JP2007336416A - Antenna unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna unit advantageous in downsizing, capable of sufficiently reducing effect from a metal layer or the like, with easy manufacturing process. <P>SOLUTION: The antenna unit includes a magnetic layer 18 and a first spiral coil 11 provided on the magnetic layer 18. The fist spiral coil 11 is arranged with offset toward one side from a viewpoint of a center line X at a plane direction of the magnetic layer 18. When placing the antenna unit having such a construction on a parallel magnetic field, most magnetic lines of force flow into from the one side from the viewpoint of the center line X on the surface of the magnetic layer 18, and flow out from the other side from the viewpoint of the center line X. Therefore, the first spiral coil 11 can detect the magnetic flux flowing into or out from the magnetic layer 18. As a result, there is provided the antenna unit advantageous in downsizing, capable of sufficiently reducing effect from the metal layer or the like, with easy manufacturing process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna device, and more particularly to a magnetic field detection type antenna device using a spiral coil.

  Conventionally, as a magnetic field detection type antenna device, an antenna device called a bar antenna has been widely known. The bar antenna has a configuration in which a wire is wound around a magnetic core made of a ferrite sintered body, etc., and a voltage caused by electromagnetic induction is applied to both ends of the coil by sensing the cross-spreading magnetic flux passing through the magnetic body. Is generated. Such a magnetic field detection type antenna device is different from a linear antenna of a type that detects an electric field, and its shape does not depend on the wavelength of the operating frequency band. It has been widely used as an antenna device for receiving AM radio broadcasts.

  In recent years, a magnetic field detection type antenna device is also used as an antenna for a wireless IC card in which an RFID is incorporated. Since the wireless IC card needs to be very thin due to its nature, the thickness of the antenna used for this needs to be sufficiently thin. In addition, since wireless IC cards are sometimes used for physical distribution management, such as sticking to products using an adhesive sheet, etc. However, sufficient communication performance is required.

  However, when a magnetic field detection type antenna device is attached to a conductor such as metal, an eddy current induced in the conductor acts in a direction to cancel the interlinkage magnetic flux. For this reason, there has been a problem that the resonance frequency shift and loss of the antenna coil used as the resonance circuit are increased, and as a result, the communication performance is lowered.

  As a method for solving this problem, for example, Patent Document 1 proposes a method of providing a magnetic layer on the bottom surface of a spiral coil. According to this method, since the magnetic flux interlinking with the spiral coil passes through the magnetic material layer, the magnetic flux flowing through the metal body is reduced even when the metal body is disposed below the antenna device. Reduce. Thereby, since generation | occurrence | production of an eddy current is suppressed, it becomes possible to suppress the deterioration of communication performance.

  However, since the method described in Patent Document 1 senses magnetic flux in the direction perpendicular to the antenna device, the thickness of the magnetic layer is sufficient to sufficiently suppress the influence of the metal body. It is necessary to thicken. For this reason, it is not necessarily suitable as an antenna device for a wireless IC card that is required to be thin.

  On the other hand, Patent Documents 2 to 4 propose a method of inserting a thin magnetic core into a planar spiral coil. According to this method, since the magnetic flux in the direction parallel to the antenna device can be sensed, even when a metal body or the like is disposed below the antenna device, it is possible to greatly suppress the influence. It becomes.

  However, the antenna devices described in Patent Documents 2 to 4 have a structure that is originally three-dimensionally formed into a planar structure by pressing, so that the manufacturing process is complicated and an irregular planar shape after pressing. There is a problem of becoming.

  Moreover, the antenna devices described in Patent Documents 2 to 4 have a problem that sufficient sensitivity cannot be ensured. Generally, in a bar antenna in which a coil is wound around a magnetic body, the sensitivity can be increased by forming the coil intensively near the center where the magnetic flux flowing through the magnetic body is most concentrated. However, in the antenna devices described in Patent Documents 2 to 4, since the coil is widely formed over the entire area of the magnetic layer, a decrease in inductance and a deterioration in sensitivity occur.

