JP2004238195A - Antenna device for ic tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely discriminate an IC tag T inside a work W on a conveyor line L. <P>SOLUTION: A gate-shape frame body 10 is provided with a shielding wire net 15 and a shielding magnetic shield plate 17 in a front surface side and a rear surface side thereof, and a receiver antenna 21 and a transmitter antenna 22 are arranged. A reader-writer connected to the transmitter antenna 22 receives the data from the IC tag T through at least one of the receiver antenna 21 and the transmitter antenna 22 to read it. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an antenna device for an IC tag used for accurately recognizing an arbitrary article with an IC tag on a conveyor line.
[0002]
[Prior art]
Using a portal-type antenna device to attach or incorporate a non-contact IC tag (including an IC card or IC chip, the same applies hereinafter) to an article and to recognize the article being conveyed via a conveyor line. There is.
[0003]
This is to exchange data by wireless communication between the IC tag on the article side and the reader / writer by attaching the transmission / reception antenna to the inner side of the frame that straddles the conveyor line and connecting the transmission / reception antenna to the reader / writer. Can be. The transmitting / receiving antenna is electromagnetically or inductively coupled to the antenna on the IC tag side to supply power for activating the IC chip in the IC tag and to realize bidirectional data communication by a load modulation method. it can. In addition, the transmitting and receiving antenna resonates with the antenna on the IC tag side at a frequency used by the IC tag, for example, 13.56 MHz.
[0004]
[Problems to be solved by the invention]
In the case of the conventional technology, the transmitting and receiving antenna has a radio wave of a necessary and sufficient high power in consideration of the fact that the size of the article on the conveyor line fluctuates or that the IC tag is housed inside the article. In the reader / writer, there is a problem that the data cannot be read from the IC tag due to the restriction of the dynamic range, or the intensity of the electric field leaking to the outside becomes excessive on the reader / writer side. .
[0005]
Therefore, an object of the present invention is to improve the stability of data reading by providing a receiving antenna and strengthening the shield for the transmitting antenna in view of the problem of the related art, and to sufficiently reduce the electric field intensity leaking to the outside. An object of the present invention is to provide an antenna device for an IC tag that can be reduced in size.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a configuration of the present invention includes a gate-shaped frame body through which articles on a conveyor line pass, a wire mesh for shielding provided on a front side and a rear side of the frame body, and a magnetic shield for shielding. The gist of the present invention is to provide a plate, a wire mesh, and a receiving antenna and a transmitting antenna disposed on the inner surface side of the magnetic shield plate, respectively.
[0007]
The transmitting antenna can be a loop antenna arranged in parallel with a gap with respect to the magnetic shield plate, and the receiving antenna can be a loop antenna arranged in parallel with a gap with respect to the wire mesh. it can.
[0008]
The magnetic shield plate may be made of either a ferrite material or a magnetic sheet material, and the wire mesh may be combined with a reinforcing transparent plate.
[0009]
[Action]
According to the configuration of the present invention, the transmitting antenna supplies power to the IC tag attached to or incorporated in the article being conveyed via the conveyor line to activate the IC chip in the IC tag, and to transmit the power to the IC tag. While transmitting data, the receiving antenna can receive the radio wave from the transmitting antenna and properly receive the data from the IC chip superimposed on the radio wave from the transmitting antenna by the load modulation method. It is assumed that the reception antenna receives radio waves from the transmission antenna while squeezing the radio wave to a sufficiently low level. Further, both the transmitting antenna and the receiving antenna are connected to a reader / writer, and the reader / writer is configured to use an IC chip based on data from the receiving antenna only or based on data from at least one of the transmitting antenna and the receiving antenna. The data from shall be read. That is, the transmitting antenna is operated substantially as a transmitting / receiving antenna, and resonates with the receiving antenna at the frequency used by the IC tag.
[0010]
On the other hand, the wire mesh on the front side of the frame body can be seen through, and the articles being conveyed on the conveyor line can be visually observed from the outside. It is preferable that the mesh of the wire mesh is about λ / 100 or less with respect to the wavelength λ of the operating frequency of the IC tag. Further, the magnetic shield plate on the rear side of the frame body prevents radio waves from the transmitting antenna from projecting only to the front side to prevent leakage to the rear side, and a moving object (including a human body) approaching outside the rear side. ), The so-called body effect can be reduced. However, as a magnetic shield plate, a large amount of magnetic powder is mixed with a ferrite material or a magnetic sheet material (a flexible sheet material such as plastic or rubber) which has a small loss at the operating frequency of the IC tag and a sufficiently high magnetic permeability. (Hereinafter the same).
