Abstract:
Disclosed is a portable wireless apparatus that can be miniaturised and reduced in thickness without increasing in manufacturing costs and that can prevent degradation of reception sensitivity when placed on a metal plate, without impairing design characteristics. In this apparatus, a conductive hinge ( 103 ) links a first case ( 101 ) and second case ( 102 ) in a mutually movable fashion. A first antenna element ( 108 ) has a base end ( 150 ) that is supplied with power from a power supply section ( 106 ) and provided in a position facing the hinge ( 103 ), and is arranged on the second case ( 102 ) in such a way that the distance r 1  from the bottom face ( 160 ) of the second case ( 102 ) on the side of the tip ( 151 ) extending from the base end ( 150 ) is larger than the distance r 2  from the bottom face ( 160 ) of the second case ( 102 ) on the side of the base end ( 150 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a portable radio device, and more particularly to a portable radio device capable of maintaining high reception sensitivity while the portable radio device is placed on a metal plate such as a steel desk. 
       BACKGROUND ART 
       [0002]    In general, a user does not necessarily carry a portable radio device such as a cell phone with him/her, and he/she often waits for incoming calls while the portable radio device is placed on a metal desk such as a steel desk. In this case, the antenna of the portable radio device is in proximity to the metal disk each other, and is coupled with the metal desk, whereby a current having a phase opposite to the antenna current flows on the metal surface of the metal desk. As a result, in the past, the directional pattern of the radiation of the antenna is changed, and the characteristics of the VSWR (Voltage Standing Wave Ratio) are greatly changed. There is a problem in that this reduces the matching state of the antenna and reduces the radiation gain. 
         [0003]    Conventionally, one of methods for solving this problem is as follows. A portable radio device is known to have a rib on the back surface of the portable radio device so as to increase the distance between the antenna of the portable radio device and the metal desk, thus achieving high reception sensitivity (for example, patent literature 1). 
         [0004]    Alternatively, a portable radio device is known to have such a configuration in which a radiation element and an auxiliary ground plate provided in the portable radio device are electrically connected to a circuit substrate of the portable radio device so that an electric field is emitted in a direction perpendicular to a desk when the portable radio device is placed on the metal desk, thus improving the reception sensitivity (for example, patent literature 2). 
       Citation List 
     Patent Literature 
     PTL 1   
       [0005]    Japanese Patent Application Laid-Open No. H10-126304 
       PTL 2   
     Japanese Patent Application Laid-Open No. 2007-329962   
     SUMMARY OF THE INVENTION 
     Technical Problem 
       [0006]    In the patent literature 1, however, the thickness of the casing increases due to the rib, which makes it difficult to reduce the thickness of the casing, and moreover there is a problem in that the rib protrudes from the casing, and this reduces the quality of the design. In the patent literature 2, it is necessary to additionally arrange the radiation element and the auxiliary ground plate. As a result, the number of component parts increases, which increases the manufacturing cost, and moreover, the casing needs to have a space for the radiation element and the auxiliary ground plate. Therefore, there is a problem in that it is difficult to reduce the size and reduce the thickness. 
         [0007]    An object of the present invention is to provide a portable radio device which is small and thin but the manufacturing cost is still low, and while the quality of the design is not deteriorated, the reduction of the reception sensitivity is prevented even when the portable radio device is placed on a metal plate. 
       Solution to Problem 
       [0008]    A portable radio device according to the present invention includes a first casing, a second casing, a conductive coupling member that couples the first casing and the second casing in a mutually movable fashion, and a first antenna element that is fed by a feeding section and has a base end section arranged at a position to face the coupling member in a vertical direction, wherein the first antenna element is arranged in the second casing such that the distance between a front end section side extending from the base end section and a bottom surface of the second casing is greater than the distance from the bottom surface of the base end section side. 