In addition, Patent Documents 5 to 8 disclose thin antenna devices, but all have problems such as complicated manufacturing processes and inability to sufficiently reduce the influence of metal layers and the like. Yes.
JP 2004-166175 A JP 2000-48152 A JP 2004-48135 A JP 2004-348497 A JP 2002-252518 A JP 2003-318633 A JP-A-3-64105 JP 2002-117383 A

  Accordingly, an object of the present invention is to provide an antenna device that is advantageous for thinning, can sufficiently reduce the influence of a metal layer, and has a simple manufacturing process.

  As a result of earnest research on the antenna device that satisfies the above requirements, the present inventor does not use a method of winding a spiral coil around the magnetic material as in the conventional antenna device, but flows into the surface of the magnetic material. Alternatively, we focused on the method of capturing the flowing magnetic field lines. The present invention has been made based on such a point of view, and an antenna device according to the present invention includes a magnetic layer and a first spiral coil formed on the magnetic layer. The spiral coil is arranged so as to be offset in a plane with respect to the magnetic layer.

  When a planar magnetic layer is placed in a parallel magnetic field, magnetic flux flows from one part of the surface of the magnetic layer and magnetic flux flows from another part. Therefore, if the first spiral coil is disposed so as to be planarly offset with respect to the magnetic layer as in the present invention, the magnetic flux flowing into or out of the magnetic layer is magnetized. be able to. For this reason, it is advantageous for thinning, it is possible to provide an antenna device that can sufficiently reduce the influence of the metal layer and the like and that can be easily manufactured.

  In the present invention, the first spiral coil is preferably disposed on one side when viewed from the center line in the planar direction of the magnetic layer. According to this, since only one of the magnetic flux flowing into the magnetic layer and the magnetic flux flowing out from the magnetic layer can be sensed, high sensitivity can be obtained.

  The antenna device according to the present invention further includes a second spiral coil disposed on the other side of the magnetic layer as viewed from the center line, and the first and second spiral coils are connected in phase. Is preferred. According to this, one of the magnetic flux flowing into the magnetic layer and the magnetic flux flowing out of the magnetic layer can be sensed by the first spiral coil, and the other can be sensed by the second spiral coil. In addition, since these outputs are synthesized, higher sensitivity can be obtained.

  In this case, it further includes third and fourth spiral coils disposed opposite to the first and second spiral coils as viewed from the magnetic layer, and the first to fourth spiral coils are in phase. More preferably, they are connected. According to this, one of the magnetic flux flowing into and out of the magnetic layer is sensed by the first and third spiral coils, and the other is sensed by the second and fourth spiral coils. Since it is possible to magnetize and these outputs are combined, it is possible to obtain even higher sensitivity.

  As described above, in the present invention, the parallel magnetic flux is sensed by a completely different method. For this reason, it is advantageous to reduce the thickness, and it is possible to provide an antenna device that can sufficiently reduce the influence of the metal layer and the like and that has a simple manufacturing process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing a configuration of an antenna device 10 according to a preferred first embodiment of the present invention.

  As shown in FIG. 1, the antenna device 10 according to the present embodiment includes a flat magnetic layer 18 and a first spiral coil 11 formed on one surface 18 a of the magnetic layer 18. Yes. The material of the magnetic layer 18 is not particularly limited, and Ni—Zn ferrite, Mn—Zn ferrite, and a resin in which these powders are dispersed can be used. Furthermore, you may comprise the magnetic body layer 18 by metal cores, such as a silicon steel plate, an amorphous metal core, a laminated metal core, a metal dust core. However, when the magnetic layer 18 has conductivity, it is necessary to interpose an insulating film for insulating the magnetic layer 18 and the first spiral coil 11.

  The first spiral coil 11 is not disposed at the center portion of the surface 18a of the magnetic layer 18, but is disposed offset in a plane. Specifically, when viewed from the center line X that bisects the plane of the magnetic layer 18 in the longitudinal direction, it is offset on one side (left side in the figure), and the other side (see FIG. The right side is left free.

