JP2006101109A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device which is made to be lightweight, is low cost and excellent in productivity, and has less variation in resonant frequency and less loss. <P>SOLUTION: The antenna device 1 in an RFID system for performing non-contact data communication has a configuration in which a planar soft magnetic body 5 is provided between the antenna and a metal surface of a back surface. In this antenna device 1, a through hole is provided on the center of the soft magnetic body 5 to realize lightweight and the influence of an eddy current to be generated in the metal of the back surface is suppressed to improve communication characteristics. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, the conventional RFID antenna has a function of reading the information of the IC tag by sending a radio wave to the IC tag in the band of 13.6 MHz, but the metal shelf or the electrolytic substance that affects the magnetic field on the back of the IC tag or the RFID antenna. There was a problem that the communication characteristics would be significantly worse if there was.

  The present invention uses a low-loss (Hi-Q) magnetic material on the back surface of the RFID antenna when the IC tag is used even if there is a metal or an electrolyte that affects the magnetic field on the back surface of the IC tag or the RFID antenna. The present invention relates to a magnetic body for improving communication characteristics and relates to the structure of the magnetic body for shielding the influence of the magnetic field on the back surface as much as possible against eddy current generation, and to an antenna device including the magnetic body.

  In recent years, RFID systems that perform data communication between a transponder provided with an IC chip and a reader / writer (or writer) have become widespread. Since this RFID system performs data communication using the antennas provided in each of the transponder and the reader / writer, communication is possible even if the transponder is several centimeters to several tens of centimeters away from the reader / writer. Due to its strength against static electricity, it has come to be used in various fields such as hospital medicine management, library book management, factory production management, logistics management, and entrance / exit management.

As an antenna used for the reader / writer and the transponder of such an RFID system, an air-core coil has been conventionally used because it is inexpensive and has excellent performance. As an antenna of this air-core coil, for example, as shown in (Patent Document 1), a conductor wire covered with an insulating layer is spirally wound and attached to a base plate, or deposited on a base plate A metal foil such as an aluminum foil or a copper foil that has been formed by etching is known.
JP-A-4-321190

  However, in the above-described air core coil antenna, magnetic flux is generated in a direction penetrating the base plate. Therefore, when the antenna coil is brought into close contact with a metal article, the magnetic flux penetrates the base plate to the metal article. As a result, an eddy current is generated in the metal, and there is a problem that the resonance frequency of the resonance circuit formed by the antenna coil and the capacitor changes or the loss increases. That is, the carrier wave (AC magnetic field) that supplies power to the tag and the modulated data signal superimposed on the carrier wave are canceled out by the demagnetizing field Hd component induced on the metal surface and greatly attenuated. . For this reason, there is a problem that the communication distance is shortened and the function of the RFID system is not performed.

In particular, in the case of a reader / writer, unlike a transponder, many electronic circuits such as a circuit for driving the reader / writer, a control circuit, and a power source are necessary. Since a large amount of material is contained, the reader / writer antenna is easily affected by these metal materials, and the change in resonance frequency and increase in loss are likely to increase. For this reason, the conventional reader / writer uses a structure in which the antenna and the electronic circuit are housed in different cases and connected between them with a cable. However, such a structure is inconvenient in use because the case of the electronic circuit and the case of the antenna must be separated each time the device is carried and connected by a cable each time it is used. Also, when carrying, it is desirable to make the case made of metal such as iron, aluminum, magnesium, etc., and to make it small and strong, but if the antenna of the air-core coil is placed in contact with the case, the resonance frequency changes and The increase in loss is significant. Even if the case is made of plastic, the loss of the coil may be significant if there is a vapor deposition film such as aluminum or if the filler or coating layer contains a metal such as aluminum flakes.

