JP4894945B2 - antenna - Google Patents

Description

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

  Patent Document 1 discloses an antenna mounted on a portable electronic device used in an RFID system. FIG. 1 is a front view showing the structure of the antenna device described in Patent Document 1. FIG.

  An antenna coil 30 shown in FIG. 1 includes an air-core coil 32 formed by spirally winding a conductor 31 (31a, 31b, 31e, 31d) in a plane on a film 32a, and the air-core coil 32. A flat magnetic core member 33 inserted into the air-core coil 32 so as to be substantially parallel to the plane is provided. The air core coil 32 is provided with a hole 32d, and a magnetic core member 33 is inserted into the hole 32d. The first terminal 31a and the connecting conductor 31e are connected by a through hole 32b, and the second terminal 31b and the connecting conductor 31e are connected by a through hole 32c. The magnetic antenna is disposed on the conductive plate 34.

JP 2002-325013 A

  The magnetic antenna of Patent Document 1 shown in FIG. 1 is a metal plate on the back surface, and the magnetic flux is released in the lateral direction (from right to left in the state shown in FIG. 1), thereby generating an electromotive force in the coil conductor. Current flows.

  However, as shown in FIG. 1, the magnetic antenna of Patent Document 1 has a structure in which a magnetic flux parallel to the back conductive plate 34 is coupled. Therefore, when the antenna coil is placed near the center of the conductive plate 34, there is a problem that communication is possible only within a short distance range, and usability is poor.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna that can increase the maximum communicable distance.

In order to solve the above problems, an antenna according to the present invention includes an antenna coil including a plate-like magnetic core having a first main surface and a second main surface, and a coil conductor wound around the magnetic core. In an antenna placed close to a planar conductor,
The outer shape of the planar conductor is larger than the planar outer shape of the antenna coil,
The first main surface of the magnetic core faces the planar conductor,
The antenna coil is disposed near the edge of the planar conductor;
Among the coil conductors, a first conductor portion that is close to the first main surface of the magnetic core and a second conductor portion that is close to the second main surface of the magnetic core are: Located in a position that does not overlap when viewed from the normal direction of the first main surface or the second main surface,
The coil axis of the coil conductor is perpendicular to the edge of the planar conductor.

The coil conductor has a shape formed by cutting a helical coil formed on a flexible substrate by a predetermined slit line, and the flexible substrate is wound around four surfaces of the magnetic core, and the slit line portion And the coil conductor is joined.

The coil conductor is a spiral conductor formed on a flexible substrate, and the flexible substrate is wound around three surfaces of the magnetic core.
The coil conductor is a spiral conductor formed on a flexible substrate, the flexible substrate has a through hole at the center of the coil conductor forming position, and the magnetic core is inserted into the through hole. And
The width of the narrowest portion of the coil conductor connecting between the first conductor portion and the second conductor portion is W, and the width of the magnetic core perpendicular to the edge of the planar conductor is W. When the length is Y, the relationship is W ≧ Y.

Further, the magnetic core is assumed to have thicker end portions where magnetic flux enters and exits than other portions.
Further, the distance from the end of the antenna closer to the edge end portion of the flat conductor to the edge end portion of the planar conductor X, the direction perpendicular to the antenna with respect to the edge end portion of the planar conductor When the length of the coil is Y, the relationship is defined as Y> X.
Further, the planar conductor that consists of a circuit board on which the antenna coil is mounted.

  According to the present invention, a highly sensitive antenna having a longest communicable distance can be obtained.