       Advantage Effects of Invention 
       [0009]    According to the present invention, a portable radio device is provided which is small and thin but the manufacturing cost is still low, and while the quality of the design is not deteriorated, the reduction of the reception sensitivity is prevented even when the portable radio device is placed on a metal plate. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a plan view illustrating a second casing of a portable radio device according to Embodiment 1 of the present invention; 
           [0011]      FIG. 2  is a front view illustrating the portable radio device according to Embodiment 1 of the present invention;  FIG. 3  is a cross sectional view taken along line C-C′ in  FIG. 1 ; 
           [0012]      FIG. 4  is a cross sectional view taken along line B-B′ in  FIG. 1 ; 
           [0013]      FIG. 5  is a cross sectional view taken along line A-A′ in  FIG. 1 ; 
           [0014]      FIG. 6  is a figure illustrating VSWR characteristic according to Embodiment 1 of the present invention; 
           [0015]      FIG. 7  is a front view of a portable radio device illustrating another example of a first antenna element according to Embodiment 1 of the present invention; 
           [0016]      FIG. 8  is a front view of a portable radio device illustrating still another example of a first antenna element according to Embodiment 1 of the present invention; 
           [0017]      FIG. 9  is a front view of a portable radio device illustrating still another example of a first antenna element according to Embodiment 1 of the present invention; 
           [0018]      FIG. 10  is a plan view illustrating a second casing of a portable radio device according to Embodiment 2 of the present invention; 
           [0019]      FIG. 11  is a cross sectional view taken along line E-E′ in  FIG. 10 ; and 
           [0020]      FIG. 12  is a cross sectional view taken along line E-E′ in  FIG. 10  illustrating another example of a second antenna element according to Embodiment 2 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]    Embodiments of the present invention will be hereinafter explained in detail with reference to the accompanying drawings. 
       Embodiment 1 
       [0022]      FIG. 1  is a plan view illustrating second casing  102  of portable radio device  100  according to the present embodiment.  FIG. 2  is a front view illustrating portable radio device  100  according to the present embodiment.  FIG. 3  is a cross sectional view taken along line C-C′ in  FIG. 1 .  FIG. 4  is a cross sectional view taken along line B-B′ in  FIG. 1 .  FIG. 5  is a cross sectional view taken along line A-A′ in  FIG. 1 . For the sake of explanation, circuit substrate  104 , matching circuit  105 , feeding section  106 , feeding element  107 , and second antenna element  109  are omitted in  FIG. 2 . Circuit substrate  104 , matching circuit  105 , feeding section  106 , and feeding element  107  are omitted in  FIGS. 3 and 4 . Matching circuit  105 , feeding section  106 , and feeding element  107  are omitted in  FIG. 5 . 
         [0023]    Portable radio device  100  mainly includes first casing  101 , second casing  102 , hinge section  103 , circuit substrate  104 , matching circuit  105 , feeding section  106 , feeding element  107 , first antenna element  108 , second antenna element  109 , and circuit substrate  110 . 
         [0024]    Each component will be explained in detail with reference to  FIGS. 1 to 5 . 
         [0025]    First casing  101  has a rectangular shape on a plan view, and as shown in  FIG. 5 , first casing  101  includes hinge section  103  and circuit substrate  110 . First casing  101  is rotatably coupled with second casing  102  via hinge section  103 . When first casing  101  is closed, first casing  101  overlaps second casing  102  as shown in  FIGS. 2 to 4  when first casing  101  and second casing  102  are seen on a plan view. Further, first casing  101  has a sub-display section such as a liquid crystal display section (LCD), not shown, that is exposed to the outside when first casing  101  is closed. When a call is received, the sub-display section provided on first casing  101  has a function of, e.g., displaying a caller registered in advance in portable radio device  100 . Therefore, when a user waits for a call, the user usually places portable radio device  100  on a desk and the like such that first casing  101  is at the upper side. 
         [0026]    Second casing  102  has a rectangular shape on a plan view, and second casing  102  is rotatably coupled with first casing  101  via hinge section  103 . As shown in  FIG. 1 , second casing  102  includes circuit substrate  104 , matching circuit  105 , feeding section  106 , feeding element  107 , first antenna element  108 , and second antenna element  109 . Further, second casing  102  includes an operation panel not shown. 