  Further, as means for solving the above problem, a flat soft magnetic material 104 is provided between the antenna pattern 102 of the reader / writer antenna in the RFID system shown in FIG. 8 and a conductive article such as a metal case. Has been devised. In this way, by interposing the soft magnetic body 104 between the antenna pattern 102 and a conductive article such as a metal case, the magnetic flux generated in the antenna pattern 102 is passed through the soft magnetic body 104 and the vortex generated in the metal. It is possible to suppress a change in resonance frequency and an increase in loss due to current.

  However, the RFID system is required to be reduced in weight, and there is a problem that the weight of the RFID system is increased by installing the soft magnetic body 104 on the back surface of the antenna pattern 102. In particular, when the soft magnetic material is made of a material such as an alloy such as ferrite, amorphous, or sendust, this problem becomes particularly noticeable.

  When the weight of the RFID system increases, the weight of the RFID system attached article increases, which is an obstacle to movement and installation.

  The present invention relates to an antenna device in an RFID system that performs non-contact data communication, and in a structure in which a flat soft magnetic body is provided between an antenna and a metal surface on the back side, the central portion of the soft magnetic body is penetrated. The structure is provided with holes.

According to the present invention, in the antenna device in the RFID system, since the through hole or the concave portion is formed in the central portion of the soft magnetic body between the antenna and the metal surface on the back surface, the magnetic flux generated by the antenna coil is generated by the soft magnetic body. Further, while suppressing changes in resonance frequency and increase in loss due to eddy currents generated in the metal on the back surface, weight reduction can be realized by the amount of through holes or recesses formed. For example, in the case of ferrite, the specific gravity is 5 to 5.5 g / cm ³ , and if a through hole or a recess is formed, the weight of the volume is reduced, which is effective in reducing the weight of the RFID system.

  Further, by adopting a structure in which a through hole or a recess is provided in the central portion, the material of the soft magnetic material can be reduced, and the cost can be reduced.

  In addition, the strength of the soft magnetic material can be maintained by filling the through hole or the recess provided in the central portion with a lightweight member such as resin.

  With the above structure, the RFID system can be reduced in weight, and a communication distance can be secured while suppressing a change in resonance frequency and an increase in loss due to an eddy current generated in the metal on the back surface.

  The invention according to claim 1 of the present invention is an antenna device in an RFID system that performs data communication in a non-contact manner, wherein a flat soft magnetic material is provided between the antenna and a metal surface on the back surface. An antenna device characterized in that a through-hole is provided in the center of a soft magnetic material, which reduces the weight of the RFID system, and changes in resonance frequency and increase in loss due to eddy currents generated in the metal on the back The communication distance can be secured while suppressing the above.

  The invention according to claim 2 of the present invention is an antenna coil constituted by a loop of one turn or more in a plane, wherein a flat soft magnetic material is provided between the antenna and the back metal surface. The antenna device according to claim 1, wherein a through hole is provided in a central portion of the soft magnetic material in the provided configuration, wherein the RFID system is reduced in weight and is generated in the metal on the back surface. The communication distance can be secured while suppressing the change of the resonance frequency and the increase of the loss due to the eddy current.

  The invention according to claim 3 of the present invention is the antenna device according to claim 1 or 2, wherein the number of through holes provided in the central portion of the soft magnetic material is one or more. The weight of the soft magnetic material can be reduced, and the use of a plurality of through holes can prevent the strength of the soft magnetic material from being lowered.

  The invention according to claim 4 of the present invention is the antenna device according to claim 1, wherein a concave portion is provided on one side of the central portion in the soft magnetic material, and the antenna device is provided on one side of the central portion. By adopting a configuration in which the concave portion is provided, the weight of the soft magnetic material can be reduced, and the central portion is a concave portion, so that a part of the soft magnetic material has a continuous structure on a plane and can prevent a decrease in strength. .

  The invention according to claim 5 of the present invention is the antenna device according to claim 4, wherein in the soft magnetic material, the number of concave portions provided on one side of the central portion is one or more. The weight of the soft magnetic material can be reduced, and the strength can be prevented from decreasing.

