Antenna device and electronic apparatus

The purpose of the present invention is to provide an antenna device that makes it possible to ensure satisfactory communication performance even when the antenna device is mounted in an electronic apparatus with limited mounting space. An antenna device, incorporated in an electronic apparatus, which communicates with an external device via an electromagnetic field signal, comprising: a metal plate provided inside a housing of the electronic apparatus and facing the external device, and an antenna coil provided by winding a conducting wire in a approximately rectangular shape so that parts of the conducting wire that face each other in a width direction via an opening of the antenna coil come close to each other, and inductively coupled to the external device, wherein the antenna coil is provided along a side face of the metal plate.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an antenna device, incorporated in an electronic apparatus, which communicates with an external device such as a transmitter via an electromagnetic field signal and to an electronic apparatus including such an antenna device. The present application claims priority based on Japanese Patent Application No. 2015-109906 filed in Japan on May 29, 2015. The total contents of the patent application are to be incorporated by reference into the present application.

Description of Related Art

Electronic apparatuses such as mobile phones use antenna modules for RFID (radio frequency identification) in order to have short-distance non-contact communications capabilities. Such an antenna module communicates with an antenna coil of a transmitter such as a reader-writer by means of inductive coupling. That is, such an antenna module allows a magnetic field from the reader-writer to be received by the antenna coil to be converted into electric power to drive an IC that functions as a communication processing unit.

In order to surely perform communication, the antenna module needs to receive magnetic flux of a certain or higher value from the reader-writer with the antenna coil. For that purpose, in an antenna module according to a conventional example provides a housing of a mobile phone or the like with a loop coil and receives magnetic flux from a reader-writer with this coil. An antenna module incorporated in an electronic apparatus such as a mobile phone may cause magnetic flux from a reader-writer to be rebounded due to an eddy current produced by reception of the magnetic field from the reader-writer by a metal plate of a substrate, a battery pack, or the like inside the device. For example, in the case of a housing surface of a mobile phone, a magnetic field coming from a reader-writer tends to be strong in the outer regions of the housing surface and weak near the middle of the housing surface.

For this reason, in order to enhance the communication efficiency of an NFC antenna module that is built in an electronic apparatus for use, a method for arranging the NFC antenna module at an end of a metal plate of a substrate, a battery pack, or the like inside the device is currently under development. As examples of the method for arranging an NFC antenna module at an end of a metal plate, Patent Literatures 1 and 2 each propose a method for folding a part of a magnetic body over a side part and Patent Literature 3 proposes an elongated antenna device that is mounted between a metal plate and a housing.

Patent Literature 1: JP 4013987 B

Patent Literature 2: JP 5472153 B

Patent Literature 3: JP 2012-217133 A

SUMMARY OF THE INVENTION

However, the type folding a part of a magnetic body over a side face raises concern about limitations on mounting due to an additional thickness of the magnetic body. Further, the type that mounts an elongated antenna device in the space between a metal plate and a housing has had a problem such as the incapability of mounting the antenna device in a case where there is no sufficient space to provide the antenna device between the main metal plate and the housing. In particular, since advances in miniaturization and functionalization of electronic apparatuses put more and more limitations on mounting space for antenna devices, it is necessary to ensure satisfactory communication performance while achieving mountability in a narrow space by placing an antenna device in such a manner that the antenna device is folded along an end of a metal plate of a battery, an LCD module, or the like.

The present invention has been made in view of the foregoing problems, and it is an object of the present invention to provide a novel and improved antenna device and electronic apparatus that make it possible to ensure satisfactory communication performance even when an antenna coil is mounted in an electronic apparatus with limited mounting space in such a manner that the antenna coil is folded along an end of a metal plate.

A first aspect of the present invention is directed to an antenna device, incorporated in an electronic apparatus, which communicates with an external device via an electromagnetic field signal, including: a metal plate provided inside a housing of the electronic apparatus and facing the external device; an antenna coil provided by winding a conducting wire in an approximately rectangular shape so that parts of the conducting wire that face each other in a width direction via an opening of the antenna coil come close to each other, configured such that a width of the antenna coil is larger than a thickness of the metal plate, and inductively coupled to the external device; and a magnetic sheet formed of a magnetic substance and provided in such a manner as to overlap with a part of the antenna coil, wherein the antenna coil is provided along a side face of the metal plate and configured such that a portion of the antenna coil that protrudes from a region overlapping the side face of the metal plate is folded along at least either a top or bottom face of the metal plate.

According to the first aspect of the present invention, the antenna device is provided along the side face of the metal plate, and the portion of the antenna coil that protrudes from the side face of the metal plate is folded along the bottom face or the like of the metal plate. This makes it possible to ensure satisfactory communication performance even when the antenna device is mounted in a limited narrow space near the side face of the metal plate.

