JP6070163B2 - Antenna device and communication device - Google Patents

Description

  The present invention relates to an antenna device used in an RFID system or a short-range wireless communication system and a communication device including the antenna device.

  In an RFID of 13.56 MHz band such as NFC (Near Field Communication) mounted on a portable terminal, an IC chip for RFID and a matching element are mainly mounted on a circuit board, and an antenna is placed inside a resin terminal housing. In general, the RFID IC chip and the antenna are connected to each other in a direct current via a spring pin or the like.

  On the other hand, recent wireless communication devices such as mobile phone terminals have been reduced in thickness, and in order to cope with the lack of strength due to the reduction in thickness, the resin casing is subjected to magnesium plating or a metal casing. Increasingly, the “metallization” of the body supplements strength.

  However, when the casing is “metallized”, the antenna built in the terminal is shielded by metal, which causes a problem that communication with the counterpart device cannot be performed.

  Therefore, as in Patent Document 1 and Patent Document 2, an antenna device having a structure in which a metal plate having a larger area than the antenna coil is brought close to the antenna coil (magnetically coupled) to the antenna coil and the metal plate is used as a radiator. Has been proposed.

JP 2011-97657 A JP 2011-249935 A

  However, in Patent Documents 1 and 2, since a slit is formed in the metal plate, when the metal plate is a part of the casing of the wireless communication device, the design is restricted by exposing the slit. There is a problem that the aesthetics are impaired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna device that maintains strength by using a metal housing and does not impair aesthetics, and a communication device including the antenna device.

  The antenna device according to the present invention is magnetically coupled to the metal housing by forming a notch portion penetrating in the thickness direction from an outer edge portion toward the inside and a magnetic flux passing through the notch portion. A coil antenna, wherein the metal housing has a first protrusion and a second protrusion opposed to each other with the notch interposed therebetween, and the first protrusion is along the thickness direction. A first surface that intersects with the one straight line, and the second protrusion has a second surface that intersects with the one straight line and faces the first surface. Features.

  In this configuration, the metal casing can act as a radiation plate of the antenna device, and when the notch formed in the metal casing is viewed from the thickness direction, the first surface of the first protrusion and Due to the second surface of the second protrusion, the opposite side of the metal housing can be made invisible through the notch. In other words, when the cutout portion is viewed from the thickness direction, the first surface (or the second surface) is visible at the cutout portion, making it difficult to understand the boundary of the cutout portion in the metal housing. This can reduce the risk of the appearance being damaged.

  The first surface and the second surface may be inclined with respect to the one straight line and face each other.

  This configuration facilitates the formation of the notch. Further, since the first surface and the second surface can be made larger than the capacitor formed in the notch when the first surface and the second surface are parallel to one straight line, an increase in the resonance frequency of the antenna device can be suppressed. That is, the resonance frequency due to the inductance of the capacitor in the notch and the inductance of the metal housing decreases, and approaches the operating frequency (13.56 MHz). As a result, the antenna can be easily coupled to the other antenna, so that good antenna characteristics can be obtained (there is resonance by a coil antenna and resonance by a metal housing).

  The first surface and the second surface may be configured to be orthogonal to the one straight line and partially opposed to each other.

  In this configuration, since the first surface and the second surface can be made larger than the capacitor formed in the notch when the first surface and the second surface are parallel to one straight line, an increase in the resonance frequency of the antenna device can be suppressed. it can.

  The structure provided with the insulator provided between the said 1st surface and the said 2nd surface is preferable.

  In this configuration, since the insulator is filled in the space of the notch, it is possible to suppress the strength reduction due to the formation of the notch.

  The coil antenna may have a coil conductor formed in an insulator layer, and the coil opening of the coil conductor may be arranged at a position overlapping at least a part of the opening when viewed from the thickness direction.

  With this configuration, the antenna device can be thinned.

