Patent Description:
Modern electronic apparatuses normally come with a wireless communication function. For example, a digital radiography (DR), which visualizes inside organs of a human body (living body) by radiating radioactive rays, is capable of remote operation such as image-capturing operation from a PC and capable of transferring a captured image to the PC over a wireless LAN or Bluetooth (R).

A wireless communication apparatus involves a problem in that a radiant quantity of radio waves at a communication frequency lowers when a component (member) formed of an electric conductor is disposed in a vicinity of a radio antenna. A DR is normally enclosed by a metallic outer housing with an opening in a vicinity of an antenna for size and thickness reduction and enhancement of drop impact resistance. In addition, in a vicinity of the antenna, a plate-shaped conductive member is disposed. The conductive member is used as a fixing member for fixing the antenna. Having the structure described above, a DR also involves a problem in that a radiant quantity of radio waves is significantly reduced at a communication frequency.

One of measures for preventing such a reduction in radiant quantity of radio waves, for example, a method of increasing an electric power supplied to an antenna to make up for a decrease in radiated electric power, increasing a radiant quantity of radio waves at a communication frequency is known, as described in NPL <NUM>. <CIT> describes a wireless communication apparatus having a non-metallic outer housing. <CIT> relates to reducing the size of the antenna system.

It is generally known that when high-power electromagnetic waves emitted by an antenna of a wireless communication apparatus enter a human body and are absorbed by the human body, a temperature of the human body locally rises. It is pointed out that the local rise in temperature of a human body may increase a risk of onset of, for example, cataract. Accordingly, limits of an energy of electromagnetic waves absorbed by a human body are determined by various countries in terms of specific absorption ratio (SAR) value. Conventional art involves a problem in that an SAR value becomes greater than a limit when an electric power supplied to an antenna is increased so as to prevent a reduction in radiant quantity of radio waves at a communication frequency.

The present invention is made in light of such a problem, and an objective of the present invention is to provide a wireless communication apparatus capable of decreasing an SAR value as well as preventing a reduction in radiant quantity of radio waves.

According to the present invention, a wireless communication apparatus according to claims <NUM> to <NUM> is provided.

Detailed features of the present invention will be clarified through the following description of exemplary embodiments with reference to the accompanying drawings.

Embodiments for carrying out the present invention will be described below with reference to the drawings.

<FIG> is a diagram illustrating an example of a schematic configuration of a wireless communication apparatus <NUM> according to a first embodiment of the present invention. Here, in the present embodiment, a digital radiography (DR) is applied as an example of the wireless communication apparatus <NUM>.

The wireless communication apparatus <NUM> includes a sensor <NUM>, a fixing member <NUM>, a battery <NUM>, a printed circuit board <NUM>, a coaxial cable <NUM>, an antenna <NUM>, an antenna supporting member <NUM>, and an outer housing <NUM>.

The battery <NUM> is a mechanism that supplies electric power, and the battery <NUM> is electrically connected to the printed circuit board <NUM>.

On the printed circuit board <NUM>, a wireless IC <NUM>, a signal wiring <NUM>, and a connector <NUM> are mounted. The wireless IC <NUM> generates a data signal for wireless communication, which is transferred via the signal wiring <NUM>, the connector <NUM>, and the coaxial cable <NUM>, to the antenna <NUM>. The printed circuit board <NUM> supplies electric power from the battery <NUM> to the antenna <NUM> via the coaxial cable <NUM>.

The coaxial cable <NUM> is electrically connected to the antenna <NUM> to supply the antenna <NUM> with the data signal for wireless communication and the electric power described above. The coaxial cable <NUM> that supplies the electric power to the antenna <NUM> is equivalent to an "electric supply unit".

The antenna <NUM> includes a first antenna element <NUM> and a second antenna element <NUM> and is adapted as a dipole antenna. Here, the first antenna element <NUM> and the second antenna element <NUM> are each formed with, for example, a rod-shaped metal. The antenna <NUM> is fixed to the fixing member <NUM> via the antenna supporting member <NUM>. <FIG> also illustrates an open end portion 161A of the first antenna element <NUM> and an open end portion 162A of the second antenna element <NUM>. Here, one end portions of the first antenna element <NUM> and the second antenna element <NUM> are adapted as the open end portions 161A and 162A, respectively, and between the other end portion of the first antenna element <NUM> and the other end portion of the second antenna element <NUM>, the coaxial cable <NUM> being the electric supply unit is provided.

The antenna supporting member <NUM> supports the antenna <NUM> and is fixed to the fixing member <NUM>.

The fixing member <NUM> is formed of an electric conductor and fixes the battery <NUM>, the printed circuit board <NUM>, and the antenna supporting member <NUM> at their respective positions on a front face (upper face) of the fixing member <NUM>.

The sensor <NUM> is a constituting unit that detects incident radioactive rays, and the sensor <NUM> is disposed on (fixed to) a rear face (lower face) of the fixing member <NUM>.

The outer housing <NUM> is a housing formed of an electric conductor and enclosing the sensor <NUM>, the fixing member <NUM>, the battery <NUM>, the printed circuit board <NUM>, the coaxial cable <NUM>, the antenna <NUM>, and the antenna supporting member <NUM>. The outer housing <NUM> includes one face 180A that is provided with an opening <NUM> for allowing electromagnetic waves from the antenna <NUM> to radiate outward from the outer housing <NUM>. In this case, the antenna <NUM> is disposed at a position closer to the opening <NUM> of the outer housing <NUM> than to the fixing member <NUM>.