At this time, in the first aspect of the present invention, the magnetic sheet may be provided through the opening in such a manner as to overlap with a part of the antenna coil.

This makes it possible to induce, toward the center of the antenna coil, magnetic flux that is sent from the external device at the time of communication, thus making it possible to mount the antenna device in a limited narrow space near the side face of the metal plate while achieving satisfactory communication characteristics of an antenna.

Further, in the first aspect of the present invention, the antenna coil may be divided into two parts at a center line longitudinally traversing the opening in a longitudinal direction of the antenna coil, the two parts being one side part in which the conducting wire turns around in one direction and other side part in which the conducting wire turns around in other direction, the magnetic sheet may be provided through the opening in such a manner as to overlap with an outer side of the one side part and overlap with an inner side of the other side part, and the antenna coil may be configured such that the one side part directly faces the side face of the metal plate and the other side part is folded along the bottom face of the metal plate.

This makes it possible to further widen the distribution of a magnetic field that is produced in the antenna coil, thus making it possible to ensure satisfactory communication performance even when the antenna device is folded and mounted in a limited narrow space near the side face of the metal plate.

Further, in the first aspect of the present invention, the antenna coil may be divided into two parts at a center line longitudinally traversing the opening in a longitudinal direction of the antenna coil, the two parts being one side part in which the conducting wire turns around in one direction and other side part in which the conducting wire turns around in other direction, the magnetic sheet may be provided through the opening in such a manner as to overlap with an inner side of the one side part and overlap with an outer side of the other side part, and the antenna coil may be configured such that the one side part faces the side face of the metal plate via the magnetic sheet and the other side part is folded along the bottom face of the metal plate.

This makes it possible to further widen the distribution of a magnetic field that is produced in the antenna coil, thus making it possible to ensure satisfactory communication performance even when the antenna device is folded and mounted in a limited narrow space near the side face of the metal plate.

Further, in the first aspect of the present invention, the antenna coil may be divided into two parts at a center line longitudinally traversing the opening in a longitudinal direction of the antenna coil, the two parts being one side part in which the conducting wire turns around in one direction and other side part in which the conducting wire turns around in other direction, and the magnetic sheet may be provided in such a manner as to overlap with only either the one side part or the other side part.

This makes it possible to further widen the distribution of a magnetic field that is produced in the antenna coil, thus making it possible to ensure satisfactory communication performance even when the antenna device is folded and mounted in a limited narrow space near the side face of the metal plate.

Further, in the first aspect of the present invention, the antenna coil may be divided into two parts at a center line longitudinally traversing the opening in a longitudinal direction of the antenna coil, the two parts being one side part in which the conducting wire turns around in one direction and other side part in which the conducting wire turns around in other direction, and the antenna coil may be configured such that an end side of the one side part is folded along the top face of the metal plate and an end side of the other side part is folded along the bottom face of the metal plate.

With this, the distribution of a magnetic field that is produced by the antenna coil can be spread over an area including both the top face side and back face side of the metal plate. This makes it possible to achieve satisfactory communication characteristics of an antenna while mounting the antenna device in a limited narrow space near the side face of the metal plate.

Further, a second aspect of the present invention is directed to an electronic apparatus that is able to communicate with an external device via an electromagnetic field signal, including the antenna device according to any of the foregoing.

The second aspect of the present invention makes it possible to ensure satisfactory antenna communication characteristics even when the antenna device is mounted in a limited narrow space, thus bringing about improvement in degree of freedom of design of an electronic apparatus that can ensure satisfactory antenna communication characteristics.

As described above, by providing the antenna coil so that the antenna coil is folded along the side face of the metal plate, the present invention makes it possible to ensure satisfactory communication performance even in a case where the antenna device is mounted in a limited narrow space near the side face of the metal plate.

DETAILED DESCRIPTION OF THE. INVENTION

In the following, preferred embodiments of the present invention are described in detail. It should be noted that the present embodiment to be described below is not intended to unduly limit the contents of the present invention as recited in the claims and not all of the configurations to be described in the present embodiment are essential as means for solving the problems of the present invention.

First, a configuration of an antenna device according to an embodiment of the present invention is described with reference to the drawings.FIG. 1is a perspective view schematically showing a configuration of a wireless communication system to which an antenna device according to an embodiment of the present invention is applied.FIG. 2Ais a perspective view showing an example of an antenna device according to an embodiment of the present invention.FIG. 2Bis a cross-sectional view for explaining the arrangement of an antenna device according to an embodiment of the present invention.

An antenna device1according to the present embodiment is a device, incorporated in an electronic apparatus30, which communicates with an external device via an electromagnetic field signal. For example, as shown inFIG. 1, the antenna device1is incorporated in a wireless communication system100for RFID for use.