  The notch has an opening and a slit connecting the opening and the outer edge, the first surface and the second surface are opposed along the slit, and the coil antenna is A configuration in which the coil opening of the coil conductor is disposed at a position overlapping at least part of the opening when viewed from the thickness direction may be employed.

  In this configuration, for example, when the antenna device is used in a mobile phone or the like, the metal casing of the mobile phone can act as a radiation plate for a magnetic field signal by using an existing opening such as a camera module portion.

  The coil antenna may have a laminated structure in which a plurality of insulator layers each having a coil conductor are laminated, and may have a configuration in which a coil opening is arranged toward the notch.

  In this configuration, even if the winding axis of the coil antenna is not perpendicular to the plane of the metal housing, the metal housing acts as a radiation plate by arranging the notch in the extending direction of the winding shaft. be able to.

  According to the present invention, the casing is metallized in order to increase the strength, the notch is provided in the casing, and the metal casing and the coil antenna are magnetically coupled to each other to act as the radiation plate. Can be made. It is possible to make it difficult to understand the boundary of the notch portion in the metal casing, and it is possible to reduce the possibility that the appearance is impaired.

FIG. 1 is a perspective view of the antenna device according to the first embodiment. FIG. 2 is a plan view and a side view of the antenna device. FIG. 3 is a diagram illustrating a structure inside a housing of the wireless communication device to which the antenna device according to the first embodiment is applied. 4A and 4B are modifications of the antenna device according to the first embodiment. FIG. 4A is a perspective view, and FIG. 4B is a side cross-sectional view. FIG. 5 is a perspective view of the antenna device according to the second embodiment. FIG. 6 is a plan view and a side view of the antenna device. FIG. 7 is an exploded perspective view of the antenna device according to the third embodiment. FIG. 8 is a plan view and a side view of the antenna device. FIG. 9 is a diagram illustrating a modification of the antenna device according to the third embodiment. FIG. 10A is a perspective view of an antenna device according to Embodiment 4, and FIG. 10B is a side view of the antenna device.

(Embodiment 1)
FIG. 1 is a perspective view of the antenna device according to the first embodiment. FIG. 2 is a plan view and a side view of the antenna device. The antenna device 1 is an antenna device that uses a high frequency signal in the HF band (13.56 MHz band) as a carrier frequency, and is configured for a reader / writer used in an NFC system. The antenna device 1 includes a planar conductor 10 and a coil antenna 20.

  The planar conductor 10 is a part of a metal casing of a communication device on which the antenna device 1 is mounted, for example. The planar conductor 10 is formed with a slit (notch) 11 extending from a part of the outer edge to the inside and an opening (notch) 12 connected to the slit 11. That is, the opening 12 is connected to the outer edge by the slit 11.

  The slit 11 is a linear notch penetrating in the thickness direction of the planar conductor 10. The portion of the planar conductor 10 along the slit 11 from a part of the outer edge to the opening 12 corresponds to the first protrusion and the second protrusion of the present invention. The first protrusion has a first surface 111, and the second protrusion has a second surface 112.

  The first surface 111 and the second surface 112 are inclined with respect to one straight line along the thickness direction of the planar conductor 10 and are opposed to each other. More specifically, as shown in FIG. 2, the first surface 111 and the second surface 112 are inclined so that the first surface 111 can be seen over the entire slit 11 when viewed in plan. . This configuration makes it difficult to visually recognize the boundary between the slit 11 and the planar conductor 10 when viewed in plan.

  The coil antenna 20 has a coil pattern formed in a rectangular spiral shape on one surface of an insulator base (not shown). The coil antenna 20 has a coil opening larger than the opening 12, and is disposed close to the planar conductor 10 so that the coil opening overlaps the opening 12. The coil antenna 20 is connected to an RFIC (not shown) as a power feeding circuit that feeds an HF band signal. The coil antenna 20 may be disposed so that the opening 12 is accommodated in the coil opening, or may be disposed so that a part of the coil opening overlaps the opening 12. Also, as shown in FIG. 4, the Q characteristic of the antenna coil may be improved by arranging a ferrite magnetic body 15 having an opening 15A on the back surface of the coil antenna 20. 4A and 4B are modifications of the antenna device according to the first embodiment. FIG. 4A is a perspective view, and FIG. 4B is a side cross-sectional view. The opening 15A has substantially the same shape and size as the coil opening of the coil antenna 12 and the opening 12 of the planar conductor. The antenna device 1 can be thinned by arranging the coil antenna 20 having a rectangular spiral coil pattern formed on one surface of the insulator base material close to the planar conductor 10.