It is a front view which shows the structure of the antenna apparatus described in patent document 1. It is a figure which shows the structure of the magnetic body antenna and antenna apparatus which concern on 1st Embodiment. 3A is a diagram showing the distribution and directivity of the magnetic flux of the antenna 101, and FIG. 3B is the distribution and directivity of the magnetic flux of the antenna having the conventional structure shown for comparison with the antenna of the first embodiment. It is a figure which shows sex. It is a figure which shows the state which communicates between electronic devices, such as a mobile telephone terminal provided with the antenna 101 which concerns on 1st Embodiment, and IC card for RFID. FIG. 3 is a diagram showing a positional relationship between a planar conductor 2 and an antenna coil 21. FIG. 6A is a plan view showing the positional relationship between the planar conductor 2 and the antenna coil 21. FIG. 6B is a diagram illustrating the relationship between the distance X and the coupling coefficient for the antenna coil 21 according to the first embodiment and the antenna coil 20 having the conventional structure. FIG. 7A is a diagram showing a state before the assembly of the antenna coil 22 according to the second embodiment, and FIG. 7B is a plan view of the antenna coil 22. FIG. 8A is a bottom view of the antenna 102 provided with the antenna coil 22 according to the second embodiment, and FIG. 8B is a front view thereof. FIG. 8C shows an example in which the antenna coil 22 is fixed inside the housing 202 that houses the planar conductor 2 that is a circuit board. FIG. 9A is a plan view before assembly of the antenna coil 23 according to the third embodiment, and FIG. 9B is a plan view of the antenna coil 23. FIG. 10A is a bottom view of the antenna 103 provided with the antenna coil 23 according to the third embodiment, and FIG. 10B is a front view thereof. FIG. 10C shows an example in which the antenna coil 23 is fixed inside the housing 203 that houses the planar conductor 2 that is a circuit board. When the width of the narrowest portion of the coil conductor connecting the first conductor portion 11 and the second conductor portion 12 is W, and the length of the magnetic core perpendicular to one side of the planar conductor is Y FIG. 6 is a diagram illustrating a relationship between W and a coupling coefficient when W is changed with a product of W and Y being constant. FIG. 12A is a plan view of the antenna coil 24A according to the fourth embodiment before assembly, and FIG. 12B is a plan view of the antenna coil 24A. FIG. 13A is a plan view before assembling another antenna coil 24B according to the fourth embodiment, and FIG. 13B is a plan view of the antenna coil 24B. FIG. 14A is a plan view before assembling another antenna coil 24C according to the fourth embodiment, and FIG. 14B is a plan view of the antenna coil 24C. 15A is a plan view before assembling the antenna coil 25 according to the fifth embodiment, FIG. 15B is a top view of the antenna coil 25, and FIG. 15C is a bottom view of the antenna coil 25. is there. FIG. 16A is a bottom view of the antenna 104 provided with the antenna coil 25 according to the fifth embodiment, and FIG. 16B is a front view thereof. FIG. 16C is an example in which the antenna coil 25 is fixed inside the housing 204 that houses the planar conductor 2 that is a circuit board. FIG. 17A is a plan view of the antenna coil 26A according to the sixth embodiment before assembly, and FIG. 17B is a plan view of the antenna coil 26A. FIG. 18A is a plan view before assembling another antenna coil 26B according to the sixth embodiment, and FIG. 18B is a plan view of the antenna coil 26B. FIG. 19A is a plan view before assembling another antenna coil 26C according to the sixth embodiment, and FIG. 19B is a plan view of the antenna coil 26C.

<< First Embodiment >>
FIG. 2 is a diagram illustrating the configuration of the antenna according to the first embodiment.
FIG. 2A is a perspective view of an antenna 101 including an antenna coil 21 and a planar conductor 2 having a rectangular plate shape such as a circuit board on which the antenna coil 21 is mounted. FIG. 2B is a front view of the antenna 101.

  The magnetic core 1 is a rectangular plate-shaped ferrite core, and the lower surface in FIG. 2 is the first main surface MS1 and the upper surface is the second main surface MS2. A coil conductor CW is wound around the magnetic core 1 as shown in FIG. A portion indicated by reference numeral 11 in the drawing is a first conductor portion of the coil conductor CW that is close to the first main surface MS1 of the magnetic core 1. Moreover, the part shown with the code | symbol 12 in a figure is a 2nd conductor part which adjoins 2nd main surface MS2 of the magnetic body core 1. FIG. An antenna coil 21 is constituted by the magnetic core 1 and the coil conductor CW.

