JP4265628B2 - Radio tag, article to which radio tag is attached, card to which radio tag is attached, and communication system for radio tag - Google Patents

Description

  The present invention relates to a wireless tag that is used by being attached to an article and can wirelessly communicate information related to an object, an article to which the wireless tag is attached, a card to which the wireless tag is attached, and a communication system for the wireless tag.

A conventional wireless tag is used by being attached to an article, and has an integrated circuit for storing information and an antenna for wireless communication, and reads information from the integrated circuit without contact or updates information on the integrated circuit. It is configured to be able to. For this reason, when a wireless tag is used, production management in a manufacturing process, product management in physical distribution, and the like can be performed. Here, some articles to which the wireless tag is attached, such as those containing metal or moisture, affect the radio waves.
It is known to use a microstrip antenna (also called a patch antenna) with directivity on one side so that the antenna of the wireless tag is not affected by the article when used attached to such metal. Yes. Some conventional microstrip antennas have a dielectric substrate provided on a ground plane ideally at infinity, and a radiation antenna portion made of copper foil is formed on the substrate. The substrate is a dielectric having a relative dielectric constant of 2 to 4 at a resonance frequency of 5.8 GHz, and a thickness of 1 to 4 mm. The ground plane has an area that is equal to or smaller than the area of the antenna section and is set to 20 × 21.82 mm. The antenna portion is disposed 7 mm away from another substrate provided on the vehicle body that is an article (see, for example, Patent Document 1).
JP 2000-31725 A

Here, it is known that the length of the open end that directly contributes to transmission / reception of radio waves at the radiation electrode (antenna portion) is efficient when it is 1/4 of the wavelength λ of radio waves for communication. Furthermore, in order to obtain single-side directivity, it is necessary to make the length of the ground plane (base plate) in the direction perpendicular to the open end larger than the width obtained by adding λ / 10 to the width of the radiation electrode. For this reason, it is difficult to reduce the size of the conventional microstrip antenna.
The present invention has been made in view of such circumstances, and it is a main object of the present invention to provide a wireless tag in which a microstrip antenna is miniaturized and a peripheral device suitable for such a wireless tag.

The invention according to claim 1 of the present invention for solving the above-mentioned problems is a planar radiation electrode having a pair of open ends capable of transmitting and receiving radio waves, a dielectric having the radiation electrode provided on one surface, A planar ground conductor provided on the other surface opposite to one surface of the dielectric, and disposed at a position offset from the center of the radiation electrode, and electrically connected to each of the radiation electrode and the ground conductor And the ground conductor has a length in a direction perpendicular to the open end of greater than 0 and a length as an antenna of 0 dBi or less. Wireless tag.
In this wireless tag, since the ground conductor has a size such that the gain as an antenna is 0 dBi or less, wireless communication is possible in a limited environment.

According to a second aspect of the present invention, in the wireless tag according to the first aspect, the grounding conductor has a length in a direction orthogonal to the open end larger than a length between the open ends, and a length between the open ends. Further, the length is equal to or shorter than 1/20 of the effective wavelength of the radio wave for communication.
In this wireless tag, the size of the ground conductor is smaller than that of the conventional configuration, and the overall size of the wireless tag is small.

According to a third aspect of the present invention, in the wireless tag according to the first aspect, the length of the ground conductor in a direction orthogonal to the open end is larger than 0 and smaller than the length between the open ends. Features.
In this wireless tag, since the ground conductor is smaller than the radiation electrode, it cannot be used alone as an antenna, but wireless communication is possible in a specific environment.

According to a fourth aspect of the present invention, in the wireless tag according to the first aspect, the length of the ground conductor in a direction orthogonal to the open ends is substantially equal to the length between the open ends.
This wireless tag has a minimum size that can be operated by the wireless tag alone by making the ground conductor and the radiation electrode substantially the same size.

The invention according to claim 5 includes the wireless tag according to any one of claims 1 to 4 and a conductor to which the ground conductor side of the wireless tag is fixed, and the conductor is the open-circuit. An article attached with a wireless tag is characterized in that a length in a direction orthogonal to an end is such that when the wireless tag is attached, a gain as an antenna of the wireless tag is 2 dBi or more.
The article to which the wireless tag is attached can wirelessly communicate even if the wireless tag is difficult to communicate by itself using the conductor portion of the article.