         [0027]    Hinge section  103  is made of a conductive metal material, and is provided on first casing  101 , so that hinge section  103  rotatably couples first casing  101  with second casing  102 . Hinge section  103  needs to have a certain level of rigidity so that hinge section  103  is not damaged when first casing  101  and second casing  102  are repeatedly pivoted. Therefore, hinge section  103  is usually made of metal material. 
         [0028]    As shown in  FIG. 1 , circuit substrate  104  is provided on second casing  102 , and includes matching circuit  105 , feeding section  106 , and feeding element  107 . 
         [0029]    Matching circuit  105  is electrically connected to feeding section  106 . 
         [0030]    Feeding section  106  is electrically connected to matching circuit  105 , and feeding section  106  feeds power to first antenna element  108  and second antenna element  109  via feeding element  107 . 
         [0031]    Feeding element  107  electrically connects feeding section  106  with second antenna element  109 . 
         [0032]    For example, first antenna element  108  is formed with a flexible substrate (FPC) or a metal plate, and is integrally formed with second antenna element  109 . Further, first antenna element  108  is fed from feeding section  106  via feeding element  107  and second antenna element  109 , and first antenna element  108  has base end section  150  provided at a position to face hinge section  103  in upward and downward directions (see  FIGS. 1 and 2 ). Further, first antenna element  108  is provided in second casing  102  so that the distance between bottom surface  160  of second casing  102  and front end section side  201  extended from base end section  150  is greater than the distance between bottom surface  160  of second casing  102  and base end section side  202  (see  FIG. 2 ). For example, first antenna element  108  oscillates in 800 MHz band. It should be noted that first antenna element  108  will be explained later in detail. 
         [0033]    Second antenna element  109  is in a substantially inverted-L shape on a plan view, and, for example, second antenna element  109  is made of a flexible substrate (FPC) or a metal plate, and is integrally formed with first antenna element  108 . Further, second antenna element  109  oscillates at a higher frequency than the resonance frequency of first antenna element  108 , and therefore, second antenna element  109  is formed so that the antenna length of second antenna element  109  is shorter than that of first antenna element  108 . For example, second antenna element  109  oscillates in 2 GHz band. 
         [0034]    Circuit substrate  110  as shown in  FIG. 5  is provided in first casing  101 . 
         [0035]    Subsequently, first antenna element  108  will be explained further in detail with reference to  FIGS. 1 to 5 . 
         [0036]    As shown in  FIG. 2 , on a plan view, first antenna element  108  includes base end section side  202  arranged parallel to bottom surface  160  of second casing  102 , front end section side  201  arranged parallel to bottom surface  160  of second casing  102  and whose distance from bottom surface  160  of second casing  102  is different from the distance of base end section side  202  therefrom, and inclined section  203  provided between base end section  150  and front end section  151  and inclining upward. 
         [0037]    More specifically, inclined section  203  is formed by bending front end section  151  side upward in position P 1  to face edge section  170  of hinge section  103  between base end section  150  and front end section  151  (see  FIGS. 2 and 3 ). Further, front end section side  201  is formed by bending an end section of inclined section  203  at the side of front end section  151  so that front end section side  201  is arranged parallel to bottom surface  160  of second casing  102  (see  FIG. 2 ). 
         [0038]    Accordingly, first antenna element  108  is provided in second casing  102  so that distance r 1  between front end section side  201  and bottom surface  160  of second casing  102  is greater than distance r 2  between base end section side  202  and bottom surface  160  of second casing  102  (r 1 &gt;r 2 ). Further, first antenna element  108  is in a meandering form from base end section  150  to a substantially intermediate section (see  FIG. 1 ). 