  The antenna coil 21 is disposed closer to a predetermined side (right side in FIG. 2) S than the center of the planar conductor 2. In addition, the first conductor portion 11 and the second conductor portion 12 do not overlap each other when viewed from the normal direction of the first main surface MS1 or the second main surface MS2 of the magnetic core 1 (see through). Has been placed. The second conductor portion 12 is disposed in a positional relationship farther from the center of the planar conductor 2 than the first conductor portion 11. Further, the coil axis CA of the coil conductor CW is perpendicular to the one side S of the planar conductor 2.

  FIG. 3A is a diagram illustrating the magnetic flux distribution and directivity of the antenna 101. FIG. 3B is a diagram showing the magnetic flux distribution and directivity of the antenna having the conventional structure shown for comparison with the antenna according to the first embodiment. The antenna 101 is arranged in such a positional relationship that the antenna coil 21 is closer to the reader / writer side antenna 301 than the planar conductor 2. This state is a state in which the electronic device incorporating the antenna 101 is held over the reading unit of the reader / writer.

  Of the coil conductor CW, the second conductor portion 12 is located outside the center of the planar conductor 2 as compared to the first conductor portion 11, so that the magnetic flux H that passes through the magnetic core of the antenna coil 21 is reduced. The major axis of the loop is inclined with respect to the plane conductor 2 as shown in the figure. That is, the component in the normal direction (Z-axis direction) of the planar conductor 2 becomes strong. Accordingly, the directional beam DB of the antenna 101 is directed toward the center of the reader / writer side antenna 301.

  On the other hand, as shown in FIG. 3B, the first conductor portion and the second conductor portion that are respectively close to the first main surface and the second main surface of the magnetic core have a positional relationship in which the front and back surfaces overlap each other. In the antenna coil 20, the major axis of the loop of the magnetic flux H passing through the magnetic core is parallel to the planar conductor 2, and the directional beam DB of the antenna is directed in the direction along the plane of the planar conductor 2. Therefore, when the antenna 100 is brought close to the reader / writer side antenna 301 in parallel, the longest communicable distance is shortened. Rather, when the antenna 100 is tilted and made close to the reader / writer side antenna 301, the longest communication distance is possible. Will be extended.

  In contrast, according to the first embodiment, the longest communicable distance can be increased, and the longest communicable distance can be obtained in a state where the center of the antenna 101 and the center of the reader / writer side antenna 301 coincide with each other.

Next, an example in which communication is performed between an RFID IC card and an electronic device such as a mobile phone terminal including the antenna 101 will be described.
FIG. 4 is a diagram showing an arrangement relationship between an RFID IC card and an electronic device such as a mobile phone terminal provided with the antenna 101. An antenna configured by arranging the antenna coil 21 at the end of the planar conductor 2 is housed in a casing 201 of the electronic device. 4A shows a state in which the electronic device and the IC card 401 are brought close to each other in the same vertical direction, and FIG. 4B shows a state in which the two are arranged in an orthogonal state. Inside the IC card 401, an antenna coil having a plurality of turns is formed along the outer periphery thereof and is magnetically coupled to the antenna coil 21.

  As described above, by arranging the antenna coil 21 at the end of the planar conductor 2, when the IC card having substantially the same size as the planar conductor 2 is brought close to the antenna coil of the IC card 401 and the antenna according to this embodiment. Since the distance between the coil conductors with the antenna coil 21 is close, strong coupling between the antennas can be obtained.

  As described above, for example, the present invention can be applied not only to communication with a reader / writer separated by about 100 mm but also to communication in a state of being substantially in contact with the IC card.