According to a sixth aspect of the present invention, in the article to which the wireless tag according to the fifth aspect is attached, the length of the conductor in a direction orthogonal to the open end is longer than the length between the open ends. It is characterized by being 1/10 or more longer than the effective wavelength.
In this article, the use of a wireless tag having a ground conductor having a smaller size than the conventional configuration saves the space for mounting the wireless tag. Furthermore, the degree of freedom of the layout of the mounting position is increased.

The invention according to claim 7 is an article to which the wireless tag according to claim 4 or 5 is attached, and has an adhesive layer that adheres the ground conductor and the conductor of the wireless tag, and the adhesive layer The thickness of is greater than 0 mm and 5 mm or less.
In the article to which the wireless tag is attached, by thinning the adhesive layer, the conductor on the article side and the wireless tag can easily cooperate to improve the gain as an antenna.

According to an eighth aspect of the present invention, in the article to which the wireless tag according to the seventh aspect is attached, the adhesive layer is made of an adhesive or a double-sided tape that detachably bonds the wireless tag and the conductor. And
The article to which the wireless tag is attached can be detached from the article or attached again as necessary.

An invention according to claim 9 includes the wireless tag according to any one of claims 1 to 4 and a card body to which the ground electrode side of the wireless tag is fixed, and the card body A portion to which the wireless tag is fixed is made of a dielectric, and the thickness thereof is greater than 0 mm and not greater than 5 mm.
Since the card to which this wireless tag is attached is difficult to communicate with the wireless tag alone, information can be prevented from being skimmed or tampered with. When it is necessary to exchange information, the wireless tag is used in an environment where communication is possible.

The invention according to claim 10 is used to perform wireless communication with the wireless tag according to any one of claims 1 to 4, and is close to the ground conductor side of the wireless tag. A conductor having a length in a direction perpendicular to the open end and having a gain of 2 dBi or more as an antenna of the wireless tag when the wireless tag is attached, and the wireless disposed adjacent to the conductor The wireless tag communication system includes an antenna that communicates with a tag and a reader / writer that includes a control unit that processes data to be communicated.
In this wireless tag communication system, a conductor is used as a means for bringing a wireless tag into a state where communication is possible from a state where it is difficult to communicate by itself, and the availability of communication is controlled by the positional relationship between the conductor and the wireless tag.

According to an eleventh aspect of the present invention, in the radio tag communication system according to the tenth aspect, the length of the conductor is greater than the length between the open ends in the direction orthogonal to the open ends. It is characterized by being 1/10 or more longer than the wavelength.
This communication system for a wireless tag can perform wireless communication using a small wireless tag.

  According to the present invention, it is possible to reduce the size of the wireless tag as compared with the conventional case by reducing the ground conductor of the wireless tag. Depending on the environment in which the wireless tag is used, communication becomes difficult. By using this, security management can be surely and easily performed.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
As shown in FIGS. 1 and 2, the wireless tag 1 includes an antenna 5 provided with a radiation electrode (conductor patch) 3 and a ground conductor 4 so as to sandwich a substrate 2 made of a dielectric, and the radiation electrode 3 and the ground conductor. 4 and an integrated circuit 6 connected to 4. In FIG. 2, the integrated circuit 6 is disposed on the radiation electrode 3. Such a wireless tag 1 is sometimes called an RFID (Radio Frequency Identification) tag or an IC (Integrated Circuit) tag.

  The radiation electrode 3 is made of a substantially rectangular and planar conductor attached to one surface 2A of the substrate 2. An integrated circuit 6 is attached at a position that passes through the center of the radiation electrode 3 and is offset by a predetermined distance from the center on the axis C1 parallel to the side of the radiation electrode 3. A through hole 7 is formed in the substrate 2 in accordance with the arrangement position of the integrated circuit 6. The through hole 7 penetrates from the one surface 2A on which the radiation electrode 3 is formed to the other surface 2B on the opposite side, and the inside is a conductor layer. Around the through hole 7, there is a removal portion 8 from which the radiation electrode 3 has been removed so that the radiation electrode 3 and the ground conductor 4 are not directly conducted. The ground conductor 4 is connected to the integrated circuit 6 through the through hole 7. The radiation electrode 3 is also connected to the integrated circuit 6. That is, the wireless tag 1 is set on the axis C1 at a position where the connection points 9A and 9b (power supply positions of the integrated circuit 6) to the radiation electrode 3 and the ground conductor 4 are offset from the center of the radiation electrode 3. .