  In the antenna device 1 having the above configuration, when a current flows through the coil antenna 20 in the direction of the broken line arrow shown in FIG. 2, a magnetic flux φ1 shown in FIG. 1 is generated. The magnetic flux φ1 passes through the opening 12, and the coil antenna 20 and the planar conductor 10 are magnetically coupled. As a result, a current is induced in the planar conductor 10 and flows mainly along the edge of the planar conductor 10 due to the edge effect, as indicated by the solid arrow direction in FIG. 1 and FIG. Produces a magnetic flux φ2. Thereby, the planar conductor 10 acts as a radiation plate of the antenna device 1.

  In this antenna device 1, an LC resonance circuit is configured by the inductance of the planar conductor 10 and the capacitance of the slit 11, specifically, the capacitance formed between the first surface 111 and the second surface 112. Is done. The inductance of the antenna device 1 varies depending on the length and width of the slit 11. For example, the capacitance in the slit 11 is increased by increasing the facing area between the first surface 111 and the second surface 112. The first surface 111 and the second surface 112 are inclined with respect to the thickness direction. Therefore, the capacitance C1 formed between the first surface 111 and the second surface 112 is the first surface 111 when the first surface 111 and the second surface 112 are parallel to the thickness direction. And larger than the capacitance C2 formed between the second surfaces 112 (C1> C2). As a result, since the resonance frequency by the LC resonance circuit can be lowered, the capacitance necessary for the HF band can be ensured. By making this resonance frequency lower than the cellular phone's cellular frequency (for example, 800 MHz), the slit 11 appears to be short-circuited at a high frequency, and when a ferrite magnetic material is disposed on the back surface of the coil antenna 20, the coil antenna The high frequency current does not flow in the ferrite coil attached to the back surface of 20. Thereby, deterioration of communication quality, such as a cellular antenna, can be prevented.

  FIG. 3 is a diagram illustrating a structure inside the housing of the wireless communication device to which the antenna device 1 according to the first embodiment is applied. FIG. 3 is a plan view of the wireless communication device 100 with the upper housing 91 and the lower housing 92 separated and the inside exposed. In this example, the lower housing 92 is made of resin, and a part of the lower housing 92 is used as the planar conductor 10 for strengthening the strength.

  Circuit boards 71 and 81, a battery pack 83, and the like are housed inside the housing 91. On the circuit board 71, an RFIC 3 provided with a communication circuit is mounted. A UHF band antenna 72, a camera module 76, and the like are also mounted on the circuit board 71. In addition, a UHF band antenna 82 and the like are mounted on the circuit board 81. The circuit board 71 and the circuit board 81 are connected via a coaxial cable 84.

  A slit 11 and an opening 12 are formed in the planar conductor 10 of the lower housing 92. In FIG. 3, the opening 12 has a circular shape. In the opening 12, the coil antenna 20 to which the RFIC 3 is connected via the connection pin 31 is disposed in the vicinity. Further, the lens of the camera module 76 is disposed in the opening 12 so as to be optically exposed.

  In this way, the planar conductor 10 that is a part of the housing can function as a radiation plate of the antenna device 1. Further, the slit 11 formed to function as a radiation plate is difficult to understand the boundary with the other part of the planar conductor 10 due to the first surface 111 and the second surface 112. Will not be damaged.