  In other words, the antenna of the present invention is wound in such a manner that a good communication performance can be obtained even when an antenna coil is arranged at the end of the planar conductor. Compared to an antenna using a conventional antenna coil in which a coil conductor is simply wound around a magnetic core, the magnetic field strength that contributes to communication is strong, and high communication performance (communication distance and communication data errors) Performance with respect to rate, etc.).

FIG. 5 is a diagram showing the positional relationship between the planar conductor 2 and the antenna coil 21. Here, the distance from the end of the antenna coil 21 near the one side S of the planar conductor 2 to the one side S is X, and the length of the antenna coil 21 perpendicular to the one side S of the planar conductor 2 is Y. Then
Y> X
The relationship.

The relationship between X and Y is connected with reference to FIG.
FIG. 6A is a plan view showing the positional relationship between the planar conductor 2 and the antenna coil 21. In this example, the planar conductor 2 is 42 mm × 90 mm, and the antenna coil 21 is 20 mm × 15 mm. FIG. 6B is a diagram illustrating the relationship between the distance X and the coupling coefficient for the antenna coil 21 according to the first embodiment and the antenna coil having the conventional structure. Here, the antenna coil having a conventional structure as a comparative example has a positional relationship in which the first conductor portion and the second conductor portion that are close to the first main surface and the second main surface of the magnetic core overlap on the front and back surfaces, respectively. is there. The reader / writer antenna was 100 × 100 mm, and was opposed to the antenna at a distance of 30 mm.

  As shown in FIG. 6B, when X <15 mm, the coupling coefficient of the antenna coil 21 is larger than that of the antenna coil having the conventional structure. Now, since Y = 15 mm, it can be seen that a higher coupling coefficient than that of the antenna coil having the conventional structure can be obtained by setting the relationship of Y> X.

As shown in FIG. 6B, the dimension X may be a negative value. That is, as shown in FIG. 5B, the end of the antenna coil 21 may be outside the one side S of the planar conductor 2.
With such a relationship, the direction of the directional beam DB shown in FIG. 3A can be raised, and the object of the present invention can be achieved.

<< Second Embodiment >>
FIG. 7A is a diagram showing a state before the assembly of the antenna coil 22 according to the second embodiment, and FIG. 7B is a plan view of the antenna coil 22. As shown in FIG. 7A, a coil conductor CW is formed on the flexible substrate 10. The coil conductor CW is a conductor pattern in which a helical coil is cut along a predetermined slit line. The flexible substrate 10 is wound around the four surfaces of the magnetic core 1 and the ends of the coil conductor CW are joined to each other at the cut line portion. In this example, the end portions aa ′, bb ′, and cc ′ are joined by solder or the like. Thereby, the antenna coil 22 shown in FIG.

  In the orientation shown in FIG. 7B, the second conductor portion 12 is close to the upper surface (second main surface) of the magnetic core 1, and the first conductor portion 11 is lower surface (first main portion) of the magnetic core 1. Close to the surface).

  8A is a bottom view of the antenna 102 provided with the antenna coil 22, and FIG. 8B is a front view thereof. The antenna coil 22 is mounted at a position along the center of one side of the planar conductor 2 that is a circuit board.

FIG. 8C shows an example in which the antenna coil 22 is fixed inside the housing 202 that houses the planar conductor 2 that is a circuit board. Even in this case, the second conductor portion 12 is disposed farther from the center of the planar conductor 2 than the first conductor portion 11.
Thus, the same operational effects as described in the first embodiment can be obtained.

<< Third Embodiment >>
FIG. 9A is a plan view before assembly of the antenna coil 23 according to the third embodiment, and FIG. 9B is a plan view of the antenna coil 23. The flexible substrate 10 is formed with a spiral coil conductor CW, and has a through hole A at the center of the position where the spiral coil conductor is formed. The magnetic core 1 is inserted into the through hole A portion of the flexible substrate 10 to constitute the antenna coil 23 shown in FIG.

