JP5321236B2 - Magnetic material antenna and antenna device - Google Patents

Description

  The present invention relates to a magnetic antenna and an antenna device used for an RFID (Radio Frequency Identification) system that communicates with an external device via an electromagnetic field signal.

  In an RFID system that has been used in recent years, an antenna for information communication is mounted on each of a portable electronic device such as a mobile phone and a reader / writer to exchange data with each other. Among these, antennas mounted on portable electronic devices are particularly demanded for high performance, low cost, and downsizing. As an attempt to achieve these, Patent Document 1 discloses a magnetic antenna having a magnetic core. It is disclosed.

  FIG. 1 is a perspective view of a magnetic antenna shown in Patent Document 1. FIG. This antenna 10 includes a single electric insulating film (flexible substrate) 14 in which a spiral portion 13a is formed on one main surface by a magnetic core member (magnetic core) 12 and a series of first conductors (coil conductors) 13. With. A second conductor 15 is formed on the other main surface of the electrical insulating film 14, and an end portion of the second conductor 15 and an end portion of the first conductor 13 are connected to the IC chip 16.

Further, Patent Document 2 discloses a magnetic antenna formed by folding a base material on which a spiral coil conductor is formed so as to surround one side of a magnetic core.
When a magnetic antenna as shown in Patent Document 2 is arranged close to a conductor plate that does not pass magnetic flux such as a metal plate, the magnetic flux incident from the direction perpendicular to the conductor surface is left and right ends of the magnetic core. It will be emitted from the part. FIG. 2 is a diagram showing this state. 2A is a top view of the antenna device including the magnetic antenna 100 and the conductor plate 31, FIG. 2B is a front view of the magnetic antenna 100, and FIG. 2C is a right side of the magnetic antenna 100. FIG. FIG.

  A flexible substrate 23 on which a rectangular spiral coil conductor 24 is formed is wound around the surface of a rectangular plate-like magnetic core 22.

Here, the antenna of the reader / writer is above in FIG.
2A and 2B, the magnetic flux incident on the conductor plate 31 from the vertical direction is radiated from the end portions of the left and right magnetic cores 22 as indicated by the broken line in the broken line. . At this time, since the magnetic flux passes through the coil, an electromotive force is generated.

JP 2003-022912 A JP 2005-033461 A

  The magnetic antenna of Patent Document 1 has a structure in which a flexible substrate is bent at the center and the magnetic material is sandwiched between them. Therefore, the magnetic antenna is basically coupled to a magnetic flux from a direction parallel to the surface of the magnetic material core. is there. Therefore, the magnetic flux from the direction perpendicular to the surface of the magnetic core does not penetrate the loop surface of the coil conductor from one to the other, and only very weak coupling is obtained.

  In the configuration of Patent Document 2, although the magnetic flux MFA does not contribute to the coupling in FIG. 2, the magnetic conductor core covers the coil conductor portion, so the self-inductance that does not contribute to the coupling increases and the coupling becomes weak There's a problem.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly sensitive magnetic antenna and antenna device that can be strongly coupled to a magnetic flux in a direction perpendicular to the surface of a magnetic core and that has improved the radiation efficiency of the magnetic flux.

In order to solve the above-described problems, the magnetic antenna of the present invention is configured as follows.
(1) In the magnetic antenna in which the flexible substrate on which the coil conductor is formed is wound along the surface of the magnetic core,
The magnetic core is a single or a plurality of magnetic cores, the overall shape is a rectangular plate,
The coil conductor includes first and second coil conductor portions that are parallel to each other, and is formed in a spiral shape with a rough shape having a rectangular winding center portion and a coil conductor opening portion.
The flexible substrate passes through a position shifted from the center of the coil conductor opening to the first coil conductor portion side and is parallel to the coil conductor portion, and is bent from the first main surface to the second main surface of the magnetic core. Folded into
The magnetic core does not cover at least a part of the second coil conductor portion.

  With this configuration, the self-inductance of the coil conductor portion that does not contribute to the coupling is reduced, and the degree of coupling with the counterpart antenna is improved. Moreover, the loss in the coil conductor part that does not contribute to the coupling is reduced and the communication performance is improved. Therefore, the radiation efficiency of magnetic flux is increased, the sensitivity of the antenna is increased, and the communicable distance is extended.

(2) The coil conductor includes third and fourth coil conductor portions orthogonal to the first and second coil conductor portions,
The magnetic core covers one or both of the third and fourth coil conductor portions.