         [0039]    Further, first antenna element  108  is provided in second casing  102  so that, on a plan view, the longitudinal direction of front end section  151  is arranged parallel to the longitudinal direction of long side section  180  of second antenna element  109  (horizontal direction of  FIG. 1 ) (see  FIG. 1 ). On a plan view, first antenna element  108  is arranged so that base end section side  202  overlaps hinge section  103  in a vertical direction. Since base end section  150  is electrically connected to second antenna element  109 , first antenna element  108  is fed by feeding section  106  via feeding element  107  and second antenna element  109 . 
         [0040]    Alternatively, in first antenna element  108 , the lower surface of inclined section  203  or front end section side  201  bent upward may be held by a separately arranged holding member or a holding member integrally arranged with second casing  102 . When first antenna element  108  is held by the holding member, the distance between first antenna element  108  and bottom surface  160  of second casing  102  can be maintained at a constant level, and therefore this further improves the performance of the antenna. On a plan view, second antenna element  109  is arranged at a position so that second antenna element  109  overlaps hinge section  103  in the vertical direction. 
         [0041]      FIG. 6  is a figure illustrating VSWR characteristic when portable radio device  100  is placed on metal plate  210  such as steel desk. In  FIG. 6 , a solid line represents VSWR characteristic according to the present embodiment, and a broken line represents conventional VSWR characteristic. In  FIG. 6 , the lower the value of VSWR is in a vertical axis, the better the VSWR characteristic becomes. 
         [0042]    As can be seen from  FIG. 6 , first antenna element  108  provides better VSWR characteristic in the resonance frequency of between 830 MHz to 885 MHz than a conventional example. 
         [0043]    It should be noted that since hinge section  103  is made of a conductive metal material, not only metal plate  210  such as a steel desk but also hinge section  103  may reduce the antenna performance of first antenna element  108  and second antenna element  109 . In particular, when feeding section  106  is in proximity to hinge section  103 , hinge section  103  may function as an antenna by way of first antenna element  108  and second antenna element  109 , whereby the antenna performance of first antenna element  108  or second antenna element  109  may be reduced. On the other hand, when second antenna element  109  oscillates in 2 GHz band, hinge section  103  has an electrical length at which hinge section  103  oscillates in 2 GHz band, like second antenna element  109 . Therefore, in the present embodiment, base end section side  202  of first antenna element  108  and second antenna element  109 , which overlap hinge section  103  on a plan view, are arranged in positions away from hinge section  103  in second casing  102  (see  FIG. 2 ). 
         [0044]    On the other hand, front end section side  201  of first antenna element  108  is more greatly affected by metal plate  210  than hinge section  103 . Therefore, front end section side  201  of first antenna element  108  not overlapping hinge section  103  on a plan view is arranged in a distant position from metal plate  210  such as a steel desk in second casing  102 . Therefore, each of the antenna elements is least affected by both hinge section  103  and metal plate  210  such as a steel desk. 
         [0045]      FIG. 7  is a front view of a portable radio device illustrating another example of a first antenna element. In  FIG. 7 , parts having the same configurations as those of  FIGS. 1 to 5  will be assigned the same reference numerals, and their descriptions will be omitted. 
         [0046]    As can be seen from  FIG. 7 , when seen from the front surface, first antenna element  701  is bent upward in a crank shape between base end section  750  and front end section  751 , and is arranged in second casing  102  so that base end section side  702  and front end section side  703  are arranged parallel to bottom surface  160  of second casing  102 . In other words, first antenna element  701  includes base end section side  702  arranged parallel to bottom surface  160  of second casing  102 , front end section side  703  arranged parallel to bottom surface  160  of second casing  102  and whose distance from bottom surface  160  of second casing  102  is different from the distance of base end section side  202  therefrom, and bent section  704  provided between base end section  750  and front end section  751  and bending upward in a vertical direction. 
         [0047]    More specifically, bent section  704  is formed by bending front end section  751  side upward in the vertical direction in position P 1  to face edge section  170  of hinge section  103  between base end section  750  and front end section  751 . Further, front end section side  703  is formed by bending in the vertical direction an end section of front end section  751  side of bent section  704  so that front end section side  703  is arranged parallel to bottom surface  160  of second casing  102 . 
