JP2007110290A - Loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop antenna having a small amount of eddy current loss, and excellent sensitivity. <P>SOLUTION: There are provided an antenna substrate 1 that becomes a substrate for mounting each electronic member, and is formed nearly rectangularly; an antenna coil 2 formed in a loop on the surface of the antenna substrate 1; and an IC chip 3 that is provided on the antenna substrate 1 and outside the loop formed by the antenna coil 2, and is connected to both the ends of the antenna coil 2 via a jumper line 4. At the inner-periphery side of the antenna coil 2, foil or a sheet-like conductive high-permeability magnetic material 5 is formed nearly over the entire region. In the conductive high-permeability magnetic material 5, a plurality of slits 6 are formed radially, thus dividing the conductive high-permeability magnetic material 5 into a plurality of portions along the surface of the substrate 1. The slits 6 suppress the generation of the eddy current in the conductive high-permeability magnetic material 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a loop antenna formed by arranging an antenna coil on a substrate, and is used, for example, for a non-contact IC tag using RFID (Radio Frequency Identification) technology or an interrogator (card reader) thereof. The present invention relates to a loop antenna suitable for performing.

  Conventionally, an identification tag in which an IC chip storing information is electrically connected to an antenna coil is known as a tag using RFID technology. These identification tags are activated by transmitting radio waves of a predetermined frequency from the transmission / reception antenna of the interrogator (card reader) to the antenna coil, and stored in the IC chip in response to a read command by radio wave data communication. It is configured to identify or monitor the article by reading the information. As an antenna coil used for such an IC tag or its interrogator, a loop antenna is mainly used, and the activation strength (communication distance) of the tag depends on the size of the antenna coil.

  In particular, a general IC tag using such RFID technology is mainly used as an IC card, and is defined as 53.92 mm in length × 85.46 mm in width × 0.76 mm in thickness for ease of use. Yes. In particular, since electronic members such as an IC chip and an antenna coil must be stored within a thickness range of 0.76 mm, there has been a problem of how to improve the communication distance within the limited range.

Therefore, as described in Patent Document 1, a technique has been proposed in which a composite material of soft magnetic metal such as amorphous or ferrite powder or flake and plastic or rubber is disposed inside the antenna coil as a magnetic core member. Has been.
JP 2002-325013 A

  Certainly, a loop antenna in which a magnetic material having a high magnetic permeability is provided as a magnetic core member as in Patent Document 1 can obtain a predetermined effect, but seeking higher communication performance and ease of manufacture. It has been proposed that a conductive high magnetic permeability magnetic material such as an amorphous foil or a sheet is disposed on the inner periphery of the antenna coil. When such a conductive high permeability magnetic material is used, compared to the technique using the amorphous or ferrite powder of Patent Document 1, it is easier to manufacture foil and sheet, and magnetic flux passes well. There is an advantage that the voltage generated in the coil is increased and sensitivity is increased.

  However, in the case of a magnetic substance obtained by solidifying magnetic powder or a ferrite magnetic substance, the conductivity is low, whereas the high permeability magnetic substance formed of an amorphous foil or a sheet has a high conductivity. On the other hand, an eddy current as shown in FIG. The magnetic flux generated by the eddy current is in a direction to cancel the external magnetic flux. Therefore, if the eddy current is large, the initial performance improvement cannot be obtained even though the high permeability magnetic material is disposed on the inner periphery of the antenna coil. The problem arises.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and its purpose is to provide a conductive high-permeability magnetic material such as an amorphous foil or sheet on the inner periphery of the antenna coil. An object of the present invention is to provide a loop antenna that can improve the communication distance by suppressing the generation of eddy currents in a conductive high magnetic permeability magnetic body despite being disposed.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a loop antenna in which an antenna coil is disposed on a substrate, and a conductive high permeability magnetic foil or sheet on the inner periphery of the antenna coil on the substrate. And forming a slit for dividing the conductive high permeability magnetic foil or sheet into a plurality of parts in the direction along the surface of the conductive high permeability magnetic foil or sheet. Features. The invention of claim 2 is characterized in that the conductive high permeability magnetic foil or sheet is separated into a plurality of portions.