  As a result, the area of the magnetic core on the surface serving as a path of magnetic flux contributing to the coupling increases, so that the degree of coupling with the counterpart antenna is improved.

(3) The coil conductor includes a portion extending in an inclined direction toward the central direction of the magnetic core in a state where the coil conductor is bent along the bending line.

  As a result, the area through which the magnetic flux that does not contribute to the coupling of the surfaces adjacent to the conductor plate is small and the area through which the magnetic flux that contributes to coupling is large is increased.

(4) The said magnetic body core is the shape isolate | separated by the said coil conductor opening part.
Thereby, the volume of a magnetic body core and a magnetic body antenna reduces. The coil conductor opening, which is the central part of the magnetic antenna, has little characteristic deterioration because there is almost no magnetic flux passing through the communication partner antenna.

(5) Further, an antenna device of the present invention includes the magnetic antenna according to any one of the above, and a conductor plate (for example, a substrate or an LCD shield plate) that is close to the magnetic antenna and spreads in a planar shape. Configure.

  As a result, a magnetic flux transmitted from one side of the magnetic core to the other side is generated, and this magnetic flux also passes through the loop of the coil conductor, so that an effective antenna opening is widened and a highly sensitive antenna The device can be configured.

  According to this invention, the self-inductance of the coil conductor portion that does not contribute to the coupling is reduced, and the degree of coupling with the counterpart antenna is improved. Moreover, the loss in the coil conductor part that does not contribute to the coupling is reduced and the communication performance is improved. Therefore, the radiation efficiency of magnetic flux is increased, the sensitivity of the antenna is increased, and the communicable distance is extended.

It is a perspective view of the magnetic body antenna shown by patent document 1. FIG. It is a three-plane figure which shows the state which has arrange | positioned the magnetic body antenna shown by patent document 2 close to the conductor plate which does not let magnetic flux pass. 3A is a top view of the magnetic antenna 101 according to the first embodiment, FIG. 3B is a bottom view of the magnetic antenna 101, and FIG. 3C is a right side view of the magnetic antenna 101. is there. FIG. 3D is a development view of the flexible substrate 23 used for the magnetic antenna 101. 4A is a top view of the antenna device 201 including the magnetic antenna 101 and the conductor plate 31, FIG. 4B is a front view of the antenna device 201, and FIG. 4C is a right side view of the antenna device 201. It is. 5A is a top view of the magnetic antenna 102 according to the second embodiment, FIG. 5B is a bottom view of the magnetic antenna 102, and FIG. 5C is a right side view of the magnetic antenna 102. is there. 6A is a top view of the magnetic antenna 103 according to the third embodiment, FIG. 6B is a bottom view of the magnetic antenna 103, and FIG. 6C is a right side view of the magnetic antenna 103. is there. 7A is a top view of the magnetic antenna 104 according to the fourth embodiment, FIG. 7B is a bottom view of the magnetic antenna 104, and FIG. 7C is a right side view of the magnetic antenna 104. is there. 8A is a top view of the magnetic antenna 105 according to the fifth embodiment, FIG. 8B is a bottom view of the magnetic antenna 105, and FIG. 8C is a right side view of the magnetic antenna 105. is there.

<< First Embodiment >>
FIG. 3A is a top view of the magnetic antenna 101 according to the first embodiment, and FIG. 3B is a bottom view of the magnetic antenna 101 (view of the surface close to the conductor plate). 3C is a right side view of the magnetic antenna 101. FIG. FIG. 3D is a development view of the flexible substrate 23 used for the magnetic antenna 101.

  As shown in FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D, the magnetic antenna 101 includes a flexible substrate 23 on which a coil conductor 24 is formed, and a magnetic core 22. And. A spiral coil conductor 24 is formed on the flexible substrate 23, and a winding center portion of the coil conductor 24 is formed as a coil conductor opening CW. That is, the spiral coil conductor 24 is formed so as to surround the coil conductor opening CW. Connection portions 25 are formed at both ends of the coil conductor 24.

The coil conductor 24 includes a first coil conductor portion A1 and a second coil conductor portion A2 that are parallel to each other. Further, a third coil conductor portion A3 and a fourth coil conductor portion A4 that are orthogonal to the first coil conductor portion A1 and the second coil conductor portion A2 are provided.

Two two-dot chain lines in FIG. 3D are bending lines of the flexible substrate 23. In a state where the flexible substrate 23 is bent by this bending line, the flexible substrate 23 wraps a part of the upper surface (first main surface), one side surface, and the lower surface (second main surface) of the magnetic core 22. A flexible substrate 23 is arranged. The folding line passes through a position shifted from the center of the coil conductor opening CW toward the first coil conductor A1 and is parallel to the first coil conductor A1.