  Further, the opening 12 is for use in the camera module 76 of the wireless communication apparatus 100. By using the opening 12, it is not necessary to separately form an opening in the planar conductor 10. In other words, by using the existing structure, the metal casing of the wireless communication device 100 can act as a radiation plate.

(Embodiment 2)
FIG. 5 is a perspective view of the antenna device according to the second embodiment. FIG. 6 is a plan view and a side view of the antenna device. In the following description, the same reference numerals are given to the members of the first embodiment and the description thereof is omitted, and only differences from the first embodiment will be described.

  The antenna device 1 </ b> A includes a planar conductor 10 </ b> A and a coil antenna 20. A slit 11 is formed in the planar conductor 10A. The planar conductor 10A has a first surface 111 and a second surface 112 that are inclined with respect to one straight line along the thickness direction and are opposed to each other. A slit 11 is formed between them. As in the first embodiment, the slit 11 is less likely to visually recognize the boundary with the planar conductor 10 </ b> A by the first surface 111, and can prevent the appearance from being impaired. Note that the length and width of the slit 11 are appropriately changed in accordance with the resonance frequency of the antenna device 1A.

  The coil antenna 20 is disposed at a position where the coil opening overlaps the slit 11. The first surface 111 and the second surface 112 are opposed to each other with a predetermined distance therebetween with the slit 11 interposed therebetween. That is, the opening is formed in the planar conductor in the first embodiment, but the opening is not formed in the second embodiment. Therefore, the manufacture of the planar conductor 10A that functions as a radiation plate is simplified, and a decrease in strength can be suppressed. By using this antenna device 1A for a wireless communication device, the strength can be improved by a metal casing without impairing the appearance.

  The induced current, magnetic flux, and the like of the planar conductor 10A that functions as a radiation plate are the same as those in the embodiment, and a description thereof will be omitted.

  In the second embodiment, unlike the first embodiment, it is not necessary to form the opening 12, and thus the planar conductor 10A can be easily manufactured. Moreover, since no opening is formed, the strength reduction of the planar conductor 10A can be further suppressed.

(Embodiment 3)
FIG. 7 is an exploded perspective view of the antenna device according to the third embodiment. FIG. 8 is a plan view and a side view of the antenna device. The antenna device 1B includes a planar conductor 10B and a coil antenna 20.

  The planar conductor 10B is formed by laminating a plurality of metal plates 10B1, 10B2, and 10B3. In the metal plate 10B1, a rectangular opening 121 and a slit 131 that connects the opening 121 and the outer edge are formed. A rectangular notch 132 is formed in the metal plate 10B2. The metal plate 10B3 is formed with a rectangular opening 122 and a slit 133 that connects the opening 122 and the outer edge.

  The opening 121, the notch 132, and the opening 122 have the same width, and the metal plates 10B1, 10B2, and 10B3 are stacked to form one opening 12. The coil antenna 20 is close to the planar conductor 10B so that the coil conductor overlaps the opening 12.

  Further, the slit 131 and the slit 133 are located on opposite sides as shown in the side view of FIG. The slit 131 and the slit 133 communicate with each other through a notch 132. Thereby, the slit 13 has a path in the thickness direction of the planar conductor 10B and a path horizontal in the thickness direction. With this configuration, since the metal plate 10B3 is visually recognized from the slit 13 in plan view, the slit 13 is difficult to visually recognize the boundary with the planar conductor 10B, and the appearance is impaired. Can be suppressed. In addition, the surface in contact with the notch 132 in the metal plates 10B1 and 10B2 corresponds to the first surface and the second surface according to the present invention.

  By using this antenna device 1B for a wireless communication device, the strength can be improved by a metal casing without impairing the appearance. Moreover, since the length of the slit 13 in the thickness direction of the planar conductor 10B is long, the capacitance formed in the slit 13 is increased, and the capacitance necessary for the HF band can be ensured.