Here, the outer housing <NUM> and the fixing member <NUM> each formed of an electric conductor are each formed of a typical metallic member, such as stainless, aluminum, copper, and iron, or a resin member having electric conductivity, such as carbon fiber reinforced plastic. In a vicinity of the antenna <NUM>, the outer housing <NUM> is provided with the opening <NUM> for allowing electromagnetic waves from the antenna <NUM> to radiate outward from the outer housing <NUM>. This configuration enables the wireless communication apparatus <NUM> to perform wireless communication with another wireless communication apparatus. In this structure, a face for measurement of an SAR value, which relates to an energy of electromagnetic waves absorbed by a human body, is the one face 180A of the outer housing <NUM> in which the opening <NUM> is provided, that is, a face through which electromagnetic waves are radiated from the outer housing <NUM> to reach a human body. The other five faces of the outer housing <NUM> are shielded by metal and do not allow electromagnetic waves to radiate outward from the outer housing <NUM>; therefore, the five faces do not serve as faces for the measurement of an SAR value. However, in a case where one or more openings are provided in one or more faces other than the face 180A, there are a plurality of faces for the measurement; in this case, a maximum value of SAR values measured for the plurality of faces will be used.

Note that <FIG> illustrates an xyz coordinate system where, for example, the front face (upper face) of the fixing member lies in an xz plane in an x direction and a z direction perpendicular to each other, and a direction perpendicular to the x direction and the z direction is a y direction.

<FIG> is an enlarged view of a region including the coaxial cable <NUM>, the first antenna element <NUM> and the second antenna element <NUM>.

The coaxial cable <NUM> includes a core wire <NUM>, an outer sheath conductor <NUM> and a resin material <NUM>. The second antenna element <NUM> and the core wire <NUM> are connected (electrically connected) to each other, and the first antenna element <NUM> and the outer sheath conductor <NUM> are connected (electrically connected) to each other. A dimension 161B relating to a length of the first antenna element <NUM> and a dimension 162B relating to a length of the second antenna element <NUM> are determined according to a frequency band to be used in the wireless communication so as to facilitate radiation of radio waves (electromagnetic waves). Note that the core wire <NUM> is connected (electrically connected) to the signal wiring <NUM> of the printed circuit board <NUM>. The outer sheath conductor <NUM> is connected to a ground pattern of the printed circuit board <NUM>, which is not illustrated, and the printed circuit board <NUM> is electrically connected to the fixing member <NUM> with a connection member, which is not illustrated.

<FIG> is a cross-sectional view of the antenna <NUM> on an xy plane as viewed from the z direction of <FIG>. An xyz coordinate system illustrated here corresponds to the xyz coordinate system illustrated in <FIG>. Components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted.

Note that the antenna elements <NUM> and <NUM> are disposed such that the antenna elements <NUM> and <NUM> fit into dimensions of the opening <NUM>; however, for example, the antenna supporting member <NUM> may be shifted in the x direction to dispose the antenna elements <NUM> and <NUM> such that the antenna elements <NUM> and <NUM> partly remain within the dimensions of the opening <NUM>.

The antenna supporting member <NUM> has a stepped shape. The coaxial cable <NUM> being an electric supply unit as well as first regions <NUM> and <NUM> that are positioned on a coaxial cable <NUM> side of the antenna elements <NUM> and <NUM> are disposed at positions closer to the fixing member <NUM> than second regions <NUM> and <NUM> including the open end portions 161A and 162A, which are positioned on opposite sides of the antenna elements <NUM> and <NUM> to the coaxial cable <NUM>, respectively. Further, the second regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM> are disposed at positions closer to the opening <NUM> of the outer housing <NUM> than the coaxial cable <NUM> as well as the antenna elements <NUM> and <NUM> of the first regions <NUM> and <NUM>, respectively. Adopting this structure of the antenna <NUM> including the first antenna element <NUM> and the second antenna element <NUM> enables decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in radiant quantity of radio waves at a communication frequency. This will be described in detail.

<FIG> and <FIG> are conceptual diagrams each illustrating an electromagnetic field distribution in a neighbor region of the antenna <NUM> illustrated in <FIG> and a human body hb. Here, <FIG> and <FIG> each illustrate an xyz coordinate system corresponding to the xyz coordinate systems illustrated in <FIG> and <FIG>. Further, in <FIG>, solid, crescent frames each indicate an electric field E, and dotted, crescent frames each indicate a magnetic field H.

<FIG> illustrates a structure of an antenna <NUM> according to a comparative example; in a vicinity of the antenna <NUM>, an electric field E is mainly produced due to high impedances of neighborhoods of the open end portions 161A and 162A of the antenna elements <NUM> and <NUM>. In contrast, a magnetic field H is mainly produced in a neighborhood of a connection portion between the antenna elements <NUM> and <NUM> and the coaxial cable <NUM> being an electric supply unit due to a low impedance of the neighborhood. When the antenna <NUM> is close to the human body hb, as illustrated in <FIG>, an electric field E in the vicinity of the antenna <NUM> does not propagate into the human body hb, while only a magnetic field H propagates into the human body hb. This is because a relative permittivity of the human body hb is as high as about <NUM>, which causes an electric field E to rapidly attenuate to about <NUM>/<NUM> at a boundary between the air and the human body hb, where an electric flux D is continuous, according to the formula D = εE. This is further because a relative permeability of the human body hb is <NUM>, which is the same as that of the air, which does not cause a magnetic field H to attenuate at the boundary between the air and the human body hb, where a magnetic flux B is continuous, according to the formula B = µH. A magnetic field H that has propagated into the human body hb propagates through the human body hb in a form of an electromagnetic wave that alternates between an electric field E and a magnetic field H and is subjected to wavelength shortening determined according to a formula of wavelength λ = c/(f × √ε). As an example of the wavelength shortening, a wavelength at a frequency f = <NUM> [GHz] is <NUM> [mm] in the air but is <NUM> [mm] inside the human body hb, where the speed of light is c = <NUM> × <NUM><NUM> [m/s]. From the above, a magnitude of an SAR value relating to an energy of electromagnetic waves absorbed by a human body has a correlation with an intensity of a magnetic field H in a vicinity of the antenna <NUM>.