  In the radiation electrode 3, a pair of sides parallel to the axis C1 is an open end 31 that contributes to transmission / reception of radio waves, and its length La is ¼ of the effective wavelength λ of radio waves for communication. The length Lb of the pair of sides 32 orthogonal to the axis C1 is substantially the same length as the open end 31 but does not directly affect communication, and may be shorter than the open end 31. If the side 32 is shortened, the wireless tag 1 can be further reduced in size.

The substrate 2 is manufactured from a dielectric such as glass epoxy or ceramics. The outer shape of the substrate 2 is larger than that of the radiation electrode 3. The length Lc of the pair of sides 22 orthogonal to the axis C1 is greater than or equal to the length of λ / 20 added to both ends of the length Lb of the side 32 of the radiation electrode 3. That is, the distance (difference Db) from the open end 31 of the radiation electrode 3 to the side 21 of the substrate 2 is λ / 20 on both sides.
The ground conductor 4 covers substantially the entire other surface 2B of the substrate 2. For this reason, the ground conductor 4 is longer than the radiation electrode 3 by λ / 20 on one side in the direction orthogonal to the axis C1.

Here, the wireless tag 1 alone is configured such that the sensitivity of the antenna 5 is lower than the practical level. From such a viewpoint, the difference Db is preferably 0 or more and λ / 20 or less. This will be described with reference to FIG.
FIG. 3 shows the calculation result of the difference Db (mm) and the antenna gain in the 2.45 GHz band. The line L1 shows the result of calculation for the case where a glass epoxy material called FR4 (dielectric constant 4.4, thickness 1.6 mmt) is used for the substrate 2. A line L2 indicates a calculation result when a high-frequency substrate called BT (dielectric constant 4.7, thickness 1.6 mmt) is used as the substrate 2.
In the line L1, the gain as an antenna is 0 dBi at a difference P2 (mm) obtained by subtracting the width of the radiation conductor 3 from the width of the ground conductor 4, and the gain as an antenna is 2 dBi at the difference P4. The difference P2 corresponds to λ / 20 and is 6 mm, for example. The difference P4 corresponds to λ / 10 and is, for example, 12 mm.
In the line L2, the gain as an antenna is 0 dBi at a difference P1 (mm) obtained by subtracting the width of the radiation conductor 3 from the width of the ground conductor 4, and the gain as an antenna is 2 dBi at the difference P3. .

The conventional antenna is generally used in a region exceeding 2 dBi which is a practical antenna gain (on the right side from the difference P4 in the line L1 and on the right side from the difference P3 in the line L2). In this embodiment, The line L1 is used in the area of the difference P4 or less, and the line L2 is used in the area of the difference P3 or less.
For example, in the case of the substrate 2 as shown by the line L1, if the difference is smaller than λ / 10 (= about 12 mm), it is less than about 2 dBi which is a generally practical gain of a conventional antenna, but it will be described later. The necessary gain can be ensured by the method. Further, if it becomes λ / 20 or less, the gain becomes 0 dBi or less and it can operate only in a limited environment, but it is preferable from the viewpoint of security maintenance described later. When the difference Db is less than 0 mm, the wireless tag 1 alone does not operate, so the security is further improved.

  Next, the reader / writer 51 of the wireless tag 1 is shown in FIG. The reader / writer 51 has an antenna 52 for communicating with the wireless tag 1 and a main body 53 to which the antenna 52 is connected. The main body 53 is modulated by a memory 55 that holds data, a control unit 56 having a CPU (central processing unit), a modulation unit 57 that modulates data created by the control unit 56 into a signal suitable for wireless communication, and the like. A transmission amplifier 58 that amplifies the signal and emits it from the antenna 52, a reception amplifier 59 that amplifies the radio signal received by the antenna 52, and a demodulator 60 that demodulates the data from the amplified radio signal and passes it to the control unit 56 And have.