  10A is a bottom view of the antenna 103 provided with the antenna coil 23, and FIG. 10B is a front view thereof. The antenna coil 23 is mounted at a position along the center of one side of the planar conductor 2 that is a circuit board.

FIG. 10C is an example in which the antenna coil 23 is fixed inside the housing 203 that houses the planar conductor 2 that is a circuit board, unlike the examples of FIGS. 10A and 10B. Even in this case, the second conductor portion 12 is disposed farther from the center of the planar conductor 2 than the first conductor portion 11.
Thus, the same operational effects as described in the first embodiment can be obtained.

As shown in FIG. 9B, the width of the narrowest portion of the coil conductor that connects between the first conductor portion 11 and the second conductor portion 12 is W, and is perpendicular to the one side of the planar conductor. The relationship between W and Y, where Y is the length of the magnetic core in the direction, will be described with reference to FIG.
FIG. 11 is a diagram showing the relationship between W and the coupling coefficient when the product of W and Y is made constant at 15 × 15 = 225 mm ² and W is changed. In this example, the reader / writer antenna is 100 × 100 mm, and is opposed to the antenna at a distance of 30 mm.

When W <Y (when W <15 mm), the smaller the W is, the smaller the coupling coefficient is, and the communication performance deteriorates. Therefore, good communication performance can be ensured by making the relationship W ≧ Y.
<< Fourth Embodiment >>
12-14 is a figure which shows each structure of antenna coil 24A, 24B, 24C which concerns on 4th Embodiment. 12A is a plan view of the antenna coil 24A before assembly, and FIG. 12B is a plan view of the antenna coil 24A. FIG. 13A is a plan view of the antenna coil 24B before assembly, and FIG. 13B is a plan view of the antenna coil 24B. Similarly, FIG. 14A is a plan view before assembly of the antenna coil 24C, and FIG. 14B is a plan view of the antenna coil 24C.

  The difference from the antenna coil 23 shown in FIG. 9 is that the end portion of the magnetic core 1 where the magnetic flux enters and exits is formed thicker than the other portions. In the antenna coil 24 </ b> A shown in FIG. 12, one end of the magnetic core 1 is formed wide (thicker) as a whole. In the antenna coil 24B of FIG. 13, one end of the magnetic core 1 is spread in a trapezoidal shape. In the example of the antenna coil 24 </ b> C in FIG. 14, the magnetic core 1 has a shape that becomes wider from the center to both ends.

  By using the magnetic core 1 having such a shape, the magnetic flux passing through the magnetic core 1 is increased, the magnetic field coupling with the antenna of the communication partner can be increased, and the maximum communicable distance is increased. Will improve.

<< Fifth Embodiment >>
15A is a plan view before assembling the antenna coil 25 according to the fifth embodiment, FIG. 15B is a top view of the antenna coil 25, and FIG. 15C is a bottom view of the antenna coil 25. is there. The flexible substrate 10 is bent at a position indicated by a broken line in the drawing so that the magnetic core 1 is sandwiched (wound around three surfaces). However, the flexible substrate 10 has a position shifted from the fold as a center. A spiral coil conductor CW is formed. And among coil conductor CW, the side far from the said fold is used as the 2nd conductor part 12, and the near side is used as the 1st conductor part 11. FIG.

  16A is a bottom view of the antenna 104 provided with the antenna coil 25, and FIG. 16B is a front view thereof. The antenna coil 25 is mounted at a position along the center of one side of the planar conductor 2 that is a circuit board.

FIG. 16C is an example in which the antenna coil 25 is fixed inside the housing 204 that houses the planar conductor 2 that is a circuit board, unlike the examples of FIGS. 16A and 16B. Even in this case, the second conductor portion 12 is disposed farther from the center of the planar conductor 2 than the first conductor portion 11.
Thus, the same operational effects as described in the first embodiment can be obtained.