  The material of the first spiral coil 11 is not particularly limited as long as it is a conductor, and a material obtained by firing a conductor paste or the like can be used. As a method for forming the first spiral coil 11, in addition to screen printing and sputtering, a conductive layer is formed on almost the entire surface 18 a of the magnetic layer 18, and then the first spiral coil 11 is etched. A method of patterning 11 can be used.

  FIG. 2 is a schematic cross-sectional view taken along the line AA in FIG. 1 and also shows the lines of magnetic force M when placed in a magnetic field parallel to the magnetic layer 18.

  As shown in FIG. 2, when the antenna device 10 according to the present embodiment is placed in a parallel magnetic field, some of the magnetic lines of force M flow in and out of the side surface 18c of the magnetic layer 18, but most of the magnetic lines of force M are magnetic. Inflow and outflow from the surfaces 18 a and 18 b of the body layer 18. More specifically, if the magnetic lines of force M flow from left to right, most of the magnetic lines of force M are on one side of the surfaces 18a and 18b of the magnetic layer 18 as viewed from the center line X (left side in the figure). ) And flows out from the other side (right side in the figure) as seen from the center line X.

  In order to increase the ratio of the lines of magnetic force M flowing in and out of the surfaces 18a and 18b of the magnetic layer 18, the ratio (T / D) between the length D and the thickness T of the magnetic layer 18 may be decreased. .

  FIG. 3 is a diagram showing a result of simulating the effect of the ratio (T / D) of the length D and the thickness T of the magnetic layer 18 on the magnetic flux, and (a) shows T / D = 1/2. (B) is T / D = 1/10, (c) is T / D = 1/20, and (d) is T / D = 1/50. Show.

  Referring to FIG. 3, as the ratio (T / D) between the length D and the thickness T of the magnetic layer 18 is reduced, the lines of magnetic force M flowing into and out of the surfaces 18a and 18b of the magnetic layer 18 are decreased. It can be seen that the ratio of increases. That is, as the magnetic layer 18 becomes thinner, the ratio of the magnetic lines M flowing in and out from the side surface 18c of the magnetic layer 18 to the total amount of magnetic lines M flowing in and out of the magnetic layer 18 decreases. The ratio of the lines of magnetic force M flowing in and out from the surfaces 18a and 18b of the magnetic layer 18 is relatively increased.

  In the present embodiment, the magnetic flux flowing from the surface 18 a of the magnetic layer 18 is thus sensed by the first spiral coil 11. That is, as shown in FIG. 2, when it is considered that the magnetic lines of force M flow from the left to the right, the magnetic lines of force M from the upper side of the first spiral coil 11 to the lower side with respect to the first spiral coil 11. It will be linked towards you. As a result, a voltage is generated by electromagnetic induction between one end 11a and the other end 11b of the first spiral coil 11 shown in FIG. In this example, a relatively positive voltage is induced at one end 11 a of the first spiral coil 11, and a relatively negative voltage is induced at the other end 11 b of the first spiral coil 11. become.

  Thereby, since the antenna device 10 according to the present embodiment can sense magnetic flux in a direction parallel to the magnetic layer 18, even if a metal body or the like is disposed below the antenna device 10, The influence can be greatly suppressed.

  FIG. 4 shows the antenna device 10 according to the present embodiment as a case so that the surface 18a of the magnetic layer 18 faces the upper lid 19a made of resin or glass, and the surface 18b of the magnetic layer 18 faces the metal case 19b. It is a figure which shows the flow of the magnetic flux in the case of accommodating.

  When the metal case 19b receives an external crossing magnetic field, an eddy current is generated therein, which generates a demagnetizing field with respect to the external crossing magnetic field. Thereby, the metal case 19b acts as a magnetic shield and inhibits the entry of magnetic lines of force into the case. On the other hand, the upper lid 19a is made of a material such as resin or glass, and has no effect on the lines of magnetic force. Therefore, the magnetic field lines M are substantially concentrated on the upper surface side of the antenna device 10 and hardly exist on the lower surface side. Then, the magnetic flux flowing from the surface 18a of the magnetic layer 18 links the first spiral coil 11 and generates a voltage at both ends 11a and 11b.