[0011]
The transmission antenna and the reception antenna are loop antennas that are arranged parallel to the magnetic shield plate and wire mesh with a gap between them, so that they do not protrude mechanically excessively on the conveyor line. There is no risk of extreme deterioration. However, it is preferable that the gap between the transmission antenna and the magnetic shield plate and the gap between the reception antenna and the wire net are respectively 2 cm or more and 5 cm or more with respect to the use frequency of 13.56 MHz of the IC tag.
[0012]
If a transparent plate is combined with a shielding wire mesh, the mechanical strength of the wire mesh can be increased, and erroneous reading of data due to vibration of a receiving antenna or the like can be avoided. Note that the transparent plate is provided in close contact with the wire mesh and provided on one or both sides of the wire mesh. Further, the wire mesh may be formed on a transparent plate by printing or etching.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
[0014]
An antenna device for an IC tag includes a gate-shaped frame body 10 through which an article W on a conveyor line L passes, a shielding wire mesh 15 attached to the front side and the rear side of the frame body 10, and a magnetic shield for shielding. The plate 17, the wire mesh 15, and the receiving antenna 21 and the transmitting antenna 22 disposed on the inner surface side of the magnetic shield plate 17, respectively, are main members (FIGS. 1 and 2). However, a structural iron plate 16 is combined with the outer surface side of the magnetic shield plate 17.
[0015]
The conveyor line L can convey any article W containing a non-contact type IC tag T (in the direction of the arrow in FIG. 1). Here, as the article W, for example, a desk-type gaming machine is illustrated.
[0016]
The frame body 10 includes a pair of pillars 11, 11... Erected on both right and left sides of the conveyor line L, upper members 12, 12, 13, 13 connecting the upper ends of the pillars 11, 11,. The lower members 14, 14 connecting the lower ends of the two pillars 11, 11 are combined along L, and are installed so as to straddle the conveyor line L. An adjuster screw 11a for height adjustment is attached to the lower end of each column member 11. The top surface of the frame body 10 is closed by, for example, a transparent plate 18.
[0017]
The wire mesh 15 on the front side is, for example, a stainless wire mesh of 5 mm mesh, and four circumferences are fixed by the pillars 11, 11, the upper material 13, and the lower material 14. Note that a transparent plate 15a such as an acrylic plate can be combined on one surface on the outer surface side or on both inner and outer surfaces of the wire mesh 15 (FIGS. 3A and 3B). However, the wire mesh 15 may be formed by printing with conductive ink on the surface of one of the transparent plates 15a, or may be formed by etching a metal conductor on the transparent plate 15a.
[0018]
The iron plate 16 on the rear side is fixed via pillar members 11, 11, an upper member 13, and a lower member 14 (FIGS. 1 and 2). The magnetic shield plate 17 is a ferrite material or a magnetic sheet material, and is provided in close contact with the inner surface side of the iron plate 16 (FIG. 3C).
[0019]
The receiving antenna 21 is a loop antenna that resonates at the frequency used by the IC tag T (FIGS. 1 and 2). The receiving antenna 21 is disposed on the inner side of the wire mesh 15 in parallel with the wire mesh 15 with a gap d1 therebetween via a spacer (not shown). The transmission antenna 22 is a loop antenna that resonates at the frequency used by the IC tag T, and is disposed on the inner side of the magnetic shield plate 17 in parallel with the magnetic shield plate 17 with a gap d2 therebetween. Note that the area of the wire net 15 is sufficiently larger than the opening area of the receiving antenna 21, and the areas of the iron plate 16 and the magnetic shield plate 17 are each sufficiently larger than the opening area of the transmitting antenna 22.
[0020]
The receiving antenna 21 and the transmitting antenna 22 are individually connected to the reader / writer 23 (FIG. 4). Note that an IC chip C is mounted on the IC tag T in the article W.