<FIG> illustrates the structure of the antenna <NUM> according to the first embodiment of the present invention. That is, as with <FIG>, the structure of the antenna <NUM> includes the first antenna element <NUM> having the first region <NUM> and the second region <NUM>, and the second antenna element <NUM> having the first region <NUM> and the second region <NUM>. Specifically, as illustrated in <FIG>, the coaxial cable <NUM> as well as the first region <NUM> of the first antenna element <NUM> and the first region <NUM> of the second antenna element <NUM>, which form regions where an intensity of a magnetic field H is particularly high, are disposed being kept at a distance from the human body hb. Note that <FIG> illustrates a case where the human body hb is assumed to be present on a face 180A side of the outer housing <NUM> illustrated in <FIG>. Here, the intensity of the magnetic field H in the vicinity of the antenna <NUM> attenuates as the distance from the antenna <NUM> increases, and thus the intensity of the magnetic field H that reaches the human body hb is reduced. Further, at regions where the antenna elements <NUM> and <NUM> are bent in a crank shape, as illustrated in <FIG>, a magnetic field H propagates in a direction parallel to the boundary of the human body hb and does not reach the human body hb. By these effects, the magnetic field H reaching the boundary of the human body hb is significantly reduced, and the SAR value relating to an energy of electromagnetic waves absorbed by a human body can be decreased.

<FIG> are conceptual diagrams each illustrating a distribution of an electric field formed by the antenna <NUM> illustrated in <FIG>. Here, an antenna <NUM> illustrated in <FIG> is equivalent to the antenna <NUM> illustrated in <FIG>, and an antenna <NUM> illustrated in <FIG> is equivalent to the antenna <NUM> illustrated in <FIG>.

As illustrated in <FIG>, for example, in a case where the first antenna element <NUM> is negatively charged, the second antenna element <NUM> is positively charged, and an electric field E is formed between the first antenna element <NUM> and the second antenna element <NUM> as illustrated by dotted arrows. An intensity of the electric field E is highest in neighborhoods of the open end portion 161A of the first antenna element <NUM> and the open end portion 162A of the second antenna element <NUM> and becomes lower at a position closer to the coaxial cable <NUM> being an electric supply unit along a longitudinal direction of the first antenna element <NUM> and the second antenna element <NUM>.

Further, as illustrated in <FIG>, in a case of presence of the fixing member <NUM>, which is formed of an electric conductor and has a size larger than a size of the antenna <NUM>, the electric field E formed between the first antenna element <NUM> and the second antenna element <NUM> is coupled with the fixing member <NUM>. This causes potential variation in the fixing member <NUM>. This coupling inhibits the antenna <NUM> from radiating radio waves out into space, which lowers a radiation efficiency of the antenna <NUM>.

As illustrated in <FIG>, the antenna <NUM> in the present embodiment has a structure in which the open end portions <NUM> A and 162A of the antenna elements <NUM> and <NUM>, which form regions where an intensity of an electric field E emitted from the antenna <NUM> fixed with the antenna supporting member <NUM> is high, are kept away from the fixing member <NUM> formed of an electric conductor. The coupling between an electric field E and the fixing member <NUM>, which has been described with reference to <FIG>, can be prevented as much as possible; as a result, the reduction in radiant quantity of radio waves at a communication frequency can be prevented (a radiant quantity of radio waves at the communication frequency can be increased compared with the case illustrated in <FIG>).

As described with reference to <FIG>, in the present embodiment, adopting this structure of the antenna <NUM> illustrated in <FIG> and <FIG> enables decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in a radiant quantity of radio waves at a communication frequency. Here, the antenna <NUM> in the present embodiment has a structure in which the coaxial cable <NUM>, and the first regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM>, which are regions where an intensity of a magnetic field H is high, are disposed close to the fixing member <NUM> made of an electric conductor.

<FIG> are each a cross-sectional view of the antenna <NUM> on an xy plane as viewed from the z direction of <FIG>. Here, <FIG> each illustrate an xyz coordinate system corresponding to the xyz coordinate systems illustrated in <FIG> and <FIG>. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted.

In the present embodiment, shapes of the antenna <NUM> including the first antenna element <NUM> and the second antenna element <NUM> and shapes of the antenna supporting member <NUM> illustrated in <FIG> can be adopted.

<FIG> illustrates a configuration in which a portion of the antenna supporting member <NUM> for mounting the first antenna element <NUM> and the second antenna element <NUM> (additionally, the coaxial cable <NUM>) thereon is formed in a V shape. In this configuration illustrated in <FIG>, the antenna supporting member <NUM> supports the first antenna element <NUM> and the second antenna element <NUM> in a linear pattern from their one end portions (open end portions 161A and 162A) to the other end portions (their end portions on the coaxial cable <NUM> side, the coaxial cable <NUM> being an electric supply unit).

<FIG> illustrates a configuration in which a portion of the antenna supporting member <NUM> for mounting the first antenna element <NUM> and the second antenna element <NUM> (additionally, the coaxial cable <NUM>) thereon is formed in a combination of a V shape and a stepped shape. In this configuration illustrated in <FIG>, the antenna supporting member <NUM> supports the first antenna element <NUM> and the second antenna element <NUM> in a folded pattern between their one end portions (open end portions 161A and 162A) and their other end portions (their end portions on the coaxial cable <NUM> side, the coaxial cable <NUM> being an electric supply unit). The present embodiment is described about a configuration in which the antenna supporting member <NUM> supports the antenna elements <NUM> and <NUM> in a folded pattern; however, there may be a configuration in which, for example, the antenna supporting member <NUM> supports the antenna elements <NUM> and <NUM> in a curved pattern. That is, in the present embodiment, the antenna supporting member <NUM> can support the antenna elements <NUM> and <NUM> in at least one of a folded pattern and a curved pattern. Further, the number of folds may be one, or two or more.