  FIG. 9 is a diagram illustrating a modification of the antenna device according to the third embodiment. As shown in FIG. 9, the insulator 14 is disposed at the position of the notch 132 sandwiched between the metal plates 10B1 and 10B3 so that the shape of the slit is stabilized and the strength of the planar conductor 10B is increased. Also good. The insulator 14 is rubber, resin or the like. By providing the insulator 14 in the slit 13, the capacitance in the slit 13 can be increased, and the capacitance necessary for the HF band can be ensured.

  Instead of the insulator 14, the entire slit 13 may be filled with metal oxide film fine particles, for example, aluminum oxide. When the planar conductor 10B is aluminum, the slits 13 in a plan view can be made more difficult to understand by making the insulator 14 aluminum oxide. Further, as the insulator, a transparent resin such as an acrylic resin or an epoxy resin may be used.

(Embodiment 4)
FIG. 10A is a perspective view of an antenna device according to Embodiment 4, and FIG. 10B is a side view of the antenna device. The antenna device 1 </ b> C includes a planar conductor 10 </ b> C and a coil antenna 30. The coil antenna 30 according to the fourth embodiment includes a magnetic core and a coil conductor, and the coil conductor is formed in a pattern that winds around the magnetic core. The coil conductor may be a conducting wire wound around a magnetic core, or may be formed as a conductor pattern on a laminate including a magnetic layer. The coil antenna 30 is connected to an RFIC that is a power feeding circuit.

  The planar conductor 10C has the same configuration as the planar conductor 10A described in FIG. 5, and the width of the slit 11, that is, the distance between the first surface 111 and the second surface 112 is the same as the planar conductor. Thinner than 10A. The coil antenna 30 is disposed on the lower surface of the planar conductor 10C. At this time, the coil antenna 30 is disposed close to the slit 11 facing the slit 11 so that the winding axis of the coil conductor is parallel to the planar conductor 10C. Further, the coil antenna 30 is arranged so that the coil opening faces the slit 11.

  By arranging the coil antenna 30 as described above, as shown in FIG. 10B, the magnetic flux φ3 generated from the coil antenna 30 passes through the slit 11 and, as described in the first embodiment, the planar conductor 10C. And the coil antenna 30 are magnetically coupled. Thus, even if the coil antenna 30 is a chip component, the planar conductor 10C can act as a radiation plate.

1, 1A, 1B, 1C-antenna devices 10, 10A. 10B, 10C-Planar conductor (metal casing)
11, 13-slit 12-opening 14-insulator 20, 30-coil antenna 111-first surface 112-second surface

Claims (8)

A metal casing in which a notch penetrating in the thickness direction is formed from the outer edge toward the inside;
A coil antenna that magnetically couples to the metal casing by allowing magnetic flux to pass through the notch,
With
The metal housing has a first projecting portion and a second projecting portion facing each other with the notch portion interposed therebetween,
The first protrusion has a first surface that intersects a straight line along the thickness direction,
The second protrusion has a second surface that intersects the one straight line and faces the first surface.
Antenna device.   The antenna device according to claim 1, wherein the first surface and the second surface are inclined with respect to the one straight line and face each other.   2. The antenna device according to claim 1, wherein the first surface and the second surface are orthogonal to the one straight line and partly face each other.   4. The antenna device according to claim 1, further comprising an insulator provided between the first surface and the second surface. 5. The coil antenna is
A coil conductor formed in an insulator layer, wherein the notch has a slit and an opening connected to the slit, and the coil opening of the coil conductor is connected to the slit as viewed from the thickness direction; Arranged at a position overlapping at least part of the opening,
The antenna device according to claim 1. The first surface and the second surface is opposed along said slit,
The coil antenna is
The coil opening of the coil conductor is disposed at a position overlapping at least part of the opening connected to the slit as viewed from the thickness direction.
The antenna device according to claim 5. The coil antenna is
A laminated structure in which a plurality of insulator layers on which coil conductors are formed are laminated, and the coil opening is arranged toward the notch,
The antenna device according to claim 1. The antenna device according to any one of claims 1 to 7, comprising the metal casing as an exterior,
Communication terminal device.

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