FIG. 5 shows how the wireless tag 1 is used. The wireless tag 1 is used by being attached to a conductor 62 included in an article 61 to be managed. The ground conductor 4 is fixed to the conductor 62 via the adhesive layer 65. As the adhesive layer 65, an adhesive or a double-sided tape is used, and has a strength that allows the wireless tag 1 to be removed from the article 61 as necessary. If it is not necessary to collect the wireless tag 1, an adhesive layer 65 that cannot be removed may be formed.
The adhesive layer 65 is preferably thin, but may have a thickness of about 5 mm. The thickness of the conductor 62 is arbitrary, and the length Ld in the direction orthogonal to the axis C1 of the wireless tag 1 is larger by λ / 10 or more on one side than the pair of open ends 31 of the radiation electrode 3. The conductor 62 may be the whole or a part of the component 61 of the article 61, or a metal sheet attached to the article 61. The article 61 to be affixed with the wireless tag 1 is a metal can in which beverages or processed products are housed, or a container for packing the contents with paper or plastic. For example, the conductor 62 may be partially attached.

Here, the result of calculating the relationship between the distance between the ground conductor 4 corresponding to the adhesive layer 65 and the conductor 62 of the article and the gain as an antenna is shown in FIG. A line L3 indicates a calculation result when a glass epoxy material called FR4 (dielectric constant 4.4, thickness 1.6 mmt) is used for the substrate 2. Line L4 shows the result of calculation for the case where a substrate for high frequency called BT (dielectric constant 4.7, thickness 1.6 mmt) is used as the substrate 2.
In the line L3, the gain as an antenna is 2 dBi at a distance P5 (mm), and the gain as an antenna is 0 dBi at a distance P6. The distance P5 is 6 mm, for example, and the distance P6 is 9 mm, for example. In the case shown in the line L3, if it is 5 mm or less, the gain as an antenna is 2 dBi, and when it is attached to the article 61, it can function sufficiently as an antenna.
In line L4, the gain as an antenna is 2 dBi at a distance P7 (mm), and the gain as an antenna is 0 dBi at a distance P8. In the case shown in the line L4, if the distance is equal to or less than P7, the gain as the antenna is 2 dBi, and when it is attached to the article 61, it can sufficiently function as the antenna.

Next, the operation of this embodiment will be described.
First, when the wireless tag 1 is manufactured, the through holes 7 are formed by a drill or the like on a copper-clad laminate in which a copper foil is affixed to both surfaces 2A and 2B of the substrate 2 made of a dielectric. The through hole 7 is electrolessly plated and then copper plated to form a conductor layer in the through hole 7. Thereafter, the pattern of the radiation electrode 3 and the pattern of the removal portion 8 are patterned on one surface 2A by a known exposure technique, and the excess copper foil is chemically etched. As a result, the connection point 9A of the radiation electrode 3 and the connection point 9B around the through hole 7 are formed, and the integrated circuit 6 is joined thereto by soldering or the like.

Since the wireless tag 1 has a small size difference Db between the radiation electrode 3 and the ground conductor 4, the radio wave is not only in the direction indicated by the arrow Y 1 in FIG. Oscillates slightly in the direction indicated by the arrow Y2. As a result, the directivity of the antenna 5 is low with the wireless tag 1 alone, and the radio wave intensity necessary for wireless communication cannot be obtained. Therefore, practical communication, that is, reading and writing of information cannot be performed with the reader / writer 51 even at a distance where wireless communication can be performed with a conventional wireless tag.
On the other hand, as shown in FIG. 5, in the state attached to the article 61, the conductor 62 cooperates with the ground conductor 4 and functions as if it were a ground conductor. To have radiation characteristics. As a result, sufficient radio wave intensity or reception characteristics for wireless communication can be obtained. Therefore, the information stored in the integrated circuit 6 can be read out by the reader / writer 51 and the information of the reader / writer 51 can be stored in the integrated circuit 6 as in the conventional wireless tag.

Here, when the wireless tag 1 becomes unnecessary, the wireless tag 1 is peeled off from the article 61. In a state where the article 61 is away from the conductor 62, that is, in the state shown in FIG. 4, the wireless tag 1 becomes incapable of communication again, so that information on the wireless tag 1 cannot be read. For example, when the article 61 is a can containing drinks, product information, production management, and distribution information are managed by the wireless tag 1 at the manufacturing and distribution stages, and the wireless tag 1 is peeled off when the can is sold to a customer. For example, it is possible to prevent product information, production management, and logistics information from leaking to third parties.
Note that if the wireless tag 1 is attached to the conductor again, wireless communication becomes possible, so that the wireless tag 1 can be reused. The conductor at this time may be the conductor 62 of the article 61 or another conductor.