  The invention according to claim 6 of the present invention is the antenna device according to claim 1 or 2, wherein the soft magnetic body is provided with recesses on both sides of the central portion. And reduction in strength can be prevented.

  The invention according to claim 7 of the present invention is the antenna device according to claim 6, characterized in that in the soft magnetic material, the number of concave portions provided on both surfaces of the central portion is one or more. The weight of the soft magnetic material can be reduced, and the strength can be prevented from decreasing.

  In the invention according to claim 8 of the present invention, in the soft magnetic material, the central portion where the through-hole and the concave portion are provided is located on the inner side of the installation surface of the antenna coil in the plane of the RFID system. The antenna device according to any one of claims 1 to 7, wherein a central position where the through-hole and the concave portion are provided is located on an inner side than an installation surface of the antenna coil, so that the metal on the back surface of the antenna coil While suppressing a change in resonance frequency and an increase in loss due to an eddy current generated in the inside, it is possible to secure a communication distance and to reduce the weight of the soft magnetic material.

  According to a ninth aspect of the present invention, in the soft magnetic material, the shape of the through hole provided in the center is a triangle or more polygon, circle, or ellipse. Any one of the antenna devices described above can reduce the weight of the soft magnetic material and can form through holes of various shapes, so that it can be used for various antenna patterns, improving productivity and reducing costs. Yes.

  According to a tenth aspect of the present invention, in the soft magnetic material, the shape of the concave portion on one or both sides provided in the center is a triangle or more polygon, circle, or ellipse. 9. The antenna device according to any one of claims 8 to 8, wherein the soft magnetic material can be reduced in weight and through holes having various shapes can be formed, so that various antenna patterns can be handled, productivity is improved, and cost is low. It can also be adapted.

The invention according to claim 11 of the present invention is characterized in that the soft magnetic material is any one of amorphous alloy, permalloy, electromagnetic steel, silicon iron, Fe-Al alloy, Sendust alloy, or soft magnetic ferrite. 11. The reader / writer antenna according to claim 1, wherein the communication is performed while efficiently suppressing a change in resonance frequency and an increase in loss due to an eddy current generated in the metal on the back surface of the antenna coil. A distance can be secured.

  According to a twelfth aspect of the present invention, the soft magnetic material is a magnetic sheet in which a metal oxide is mixed with a resin binder and coated, and dried sheets are laminated. The antenna device according to any one of Items 11 to 11, wherein a soft magnetic body that is flexible and resistant to impact can be manufactured, and further, the weight can be reduced.

  According to a thirteenth aspect of the present invention, the soft magnetic material is a soft magnetic ferrite, and the ferrite powder is formed into a bulk shape by dry molding and firing. The antenna device according to any one of the above, can be reduced in weight with a soft magnetic material excellent in productivity.

  The invention according to claim 14 of the present invention is the antenna device according to any one of claims 1 to 10, characterized in that the soft magnetic material is an amorphous foil or a laminated material of an amorphous foil. It is a soft magnetic material that is resistant to weight and can be reduced in weight.

  According to a fifteenth aspect of the present invention, in the soft magnetic material, a non-magnetic material such as a resin is formed in a through hole provided in the central portion of the soft magnetic material, or in a concave portion provided on one or both surfaces of the central portion of the soft magnetic material. The antenna device according to any one of claims 1 to 14, wherein a soft magnetic material is filled with a non-magnetic material such as a resin in a through-hole or a concave portion of the soft magnetic material. The strength can be maintained while reducing the weight of the magnetic material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
1 is an antenna device showing the internal structure of the RFID system, 2 is a resin case (main body), 3 is an antenna pattern formed on an antenna substrate, 4 is a matching circuit, 5 is a soft magnetic material, 6 is a resin spacer, 7 Is a metal plate, and 8 is a resin case (back cover).

  First, in the structure of the antenna device 1, the features and effects of the structure shown in each figure will be briefly described.