As shown inFIG. 1, the wireless communication system100includes the antenna device1, which is included in the electronic apparatus30, and a reader-writer40serving as an external device that makes access to the antenna device1. Assume here that the antenna device1and the reader-writer40are arranged to face each other at the XY plane of the three-dimensional orthogonal coordinate system XYZ shown inFIG. 1.

The reader-writer40functions as a transmitter that transmits a magnetic field in a Z-axis direction toward the antenna device1, which faces the reader-writer40at the XY plane. Specifically, the reader-writer40includes an antenna41that transmits a magnetic field toward the antenna device1and a control board42that communicates with the antenna device1, which is inductively coupled, via the antenna41.

That is, the reader-writer40is provided with the control board42electrically connected to the antenna41. This control board42is mounted with a control circuit43composed of one or more electronic components such as integrated circuit chips. This control circuit43executes various types of process on the basis of data received from the antenna device1.

For example, in a case where the control circuit43transmits data to the antenna device1, the control circuit43codes the data, modulates a carrier wave of a predetermined frequency (e.g. 13.56 MHz) on the basis of the data thus coded, amplifies the modulated signal thus modulated, and drives the antenna41with the modulated signal thus amplified. Further, in a case where the control circuit43reads out data from the antenna device1, the control circuit43amplifies a modulated signal of data received by the antenna41, demodulates the modulated signal of data thus amplified, and decodes the data thus demodulated.

It should be noted that the control circuit43uses a coding scheme and a modulation scheme that are used by a common reader-writer; for example, the control circuit43uses a Manchester coding scheme and an ASK. (amplitude shift keying) modulation scheme. Further, the following describes an antenna device and the like in a non-contact communication system but assumes that a non-contact charging system such as Qi can be similarly applied.

The antenna device1is, for example, incorporated into a housing32of the electronic apparatus30, such as a mobile phone, which is arranged to face the reader-writer40at the XY plane. In the present embodiment, the antenna device1includes an antenna module2, a communication processing unit13, and a metal plate3. The antenna module2includes an antenna substrate11(seeFIG. 2A) mounted with an antenna coil12that becomes able to communicate with the reader-writer40, which is inductively coupled. The communication processing unit13is driven by an electric current flowing through the antenna coil12and communicates with the reader-writer40.

The antenna module2is provided inside the housing32(seeFIG. 2A) of the electronic apparatus30and communicates with the reader-writer40, which is inductively coupled. In the present embodiment, as shown inFIG. 1, the antenna module2includes the antenna substrate11, the communication processing unit13, and a terminal area14.

The antenna substrate11is mounted with the antenna coil12and the terminal area14. The antenna coil12is formed by a patterning process or the like of a flexible conducting wire12asuch as a flexible flat cable. The terminal area14electrically connects the antenna coil12and the communication processing unit13to each other.

The antenna coil12has a function of, upon receipt of a magnetic field that is transmitted from the reader-writer40, being magnetically coupled to the reader-writer40by inductive coupling, receiving a modulated electromagnetic wave, and supplying the received signal to the communication processing unit13via the terminal area14. In the present embodiment, as shown inFIG. 2i, the antenna coil12has an approximately rectangular shape elongated in a longitudinal direction, has its single conductive wire12aturned around the edge thereof, and has an opening12blocated on a center side thereof. That is, the antenna coil12is provided by winding the conducting wire12aso that parts of the conducting wire12athat face each other in a width direction (i.e. an X direction shown inFIG. 2A) via the opening12bcome close to each other. Further, the antenna coil12has a principal surface on which the conducting wire12ais turned around, and is arranged so that, at the time of communication, the principal surface faces the reader-writer40at the XY plane shown inFIG. 1.

The communication processing unit13is driven by an electric current flowing through the antenna coil12and communicates with the reader-writer40. Specifically, the communication processing unit13demodulates a received modulated signal, decodes the data thus demodulated, and writes the data thus decoded into an internal memory of the communication processing unit13. Further, the communication processing unit13reads out, from the internal memory, data to be transmitted to the reader-writer40, codes the data thus read out, modulates the carrier wave on the basis of the data thus coded, and transmits the radio wave thus modulated to the reader-writer40via the antenna coil12, which is magnetically coupled by inductive coupling. It should be noted that the communication processing unit13may be driven not by electric power flowing through the antenna coil12but by electric power supplied from electricity supply means, such as a battery pack or an external power source, incorporated in the electronic apparatus30.