         [0048]    Accordingly, first antenna element  701  is provided in second casing  102  so that distance r 1  between front end section side  703  and bottom surface  160  of second casing  102  is greater than distance r 2  between base end section side  702  and bottom surface  160  of second casing  102  (r 1 &gt;r 2 ). On a plan view (not shown), first antenna element  701  is arranged so that base end section side  702  overlaps hinge section  103  of second casing  102 , like  FIG. 1 . 
         [0049]      FIG. 8  is a front view of a portable radio device illustrating still another example of a first antenna element. In  FIG. 8 , parts having the same configurations as those of  FIGS. 1 to 5  will be assigned the same reference numerals, and their descriptions will be omitted. 
         [0050]    As can be seen from  FIG. 8 , when seen from the front surface, first antenna element  801  is arranged in second casing  102  such that first antenna element  801  is bent and brought upward so that the distance between first antenna element  801  and bottom surface  160  of second casing  102  gradually increases toward front end section  851 . In other words, first antenna element  801  includes base end section side  802  arranged parallel to bottom surface  160  of second casing  102  and front end section side  803  provided between base end section  850  and front end section  851  and bending upward to the side of front end section  851 . 
         [0051]    More specifically, front end section side  803  is formed by bending front end section  851  side diagonally upward in position P 1  to face edge section  170  of hinge section  103  between base end section  850  and front end section  851 . 
         [0052]    Accordingly, first antenna element  801  is provided in second casing  102  so that distance r 1  between front end section side  803  and bottom surface  160  of second casing  102  is greater than distance r 2  between base end section side  802  and bottom surface  160  of second casing  102  (r 1 &gt;r 2 ). On a plan view, first antenna element  801  is arranged so that base end section side  802  overlaps hinge section  103  of second casing  102 . 
         [0053]      FIG. 9  is a front view of a portable radio device illustrating still another example of a first antenna element. In  FIG. 9 , parts having the same configurations as those of  FIGS. 1 to 5  will be assigned the same reference numerals, and their descriptions will be omitted. 
         [0054]    As can be seen from  FIG. 9 , when seen from the front surface, first antenna element  901  is arranged in second casing  102  such that first antenna element  901  is bent and brought upward between base end section  950  and front end section  951  so that the distance between first antenna element  901  and bottom surface  160  of second casing  102  gradually increases toward front end section  951 , and front end section side  903  is bent so that front end section side  903  is parallel to bottom surface  160  of second casing  102 . In other words, first antenna element  901  includes base end section side  902  arranged parallel to bottom surface  160  of second casing  102 , front end section side  903  arranged parallel to bottom surface  160  of second casing  102  and whose distance from bottom surface  160  of second casing  102  is different from the distance of base end section side  902  therefrom, and curved section  904  provided between base end section  950  and front end section  951  and bending upward in a parabolic curve. 
         [0055]    More specifically, curved section  904  is formed by bending front end section  951  side upward in a parabolic shape in position P 1  to face edge section  170  of hinge section  103  between base end section  950  and front end section  951 . Further, front end section side  903  is formed by bending an end section of front end section  951  side of curved section  904  so that front end section side  903  is arranged parallel to bottom surface  160  of second casing  102 . 
         [0056]    Accordingly, first antenna element  901  is provided in second casing  102  so that distance r 1  between front end section side  903  and bottom surface  160  of second casing  102  is greater than distance r 2  between base end section side  902  and bottom surface  160  of second casing  102  (r 1 &gt;r 2 ). On a plan view, first antenna element  901  is arranged so that base end section side  902  overlaps hinge section  103  of second casing  102 . 
         [0057]    As described above, according to the present invention, the base end section side of the first antenna element is arranged away from the hinge section, and the front end section side of the first antenna element is arranged away from the metal plate such as a steel desk, so that the portable radio device is small and thin but the manufacturing cost is still low, and while the quality of the design is not deteriorated, the reduction of the reception sensitivity is prevented even when the portable radio device is placed on a metal plate. 