<< Sixth Embodiment >>
17 to 19 are diagrams showing the configuration of each of the antenna coils 26A, 26B, and 26C according to the sixth embodiment. FIG. 17A is a plan view of the antenna coil 26A before assembly, and FIG. 17B is a plan view of the antenna coil 26A. 18A is a plan view of the antenna coil 26B before assembly, and FIG. 18B is a plan view of the antenna coil 26B. Similarly, FIG. 19A is a plan view before assembly of the antenna coil 26C, and FIG. 19B is a plan view of the antenna coil 26C.

  The difference from the antenna coil 25 shown in FIG. 15 is that the end portion of the magnetic core 1 through which the magnetic flux enters and exits is thicker than the other portions. In the antenna coil 26 </ b> A shown in FIG. 17, one end of the magnetic core 1 is formed wide (thicker) as a whole. In the antenna coil 26B shown in FIG. In the example of the antenna coil 26 </ b> C in FIG. 19, the magnetic core 1 has a shape that becomes wider from the center to both ends.

  By using the magnetic core 1 having such a shape, the magnetic flux passing through the magnetic core 1 is increased, the magnetic field coupling with the antenna of the communication partner can be increased, and the maximum communicable distance is increased. Will improve.

A ... Through hole CA ... Coil axis CW ... Coil conductor DB ... Directional beam H ... Magnetic flux MS1 ... First main surface MS2 ... Second main surface S ... One side 1 ... Magnetic core 2 ... Planar conductor 10 ... Flexible substrate 11 ... 1st conductor part 12 ... 2nd conductor part 21-23 ... Antenna coil 24A, 24B, 24C ... Antenna coil 25 ... Antenna coil 26A, 26B, 26C ... Antenna coil 100-104 ... Antenna 201-204 ... Case 301 ... Reader / writer side antenna 401 ... IC card

Claims (8)

In an antenna in which an antenna coil including a plate-like magnetic core having a first main surface and a second main surface and a coil conductor wound around the magnetic core is disposed close to a planar conductor,
The outer shape of the planar conductor is larger than the planar outer shape of the antenna coil,
The first main surface of the magnetic core faces the planar conductor,
The antenna coil is disposed near the edge of the planar conductor;
Among the coil conductors, a first conductor portion that is close to the first main surface of the magnetic core and a second conductor portion that is close to the second main surface of the magnetic core are: Located in a position that does not overlap when viewed from the normal direction of the first main surface or the second main surface,
The antenna, wherein the coil axis of the coil conductor is perpendicular to the edge of the planar conductor.   The coil conductor is formed of a conductive pattern in which a helical coil formed on a flexible substrate is cut by a predetermined slit line, and the flexible substrate is wound around four surfaces of the magnetic core, so that the slit is opened. The antenna according to claim 1, wherein the conductor patterns are joined at a line portion.   The antenna according to claim 1, wherein the coil conductor is a spiral conductor formed on a flexible substrate, and the flexible substrate is wound around three surfaces of the magnetic core.   The coil conductor is a spiral conductor formed on a flexible substrate, the flexible substrate includes a through hole at the center of the formation position of the coil conductor, and the magnetic core is inserted into the through hole. The antenna according to 1.   The width of the narrowest portion of the coil conductor that connects between the first conductor portion and the second conductor portion is W, and the length of the magnetic core perpendicular to the edge of the planar conductor The antenna according to claim 1, wherein a relationship of W ≧ Y is established, where Y is Y.   The antenna according to claim 1, wherein the magnetic core has a thicker end portion where magnetic flux enters and exits than other portions.   The distance X from the end of the antenna on the side close to the edge of the planar conductor to the edge of the planar conductor is X, and the magnetic core perpendicular to the edge of the planar conductor is X The antenna according to claim 1, wherein a relationship of Y> X is defined, where Y is a length.   The antenna according to claim 1, wherein the planar conductor is configured by a circuit board on which the antenna coil is mounted.

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