The metal plate3is provided in the housing32of the electronic apparatus30and serves as a first electric conductor that faces the reader-writer40, which serves as an external device. The metal plate3is, for example, provided in a housing of an electronic apparatus such as a mobile phone, a smartphone, or a tablet PC, and constitutes the first electric conductor, which faces the reader-writer40, at the time of communication of the antenna module2. The first electric conductor is equivalent, for example, to a metal cover attached to an inner surface of a housing of a smartphone, a metal housing of a battery pack contained in a smartphone, a metal plate provided on the back face of a liquid crystal module of a tablet PC, or the like.

Since the metal plate3of a battery pack or the like allows passage of electricity comparatively well, the application of an AC magnetic field from an outside source produces an eddy current that undesirably rebounds the magnetic field. An examination of a magnetic field distribution at the time of the application of an AC magnetic field from an outside source shows such a characteristic that the magnetic field is strong on an outer edge side of the metal plate3facing the reader-writer40. For this reason, in the present embodiment, the antenna coil12of the antenna module2is provided on the outer edge side of the metal plate3of a battery pack or the like provided inside the housing32of the mobile phone30. Such provision of the antenna coil12on the outer edge side of the metal plate3makes it possible to achieve satisfactory communication characteristics with the reader-writer40while achieving miniaturization of the electronic apparatus30such as a mobile phone at the time of incorporation into the electronic apparatus30.

In the present embodiment, the antenna coil12is for example on the XZ plane of such a three-dimensional orthogonal coordinate system XYZ as that shown inFIG. 2A. As shown inFIG. 2B, the antenna coil12is arranged between a side face3aof the metal plate3of a battery pack or the like provided inside the housing32of the mobile phone30and an inner peripheral wall32aof the housing32. The antenna coil12is provided along the side face3aof the metal plate3. That is, the antenna coil12is provided so that the opening12bfaces not a top face side of the metal plate3that faces the reader-writer40but the side face3a.

Further, n the present embodiment, the antenna coil12is provided by winding the conducting wire12ainto an approximately rectangular shape, and is configured to be divided into two parts at a center line L1longitudinally traversing the opening12bin a longitudinal direction of the antenna coil12, the two parts being one side part12a1in which the conducting wire12aturns around in one direction and other side part12a2in which the conducting wire12aturns around in other direction. Furthermore, in order to enhance communication performance by producing a greater induced electromotive force with the antenna coil12, the present embodiment is configured such that, as shown inFIG. 2B, the width of the antenna coil12is larger than the thickness of the metal plate3.

Moreover, in the present embodiment, the antenna device1is configured such that a portion of the antenna coil12that protrudes from a region overlapping the side face3aof the metal plate3is folded along a bottom face3bof the metal plate3. In the present embodiment, as shown inFIG. 2B, the other side part12a2is the portion of the antenna coil12that protrudes from the region overlapping the side face3aof the metal plate3; therefore, the other side part12a2is configured to be folded along the bottom face3bof the metal plate3.

Furthermore, in the present embodiment, as shown inFIGS. 2A and 2B, a magnetic sheet20is provided in such a manner to overlap with a part of the antenna coil12for more satisfactory antenna communication performance. The magnetic sheet20is formed of a magnetic substance such as iron oxide, chromium oxide, cobalt, or ferrite. In order to enhance the communication characteristics of the antenna module2(seeFIG. 1), the magnetic sheet20has a function of inducing, toward the center side of the antenna coil12, magnetic flux that is sent from the reader-writer40(seeFIG. 1) at the time of communication of the antenna module2.

Thus, the present embodiment is configured such that the approximately rectangular antenna coil12, which is elongated in the longitudinal direction and whose width is larger than the thickness of the metal plate3, is folded at the center line L1so that the one side part12a1is arranged in a narrow space between the side face3aof the metal plate3and the inner peripheral wall32aof the housing32of the electronic apparatus30and the other side part12a2is arranged in a narrow space between the bottom face3bof the metal plate3and a bottom face32bof the housing32. The present inventor diligently studied to attain the aforementioned object of the present invention. As a result, the present inventor found that particularly in a case where the shape of the antenna coil12is an approximately rectangular shape elongated in a longitudinal direction and the width of the antenna coil12is larger than the thickness of the metal plate3, a satisfactory communication function can be maintained without deterioration in communication performance of the antenna device1even when the antenna coil12is not provided on a side of the metal plate3that faces the reader-writer40but folded so that the one side part12a1faces the side face3aof the metal plate3and the other side part12a2faces the bottom face3bof the metal plate3.

For this reason, the present embodiment ensures satisfactory communication performance even in the case of mounting in a limited narrow space by providing the antenna coil12along the side face3aof the metal plate3first and then folding the antenna coil12at the center line L1to provide the other side part12a2along the bottom face3bof the metal plate3, thus making it possible to respond to a request for miniaturization of the electronic apparatus30. Further, even when the area of the antenna coil12is made larger for enhanced communication performance of the antenna device1, mounting in a narrow space inside the electronic apparatus30is made possible without deterioration in communication performance by providing the antenna coil12along the side face3aof the metal plate3first and then folding the antenna coil12to provide the other side part12a2, which serves as a portion of the antenna coil12that protrudes from the side face3aof the metal plate3, along the bottom face3bof the metal plate3. This brings about improvement in degree of freedom of design of the electronic apparatus30.