  As described above, the antenna device 10 according to the present embodiment has a configuration in which the first spiral coil 11 is arranged so as to be offset in a plane with respect to the magnetic layer 18. The magnetic flux in the parallel direction can be efficiently sensed. In addition, unlike a conventional antenna device of a type that senses parallel magnetic flux, it is no longer necessary to flatten a three-dimensional structure by pressing or the like. In addition, it can be manufactured by a simple process.

  Next, a second preferred embodiment of the present invention will be described.

  FIG. 5 is a schematic perspective view showing the configuration of the antenna device 20 according to the second preferred embodiment of the present invention.

  As shown in FIG. 5, the antenna device 20 according to the present embodiment further includes a second spiral coil 12 formed on one surface 18a of the magnetic layer 18, so that the antenna according to the first embodiment. This is different from the apparatus 10. Since the other points are the same as those of the antenna device 10 according to the first embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  The second spiral coil 12 is opposite to the first spiral coil 11 when viewed from the center line X that bisects the plane of the magnetic layer 18 in the longitudinal direction, that is, the other side when viewed from the center line X ( It is offset on the right side in the figure.

  FIG. 6 is a schematic cross-sectional view along the line BB in FIG. 5, and also shows the lines of magnetic force M when placed in a magnetic field parallel to the magnetic layer 18.

  Assuming that the magnetic field lines M are flowing from left to right as shown in FIG. 6, the magnetic field lines M are linked to the first spiral coil 11 from the upper side to the lower side. M passes through the magnetic layer 18 and reaches the second spiral coil 12, and is linked to the second spiral coil 12 from below to above. In other words, the first spiral coil 11 senses the magnetic flux flowing into the magnetic layer 18, and the second spiral coil 12 senses the magnetic flux flowing out of the magnetic layer 18.

  As a result, a voltage is generated in each of the coils 11 and 12 by electromagnetic induction. Thus, voltages are generated by electromagnetic induction between the one end 11a and the other end 11b of the first spiral coil 11 and between the one end 12a and the other end 12b of the second spiral coil 12, respectively. To do. In this example, a relatively positive voltage is induced at one end 11a, 12a of the first and second spiral coils 11, 12, and the other end 11b of the first and second spiral coils 11, 12 is detected. A relatively negative voltage is induced in 12b.

  In the present embodiment, the other end 11 b of the first spiral coil 11 and the second spiral coil 12 are connected to each other via a via-hole conductor (not shown) penetrating the magnetic layer 18 and the connection line 16. Since the one end 12a is connected, the first and second spiral coils 11 and 12 are connected in phase in series. As a result, the voltage obtained by the first spiral coil 11 and the voltage obtained by the second spiral coil 12 are superimposed, and a higher output can be obtained.

  Thus, the antenna device 20 according to the present embodiment senses not only the first spiral coil 11 that senses the magnetic flux flowing into the magnetic layer 18 but also the second magnetic flux that flows out of the magnetic layer 18. Since the spiral coil 12 is provided, the magnetic flux in the direction parallel to the magnetic layer 18 can be more efficiently sensed without increasing the size of the magnetic layer 18.

  The antenna device 20 according to the present embodiment can also be accommodated in the case shown in FIG. Also in this case, it is possible to efficiently sense the parallel magnetic flux without being substantially affected by the metal case 19b positioned below the antenna device 20.

  Next, a preferred third embodiment of the present invention will be described.

  FIG. 7 is a schematic exploded perspective view showing a configuration of an antenna device 30 according to a preferred third embodiment of the present invention.

  As shown in FIG. 7, the antenna device 30 according to the present embodiment further includes the third and fourth spiral coils 13 and 14 formed on the other surface 18 b of the magnetic layer 18. This is different from the antenna device 20 according to the embodiment. Since the other points are the same as those of the antenna device 20 according to the second embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted. Although the third and fourth spiral coils 13 and 14 are formed on the other surface 18b of the magnetic layer 18, they are separated from the magnetic layer 18 in FIG. Is shown.