         [0058]    Further, according to the present embodiment, when the first antenna element is made in the shape as shown in  FIG. 8 , the maximum distance between the first antenna element and the bottom surface of the second casing can be increased, so that it is possible to reliably reduce the influence caused by the metal plate such as a steel desk. 
       Embodiment 2 
       [0059]      FIG. 10  is a plan view illustrating second casing  102  of portable radio device  1000  according to Embodiment 2 of the present invention.  FIG. 11  is a cross sectional view taken along line E-E′ in  FIG. 10 . The cross sectional view taken along line D-D′ in  FIG. 10  is the same as that of  FIG. 5 , the cross sectional view taken along line F-F′ in  FIG. 10  is the same as that of  FIG. 3 . Accordingly, their descriptions will be omitted. 
         [0060]    In second casing  102  of portable radio device  1000  as shown in  FIG. 10 , second antenna element  1001  is provided instead of second antenna element  109  in second casing  102  of portable radio device  100  according to Embodiment 1 as shown in  FIG. 1 . In  FIG. 10 , parts having the same configurations as those of  FIG. 1  will be assigned the same reference numerals, and their descriptions will be omitted. 
         [0061]    Portable radio device  1000  mainly includes first casing  101 , second casing  102 , hinge section  103 , circuit substrate  104 , matching circuit  105 , feeding section  106 , feeding element  107 , first antenna element  108 , circuit substrate  110 , and second antenna element  1001 . 
         [0062]    Second antenna element  1001  is in a substantially inverted-L shape on a plan view, and, for example, second antenna element  1001  is made of a flexible substrate (FPC) or a metal plate, and is integrally formed with first antenna element  108 . Further, second antenna element  1001  oscillates at a higher frequency than the resonance frequency of first antenna element  108 , and therefore, second antenna element  1001  is formed so that the antenna length of second antenna element  1001  is shorter than that of first antenna element  108 . Second antenna element  1001  includes long side section  1002  and short side section  1003  integrally formed with long side section  1002 , and second antenna element  1001  feeds power to one end section of short side section  1003  from feeding section  106  via feeding element  107 . Second antenna element  1001  is configured such that front end section  1004  of long side section  1002  is bent upward. One end section of short side section  1003  is integrally connected to base end section  150  of first antenna element  108 . 
         [0063]    More specifically, second antenna element  1001  is arranged such that short side section  1003  is arranged in second casing  102  such that short side section  1003  is parallel to bottom surface  160  of second casing  102  when seen from the front surface. Further, second antenna element  1001  is arranged such that one end section of long side section  1002  in a longitudinal direction is formed integrally with short side section  1003 , and second antenna element  1001  is formed with inclined section  1005  that is inclined upward between one end section and the other end section in the longitudinal direction of second antenna element  1001 . Inclined section  1005  is formed by bending front end section  1004  side upward in position P 2  to face edge section  170  of hinge section  103  (see  FIG. 11 ). Accordingly, second antenna element  1001  is provided in second casing  102  so that distance r 1  between inclined section  1005  and bottom surface  160  of second casing  102  is greater than distance r 2  between short side section  1003  and bottom surface  160  of second casing  102  (r 1 &gt;r 2 ). On a plan view, second antenna element  1001  is arranged in second casing  102  such that long side section  1002  overlaps hinge section  103 , and short side section  1003  overlaps hinge section  103 . Alternatively, in second antenna element  1001 , the lower surface of inclined section  1005  bent upward may be held by a separately arranged holding member or a holding member integrally arranged with second casing  102 . When second antenna element  1001  is held by the holding member, the distance between second antenna element  1001  and bottom surface  160  of second casing  102  can be maintained at a constant level, and therefore this further improves the performance of the antenna. 