  The dimension indicated by Lc in the drawing of the magnetic core 22 is shorter than the dimension Lb from the folding line to the end of the second coil conductor portion A2, and the magnetic core 22 does not cover the second coil conductor portion A2.

  4A is a top view of the antenna device 201 including the magnetic antenna 101 and the conductor plate 31, FIG. 4B is a front view of the antenna device 201, and FIG. 4C is a right side surface of the antenna device 201. FIG.

  In this example, the conductor plate 31 is a circuit board of an electronic device. When the magnetic antenna 101 is mounted on the circuit board, the connecting portion 25 is electrically connected to the circuit board via a spring probe or the like provided on the circuit board side.

  The magnetic flux that enters from the coil conductor opening CW and exits to the side of the magnetic core 22 contributes to the coupling with the communication partner antenna. On the other hand, the magnetic flux MFA that enters from other than the coil conductor opening CW and exits to the side of the magnetic core 22 does not contribute to the coupling. Since the magnetic core 22 is not covered with the second coil conductor portion A2 where the magnetic flux that does not contribute to the coupling passes, the self-inductance due to the second coil conductor portion is reduced, and the degree of coupling is improved. Further, the loss in the second coil conductor portion A2 that does not contribute to the coupling is reduced, and the communication performance is improved.

<< Second Embodiment >>
FIG. 5A is a top view of the magnetic antenna 102 according to the second embodiment, and FIG. 5B is a bottom view of the magnetic antenna 102 (view of the surface close to the conductor plate). FIG. 5C is a right side view of the magnetic antenna 102.

  What is different from the magnetic antenna 101 shown in FIG. 3 in the first embodiment is the shape of the magnetic core 22. 5 shows only the magnetic antenna 102, this magnetic antenna 102 is replaced with the magnetic antenna 101 shown in FIG. 4 in the first embodiment. That is, the magnetic antenna 102 is disposed so that the lower surface faces the conductor plate 31 as in the antenna apparatus shown in FIG.

  In the example shown in FIG. 5, the magnetic core 22 includes a position A23 where the second coil conductor portion A2 and the third coil conductor portion A3 overlap, and the second coil conductor portion A2 and the fourth coil conductor portion. The shape of the magnetic core 22 is determined so that the magnetic core 22 also covers the position A24 where A4 overlaps.

  With this configuration, the area of the magnetic core on the surface serving as a path for the magnetic flux contributing to the coupling increases, so that the degree of coupling with the counterpart antenna is improved.

  The shape of the magnetic core 22 may be determined so that one of the positions A23 and A24 is covered by the magnetic core and not the other.

<< Third Embodiment >>
FIG. 6A is a top view of the magnetic antenna 103 according to the third embodiment, and FIG. 6B is a bottom view of the magnetic antenna 103 (view of the surface close to the conductor plate). 6C is a right side view of the magnetic antenna 103. FIG.

  What is different from the magnetic antenna 101 shown in FIG. 3 in the first embodiment is the shape of the magnetic core 22. Although only the magnetic antenna 103 is shown in FIG. 6, this magnetic antenna 103 is replaced with the magnetic antenna 101 shown in FIG. 4 in the first embodiment. That is, the magnetic antenna 103 is arranged so that the lower surface faces the conductor plate 31 as in the antenna device shown in FIG.

  In the example shown in FIG. 6, the magnetic core 22 covers almost all of the third coil conductor part A3 and the fourth coil conductor part A4 and does not cover almost all of the second coil conductor part A2. Further, the shape of the magnetic core 22 is defined.

  With this configuration, the area of the magnetic core on the surface serving as a path for the magnetic flux contributing to the coupling increases, so that the degree of coupling with the counterpart antenna is improved.

<< Fourth Embodiment >>
FIG. 7A is a top view of the magnetic antenna 104 according to the fourth embodiment, and FIG. 7B is a bottom view of the magnetic antenna 104 (view of a surface close to the conductor plate), FIG. 7C is a right side view of the magnetic antenna 104. FIG.

  What differs from the magnetic antenna 102 shown in FIG. 5 in the second embodiment is the shape of the coil conductor 24 formed on the flexible substrate 23. Although only the magnetic antenna 104 is shown in FIG. 7, this magnetic antenna 104 is replaced with the magnetic antenna 104 shown in FIG. 4 in the first embodiment. That is, the magnetic antenna 104 is disposed so that the lower surface faces the conductor plate 31 as in the antenna device shown in FIG.