  In the first or second aspect of the invention, since the conductive high permeability magnetic body on the inner periphery of the antenna coil is divided into a plurality of portions by slits or divided portions, the eddy current is divided as shown in FIG. Will be greatly reduced. In this case, if the entire area of the conductive high permeability magnetic body is the same, the generation of eddy current is suppressed as the number of slits and divided parts increases. And the smaller the eddy current, the more magnetic flux that passes through the magnetic material, the higher the voltage generated in the coil, and the longer the communication distance.

  According to a third aspect of the present invention, the conductive high-permeability magnetic material foil or sheet has a slit formed radially from the center thereof, and a magnetic path whose center passes through the inside of the antenna coil. It is characterized by being curved along. In the invention of claim 3, since the high-permeability magnetic body is curved along the magnetic path, the passage of the magnetic flux passing through the inside of the magnetic body is improved, the demagnetizing field is reduced, and the passage of the magnetic flux is further improved. effective.

  The invention of claim 4 is characterized in that the conductive high permeability magnetic foil or sheet is formed of an amorphous foil or sheet. In the fourth aspect of the invention, an excellent magnetic flux intensity can be obtained by disposing an amorphous magnetic material, which is an amorphous solid having an irregular atomic arrangement, on a substrate.

  As described above, according to the present invention, it is possible to provide a loop antenna that can prevent the generation of eddy current and improve the communication distance while using a conductive high magnetic permeability magnetic body.

  Next, an example of an embodiment of the present invention will be specifically described with reference to the drawings.

[First Embodiment]
FIG. 1 is a plan view showing a loop antenna according to the first embodiment of the present invention. The loop antenna according to this embodiment includes an antenna substrate 1 formed in a substantially rectangular shape serving as a substrate on which each electronic member is mounted, an antenna coil 2 formed in a loop shape on the surface of the antenna substrate 1, an IC chip 3, and the like. It has. In the present embodiment, the IC chip 3 is disposed on the antenna substrate 1 and outside the loop formed by the antenna coil 2, and is connected to both ends of the antenna coil 2 via the jumper wire 4. Is not particularly limited.

  The antenna substrate 1 is a base substrate on which electronic members such as the antenna coil 2 and the IC chip 3 are mounted, and is made of an insulating material such as a resin film. The antenna coil 2 is formed by winding, printed wiring, or an etching method.

  A rectangular foil or sheet-like conductive high permeability magnetic body 5 is formed on the inner peripheral side of the antenna coil 2 over almost the entire area. The conductive high permeability magnetic body 5 is formed, for example, by attaching a magnetic amorphous foil or amorphous sheet to the surface of the substrate 1 or by burying the amorphous foil or amorphous sheet in the substrate 1. Yes. Further, the conductive high permeability magnetic material is not limited to an amorphous magnetic material, but other high permeability magnetic materials such as Sendust (Fe-Si-Al alloy invented by Masumoto et al. In 1937. Saturated magnetic flux density).・ High magnetic permeability, low iron loss, and excellent wear resistance. A plurality of slits 6 are formed radially in the foil or sheet-like conductive high permeability magnetic body 5 and divided into a plurality of portions in the direction along the surface of the substrate 1.

  In the first embodiment having such a configuration, since the foil or sheet-like conductive high magnetic permeability magnetic body 5 is divided by the slit 6, the generation of eddy currents formed along the surface thereof is suppressed. it can. That is, as shown in FIG. 6, when a conductive high magnetic permeability magnetic body having a large area exists inside the antenna coil 2, a large eddy current is generated along the surface, and the current induced in the antenna coil flows. However, if the conductive high magnetic permeability magnetic material is divided as shown in FIG. 7 of the present embodiment, the generation of eddy current is suppressed, and the resulting loss is reduced. Loss is reduced.