  The third spiral coil 13 is disposed opposite to the first spiral coil 11 as viewed from the magnetic layer 18, that is, disposed on the back side. Similarly, the fourth spiral coil 14 is disposed opposite to the second spiral coil 12 as viewed from the magnetic layer 18, that is, on the back side. Thus, the first and third spiral coils 11 and 13 are both offset from one side (left side in the figure) when viewed from the center line X, and the second and fourth spiral coils 12 and 14 are arranged. Are offset on the other side (right side in the figure) as viewed from the center line X.

  FIG. 8 is a schematic cross-sectional view taken along the line C-C in FIG. 7, and also shows the lines of magnetic force M when placed in a magnetic field parallel to the magnetic layer 18.

  If it is considered that the magnetic force lines M flow from left to right as shown in FIG. 8, the magnetic force lines M on the surface 18 a side of the magnetic layer 18 are chained from the upper side to the lower side with respect to the first spiral coil 11. The magnetic lines of force M on the surface 18b side of the magnetic layer 18 are linked to the third spiral coil 13 from below to above. Further, the magnetic lines of force M pass through the magnetic layer 18 and reach the second and fourth spiral coils 12 and 14, and are linked to the second spiral coil 12 from below to above, The four spiral coils 14 are linked from above to below. Thus, the first and third spiral coils 11 and 13 sense the magnetic flux flowing into the magnetic layer 18, and the second and fourth spiral coils 12 and 14 flow out of the magnetic layer 18. Magnetic flux will be sensed.

  As a result, a voltage is generated in each of the coils 11 to 14 by electromagnetic induction. In this example, a relatively positive voltage is induced at one end 11a to 14a of the first to fourth spiral coils 11 to 14, and the other end 11b to the other end 11b to 14th of the first to fourth spiral coils 11 to 14. A relatively negative voltage is induced in 14b.

  In the present embodiment, the other end 11 b of the first spiral coil 11 and the third spiral coil 13 are connected via a via-hole conductor (not shown) penetrating the magnetic layer 18 and the connection line 16. One end 13a, the other end 13b of the third spiral coil 13 and one end 14a of the fourth spiral coil 14, and the other end 14b of the fourth spiral coil 14 and one end of the second spiral coil 12. 12a is connected. As a result, the first to fourth spiral coils 11 to 14 are all connected in series in phase. As a result, the voltages obtained by the first to fourth spiral coils 11 to 14 are superimposed on each other, so that an even higher output can be obtained.

  Thus, in the antenna device 30 according to the present embodiment, the third and fourth spiral coils 13 and 14 are added to the other surface 18b of the magnetic layer 18, so that the size of the magnetic layer 18 is reduced. Without increasing the size, the magnetic flux in the direction parallel to the magnetic layer 18 can be more efficiently sensed.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in each of the above embodiments, the planar shape of the magnetic layer 18 is a rectangle, and the outer peripheral shape and the inner peripheral shape of the spiral coils 11 to 14 are substantially square. However, these shapes are limited in the present invention. Instead, for example, the planar shape of the magnetic layer 18 may be circular, and the outer peripheral shape and inner peripheral shape of each of the spiral coils 11 to 14 may be semicircular.

  In the second and third embodiments, a plurality of spiral coils are connected in series. However, the connection method is not limited to this as long as they are connected in phase, and may be connected in parallel. Absent. In this case, the impedance of the antenna device can be reduced. However, in general, it is more important to increase the output voltage than to reduce the impedance of the antenna device. Therefore, it is preferable to connect a plurality of spiral coils in series as in the above embodiment.

  Further, in each of the above embodiments, the magnetic layer 18 also serves as the antenna device substrate. However, as shown in FIG. 9, the magnetic layer 18 is formed on the surface of the substrate 40 made of a non-magnetic material such as resin. It is also possible to do. In this case as well, the spiral coil may be disposed offset from the magnetic layer 18.

  In each of the above embodiments, the spiral coil is formed on the surface of the magnetic layer 18, but it may be formed so as to be embedded in the magnetic layer 18 as shown in FIG. Alternatively, as shown in FIG. 10B, the surface of the magnetic layer 18 may be covered with a thin dielectric layer 42, and a spiral coil may be formed on the dielectric layer 42.

