Abstract:
Disclosed is a portable wireless apparatus that can be miniaturized and that can achieve high antenna performance even when the antenna and circuit board overlap in the vertical direction. In this apparatus, a second case ( 102 ) is mounted so as to be slidable with respect to a first case ( 101 ). An antenna ( 106 ) is provided on the second case ( 102 ). A circuit board ( 104 ) is provided on the first case ( 101 ) and has a slit ( 108 ) that extends in the direction intersecting the sliding direction, at the boundary of a region (r 1 ) including a region opposite the antenna ( 106 ) in the vertical direction and a region (r 2 ) other than this region (r 1 ), when the first case ( 101 ) and second case ( 102 ) are overlapping and closed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a portable radio device. More particularly, the present invention relates to a portable radio device in which multiple casings are connected with each other in a slidable fashion and are placed in an open state and a closed state in accordance with slide operations. 
       Background Art 
       [0002]    Conventionally, a portable radio device formed with two casings which are placed in a mutually slidable fashion is known. With this slide portable radio device, there is a problem that an antenna provided in one casing and a circuit board arranged in the other casing are placed close to each other and cause deterioration of antenna performance. This deterioration of antenna performance arises from the fact that the circuit board in one casing where an antenna is provided and the circuit board in the other casing are placed close to each other and are capacitively coupled, or are connected by a connecting cable for transmitting information, and consequently the impedance of the circuit board facing an antenna in a vertical direction is decreased, so that radiation resistance of antenna is decreased. 
         [0003]    The above problem is especially notable with this slide portable radio device for the following reasons. Thus, the major reasons include that when a slide portable radio device is in an open state, circuit boards partly overlap each other and are prone to couple electromagnetically with each other, and that, given that slide mechanism component to allow slide operations are in most cases metallic to maintain its strength, the circuit boards are prone to couple electromagnetically with each other through a slide portable radio device. 
         [0004]    Also, a portable radio device, which, in one casing to prevent antenna performance from deteriorating, provides a ground wire in a position close to an antenna that is provided in the other casing and improves radiation efficiency of the antenna, is known (for example, PTL 1). 
         [0005]    Citation List 
         [0006]    Patent Literature 
         [0007]    PTL1 
         [0008]    Japanese Patent Application Laid-Open No. 2006-148669 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0009]    However, with patent literature 1, there are problems that it is difficult to make a portable radio device smaller because a space has to be kept to provide a ground wire in a casing, and that, with a slide portable radio device in which an antenna and a circuit board overlap in a vertical direction, it is impossible to improve antenna performance for the above reason. 
         [0010]    It is therefore an object of the present invention to provide a portable radio device that can be miniaturized, and that, can gain high antenna performance even when an antenna and a circuit board overlap in a vertical direction. 
       Solution to Problem 
       [0011]    A portal radio device of the present invention employs a configuration to include: a first casing; a second casing attached slidably to the first casing; an antenna which is provided in the second casing; and a conductive section which is flat and which is provided in the first casing, and, in this portable radio device, the conductive section has an insulation section which is provided in a boundary part between a first area which includes at least an area facing the antenna in a vertical direction and a second area which includes the rest area, in a closed state when the first casing and the second casing overlap, to extend in a direction to cross the slide direction. 
       Advantageous Effects of Invention 
       [0012]    According to the present invention, a portable radio device can be miniaturized, and that, can gain high antenna performance even when an antenna and a circuit board overlap in a vertical direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a front view of a portable radio device in a closed state according to embodiment 1 of the present invention; 
           [0014]      FIG. 2  is a front view of a portable radio device in an open state according to embodiment 1 of the present invention; 
           [0015]      FIG. 3  is a plane view of the first casing according to embodiment 1 of the present invention; 
           [0016]      FIG. 4  is a front view of a portable radio device in a closed state according to embodiment 2 of the present invention; 
           [0017]      FIG. 5  is a front view of a portable radio device in a closed state according to embodiment 3 of the present invention; and 
           [0018]      FIG. 6  is a plane view of the first casing according to embodiment 3 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]    Now, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. 
       Embodiment 1 
       [0020]      FIG. 1  is a front view of portable radio device  100  in a closed state according to the present embodiment.  FIG. 2  is a front view of portable radio device  100  in an open state according to the present embodiment. 
         [0021]    Portable radio device  100  is mainly formed with first casing  101 , second casing  102 , circuit boards  103  and  104 , power feeding section  105 , and antenna  106 . 
         [0022]    Each configuration will be described below. 
         [0023]    First casing  101  is formed in a rectangular shape and is slidably attached to second casing  102  to switch from the closed state of  FIG. 1  to the open state of  FIG. 2  or to switch from the open state of  FIG. 2  to the closed state of  FIG. 1 . Thus, first casing  101  is attached to second casing  102  to be able to slide along the lengthwise direction of first casing  101  (a horizontal direction of  FIG. 1  and  FIG. 2 ). First casing  101  switches from the closed state of  FIG. 1  to an open state by sliding on second casing  102  in a direction to part from antenna  106 . First casing  101  has circuit board  103 . 
         [0024]    Second casing  102  is formed in a rectangular shape and is slidably attached to second casing  102  to switch from the closed state of  FIG. 1  to the open state of  FIG. 2  or to switch from the open state of  FIG. 2  to the closed state of  FIG. 1 . Second casing  102  has circuit board  104 , power feeding section  105 , and antenna  106 . 
         [0025]    Circuit board  103  is provided in first casing  101  and a display section such as LCD (not shown) is attached. In the closed state of  FIG. 1  when first casing  101  and second casing  102  overlap, circuit board  103  has slit  108  in the boundary part between area r 1  which includes an area facing antenna  106  in a vertical direction (a vertical direction of  FIG. 1 ) and area r 2  which includes the rest area. Area r 2  of circuit board  103  functions as a passive element by coupling electromagnetically with circuit board  104 . Now, details of slit  108  will be described later. 