  FIG. 1A shows a perspective view of an antenna device in an exploded state according to an embodiment of the present invention. A soft magnetic body 5 is disposed below the antenna substrate on which the antenna pattern 3 and the matching circuit 4 are formed. A resin spacer 6 and a metal plate 7 are installed below the soft magnetic body 5. The above components are housed in a resin case (main body) 2 and a resin case (back cover) 8. A through-hole is provided in the center of the soft magnetic body 5 to reduce the weight of the RFID system, while suppressing changes in resonance frequency and increase in loss due to eddy currents generated in the metal on the back surface. There is an effect that a communication distance can be secured. FIG. 1B shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 1C shows a side view of the soft magnetic material in the embodiment of the present invention. FIG. 1D shows a perspective view of the soft magnetic material in the embodiment of the present invention.

  FIG. 2A shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 2B shows a side view of the soft magnetic material in the embodiment of the present invention. FIG. 2C is a perspective view of the soft magnetic material in the embodiment of the present invention. With this structure, the weight of the soft magnetic material can be reduced, and since the central portion is the concave portion 10, a part of the soft magnetic material becomes a continuous structure on a flat surface, thereby preventing a decrease in strength.

  FIG. 3A shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 3B shows a side view of the soft magnetic material according to the embodiment of the present invention. FIG. 3C shows a perspective view of the soft magnetic material in the embodiment of the present invention. With this structure, the weight of the soft magnetic material can be reduced, and both sides of the central portion are concave portions, so that a part of the soft magnetic material becomes a continuous structure on a plane and the strength can be prevented from being lowered.

  FIG. 4A shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 4B shows a side view of the soft magnetic material in the embodiment of the present invention. FIG. 4C shows a perspective view of the soft magnetic material in the embodiment of the present invention. With this structure, the strength can be maintained while reducing the weight of the soft magnetic material.

  FIG. 5A shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 5B shows a side view of the soft magnetic material in the embodiment of the present invention. FIG. 5 (c) shows a perspective view of the soft magnetic material in the embodiment of the present invention. With this structure, it is possible to reduce the weight of the soft magnetic material and to cope with various antenna patterns.

  FIG. 6A shows a top view of the soft magnetic material in the embodiment of the present invention. FIG. 6B shows a side view of the soft magnetic material in the embodiment of the present invention. FIG. 6C shows a perspective view of the soft magnetic material in the embodiment of the present invention. The soft magnetic body 22 has a structure in which two or more layers of soft magnetic bodies 17 are laminated. Reference numeral 16 denotes a joint portion where the soft magnetic bodies 17 are laminated. With this structure, the weight of the soft magnetic material can be reduced and the thickness can be reduced.

  FIG. 7A shows a cross-sectional view of an antenna device according to the prior art. FIG. 7B shows a cross-sectional view of the antenna device according to the embodiment of the present invention. Even if through holes are formed in the soft magnetic material, the magnetic field strength does not decrease, and a communication distance can be secured. Further, it is possible to maintain an effect of suppressing a change in resonance frequency and an increase in loss due to an eddy current generated in the metal on the back surface.

  The above is an outline of the structure of each drawing and the points thereof.

  Next, the detail of each part is demonstrated.

  Reference numeral 1 denotes an antenna device showing the internal structure of an RFID system. As shown in FIG. 1 and the like, a resin case (main body) 2, an antenna pattern 3 formed on an antenna substrate, a matching circuit 4, a soft magnetic material 5, a resin spacer 6, a metal plate 7, and a resin case (back cover) 8.

  Reference numeral 3 denotes an antenna pattern having a loop antenna structure. The loop antenna may have a loop shape with an opening at the center, and the shape may be circular, substantially rectangular, or polygonal. Furthermore, the material of the loop antenna can be appropriately selected from conductive metal wire, metal plate, metal foil, metal cylinder, and the like.

  4 shows a matching circuit. By connecting the matching circuit 4, it is less likely to be affected by the antenna characteristics due to the metal around the installation site, and the occurrence of standing waves due to mismatching is suppressed. The antenna has a stable operation and a small loss.