In an example illustrated in <FIG> can be included), the first regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM> are regions that do not reach midpoints of lengths of the antenna elements <NUM> and <NUM>, respectively.

As described above, in the wireless communication apparatus <NUM> according to the first embodiment, the coaxial cable <NUM> being an electric supply unit as well as the first regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM> are disposed at positions closer to the fixing member <NUM> formed of an electric conductor than the second regions <NUM> and <NUM> including the open end portions 161A and 162A of the antenna elements <NUM> and <NUM>, respectively. Further, the second regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM> are disposed at positions closer to the opening <NUM> for allowing electromagnetic waves from the antenna <NUM> to radiate outward from the outer housing <NUM> than the coaxial cable <NUM> being an electric supply unit as well as the first regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM>, respectively. This configuration enables, as described with reference to <FIG>, decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in a radiant quantity of radio waves at a communication frequency.

In the following description given of a second embodiment, description of matters shared with the first embodiment will be omitted, and matters different from the first embodiment will be described.

While the first embodiment is described about an example in which the antenna <NUM> is configured as a dipole antenna, the second embodiment will be described about a configuration to which an inverted-F antenna is applied.

A schematic configuration of a wireless communication apparatus according to the second embodiment is basically similar to the schematic configuration of the wireless communication apparatus <NUM> according to the first embodiment illustrated in <FIG> except for a configuration of an antenna <NUM> (an antenna supporting member <NUM> supporting the antenna <NUM> is included). In the present embodiment, a wireless communication apparatus <NUM> is described as the wireless communication apparatus according to the second embodiment.

<FIG> illustrates the second embodiment of the present invention and is a diagram illustrating a schematic configuration example in which an inverted-F antenna supported by the antenna supporting member <NUM> is applied as an antenna <NUM>. Here, <FIG> illustrates an xyz coordinate system corresponding to the xyz coordinate system illustrated in <FIG>. In the example illustrated in <FIG>, the antenna <NUM> supported by the antenna supporting member <NUM> formed of a flexible printed wiring board is illustrated.

As illustrated in <FIG>, the antenna (inverted-F antenna) <NUM> includes an antenna element <NUM>, a ground conductor portion <NUM> that forms a ground pattern, and a power supply line <NUM>. A core wire <NUM> of a coaxial cable <NUM> is electrically connected to the power supply line <NUM>, and an outer sheath conductor <NUM> is electrically connected to the ground conductor portion <NUM>. The antenna element <NUM> includes one end portion that forms an open end portion 261A, the other end portion that is electrically connected to the ground conductor portion <NUM> to be short-circuited, and a portion between the one end portion and the other end portion that serves as the power supply line <NUM>, which is electrically connected to the coaxial cable <NUM> being an electric supply unit. <FIG> further illustrates side edge portions 262A and 262B of the ground conductor portion <NUM>.

<FIG> is a diagram illustrating an example of an intensity distribution of an electromagnetic field in a vicinity of the antenna (inverted-F antenna) <NUM> illustrated in <FIG>. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted.

In <FIG>, regions <NUM> and <NUM> illustrated by dotted lines are regions where an intensity of an electric field E is the highest, and a region <NUM> illustrated by a chain line is a region where the intensity of the electric field E is the second highest. A region <NUM> illustrated by a chain double-dashed line is a region where an intensity of a magnetic field H is high.

<FIG> is a diagram illustrating an example of a schematic configuration of the wireless communication apparatus <NUM> according to the second embodiment of the present invention. Components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted. <FIG> illustrates only part of a configuration of constituting units of the wireless communication apparatus <NUM> according to the second embodiment. An xyz coordinate system illustrated corresponds to the xyz coordinate system illustrated in <FIG>.

As described above with reference to <FIG> and <FIG>, since a magnitude of an SAR value relating to an energy of electromagnetic waves absorbed by a human body has a correlation with the intensity of the magnetic field H, a neighbor region of the power supply line <NUM>, which is included in the region <NUM> where the intensity of the magnetic field H is high, is disposed close to the fixing member <NUM> in the present embodiment as illustrated in <FIG>. That is, the coaxial cable <NUM> being an electric supply unit and a first region <NUM> of the antenna element <NUM> are disposed at positions closer to the fixing member <NUM> than a second region <NUM> including the open end portion 261A of the antenna element <NUM>. Further, since the decrease in radiant quantity of radio waves at a communication frequency is caused by coupling between the antenna <NUM> and the fixing member <NUM> formed of an electric conductor, a neighbor regions of the open end portion 261A of the antenna element as well as neighbor regions of the side edge portions 262A and 262B of the ground conductor portion <NUM>, which are included in the regions <NUM> to <NUM> where the intensity of the electric field E is high, are disposed close to the opening <NUM> in the present embodiment as illustrated in <FIG>. That is, the second region <NUM> of the antenna element <NUM> is disposed at a position closer to the opening <NUM> of the outer housing <NUM> than the coaxial cable <NUM> and the first region <NUM> of the antenna element <NUM>. This structure enables, for the antenna (inverted-F antenna) <NUM>, decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in radiant quantity of radio waves at a communication frequency. Note that the side edge portion 262B of the ground conductor portion <NUM> need not be brought close to the opening <NUM> since the side edge portion 262B forms a region where the intensity of the electric field E is the second highest.

<FIG> is a diagram illustrating another example of the schematic configuration of the wireless communication apparatus <NUM> according to the second embodiment of the present invention. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted. <FIG> illustrates only part of the configuration of the constituting units of the wireless communication apparatus <NUM> according to the second embodiment. <FIG> illustrates an xyz coordinate system corresponding to the xyz coordinate systems illustrated in <FIG> and <FIG>.