  In the example illustrated in FIG. 7, the coil conductor 24 includes an inclined portion S that extends in an inclined direction toward the center of the magnetic core 22 in a state where the flexible substrate 23 is bent along a bending line. Therefore, a magnetic flux radiating portion T that opens in a triangular shape is formed adjacent to the inclined portion S of the coil conductor 24.

  If the lower surface of the magnetic antenna 104 (the surface shown in FIG. 7 (B)) faces the conductor plate that does not pass magnetic flux, the magnetic flux from the direction perpendicular to the conductor plate is coil conductor. In addition to entering from the left and right ends of the magnetic core 22 by entering from the opening CW, the radiation part T of the magnetic flux opened in a triangular shape also escapes.

With this configuration, the magnetic flux transmitted perpendicularly to the main surface of the magnetic core 22 passes through the loop of the spiral coil conductor 24 and is strongly coupled to the communication partner antenna.
Therefore, the radiation efficiency of magnetic flux is increased, the sensitivity of the antenna is increased, and the communicable distance is extended.

<< Fifth Embodiment >>
FIG. 8 is a top view of the magnetic antenna 105 according to the fifth embodiment, FIG. 8B is a bottom view of the magnetic antenna 105 (view of the surface close to the conductor plate), and FIG. ) Is a right side view of the magnetic antenna 105.

  The fourth embodiment is different from the magnetic antenna 104 shown in FIG. 7 in that the magnetic core is separated into two magnetic cores 22A and 22B. The general shape of the entire arrangement portion of the two magnetic cores 22A and 22B is a rectangular plate shape. Although only the magnetic antenna 105 is shown in FIG. 8, this magnetic antenna 105 is replaced with the magnetic antenna 101 shown in FIG. 4 in the first embodiment. That is, the magnetic antenna 105 is disposed so that the lower surface faces the conductor plate 31 as in the antenna device shown in FIG.

  This reduces the volume of the magnetic core and the magnetic antenna. Since there is almost no magnetic flux passing through the communication partner antenna at the coil conductor opening CW, which is the center of the magnetic antenna, the characteristic deterioration due to the separation of the magnetic core is small.

  In each embodiment, the flexible substrate is arranged to be bent at 90 degrees by two folding lines so as to wrap around the three surfaces of the magnetic core. You may arrange | position so that it may wind around.

  In each embodiment, an example in which an antenna device is configured by a magnetic antenna and a conductor plate adjacent thereto is shown. However, the conductor plate may be a plate material having a conductor spreading in a planar shape, and a battery other than a circuit board may be used. It may be a pack or an LCD shield plate.

A1 to A4 ... Coil conductor part CW ... Coil conductor opening MFA ... Magnetic flux S ... Inclined part T ... Magnetic flux radiation part 22 ... Magnetic body core 22A, 22B ... Magnetic body core 23 ... Flexible substrate 24 ... Coil conductor 25 ... Connection part 31 ... Conductor plates 100 to 105 ... Magnetic antenna 201 ... Antenna device

Claims (5)

In the magnetic antenna in which the flexible substrate on which the coil conductor is formed is wound along the surface of the magnetic core,
The magnetic core is a single or a plurality of magnetic cores, the overall shape is a rectangular plate,
The coil conductor includes first and second coil conductor portions that are parallel to each other, and is formed in a spiral shape with a rough shape having a rectangular winding center portion and a coil conductor opening portion.
The flexible substrate passes through a position shifted from the center of the coil conductor opening to the first coil conductor portion side and is parallel to the first coil conductor portion, and is bent at a first main surface of the magnetic core. To the second main surface,
The magnetic core is a magnetic antenna that does not cover at least a part of the second coil conductor. The coil conductor includes third and fourth coil conductor portions orthogonal to the first and second coil conductor portions,
2. The magnetic antenna according to claim 1, wherein the magnetic core covers one or both of the third and fourth coil conductor portions.   3. The coil conductor according to claim 1, wherein the coil conductor includes a portion extending in a direction orthogonal to the folding line and extending in an inclined direction toward the central direction of the magnetic core in a state of being bent by the folding line. Magnetic antenna.   The said magnetic body core is a magnetic body antenna in any one of Claims 1-3 which is the shape isolate | separated or removed by the said coil conductor opening part.   An antenna device comprising: the magnetic antenna according to any one of claims 1 to 4; and a conductor plate extending in a planar shape adjacent to the second main surface side of the magnetic core of the magnetic antenna.

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