Reference numeral 5 denotes a soft magnetic material, and the soft magnetic material 5 is disposed on the back surface of the antenna pattern 3 and includes soft magnetic ferrite, amorphous alloy, permalloy, electromagnetic steel, silicon iron, Fe-Al alloy, Sendust alloy, and the like. Can be used. As the shape of the soft magnetic material, for example, in the case of ferrite, a plate shape or a sheet shape can be used. The sheet-like ferrite can be produced by kneading ferrite powder in an organic binder such as a resin material and drying it. By using a magnetic sheet, flexibility can be ensured and impact resistance and durability can be improved. Reference numeral 9 denotes a through hole provided in the central portion of the soft magnetic body 5. By providing the through hole, the weight can be reduced.

  18 shows a soft magnetic material according to another embodiment of the present invention, in which a concave portion 10 is formed on one surface of the central portion. With this structure, the weight of the soft magnetic material can be reduced and the strength can be maintained.

  Reference numeral 19 denotes a soft magnetic material according to another embodiment of the present invention, in which concave portions 11 are formed on both surfaces of the central portion. With this structure, the weight of the soft magnetic material can be reduced and the strength can be maintained.

  20 shows a soft magnetic material according to another embodiment of the present invention, in which a through hole is formed on one side of the central portion, and the resin 13 of a nonmagnetic material such as resin is filled in the through hole portion. is there. With this structure, the weight of the soft magnetic material can be reduced and the strength can be maintained.

  21 shows a soft magnetic material according to another embodiment of the present invention, in which the shape of the through hole 14 provided in the central portion is cylindrical. The through hole 14 is not limited to this shape, and may have any shape. Since the shape of the through hole 14 can be freely changed, various antenna patterns can be supported.

  22 shows a soft magnetic body according to another embodiment of the present invention, and shows a through hole 15 provided in the center of the soft magnetic body 22. The soft magnetic body 22 has a structure in which a plurality of soft magnetic bodies 17 are stacked. Reference numeral 16 denotes a joint portion of the laminate.

  Reference numeral 6 denotes a resin spacer disposed below the soft magnetic body 5. The material can be reduced in weight by selecting a resin or the like as the material.

  7 is a metal plate, and the material is preferably non-magnetic such as an aluminum plate.

  2 is a resin case (main body), and 8 is a resin case (back cover). Since the resin case (main body) 2 and the resin case (back cover) 8 sandwich the parts such as the antenna substrate and magnetic material, the ease of assembly during manufacturing increases, and the positioning and assembly accuracy of each element increases. By improving, it is possible to reduce variation in performance.

  The RFID system antenna device 1 having the above-described structure makes it possible to reduce the weight and reduce the communication distance while suppressing the change in resonance frequency and the increase in loss due to the eddy current generated in the metal on the back surface. It can be secured.

  The present invention is a wireless communication medium processing apparatus that supplies power and transmission data to a wireless communication medium such as a non-contact IC card or IC tag stored in a product shelf and obtains reception data from the wireless communication medium due to load fluctuations. Especially for applications that need to expand the communication range, such as storage shelves that enable automatic product management and book management, medicine management other than display shelves, dangerous goods management, valuables management system, etc. Applicable.

