribbon feeder, the cable can be cut at an arbitrary length, and then an appropriate termination resistor 23 can be connected so that the return can be flexibly performed. It is possible to flexibly respond to the characteristics of the installation location.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of the above-described embodiment.

  INDUSTRIAL APPLICABILITY The present invention can be used for an RFID tag sensor for reading an RFID tag attached to a plurality of articles stored in a shelf or the like by a reader installed on the shelf and a method for installing the RFID tag sensor.

10 ... reader,
20 ... RFID tag sensor, 20 '... Ribbon feeder, 21 ... Balanced transmission path, 22 ... Half-wave mark, 23 ... Termination resistor,
30 ... RFID tag,
41 ... shelf, 42 ... side plate,
51. Managed object, 52 ... Managed object.

Claims (4)

RFID comprising a balanced transmission line that is connected to a reader device that wirelessly communicates with an RFID tag and reads the contents thereof, and outputs a leaked electromagnetic wave for performing the wireless communication when transmitting the electromagnetic wave output from the reader device A tag sensor,
The balanced transmission line has a pair of balanced transmission lines arranged at a predetermined interval and formed into a ribbon shape by an insulating material, and a termination that is substantially equivalent to the characteristic impedance of the balanced transmission line at the termination of the balanced transmission line An RFID tag sensor to which a resistor is connected and folded in a state in which a terminal portion and a starting point portion are shifted by approximately a quarter of the wavelength of the electromagnetic wave . The RFID tag sensor according to claim 1, wherein
An RFID tag sensor, wherein marks are displayed on the balanced transmission line at intervals of approximately one half of the wavelength from the start point, and the marks are folded back so as not to overlap. An RFID comprising a sheet-like member that is connected to a reader device that wirelessly communicates with an RFID tag and reads the contents thereof, and that outputs a leaked electromagnetic wave for performing the wireless communication when transmitting the electromagnetic wave output from the reader device A tag sensor,
In the sheet-like member, a pair of balanced transmission lines are arranged at a predetermined interval, and a termination resistor substantially equivalent to the characteristic impedance of the balanced transmission line is connected to the termination part of the balanced transmission line, and the termination part and the starting point part preparative in fold returned to a state where substantially displaced by a quarter of the wavelength of the electromagnetic wave are formed into a sheet by insulation material, RFID tag sensor. An RFID tag sensor comprising a balanced transmission line connected to a reader device that wirelessly communicates with an RFID tag and reading the contents thereof, and outputs a leaked electromagnetic wave for performing the wireless communication when transmitting the electromagnetic wave output from the reader device The installation method of
In the balanced transmission line in which a pair of balanced transmission lines are arranged at a predetermined interval and formed into a ribbon shape by an insulating material, a termination resistor substantially equivalent to the characteristic impedance of the balanced transmission line is connected to the termination part of the balanced transmission line And a process of
Said balanced transmission line, and a step of installing the terminal end and the starting point portion returned Ri folded in a state where substantially displaced by a quarter of the wavelength of the electromagnetic wave, a method of installing the RFID tag sensor.

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