It should be noted that the antenna device1according to an embodiment of the present invention is not limited in configuration toFIGS. 2A and 2B. That is, in order to improve the communication characteristics of an antenna by inducing, toward the center of an antenna coil112, magnetic flux that is sent from an external device at the time of communication, an antenna device101may be configured such that, as shown inFIGS. 3A and 3B, a magnetic sheet120is provided through an opening112bof the antenna coil112in such a manner as to overlap with a part of the antenna coil112.

In the present embodiment, the magnetic sheet120is provided through the opening112bin such a manner as to overlap with an outer side of one side part112a1and overlap with an inner side of other side part112a2, and the antenna coil112is configured such that the one side part112a1directly faces a side face103aof a metal plate103and the other side part112a2is folded along a bottom face103bof the metal plate103. That is, the present embodiment is configured such that the approximately rectangular antenna coil112, which is elongated in the longitudinal direction and whose width is larger than the thickness of the metal plate103, is folded at the center line L1so that the one side part112a1is arranged in a narrow space between the side face103aof the metal plate103and an inner peripheral wall132aof a housing132of an electronic apparatus130and the other side part112a2is arranged in a narrow space between the bottom face103bof the metal plate103and a bottom face132bof the housing132.

Thus, since the distribution of a magnetic field that is produced by the antenna coil112can be further widened by thus providing the magnetic sheet120through the opening112bof the antenna coil112so that the magnetic sheet120overlaps with a part of the antenna coil112, the communication characteristics of the antenna can be brought into a more favorable condition in mounting the antenna device101in a limited narrow space near the side face103aof the metal plate103. In particular, in the present embodiment, since the magnetic sheet120is provided through the opening112bin such a manner as to overlap with the outer side of one side part112a1and overlap with the inner side of other side part112a2, the distribution of a magnetic field that is produced by the antenna coil112can be spread over a wider area including and surrounding the side face103aof the metal plate103. This makes it possible to bring the communication characteristics of the antenna into a more favorable condition in folding and mounting the antenna device101in a limited narrow space near the side face103aof the metal plate103.

Further, another aspect may be configured such that, as shown inFIGS. 4A and 4B, a magnetic sheet220is provided through an opening212bof an antenna coil212in such a manner as to overlap with a part of the antenna coil212. The antenna coil212according to the present embodiment may be configured such that by providing the magnetic sheet220through the opening212bso that the magnetic sheet220overlaps with an inner side of one side part212a1and overlaps with an outer side of other side part212a2, the one side part212a1faces a side face203aof a metal plate203via the magnetic sheet220and the other side part212a2is folded along a bottom face203bof the metal plate203. That is, the present embodiment is configured such that the approximately rectangular antenna coil212, which is elongated in the longitudinal direction and whose width is larger than the thickness of the metal plate203, is folded at the center line L1so that the one side part212a1is arranged in a narrow space between the side face203aof the metal plate203and an inner peripheral wall232aof a housing232of an electronic apparatus230and the other side part212a2is arranged in a narrow space between the bottom face203bof the metal plate203and a bottom face232bof the housing232.

Thus, since the distribution of a magnetic field that is produced by the antenna coil212can be further widened by thus providing the magnetic sheet220through the opening212bof the antenna coil212so that the magnetic sheet220overlaps with a part of the antenna coil212, the communication characteristics of an antenna can be brought into a more favorable condition in mounting the antenna device201in a limited narrow space near the side face203aof the metal plate203. In particular, in the present embodiment, since the magnetic sheet220is provided through the opening212bin such a manner as to overlap with the inner side of the one side part212a1and overlap with the outer side of the other side part212a2, the distribution of a magnetic field that is produced by the antenna coil212can be spread over a wider area including and surrounding the side face203aof the metal plate203. This makes it possible to bring the communication characteristics of the antenna into a more favorable condition in folding and mounting the antenna device201in a limited narrow space near the side face203aof the metal plate203.

It should be noted that the way in which the magnetic sheets20,120, and220are provided is not limited to any of the aspects of the embodiments described above. That is, as shown inFIGS. 5A and 5B, a magnetic sheet320may overlap only with other side part312a2without overlapping with one side part312a1. Further, as shown inFIGS. 6A and 6B, a magnetic sheet420may overlap only with one side part412a1without overlapping with other side part412a2. Since the distribution of a magnetic field that is produced by the antenna coil312or412can be further widened by thus providing the magnetic sheet320or420so that the magnetic sheet320or420overlaps only with either the other side part312a2or the one side part412a1, satisfactory communication performance can be ensured even in the case of folding and mounting in a limited narrow space near a side face303aor403aof a metal plate303or403.