         [0064]    It should be noted that since hinge section  103  is made of a conductive metal material, not only metal plate  210  such as a steel desk but also hinge section  103  may reduce the antenna performance of second antenna element  1001 . In particular, when feeding section  106  is in proximity to hinge section  103 , hinge section  103  may function as an antenna by way of second antenna element  1001 , whereby the antenna performance of second antenna element  1001  may be reduced. Therefore, in the present embodiment, a portion of long side section  1002  and short side section  1003  of second antenna element  1001  except inclined section  1005 , which overlaps hinge section  103  on a plan view, is arranged at a position of second casing  102  that is away from hinge section  103 . On the other hand, inclined section  1005  of long side section  1002  of second antenna element  1001 , which does not overlap hinge section  103  on a plan view, is arranged at a position of second casing  102  that is away from the metal plate such as a steel desk. Therefore, each of the antenna elements is least affected by both hinge section  103  and the metal plate such as a steel desk. 
         [0065]    As described above, the present embodiment has not only the advantages of above Embodiment 1 but also advantages stated below. Since the front end section side of the second antenna element is bent upward, the size and the thickness of the portable radio device can be reduced without increasing the manufacturing costs of not only the first antenna element but also the second antenna element, and while the quality of the design is not deteriorated, the reduction of the reception sensitivity is prevented even when the portable radio device is placed on a metal plate. 
         [0066]    In the present embodiment, the first antenna element has the same shape as that of  FIG. 2 . However, the present embodiment is not limited to this. The first antenna element may be formed in any one of the shapes shown in  FIGS. 7 to 9 . In the present embodiment, the second antenna element is bent upward in position P 2  to face the edge section of the hinge section. However, the present embodiment is not limited to this. As shown in  FIG. 12 , the second antenna element may be bent upward at any position.  FIG. 12  is a cross sectional view taken along line E-E′ in  FIG. 10  illustrating another example of a second antenna element according to the present embodiment. Second antenna element  1200  has the same structure as second antenna element  1001  as shown in  FIGS. 10 and 11  except for the position at which second antenna element is bent upward. Second antenna element  1200  as shown in  FIG. 12  is bent upward at a side of short side section  1003  (right side of  FIG. 12 ) with respect to position P 2  to face edge section  170  of hinge section  103  of long side section  1002 . In other words, as shown in  FIG. 12 , second antenna element  1200  is bent upward at any position in accordance with how second antenna element  1200  is affected by hinge section  103  and metal plate  210 . Therefore, second antenna element  1200  is less affected by both hinge section  103  and metal plate  210 . 
         [0067]    In above Embodiments 1 and 2, the first antenna element is made in the shapes shown in  FIG. 2 ,  7 ,  8  or  9 . However, the present invention is not limited to this. As long as the first antenna element is provided in second casing  102  so that distance r 1  between the front end section side and the bottom surface of second casing  102  is greater than distance r 2  between the base end section side and bottom surface  160  of second casing  102 , the first antenna element can be formed in any shape. In above Embodiments 1 and 2, only two antenna elements are provided. More specifically, the first antenna element and the second antenna element are provided. However, the present invention is not limited to this. Only the first antenna element may be provided, or three or more antenna elements may be provided. In above Embodiments 1 and 2, the first casing and the second casing are rotatably coupled via the hinge section. However, the present invention is not limited to this. The present invention may also be applied to a case where a metal rail is provided to slidably couple the first casing with the second casing. In this case, the meaning of “movable” includes both rotation operation and slide operation. In above Embodiments 1 and 2, the first antenna element is bent upward at the position to face the edge section of the hinge section. However, the present invention is not limited to this. The first antenna element may be bent upward at any position. In above Embodiments 1 and 2, the hinge section is provided in the first casing. However, the present invention is not limited to this. The hinge section may be provided in the second casing. 
         [0068]    The disclosure of Japanese Patent Application No. 2008-317387, filed on Dec. 12, 2008, including the specification, drawings, and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0069]    The portable radio device according to the present invention is particularly suitable for maintaining high reception sensitivity while the portable radio device is placed on a metal plate such as a steel desk.