As illustrated in <FIG>, in a case where the antenna (inverted-F antenna) <NUM> is supported by the antenna supporting member <NUM> formed of a printed wiring board, the antenna <NUM> cannot be bent as illustrated in <FIG>. In the case, as illustrated in <FIG>, the antenna supporting member <NUM> is disposed being inclined such that the power supply line <NUM> becomes closer to the fixing member <NUM> formed of an electric conductor than the end portion 261A of the antenna element <NUM> and the side edge portion 262A of the ground conductor portion <NUM>, which is close to the open end portion 261A. That is, such configuration may be such that, as illustrated in <FIG>, a dotted line that is parallel to an xz plane and passes through part of the power supply line <NUM> is closer to the fixing member <NUM> formed of an electric conductor than a chain line that passes through part of the open end portion 261A of the antenna element <NUM> or part of the side edge portion 262A of the ground conductor portion <NUM>, which is close to the open end portion 261A.

<FIG> and <FIG> are diagrams each illustrating still another example of the schematic configuration of the wireless communication apparatus <NUM> according to the second embodiment of the present invention. In <FIG> and <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted. <FIG> and <FIG> each illustrate only part of the configuration of the constituting units of the wireless communication apparatus <NUM> according to the second embodiment. <FIG> and <FIG> each illustrate an xyz coordinate system corresponding to the xyz coordinate systems illustrated in <FIG>, <FIG>, and <FIG>.

<FIG> described above illustrates a case where the fixing member <NUM>, the antenna <NUM>, and the opening <NUM> are disposed in this order in the y direction and where the antenna <NUM> is disposed such that the xz plane illustrated in <FIG> and the xz plane illustrated in <FIG> face the same plane; however, the present embodiment is not limited to this case. For example, as illustrated in <FIG>, a configuration in which the xz plane illustrated in <FIG> and an xy plane illustrated in <FIG> face the same plane, that is, a configuration in which the antenna element <NUM> is disposed in an orientation perpendicular to a front face of the fixing member <NUM> is conceivable. As illustrated in <FIG>, a configuration in which the antenna element <NUM> is disposed being inclined with respect to the front face of the fixing member <NUM> is applicable to the present embodiment.

In the examples illustrated in <FIG>, the antenna supporting member <NUM> supports the antenna element <NUM> and the ground conductor portion <NUM> in a planar pattern. Further, in the example illustrated in <FIG>, the antenna supporting member <NUM> supports the antenna element <NUM> and the ground conductor portion <NUM> in a folded pattern. The example illustrated in <FIG> is described about a configuration in which the antenna supporting member <NUM> supports the antenna element <NUM> and the ground conductor portion <NUM> in a folded pattern; however, there may be a configuration in which the antenna supporting member <NUM> supports the antenna element <NUM> and the ground conductor portion <NUM> in a curved pattern. That is, in the present embodiment, it is only necessary that the antenna supporting member <NUM> support the antenna element <NUM> and the ground conductor portion <NUM> in at least one of a folded pattern and a curved pattern. Further, the number of folds may be one, or two or more.

For the wireless communication apparatus <NUM> according to the second embodiment, a configuration similar to the configuration of the wireless communication apparatus <NUM> in the first embodiment is adopted. That is, the coaxial cable <NUM> being an electric supply unit and a first region <NUM> of the antenna element <NUM> are disposed at positions closer to the fixing member <NUM> formed of an electric conductor than a second region <NUM> including the open end portion 261A of the antenna element <NUM>. Further, the second region <NUM> of the antenna element <NUM> is disposed at a position closer to the opening <NUM> for allowing electromagnetic waves from the antenna <NUM> to radiate outward from the outer housing <NUM> than the coaxial cable <NUM> being an electric supply unit and the first region <NUM> of the antenna element <NUM>. This configuration enables, as in the first embodiment described above, decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in a radiant quantity of radio waves at a communication frequency.

In the following description given of a third embodiment, description of matters shared with the first and second embodiments will be omitted, and matters different from the first and second embodiments will be described.

While the first embodiment is described about an example in which the antenna <NUM> is configured as a dipole antenna, the third embodiment will be described about a configuration to which an inverted-F antenna is applied, as in the second embodiment.

A schematic configuration of a wireless communication apparatus according to the third embodiment is basically similar to the schematic configuration of the wireless communication apparatus <NUM> according to the first embodiment illustrated in <FIG> except for a configuration of an antenna <NUM> and an antenna supporting member <NUM>. In the present embodiment, a wireless communication apparatus <NUM> is described as the wireless communication apparatus according to the third embodiment.

<FIG> is a diagram illustrating an example of a schematic configuration of the wireless communication apparatus <NUM> according to the third embodiment of the present invention. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted. <FIG> illustrates only part of the configuration of the constituting units of the wireless communication apparatus <NUM> according to the third embodiment. <FIG> illustrates an xyz coordinate system corresponding to the xyz coordinate systems illustrated in <FIG> and <FIG>.

An antenna <NUM> is an inverted-F antenna that is grounded to a fixing member <NUM> formed of an electric conductor. The antenna (inverted-F antenna) <NUM> includes an antenna element <NUM>, a power supply line (electric conductor portion) <NUM> formed of an electric conductor, and a projection <NUM> that has a projecting shape and is formed of an electric conductor. The projection <NUM> is provided between the antenna element <NUM> and the fixing member <NUM>. Note that such a projection <NUM> may be applied to a dipole antenna, a monopole antenna, and an inverted-L antenna.

The antenna element <NUM> includes one end portion that forms an open end portion 361A and the other end portion that is electrically connected to the fixing member <NUM> that is formed of an electric conductor and serves as the ground, and the power supply line <NUM> is provided between the one end portion and the other end portion of the antenna element <NUM>. In this case, the projection <NUM> formed of an electric conductor is provided on the fixing member <NUM> formed of an electric conductor, and a dotted line passing through part of the power supply line <NUM> is disposed closer to the fixing member <NUM> formed of an electric conductor than a chain line passing through part of the projection <NUM> serving as the ground.