Furthermore, as shown inFIGS. 7A and 7B, an approximately rectangular antenna coil512, which is elongated in the longitudinal direction and whose width is larger than the thickness of a metal plate503, may be configured such that an end side of one side part512a1of the antenna coil512is folded along a top face503cof the metal plate503and an end side of other side part512a2of the antenna coil512is folded along a bottom face503bof the metal plate503. That is, the present embodiment is configured such that the approximately rectangular antenna coil512is folded at both end sides thereof in a width direction so that the end side of the one side part512a1in which a conducting wire512ais provided extends along the top face503cof the metal plate503and an opening512bextends between a side face503aof the metal plate503and an inner peripheral wall532aof a housing532of an electronic apparatus530and the other side part512a2in which the conducting wire512ais provided is arranged in a narrow space between the bottom face503bof the metal plate503and a bottom face532bof the housing532. By configuring an antenna device501in this manner, the distribution of a magnetic field that is produced by the antenna coil512can be spread over an area including both the top face side and back face side of the metal plate503. This makes it possible to achieve satisfactory communication characteristics of an antenna while mounting the antenna device501in a limited narrow space near the side face of the metal plate503.

EXAMPLES

Next, examples of examinations and evaluations of an antenna device according to an embodiment of the present invention are described with reference to the drawings. It should be noted that the present invention is not limited to the present examples.

First, examples showing the results of evaluations of magnetic field strength on the basis of changes in configuration of antenna coil of an antenna device according to an embodiment of the present invention are described with reference to the drawings.

FIG. 8Ais a perspective view schematically showing a configuration of an antenna device serving as a comparative example of an antenna device according to an embodiment of the present invention.FIG. 8Bis a diagram showing the magnetic field strength of the antenna device shown inFIG. 8A. An antenna device601serving as the comparative example was configured such that an antenna coil612measuring 30 mm×5 mm and consisting of four turns of conducting wire was provided on a side face603aof a metal plate603included in an aluminum housing632measuring 50 mm×50 mm×5 mm. For the distribution of the magnetic field strength that was produced in the antenna coil612in a state where an electric power of 0.1 W was fed to a terminal of the antenna device601, a cross-section of the antenna coil612was observed. As shown inFIG. 8B, it was found that a strong magnetic field distribution appears on and around the side face603aof the metal plate603.

FIG. 9Ais a perspective view schematically showing a configuration of an antenna device serving as another comparative example of an antenna device according to an embodiment of the present invention.FIG. 9Bis a diagram showing the magnetic field strength of the antenna device shown inFIG. 9A. An antenna device701serving as the comparative example included an antenna coil712that was twice wider than that of the comparative example shown inFIG. 8A, and the magnetic field strength that was produced in the antenna coil712was observed. That is, in the present comparative example, in which the antenna coil712measuring 30 mm×10 mm and consisting of four turns of conducting wire was provided on a side face703aof a metal plate703included in an aluminum housing732measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil712was observed for the distribution of the magnetic field strength that was produced in the antenna coil712in a state where an electric power of 0.1 W was fed to a terminal of the antenna device701.

As shown inFIG. 9B, it was found that a strong magnetic field distribution appears in and around a portion of the antenna coil712that protrudes from the side face703aof the metal plate703. That is, it was found that increasing the width of the antenna coil712expands the distribution of the magnetic field strength that was produced in the antenna coil712.

Next, in view of the distribution result of magnetic field strength of the antenna coil712according to the comparative example ofFIG. 9A, the magnetic field strength distribution of an example of the antenna device1(seeFIG. 2) according to an embodiment of the present invention was observed. In the present example, in which the antenna coil12measuring 30 mm×10 mm and consisting of four turns of conducting wire had a portion protruding from the side face3aof the metal plate3and, with the portion folded, the antenna coil12was provided on the side face3aof the metal plate3included in the aluminum housing32measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil12was observed for the distribution of the magnetic field strength that was produced in the antenna coil12in a state where an electric power of 0.1 W was fed to a terminal of the antenna device1.

FIG. 10is a diagram showing the magnetic field strength of an example of the antenna device1(seeFIG. 2) according to an embodiment of the present invention. As shown inFIG. 10, it was found that folding the portion of the antenna coil12that protrudes from the side face3aof the metal plate3causes a strong magnetic field distribution to appear around an area extending from the side face3ato the bottom face3bof the metal plate3. That is, it was found that by folding the antenna coil12, the distribution region of the magnetic field strength that is produced in the antenna coil12is expanded from the side face3ato the bottom face3bof the metal plate3.