Furthermore, with reference to FIG. 7, the communication system 70 at the time of inspecting many radio tags 1 or writing initial information will be described. The communication system 70 includes a conveyor device 71 that conveys the wireless tag 1. On the belt 72 of the conveyor device 71, a large number of wireless tags 1 are placed in a line at equal intervals. The belt 72 is made of an insulating material having a thickness of about 5 mm or less, and is arranged so as to move on the base 73. The base 73 is fitted with a conductor plate 74 at one location, and the other regions are made of an insulating material. The length Le of the plate 74 is larger by λ / 10 or more on one side than the length Lb (see FIG. 1) of the pair of open ends 31 when one wireless tag 1 is arranged in the center. In this communication system 70, the length Le is set in a direction parallel to the conveyance direction X of the wireless tag 1. However, when the wireless tag 1 is rotated by 90 °, the length in the direction orthogonal to the conveyance direction X is set. Becomes Le.
Furthermore, the communication system 70 is arranged such that the reader / writer 51 enters an area where the wireless tag 1a arranged on the plate 74 can communicate. Note that when the wireless tag 1a is located in the center of the plate 74, the wireless tags 1 are arranged so that the adjacent wireless tags 1b and 1c do not cooperate with the plate 74 and communicate with the reader / writer 51. The arrangement interval is such that it cannot be maintained.

  When performing inspection or writing of initial information, the conveyor device 71 is driven to convey the wireless tags 1 onto the plate 74 one by one in order. The gain of the antenna 5 of the wireless tag 1 (for example, the wireless tags 1b and 1c) that is away from the plate 74 is low and cannot communicate with the reader / writer 51, whereas the wireless tag 1a on the plate 74 is connected to the plate 74. By cooperation, the gain of the antenna 5 is increased, and communication with the reader / writer 51 is performed. The operation check and the writing of necessary information are performed by the reader / writer 51, and then the wireless tag 1 is moved from the plate 74. By moving away from the plate 74, the gain of the antenna 5 decreases and practical communication with the reader / writer 51 becomes impossible. As a result, the reader / writer 51 does not inspect and write information twice for one wireless tag 1. Then, inspection and writing of information by the reader / writer 51 are performed on the wireless tag 1 newly arranged on the plate 74. When the plate 74 is large and the distance between the wireless tags 1 is sufficiently large, inspection and writing can be performed without stopping the belt 72.

  In this way, since only one wireless tag 1 is always communicable, a large number of wireless tags 1 can be processed in order without interfering with each other. It is not necessary to take measures such as covering other wireless tags 1 with a member that absorbs radio waves, which is effective when handling a large number of wireless tags 1 in a production line of a factory. Note that the plate 74 may be moved instead of moving the wireless tag 1.

  Next, another usage pattern and communication system of the wireless tag will be described with reference to FIG. An object (article) to which the wireless tag 1 is attached is a non-contact type IC card 81 such as a personal authentication card. The card body 82 of the IC card 81 is manufactured from an insulating material, and a fixing portion 83 to which the ground conductor 4 of the wireless tag 1 is attached is recessed. The fixed portion 83 is larger by λ / 10 or more on both sides than the length Lb between the open ends 31 of the radiation electrode 3. Furthermore, the thickness of the fixing | fixed part 83 is 0-5 mm. For the adhesive layer to which the ground conductor 4 is attached, it is preferable to use a layer from which the wireless tag 1 cannot be removed. When the card body 82 is thin, the fixing portion 83 may not be formed in a concave shape. Further, the wireless tag 1 may be sandwiched between the card body 82. The dielectric 21 of the wireless tag 1 may be a card substrate. In this case, the ground conductor 4 may be exposed on the back side of the card. Furthermore, a conductor may be used for a part of the card body 82 (a part that is away from the fixing part 83 and does not affect the function of the wireless tag 1).