[Second Embodiment]
FIG. 2 shows a second embodiment of the present invention. In the second embodiment, as in the first embodiment, a single foil or sheet-like conductive high permeability magnetic body 5 is formed by slits 6. Instead of dividing, it is separated into a plurality of parts. Also in the second embodiment, as in the first embodiment, it is possible to suppress the generation of a large eddy current in the conductive high permeability magnetic body 5 formed in the antenna coil 2, resulting in eddy current loss. Decrease in antenna sensitivity can be prevented.

[Third Embodiment]
FIG. 3 shows a third embodiment of the present invention. In this third embodiment, a circular foil or sheet-like conductive high permeability magnetic body 5 is arranged on the inner periphery of a circular antenna coil 2. The conductive high permeability magnetic body 5 is formed with slits radially from the center. Then, by curving the central portion of the conductive high permeability magnetic body 5 along the magnetic path formed in the antenna coil 2, the magnetic flux passing through the inside of the magnetic body is improved and the demagnetizing field is reduced. The effect of improving the passage of magnetic flux by reducing the magnetic flux is obtained. In this case, as shown in the cross-sectional view of FIG. 3, the conductive high permeability magnetic body 5 may be disposed inside the antenna coil 2 or between the antenna coil 2 and the substrate 1. good.

[Other Embodiments]
In addition, this invention is not limited to the above embodiment, The following other embodiment is also included.
(1) If it is a loop-shaped antenna, even if it is a thing other than a card type as a shape of a tag, it is applicable.
(2) The conductive high magnetic permeability magnetic body 5 may be disposed on the front side or the back side of the card, and may be on the same surface as the antenna coil 2 or on a different surface. That is, FIG. 4 shows an example of the substrate 1, the antenna coil 2, and the conductive high permeability magnetic body 5, and the conductive high permeability magnetic body 5 is provided on the front side or the back side of the substrate 1. Two conductive high-permeability magnetic bodies 5 can be provided with 1 interposed therebetween, and the antenna coil 2 and two conductive high-permeability magnetic bodies 5 can be disposed on the back surface of the substrate 1.
(3) The slit shape is not limited to a radial shape, and a lattice shape or a ladder shape as shown in FIG. 5 can be used.

The top view which shows 1st Embodiment of this invention. The top view which shows 2nd Embodiment of this invention. The top view and sectional drawing which show 3rd Embodiment of this invention. Sectional drawing which shows the example of arrangement | positioning of the electroconductive high magnetic permeability magnetic body in other embodiment of this invention. Sectional drawing which shows the example of arrangement | positioning of the slit in other embodiment of this invention. The top view explaining the state which an eddy current generate | occur | produces in a conductive high magnetic permeability magnetic body. The top view explaining the state by which the eddy current is suppressed in the electroconductive high magnetic permeability magnetic body of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Antenna coil 3 ... IC chip 4 ... Jumper wire 5 ... Conductive high magnetic permeability magnetic body 6 ... Slit

Claims (4)

In the loop antenna with the antenna coil on the substrate,
A conductive high permeability magnetic foil or sheet is disposed on the inner periphery of the antenna coil on the substrate, and the conductive high permeability magnetic foil or sheet is placed on the conductive high permeability magnetic foil or sheet. A loop antenna characterized in that a slit for dividing into a plurality of parts in a direction along the surface is formed.   The loop antenna according to claim 1, wherein the conductive high permeability magnetic foil or sheet is separated into a plurality of portions.   The conductive high permeability magnetic foil or sheet has slits formed radially from the center thereof, and the center portion is curved along a magnetic path passing through the inside of the antenna coil. The loop antenna according to claim 1.   The loop antenna according to claim 1, 2 or 3, wherein the conductive high permeability magnetic foil or sheet is formed of an amorphous foil or sheet.

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