That is, in the third embodiment, the coaxial cable <NUM> being an electric supply unit and a first region <NUM> of the antenna element <NUM> are disposed at positions closer to the fixing member <NUM> than a second region <NUM> including the open end portion 361A of the antenna element <NUM>. Further, the second region <NUM> of the antenna element <NUM> is disposed at a position closer to the opening <NUM> of the outer housing <NUM> than the coaxial cable <NUM> and the first region <NUM> of the antenna element <NUM>. This configuration enables, as in the first and second embodiments described above, decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in a radiant quantity of radio waves at a communication frequency.

In the following description given of a fourth embodiment, description of matters shared with the first to third embodiments will be omitted, and matters different from the first to third embodiments will be described.

<FIG> are diagrams each illustrating an example of a schematic configuration of a wireless communication apparatus <NUM> according to the fourth embodiment of the present invention. <FIG> each illustrate only part of a configuration of constituting units of the wireless communication apparatus <NUM> according to the fourth embodiment. An xyz coordinate system illustrated here corresponds to the xyz coordinate system illustrated in <FIG>.

As illustrated in <FIG>, the wireless communication apparatus <NUM> includes a fixing member <NUM> that is equivalent to the fixing member <NUM> illustrated in <FIG>, a coaxial cable <NUM> that is equivalent to the coaxial cable <NUM> illustrated in <FIG>, an antenna <NUM> that is equivalent to the antenna <NUM> illustrated in <FIG>, an antenna supporting member <NUM> that is equivalent to the antenna supporting member <NUM> illustrated in <FIG>, and an outer housing <NUM> that is equivalent to the outer housing <NUM> illustrated in <FIG>. The wireless communication apparatus <NUM> according to the fourth embodiment is supposed to further include constituting units equivalent to the sensor <NUM>, the battery <NUM>, and the printed circuit board <NUM> illustrated in <FIG>. The outer housing <NUM> includes a face 480A that is provided with openings <NUM>, <NUM>, and <NUM> and includes a face 480B that is provided with an opening <NUM>.

<FIG> illustrates an xz cross-sectional view in <FIG>, <FIG> illustrates an xy cross-sectional view in <FIG>, and <FIG> illustrates an yz cross-sectional view in <FIG>. As illustrated in <FIG>, when viewed from a direction perpendicular to an opening face of the opening <NUM> (y direction), the antenna <NUM> at least partly overlaps the opening <NUM>, as illustrated in <FIG>.

Here, as an example of the fourth embodiment, a numerical experiment was conducted with MW-STUDIO, which is an electromagnetic field simulator from AET, INC. , to demonstrate an advantageous effect of applying a digital radiography (DR) as the wireless communication apparatus <NUM>.

In this case, the antenna <NUM> illustrated in <FIG> is a dipole antenna and includes a first antenna element <NUM> and a second antenna element <NUM>. The antenna <NUM> is fixed by bonding to the antenna supporting member <NUM> having a step shape. The antenna supporting member <NUM> is fixed by bonding to the fixing member <NUM> formed of an electric conductor. The outer housing <NUM>, which is formed of an electric conductor, is fixed to the fixing member <NUM> formed of an electric conductor, and the face 480A of the outer housing <NUM> formed of an electric conductor is provided with the openings <NUM>, <NUM>, and <NUM> illustrated by chain lines. The face 480B of the outer housing <NUM> formed of an electric conductor is provided with the opening <NUM> illustrated by a chain line. The openings are each closed with a resin member. Note that the openings <NUM> and <NUM> provided in a vicinity of the antenna <NUM> are provided for allowing electromagnetic waves emitted by the antenna <NUM> to radiate outward from the outer housing <NUM>, and the opening <NUM> is an opening provided at a position that is the closest to the antenna <NUM>. Note that the sensor <NUM> that detects radioactive rays is not illustrated because the sensor <NUM> is disposed on a rear face side of the antenna <NUM> with respect to the fixing member <NUM> formed of an electric conductor, thus having a low influence.

Table <NUM> below shows dimensions illustrated in <FIG>, <FIG>, <FIG>, and <FIG>.

<FIG> is a diagram illustrating an example of a conductor pattern of the antenna <NUM> illustrated in <FIG>. Here, as the antenna <NUM>, a <NUM>/<NUM> dual-band flexible antenna from Molex, LLC (<NUM> series) was employed. In this antenna <NUM>, its first antenna element <NUM> and second antenna element <NUM> are folded for size reduction; therefore, open end portions 1401A and 1402A of the antenna elements <NUM> and <NUM> face toward a center of the antenna <NUM>. Further, the antenna <NUM> has a shape for radiating radio waves efficiently in a <NUM> band and <NUM> band so as to support a frequency band of Wifi communication. The coaxial cable <NUM> being an electric supply unit is connected between a side edge portion 1401B of the first antenna element <NUM> and a side edge portion 1402B of the second antenna element <NUM>.

To grasp regions in this antenna <NUM> illustrated in <FIG> where an intensity of an electric field E or an intensity of a magnetic field H is high, dimensions of the conductor pattern of the antenna <NUM> were measured, and calculation was conducted with MW-STUDIO, an electromagnetic field simulator from AET, INC.

<FIG> are diagrams illustrating intensity distributions of a magnetic field H and an electric field E calculated for the antenna <NUM> illustrated in <FIG>, respectively. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted.