  Since the wireless tag 1 has a small grounding conductor 4, the gain of the antenna 5 is low. When the wireless tag 1 is handled as a single IC card 81, the wireless tag 1 can be connected to the reader / writer 51 even at a distance that can be communicated with the conventional wireless tag. In this case, practical communication cannot be performed. Therefore, when communicating with the IC card 81, the communication system 85 is used. The communication system 85 includes a reader / writer 51 and a conductor 86 disposed within the communicable range of the reader / writer 51. The conductor 86 is large enough to place the IC card 81 and is sufficiently larger than the wireless tag 1. When the IC card 81 is placed on the conductor 86 with the grounding conductor 4 side of the wireless tag 1 facing toward the conductor 86, the wireless tag 1 and the conductor 86 cooperate to increase the gain of the antenna 5, thereby enabling wireless communication with the reader / writer 51. Become.

In this way, when the IC card 81 is stored or carried, if the ground conductor 4 side is not in contact with the conductor, information on the wireless tag 1 can be read or written by an external reader / writer. Can not be. Therefore, it is possible to prevent information from being skimmed or tampered with in a situation not intended by the owner. Specifically, practical communication cannot be performed not only when the IC card 81 is in a bag but also in a wallet or a pocket.
In addition, when it is necessary to read and write information, wireless communication can be performed simply by placing it on a conductor 86 such as a metal plate, so that communication control can be easily performed. Therefore, security can be improved when the wireless tag 1 is used. In addition, a communication obstruction member that absorbs radio waves is provided separately, and measures such as covering the wireless tag 1 with the communication obstruction member other than during use are unnecessary.

Thus, the wireless tag 1 of the present embodiment has an antenna gain of 0 dBi or less (specifically, the length of the ground conductor 4 between the open ends 31 of the radiation electrode 3 plus 0 to λ / 20). Since the antenna 5 alone cannot provide a practically sufficient gain, it is possible to increase the gain of the antenna 5 and perform communication by arranging a conductor having a large area on the ground conductor 4 side. . By doing so, it is possible to ensure the necessary antenna sensitivity while reducing the outer shape of the wireless tag 1. Further, since it is not necessary to peel off the ground conductor 4 during use, handling is easy.
Further, since the conductor 62 of the article 61 is formed so that the gain as the antenna of the wireless tag 1 becomes 2 dBi or more when the wireless tag 1 is attached, even if it is difficult to obtain sufficient characteristics with the wireless tag 1 alone. The communication is possible by pasting on the conductor 62 and using it.

  Note that, as in the wireless tag 1d shown in FIG. 9, the wireless tag 1d can be most miniaturized by adopting a configuration in which the lengths of the radiation electrode 3, the ground conductor 4, and the substrate 2 are substantially the same at Lb.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component as 1st Embodiment. Moreover, the description which overlaps with 1st Embodiment is abbreviate | omitted.
As shown in FIGS. 10 and 11, the wireless tag 91 includes an antenna laminate 95 in which the radiation electrode 3 is provided on one surface 92A of a substrate 92 made of a dielectric, and the ground conductor 94 is provided on the other surface 92B. And an integrated circuit 6 attached to the radiation electrode 3 side. The ground conductor 94 has a length Lf in a direction orthogonal to the axis C <b> 1 smaller than a length Lb between the open ends 31 of the radiation electrode 3. In the wireless tag 91, the antenna laminate 95 cannot function as an antenna by itself.

  The wireless tag 91 is used by being attached to a conductor 62 of an article 61 as illustrated in FIG. The conductor 62 has a size such that the length from the open end 31 (the antenna laminate 95) to the periphery of the conductor 62 is larger than λ / 20 when the wireless tag 91 is attached. The wireless tag 91 cannot communicate with the reader / writer 51 until it is attached to the conductor 62 of the article 61. By being attached to the conductor 62, wireless communication becomes possible.

  When inspecting or writing initial information, it is performed while conveying a large number of wireless tags 91 by a conveyor device 71 of the communication system 70 as illustrated in FIG. The antenna laminate 95 of the wireless tag 91 can only transmit and receive radio waves when placed on the conductor plate 74, and cannot transmit or receive radio waves at other positions. For this reason, information is not written to other than the target wireless tag 91, and the wireless tags 91 do not interfere with each other.