Next, the magnetic field strength distribution of an example of the antenna device101(seeFIG. 3) according to another embodiment of the present invention was observed. In the present example, in which the antenna coil112measuring 30 mm×10 mm and consisting of four turns of conducting wire had a portion protruding from the side face103aof the metal plate103and, with the portion folded, the antenna coil112was provided on the side face103aof the metal plate103included in the aluminum housing132measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil112was observed for the distribution of the magnetic field strength that was produced in the antenna coil.112in a state where an electric power of 0.1 W was fed to a terminal of the antenna device101.

FIG. 11is a diagram showing the magnetic field strength of an example of the antenna device101according to another embodiment of the present invention. As shown inFIG. 11, it was found that folding the portion of the antenna coil112that protrudes from the side face103aof the metal plate103causes a strong magnetic field distribution to appear around an area extending from the side face103ato the bottom face103bof the metal plate103.

In the present example, since the magnetic sheet120is provided through the opening112bin such a manner as to overlap with the outer side of the one side part112a1and overlap with the inner side of the other side part112a2, it was found that the distribution of a magnetic field that is produced by the antenna coil112is spread over a wider area including and surrounding the side face103aof the metal plate103. In particular, in the present example, it was found that a magnetic field having a certain intensity was distributed not only on the side face103aof the metal plate103but also in an area extending to both the top face side and bottom face side of the metal plate103. From this, it was found that the antenna device101according to the present example has a wider distribution range of a magnetic field having a predetermined or higher intensity.

Next, the magnetic field strength distribution of an example of the antenna device201(seeFIG. 4) according to another embodiment of the present invention was observed. In the present example, in which the antenna coil212measuring 30 mm×10 mm and consisting of four turns of conducting wire had a portion protruding from the side face203aof the metal plate203and, with the portion folded, the antenna coil212was provided on the side face203aof the metal plate203included in the aluminum housing232measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil212was observed for the distribution of the magnetic field strength that was produced in the antenna coil212in a state where an electric power of 0.1 W was fed to a terminal of the antenna device201.

FIG. 12is a diagram showing the magnetic field strength of an example of the antenna device201according to another embodiment of the present invention. As shown inFIG. 12, it was found that folding the portion of the antenna coil212that protrudes from the side face203aof the metal plate203causes a strong magnetic field distribution to appear around an area extending from the side face203ato the bottom face203bof the metal plate203.

In the present example, since the magnetic sheet220is provided through the opening212bin such a manner as to overlap with the inner side of the one side part212a1and overlap with the outer side of the other side part212a2, it was found that the distribution of a magnetic field that is produced by the antenna coil212is spread over a wider area including and surrounding the side face203aof the metal plate203. In particular, in the present example, it was found that a magnetic field having a certain intensity was distributed not only on the side face203aof the metal plate203but also in an area extending to the bottom face side of the metal plate203. From this, it was found that the antenna device201according to the present example has a wider magnetic field distribution range than the antenna device1of the aforementioned example and therefore has a wider distribution range of a magnetic field having a predetermined or higher intensity, although it does not have a wider magnetic field distribution range than the antenna device101of the aforementioned example.

Next, the magnetic field strength distribution of an example of the antenna device301(seeFIG. 5) according to another embodiment of the present invention was observed. In the present example, in which the antenna coil312measuring 30 mm×10 mm and consisting of four turns of conducting wire had a portion protruding from the side face303aof the metal plate303and, with the portion folded, the antenna coil312was provided on the side face303aof the metal plate303included in the aluminum housing332measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil312was observed for the distribution of the magnetic field strength that was produced in the antenna coil312in a state where an electric power of 0.1 W was fed to a terminal of the antenna device301.

FIG. 13is a diagram showing the magnetic field strength of an example of an antenna device301according to another embodiment of the present invention. As shown inFIG. 13, it was found that folding the portion of the antenna coil312that protrudes from the side face303aof the metal plate303causes a strong magnetic field distribution to appear around an area extending from the side face303ato the bottom face303bof the metal plate303.

In the present example, since the magnetic sheet320is provided in such a manner as to overlap only with the inner side of the other side part312a2, it was found that the distribution of a magnetic field that is produced by the antenna coil312is spread over a wider area centered at and surrounding the bottom face303bof the metal plate303. In particular, in the present example, it was found that a magnetic field having a certain intensity was distributed not only on the bottom face303bof the metal plate303but also in an area extending to the side face side of the metal plate303. From this, it was found that the antenna device301according to the present example has a wider distribution range of a magnetic field having a predetermined or higher intensity, although it has a narrower distribution range of a magnetic field than the examples of the aforementioned antenna devices101and201.