<FIG> illustrates regions where an intensity of the magnetic field H of the antenna <NUM> is high, and <FIG> illustrates regions where an intensity of the electric field E is high. Note that observation frequencies were <NUM> and <NUM>. The regions illustrated in <FIG> where an intensity of the magnetic field is high are substantially the same between <NUM> and <NUM>; a region <NUM>, where the intensity of the magnetic field is the highest, is a region including an electric supply point at which the coaxial cable <NUM> is connected, namely the side edge portions 1401B and 1402B, as illustrated by a dotted line in <FIG>. Further, regions <NUM> and <NUM>, where the intensity of the magnetic field is the second highest, are regions adjacent to the electric supply point, as illustrated by chain lines in <FIG>, and regions <NUM> and <NUM>, where the intensity of the magnetic field is the third highest, are regions between the electric supply point and the open end portions 1401A and 1402A in the antenna elements <NUM> and <NUM>, as illustrated by chain double-dashed lines in <FIG>. Note that the intensity of the magnetic field H is not uniform in each of the regions; the intensity becomes lower at a position closer to the open end portions 1401A and 1402A of the antenna.

Regions <NUM> to <NUM> and <NUM> to <NUM> illustrated in <FIG>, where the intensity of the electric field E is high at a frequency of <NUM>, are regions of the open end portions 1401A and 1402A of the antenna elements <NUM> and <NUM>, regions of side edge portions 1401C and 1402C in a longitudinal direction of an outline of the antenna <NUM>, and regions of the side edge portions 1401F and 1402F between the open end portions 1401A and 1402A and the side edge portions 1401C and 1402C, respectively, as illustrated by dotted lines in <FIG>. Regions <NUM> and <NUM>, where the intensity of the electric field E is high at a frequency of <NUM>, include regions of the open end portions 1401A and 1402A of the antenna elements <NUM> and <NUM> and regions of side edge portions 1401D and 1401E of the antenna element <NUM> and side edge portions 1402D and 1402E of the antenna element <NUM>, respectively, as illustrate by chain lines in <FIG>. Note that the intensity of the electric field E is not uniform in each of the regions; the intensity becomes higher at a position closer to the open end portions 1401A and 1402A of the antenna elements <NUM> and <NUM>.

In the present embodiment, a member that is formed of a dielectric and has a stepped shape is employed as the antenna supporting member <NUM> so that the regions described above where the intensity of the magnetic field H is high is disposed close to the fixing member <NUM> formed of an electric conductor and that the regions described above where the intensity of the electric field E is high is disposed close to the opening <NUM>.

<FIG> is a diagram illustrating an example of dimensions of the conductor pattern of the antenna <NUM> illustrated in <FIG>. In <FIG>, components similar to those illustrated in <FIG> are denoted by the same reference characters, and detailed description thereof will be omitted.

In a region having an area of w1 × f illustrated in <FIG>, the antenna supporting member <NUM> was formed such that the shortest distance from the fixing member <NUM> to the antenna <NUM> was set to <NUM>. In a region having an area of w2 × f, the antenna supporting member <NUM> was formed to have a shape such that the shortest distance from the fixing member <NUM> to the antenna <NUM> was set to a dimension of <NUM>. To demonstrate an advantage of the present embodiment, calculation was performed on antennas with antenna supporting members <NUM> that had no step and in which the shortest distances from the fixing member <NUM> formed of an electric conductor to their antenna elements <NUM> were made constant: <NUM>, <NUM>, and <NUM>, and results of the calculation were compared with results of calculation performed on the antenna according to the present embodiment.

To calculate SAR values, an anthropomorphic phantom having dimensions of <NUM> × <NUM> × <NUM> [mm], which were larger than those of an outline of the DR, was placed being in intimate contact with the faces 480A and 480B. For the calculation of SAR values, material properties of a solvent of the anthropomorphic phantom used in measurement conforming to an international standard were used, and the material properties include an electric conductivity σ of <NUM> [S/m], a relative permittivity of <NUM>, a Tan δ of <NUM>, and a material density ρ of <NUM>. The electric conductors of the fixing member <NUM> and the like were each a stainless having an electric conductivity σ of <NUM> [S/m], An electric field E in the anthropomorphic phantom was observed, and the SAR values were calculated from SAR [W/Kg] = E × E × ρ/σ. For communication characteristics, radiation efficiencies of the antennas were calculated with the anthropomorphic phantom removed. The radiation efficiencies were each calculated as a ratio between an electric power supplied to a signal line at a communication frequency and a total electric power of radiated electromagnetic waves passing through locations around the antenna <NUM> that are <NUM> [m] away from the antenna <NUM>. Table <NUM> shows results of the calculations of the SAR values and the radiation efficiencies.

Comparing results from the <NUM> constant distance, the <NUM> constant distance, and the <NUM> constant distance, the SAR value decreases with a decrease in distance from the fixing member <NUM> to the antenna <NUM>, and the <NUM> constant distance gives the lowest SAR value. In contrast, the values of the radiation efficiency increase with a decrease in distance from the opening to the antenna <NUM>, and the <NUM> constant distance gives the best radiation efficiency. Of the three levels described above, the balance between a radiant quantity of radio waves and an SAR value can be established by employing the <NUM> constant distance. Comparing results from the stepped shape in the present embodiment and the results from the <NUM> constant distance, the stepped shape improved more in radiation efficiency than the <NUM> constant distance at <NUM> but slightly less improved at <NUM>. In contrast, the stepped shape gives decreased SAR values at <NUM> and <NUM>. That is, the structure in the present embodiment enables decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in radiant quantity of radio waves at a communication frequency.

In addition, a percentage of a region in the stepped shape that is to be brought close to the fixing member <NUM> formed of an electric conductor to a length of the antenna elements <NUM> and <NUM> was roughly calculated.