[0021]
When the reader / writer 23 is operated via the conveyor line L while the article W containing the IC tag T is being conveyed, electric power is supplied to the IC chip C on the IC tag T by a radio wave from the transmission antenna 22, and the IC chip C Can be activated. At this time, the reader / writer 23 can send necessary data D1 to the IC chip C.
[0022]
On the other hand, the data D2 from the IC chip C is transmitted to the reader / writer 23 as an equivalent impedance change signal of the transmission antenna 22 by the load modulation method and is read. That is, the transmitting antenna 22 operates as a transmitting and receiving antenna. At this time, the receiving antenna 21 receives a part of the radio wave from the transmitting antenna 22 and sends it to the reader / writer 23. Therefore, the reader / writer 23 can also read the data D2 from the IC chip C by analyzing the level change signal from the receiving antenna 21.
[0023]
Generally, when the radio wave from the transmitting antenna 22 has a large power, it is difficult for the reader / writer 23 to read the load modulation signal based on the data D2 from the IC chip C, that is, the equivalent impedance change signal. However, even in this case, the data D2 from the IC chip C can be stably read through the reception antenna 21 by reducing the reception level of the reception antenna 21. That is, the reader / writer 23 can read the data D2 more accurately by calculating the logical sum of the data D2, D2 obtained via the transmission antenna 22 and the reception antenna 21. However, the reader / writer 23 may read only one of the data D2 and D2 obtained via the transmission antenna 22 and the reception antenna 21.
[0024]
In the above description, the iron plate 16 supporting the magnetic shield plate 17 may be omitted, or may be replaced with any other structural material having a low magnetic permeability. However, at this time, the column members 11, 11, the upper member 13, and the lower member 14 surrounding the four circumferences of the magnetic shield plate 17 electrically insulate at least one connection portion, or reduce at least one member to two or more. The division is performed so that an electric loop is not formed by division. This is because the loop close to the transmission antenna 22 functions as a cancel coil and extremely deteriorates the radiation efficiency of the transmission antenna 22.
[0025]
According to the present invention, since the data D2 from the IC chip C is read by the reader / writer 23 via at least one of the transmission antenna 22 and the reception antenna 21, the transmission antenna 22, the reception antenna 21, and the IC chip C The reading performance of the data D2 from the IC chip C can be stably maintained even if the coupling strength of the data changes. That is, when a plurality of types of articles W, W... Are mixed and conveyed on the conveyor line L, even when the place where the IC tag T is built in or attached to each article W is not constant, each article W Can be reliably identified.
[0026]
【The invention's effect】
As described above, according to the present invention, the reception antenna and the transmission antenna are provided inside the gate-shaped frame body, and the magnetic shield plate is provided on the rear surface side of the frame body, so that the transmission antenna is provided. Since the data from the IC tag can be read through the receiving antenna, the reading stability of the data can be greatly improved, and the intensity of the electric field leaking outside through the magnetic shield plate can be sufficiently reduced. There is an excellent effect that harmful body effects can be reduced.
[Brief description of the drawings]
1 is an overall perspective explanatory view; FIG. 2 is a sectional view corresponding to the line XX in FIG. 1; FIG. 3 is an enlarged sectional explanatory view of a main part; FIG. 4 is an electric system diagram;
W: Article L: Conveyor lines d1, d2: Gap 10: Frame body 15: Wire mesh 15a: Transparent plate 17: Magnetic shield plate 21: Receiving antenna 22: Transmitting antenna

Claims (5)

A gate-shaped frame body that allows articles on the conveyor line to pass therethrough, a wire mesh for shielding provided on the front side and a rear side of the frame body, a magnetic shield plate for shielding, and inner sides of the wire mesh and the magnetic shield plate An antenna device for an IC tag, comprising: a receiving antenna and a transmitting antenna respectively disposed in the antenna. The antenna device for an IC tag according to claim 1, wherein the transmitting antenna is a loop antenna that is arranged in parallel with the magnetic shield plate with a gap therebetween. The antenna device for an IC tag according to claim 1 or 2, wherein the receiving antenna is a loop antenna that is disposed parallel to the wire netting with a gap therebetween. The antenna device for an IC tag according to any one of claims 1 to 3, wherein the magnetic shield plate is made of one of a ferrite material and a magnetic sheet material. The antenna device for an IC tag according to any one of claims 1 to 4, wherein the wire mesh is combined with a reinforcing transparent plate.

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