  Further, in each of the above embodiments, the magnetic flux flowing into and out of the magnetic layer 18 is detected by each spiral coil when the antenna device is placed in a magnetic field parallel to the magnetic layer 18. When a magnetic field perpendicular to the magnetic field 18 is placed, a spiral coil for detecting the magnetic flux flowing into the magnetic layer may be added so that both the parallel magnetic field and the vertical magnetic field can be detected.

  In this case, instead of providing a spiral coil for detecting the vertical magnetic field, the vertical magnetic field may be detected by switching the connection state of the spiral coil. For example, in the second embodiment shown in FIG. 5, the first and second spiral coils 11 and 12 are provided with a detection circuit for detecting the polarity of the electromagnetically induced voltage, and the first and second spirals are provided. A switching circuit is provided for switching the connection state of the coiled coils 11 and 12, and the polarity of the voltage induced at the one end 11a of the first spiral coil 11 and the voltage induced at the one end 12a of the second spiral coil 12 are reversed. If it is detected that the one end 11a of the first spiral coil 11 is connected to the other end 12b of the second spiral coil 12, it may be switched. With this configuration, the magnetic flux can be detected even when a magnetic field perpendicular to the magnetic layer 18 exists.

1 is a schematic perspective view showing a configuration of an antenna device 10 according to a preferred first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view along the line AA in FIG. 1. It is a figure which shows the result of having simulated the influence which ratio (T / D) of length D of the magnetic body layer 18 has on magnetic flux, (a) is T / D = 1/2, (B) shows the case where T / D = 1/10, (c) shows the case where T / D = 1/20, and (d) shows the case where T / D = 1/50. It is a figure which shows the flow of the magnetic flux in case the antenna apparatus 10 is accommodated in a case. It is a schematic perspective view which shows the structure of the antenna device 20 by preferable 2nd Embodiment of this invention. FIG. 6 is a schematic cross-sectional view along the line BB in FIG. 5. It is a substantially exploded perspective view which shows the structure of the antenna apparatus 30 by preferable 3rd Embodiment of this invention. FIG. 8 is a schematic cross-sectional view taken along the line CC in FIG. 7. FIG. 5 is a schematic perspective view showing a configuration of an antenna device according to a modification in which a magnetic layer 18 is formed on the surface of a substrate 40 made of a nonmagnetic material. (A) is a schematic sectional view showing an example in which a spiral coil is embedded in a magnetic layer, and (b) is an example in which a dielectric layer is interposed between the magnetic layer and the spiral coil. It is sectional drawing shown.

Explanation of symbols

10, 20, 30 Antenna device 11 1st spiral coil 12 2nd spiral coil 13 3rd spiral coil 14 4th spiral coil 11a-14a One end 11b-14b of spiral coil of spiral coil Other end 16 Connection line 18 Magnetic layer 18a One surface 18b of magnetic layer 18 The other surface 18c of magnetic layer 18 Side surface 19a of magnetic layer 18 Upper lid 19b Metal case 40 Substrate 42 Dielectric layer M Magnetic field lines

Claims (5)

A magnetic layer, and a first spiral coil formed on the magnetic layer,
The antenna device according to claim 1, wherein the first spiral coil is arranged to be offset in a plane with respect to the magnetic layer.   2. The antenna device according to claim 1, wherein the first spiral coil is disposed on one side when viewed from a center line in a planar direction of the magnetic layer.   A second spiral coil disposed on the other side of the magnetic layer as viewed from the center line is further provided, and the first and second spiral coils are connected in phase. Item 3. The antenna device according to Item 2.   Third and fourth spiral coils disposed opposite to the first and second spiral coils as viewed from the magnetic layer, respectively, wherein the first to fourth spiral coils are in phase. The antenna device according to claim 3, wherein the antenna device is connected. A second spiral coil formed on the magnetic layer;
When placed in a magnetic field substantially parallel to the magnetic layer, the first spiral coil senses a magnetic flux flowing into the magnetic layer, and the second spiral coil is the magnetic body. The antenna device according to claim 1, wherein the antenna device is disposed so as to sense a magnetic flux flowing out from the layer.

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