(A) The perspective view in the decomposition | disassembly state of the antenna apparatus in embodiment of this invention, (b) The top view of the soft magnetic body in embodiment of this invention, (c) The soft magnetic body in embodiment of this invention (D) The perspective view of the soft-magnetic body in embodiment of this invention (A) Top view of soft magnetic material in embodiment of the present invention, (b) Side view of soft magnetic material in embodiment of the present invention, (c) Perspective view of soft magnetic material in embodiment of the present invention (A) Top view of soft magnetic material in embodiment of the present invention, (b) Side view of soft magnetic material in embodiment of the present invention, (c) Perspective view of soft magnetic material in embodiment of the present invention (A) Top view of soft magnetic material in embodiment of the present invention, (b) Side view of soft magnetic material in embodiment of the present invention, (c) Perspective view of soft magnetic material in embodiment of the present invention (A) Top view of soft magnetic material in embodiment of the present invention, (b) Side view of soft magnetic material in embodiment of the present invention, (c) Perspective view of soft magnetic material in embodiment of the present invention (A) Top view of soft magnetic material in embodiment of the present invention, (b) Side view of soft magnetic material in embodiment of the present invention, (c) Perspective view of soft magnetic material in embodiment of the present invention (A) Cross-sectional view of an antenna device in the prior art, (b) Cross-sectional view of the antenna device in an embodiment of the present invention (A) A perspective view of an antenna device in a conventional technique in an exploded state, (b) a top view of a soft magnetic body in the conventional technique, (c) a side view of the soft magnetic body in the conventional technique, (d) a conventional one. Perspective view of soft magnetic material in technology

Explanation of symbols

1 Antenna device 2 Resin case (main body)
3 Antenna Pattern 4 Matching Circuit 5 Soft Magnetic Material 6 Resin Spacer 7 Metal Plate 8 Resin Case (Back Cover)
9 Through-hole 100 Antenna device 101 Resin case (main body)
102 Antenna Pattern 103 Matching Circuit 104 Soft Magnetic Material 105 Resin Spacer 106 Metal Plate 107 Resin Case (Back Cover)

Claims (15)

An antenna device in an RFID system that performs non-contact data communication, wherein a flat soft magnetic material is provided between an antenna and a metal surface on the back surface, and a through hole is provided in the center of the soft magnetic material. An antenna device characterized by that. In the antenna device, the antenna coil is configured by a loop having one or more turns in a plane, and a flat soft magnetic body is provided between the antenna and a metal surface on the back surface. The antenna device according to claim 1, wherein a through hole is provided in the antenna device. 3. The antenna device according to claim 1, wherein the soft magnetic body has one or more through holes provided in a central portion thereof. The antenna device according to claim 1, wherein a concave portion is provided on one surface of a central portion of the soft magnetic body. 5. The antenna device according to claim 4, wherein in the soft magnetic body, the number of concave portions provided on one surface of the central portion is one or more. The antenna device according to claim 1, wherein a concave portion is provided on both surfaces of the central portion of the soft magnetic body. The antenna device according to claim 6, wherein in the soft magnetic body, the number of concave portions provided on both surfaces of the central portion is one or more. 8. The soft magnetic body according to claim 1, wherein a central portion provided with a through hole or a concave portion is positioned on an inner side of an installation surface of the antenna coil in the plane of the RFID system. Antenna device. 9. The antenna device according to claim 1, wherein a shape of a through hole provided in a central portion of the soft magnetic body is a triangle or more of a polygon, a circle, or an ellipse. The antenna device according to any one of claims 1 to 8, wherein the soft magnetic body has a single-sided or double-sided concave portion provided in a central portion, which is a triangle, a polygon, a circle, or an ellipse. The soft magnetic body is any one of amorphous alloy, permalloy, electromagnetic steel, silicon iron, Fe-Al alloy, Sendust alloy, or soft magnetic ferrite. Antenna device. The antenna device according to any one of claims 1 to 11, wherein the soft magnetic material is a magnetic sheet in which a metal oxide is mixed with a resin binder, applied, and dried. 11. The antenna device according to claim 1, wherein the soft magnetic material is soft magnetic ferrite, and is formed into a bulk shape by dry-molding and firing a ferrite powder. The antenna device according to claim 1, wherein the soft magnetic material is an amorphous foil or a laminated material of an amorphous foil. The soft magnetic material is characterized in that a non-magnetic material such as a resin is filled in a through hole provided in the central portion of the soft magnetic material, or a concave portion provided on one or both surfaces of the central portion of the soft magnetic material. The antenna device according to claim 1.

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