Next, the magnetic field strength distribution of an example of the antenna device401(seeFIG. 6) according to another embodiment of the present invention was observed. In the present example, in which the antenna coil412measuring 30 mm×10 mm and consisting of four turns of conducting wire had a portion protruding from the side face403aof the metal plate403and, with the portion folded, the antenna coil412was provided on the side face403aof the metal plate403included in the aluminum housing432measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil412was observed for the distribution of the magnetic field strength that was produced in the antenna coil412in a state where an electric power of 0.1 W was fed to a terminal of the antenna device401.

FIG. 14is a diagram showing the magnetic field strength of an example of an antenna device401according to another embodiment of the present invention. As shown inFIG. 14, it was found that folding the portion of the antenna coil412that protrudes from the side face403aof the metal plate403causes a strong magnetic field distribution to appear around an area extending from the side face403ato the bottom face403bof the metal plate403.

In the present example, since the magnetic sheet420is provided in such a manner as to overlap only with the inner side of the one side part412a1, it was found that the distribution of a magnetic field that is produced by the antenna coil412is spread over a wider area centered at and surrounding the side face403aof the metal plate403. In particular, in the present example, it was found that a magnetic field having a certain intensity was distributed not only on the side face403aof the metal plate403but also in an area extending to the top face and bottom face side of the metal plate403. From this, it was found that the antenna device401according to the present example has a wider distribution range of a magnetic field having a predetermined or higher intensity, although it has a narrower distribution range of a magnetic field than the examples of the aforementioned antenna devices101and201.

From these verification results of magnetic field strength, it was found that an example of the antenna device101according to another embodiment of the present invention has the widest magnetic field distribution and therefore can ensure more satisfactory communication performance. That is, it was found that, for ensuring of more satisfactory antenna communication performance, such a configuration is preferable that in providing the magnetic sheet120through the opening112bof the antenna coil112, the opening112bis passed through so that the magnetic sheet120overlaps with the outer side of the one side part112a1and overlaps with the inner side of the other side part112a2, the one side part112afaces the side face103aof the metal plate103, and the other side part112a2faces the bottom face103bof the metal plate103via the magnetic sheet120.

FIG. 15Ais a perspective view schematically showing a configuration of an antenna device serving as another comparative example of an antenna device according to another embodiment of the present invention.FIG. 15Bis a cross-sectional view for explaining the arrangement of an antenna device serving as another comparative example of an antenna device according to another embodiment of the present invention.FIG. 15Cis a diagram showing the magnetic field strength of the antenna device shown inFIG. 15A.

An antenna device801serving as the comparative example was configured such that an antenna coil812measuring 30 mm×15 mm and consisting of four turns of conducting wire was provided on a side face803aof a metal plate803included in an aluminum housing832measuring 50 mm×50 mm×15 mm. For the distribution of the magnetic field strength that was produced in the antenna coil812in a state where an electric power of 0.1 W was fed to a terminal of the antenna device801, a cross-section of the antenna coil812was observed. As shown inFIG. 15C, it was found that a strong magnetic field distribution appears on and around the side face803aof the metal plate803, centered at the site where the antenna coil812is provided.

Next, the magnetic field strength distribution of an example the antenna device501(seeFIG. 7) according to anther embodiment of the present invention was observed. In the present example, in which the antenna coil512measuring 30 mm×15 mm and consisting of four turns of conducting wire had portions protruding from the side face503aof the metal plate503and, with the portions folded from both end sides, respectively, the antenna coil512was provided on the side face503aof the metal plate503included in the aluminum housing532measuring 50 mm×50 mm×5 mm, a cross-section of the antenna coil512was observed for the distribution of the magnetic field strength that was produced in the antenna coil512in a state where an electric power of 0.1 W was fed to a terminal of the antenna device501.

FIG. 16is a diagram showing the magnetic field strength of an example of the antenna device501according to another embodiment of the present invention. As shown inFIG. 16, it was found that strong magnetic field distributions appear in areas centered at and surrounding ends of the top face side and bottom face side of the metal plate503, respectively, centered at the site where the conducting wire512aof the antenna coil512is provided. From this, it was found that the antenna device501according to the present example is suitable to a laptop personal computer required to have communication performance from both the front face and back face of the metal plate503.

While embodiments and examples of the present invention have been described in detail above, it is easily understood by persons skilled in the art that many modifications are possible without substantially departing from the new matters and effects of the present invention. Therefore, all such modifications are encompassed in the scope of the present invention.

For example, a term used at least once in the description or drawings together with a different term that is broader or the same in meaning can also be replaced the different term in any place in the description or drawings. Further, the configurations and operations of an antenna device and an electronic apparatus are not limited to those described in embodiments and examples of the present invention but may be carried out in various modifications.

GLOSSARY OF DRAWING REFERENCES