<FIG> is a diagram illustrating an example of the conductor pattern of the antenna <NUM> illustrated in <FIG>. Dotted lines <NUM> and <NUM> are drawn by connecting middle points of widths of the antenna elements <NUM> and <NUM> along the antenna elements, respectively. An antenna element length of the first antenna element <NUM> is a dimension of <NUM> [mm] from the side edge portion 1401B to the open end portion 1401A. An antenna element length of the second antenna element <NUM> is a dimension of <NUM> [mm] from the side edge portion 1402B to the open end portion 1402A. Locations P1 and P2 are at end portions of the dimension w1 in Table <NUM>, and a distance from the side edge portion 1401B to the location P1 is <NUM> [mm]. A distance from the side edge portion 1402B to the location P2 is <NUM> [mm]. That is, the first antenna element <NUM> is disposed such that <NUM>% of a total length <NUM> of the antenna element from the electric supply unit is brought close to the electric conductor. Further, the second antenna element <NUM> is disposed such that <NUM>% of a total length <NUM> of the antenna element from the electric supply unit is brought close to the electric conductor.

From the above, an advantageous effect of the present embodiment is provided by bringing regions from the electric supply unit to locations of about <NUM>% of the total lengths of the antenna elements <NUM> and <NUM>, namely to midpoints of their antenna element lengths, close to the fixing member <NUM> formed of an electric conductor.

<FIG> are diagrams each illustrating an example of constituting units equivalent to the antenna <NUM> and the antenna supporting member <NUM> illustrated in <FIG>. In place of the antenna supporting member <NUM> having a stepped shape illustrated in <FIG>, an antenna supporting member <NUM> having a V shape is applied as illustrated in <FIG>, also in this case, the advantageous effect is provided to the same extent. A dimension w3 illustrated in <FIG> is <NUM>, and distances from the fixing member <NUM> are s = <NUM> and r = <NUM>. A percentage of a distance by which a region in this shape to be disposed close to the fixing member <NUM> was calculated. At the location P1 and the location P2, a distance w4 from the fixing member <NUM> is <NUM>. That is, a dimension of <NUM>% of a difference value between a longest distance r from the fixing member <NUM> to the antenna elements <NUM> and <NUM> and a shortest distance s from the fixing member <NUM> to the antenna elements <NUM> and <NUM> is disposed close to the shortest distance s. In other words, the antenna elements <NUM> and <NUM> are disposed such that the distance w4 from the fixing member <NUM> at the location P1 and the location P2 is less than a dimension obtained by adding a dimension less than half a difference between the longest distance r and the shortest distance s from the fixing member <NUM> to the antenna elements <NUM> and <NUM> and a dimension of the shortest distance s.

From the above, an advantageous effect of the present embodiment is provided by disposing the antenna elements <NUM> and <NUM> such that, for a region to be brought close to the electric conductor, a dimension of less than half of the difference between the longest distance and the shortest distance from the fixing member <NUM> to the antenna elements <NUM> and <NUM> is brought close to the shortest distance.

For the wireless communication apparatus <NUM> according to the fourth embodiment, a configuration similar to the configuration of the wireless communication apparatus <NUM> in the first embodiment is adopted. That is, as illustrated in <FIG>, the coaxial cable <NUM> being an electric supply unit as well as the first regions <NUM><NUM> and <NUM> of the antenna elements <NUM> and <NUM> are disposed at positions closer to the fixing member <NUM> formed of an electric conductor than second regions <NUM> and <NUM> of the antenna elements <NUM> and <NUM>, respectively. This configuration enables, as in the first embodiment, decreasing an SAR value relating to an energy of electromagnetic waves absorbed by a human body as well as preventing a reduction in a radiant quantity of radio waves at a communication frequency.

In the embodiments of the present invention described above, a dipole antenna or an inverted-F antenna is applied as the antenna, but the antenna in the present invention is not limited to a dipole antenna and an inverted-F antenna; as the antenna, what is called an inverted-L antenna or a monopole antenna is also applicable. In a case where a monopole antenna is applied, the antenna further includes, in addition to an antenna element, a ground conductor portion (or an electric conductor portion formed of an electric conductor) to be used as a ground of the antenna element and has a configuration in which one end portion of the antenna element forms an open end portion, and an electric supply unit is provided between the other end portion and the ground conductor portion (or the electric conductor portion). In a case where an inverted-L antenna is applied, the antenna further includes, in addition to an antenna element, a ground conductor portion (or an electric conductor portion formed of an electric conductor) to be used as a ground of the antenna element and has a configuration in which one end portion of the antenna element forms an open end portion, the antenna has a crank shape between the one end portion and the other end portion, and an electric supply unit is provided between the other end portion and the ground conductor portion (or the electric conductor portion).

The embodiments are described above about examples in which the present invention is applied to a DR as a wireless communication apparatus; however, the present invention may be applied to a camera or the like having a wireless communication function.

According to the embodiments described above, an SAR value relating to an energy of electromagnetic waves absorbed by a human body can be decreased while a reduction in radiant quantity of radio waves at a communication frequency is prevented.

Claim 1:
A wireless communication apparatus (<NUM>) comprising:
an antenna (<NUM>) including an antenna element (<NUM>, <NUM>);
a fixing member (<NUM>) formed of an electric conductor and configured to fix the antenna;
an electric supply unit (<NUM>) electrically connected to the antenna and configured to supply electric power to the antenna; and
an outer housing (<NUM>) formed of an electric conductor and configured to enclose the antenna, the fixing member, and the electric supply unit, the outer housing having an opening (<NUM>) for allowing electromagnetic waves from the antenna to radiate outward from the outer housing, wherein
the antenna is disposed at a position closer to the opening of the outer housing than to the fixing member, and
the electric supply unit and a first region (<NUM>, <NUM>) of the antenna element that is positioned on the electric supply unit side of the antenna element are disposed at a position closer to the fixing member than a second region (<NUM>, <NUM>) of the antenna element including an open end portion (161A, 162A) of the antenna element positioned on an opposite side of the antenna element to the electric supply unit.