  Further, when the IC card 81 is used as an IC card 81 such as a personal authentication card as illustrated in FIG. 8, the antenna laminate 95 does not function as an antenna by itself, so that communication is performed even when the reader / writer 51 is brought close. It cannot be done and security is high. When the IC card 81 is disposed on the conductor 86 with the ground conductor 94 of the antenna laminate 95 facing the conductor 86 as in the communication system 85, the antenna laminate 95 and the conductor 86 cooperate to provide a practical antenna. Thus, communication can be performed.

According to this embodiment, the ground conductor 94 is smaller than the length between the open ends 31 of the radiation electrode 3, and the conductor having a large area is arranged on the ground conductor 94 side, thereby functioning as an antenna. For this reason, it is possible to further reliably prevent unintended communication while reducing the outer shape of the wireless tag 91.
Further, since the conductor 62 of the article 61 is formed so that the gain of the wireless tag 91 as an antenna becomes 2 dBi or more when the wireless tag 91 is attached, even if it is difficult to obtain sufficient characteristics with the wireless tag 91 alone. The communication is possible by pasting on the conductor 62 and using it.

  Note that the present invention can be widely applied without being limited to the above-described embodiment. The manufacturing method of the wireless tags 1 and 91 and the material to be used are not limited to the embodiment. In addition, the article to which the wireless tags 1 and 91 are attached may be an article used for another shape or application.

It is a top view which shows the structure of the wireless tag which concerns on embodiment of this invention. It is a side view of the wireless tag shown in FIG. It is the graph which calculated the relationship between the difference of the length of a radiation electrode and a ground conductor, and the gain as an antenna. FIG. 4 is a diagram illustrating a configuration of a reader / writer and explaining that the reader / writer cannot communicate with a single wireless tag. FIG. 4 is a diagram illustrating an example of an article to which a wireless tag is attached and explaining that the wireless tag attached to the article and a reader / writer can communicate with each other. It is the graph which calculated the relationship between the distance between a ground conductor and the conductor of goods, and the gain as an antenna. It is a figure explaining an example of the inspection process of a wireless tag, and explaining that only the wireless tag on a plate can communicate with a reader / writer. It is a figure explaining an example of an IC card to which a wireless tag is attached and explaining that communication with a reader / writer is possible only when the IC card is placed on a plate. It is a side view which shows the structure of the radio | wireless tag in which the length of a radiation electrode and a ground electrode is substantially equal. It is a top view which shows the structure of the radio | wireless tag in which a ground electrode is smaller than a radiation electrode. It is a side view of the wireless tag shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1d, 91 Wireless tag 2,92 Board | substrate 3 Radiation electrode 4,94 Ground electrode 6 Integrated circuit 31 Open end 51 Reader / writer 52 Antenna 53 Control part 61 Article 62, 74, 86 Conductor 70 Communication system 81 IC card 83 Fixed part C1 axis Lb length (length between open ends)
Lc, Lf Length (Grounding conductor length)
Ld, Le length (conductor length)

Claims (3)

Wireless tag
A flat rectangular radiation electrode in which a pair of parallel sides formed at a length of ¼ of the effective wavelength of a radio wave for communication is an open end for transmitting and receiving the radio wave,
A dielectric provided with the radiation electrode on one surface;
A planar ground conductor provided on the other surface opposite to one surface of the dielectric;
An integrated circuit disposed at a position offset from the center of the radiation electrode and electrically connected to each of the radiation electrode and the ground conductor;
The ground conductor has a length such that the projected length of the radiation electrode is greater than 0, and the antenna gain is 0 dBi or less,
A card body to which the ground conductor side of the wireless tag is fixed;
A card to which a wireless tag is attached, wherein a portion of the card body to which the wireless tag is fixed is made of a dielectric, and the thickness is greater than 0 mm and 5 mm or less. It is used for performing wireless communication with the wireless tag in the card according to claim 1 ,
A conductor disposed close to the ground conductor side of the wireless tag;
A reader / writer having an antenna that communicates with the wireless tag disposed close to the conductor and a control unit that processes data to be communicated;
A communication system for a wireless tag, comprising: 3. The wireless tag according to claim 2 , wherein a length of the conductor projected on the radiation electrode is 1/10 or more of an effective wavelength of a radio wave for communication than a distance between the pair of sides. Communication system.

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