         [0026]    Circuit board  104  is provided in second casing  102 , and antenna  105  and power feeding section  106  are provided. Circuit board  104  is electromagnetically coupled with circuit board  103 . 
         [0027]    Power feeding section  105  is provided in circuit board  104  and feeds power for antenna  106 . Power feeding section  105  is provided in an end part which is in a direction to part from first casing  101  of circuit board  104  in an open state, that is, in an end part which does not overlap in a vertical direction with first casing  101  of circuit board  104  in an open state. Ground section  107  of power feeding section  105  is electrically connected to a ground section of circuit board  104 . 
         [0028]    Antenna  106  is provided in circuit board  104  and is fed power from power feeding section  105 . Antenna  106  is provided in an end part which is in a direction to part from first casing  101  of circuit board  104  in an open state, that is, in an end part which does not overlap in a vertical direction with first casing  101  of circuit board  104  in an open state. Antenna  106  is, for example, an antenna for receiving digital television broadcasting. 
         [0029]    Next, slit  108  provided in circuit board  103  will be described by using  FIG. 3(   a ) and  FIG. 3(   b ).  FIG. 3(   a ) and  FIG. 3(   b ) are plane views of first casing  101 . Antenna  106  is provided in second casing  102  but in  FIG. 3(   a ) and  FIG. 3(   b ) is drawn using a broken line to compare with the location of slit  108 . 
         [0030]    Circuit board  103  is provided over the entire surface of first casing  101  in a plain view. In circuit board  103 , slit  108  is formed from end part  301  in a perpendicular direction to a slide direction (a horizontal direction of  FIG. 3(   a ) and  FIG. 3(   b )) of first casing  101 . Here, slit  108  is provided to separate electrically area r 1  of circuit board  103  from circuit board  103 . Thus, the slit is not mandatory, and as long as an insulation section is provided it is possible to gain the effect of the present embodiment. With the present embodiment, a case will be described where slit  108  is provided as one example of an insulation section. 
         [0031]    In circuit board  103 , slit  108  is provided to extend from end part  301  in a perpendicular direction to a slide direction of first casing  101 . Slit  108  is a through hole to penetrate circuit board  103  in a thickness direction (a perpendicular direction to the sheet of  FIG. 3(   a ) and  FIG. 3(   b )). With circuit board  103 , slit  108  is provided in the boundary part between area r 1 , which includes an area facing antenna  106  in a vertical direction in a closed state, and area r 2  which includes the rest area. Here, in the closed state of  FIG. 1  when first casing  101  and second casing  102  overlap, both cases are possible where area r 1  which faces antenna  106  in a vertical direction (a vertical direction of  FIG. 1)  and an area which faces antenna  106  in a vertical direction (a vertical direction of  FIG. 1 ) are equal, and where as shown in  FIG. 3  ( b ), area r 1  includes area r 3 , which faces antenna  106  in a vertical direction (a vertical direction of  FIG. 1 ), as a part. Slit  108  does not necessarily have to extend from end part  301 , but it is equally possible to extend from end part  302  in a perpendicular direction to a slide direction of first casing  101 . 
         [0032]    In portable radio device  100  which has the above configuration, slit  108  is provided, so that, as shown in  FIG. 1 , it is possible to separate electrically area r 1  which faces antenna  106  in a vertical direction from area r 2  in a closed state. 
         [0033]    Therefore, according to the present embodiment, by providing a slit and electrically separating the area of the circuit board which faces an antenna in a vertical direction, the impedance of the area of the circuit board which faces an antenna in a vertical direction can be increased, so that it is possible to reduce deterioration of a radiation resistance of antenna and gain high antenna performance. The present embodiment has only to provide a slit on a circuit board and does not even require any space to arrange a component for improving antenna performance, so that miniaturization can be realized. The present embodiment can improve antenna performance only by providing a slit on a circuit board, so that it is possible to minimize the reduction of footprint of a circuit board in association with an improvement of antenna performance. The present embodiment can prevent deterioration of an antenna performance due to an area which faces to an antenna of a circuit board in a vertical direction, so that it is possible to use actively an area which does not face an antenna of a circuit board as a passive element. According to the present embodiment, in an open state, the first casing does not face an antenna in a vertical direction and can improve antenna performance, so that in both open and closed state, it is possible to achieve good antenna performance. 
         [0034]    Although with the present embodiment the slit is formed to penetrate a circuit board in a thickness direction, the present embodiment is not limited to this, and it is equally possible to form an insulation section instead of the slit by removing a conductive section in the location to form the slit on a circuit board. 
       Embodiment 2 
       [0035]      FIG. 4  is a front view of portable radio device  400  in a closed state according to embodiment 2 of the present invention. 
         [0036]    Portable radio device  400  shown in  FIG. 4  adds connecting part  401 , connecting part  402 , and connecting cable section  403  to portable radio device  100  according to embodiment 1 shown in  FIG. 1 . Also, parts in  FIG. 4  that are the same as in  FIG. 1  will be assigned the same reference numerals as in  FIG. 1  and overlapping descriptions will be omitted. 
         [0037]    Circuit board  103  is provided in first casing  101  and operates as a passive element, and also a display section such as LCD (not shown) is attached. In the closed state of  FIG. 1  when first casing  101  and second casing  102  overlap, circuit board  103  has slit  108  in the boundary part between area r 1  which includes an area facing antenna  106  in a vertical direction (a vertical direction of  FIG. 1 ) and area r 2  which includes the rest area. Circuit board  103  has connecting part  401 . Circuit board  103  has slit  108  between antenna  106  and connecting part  401  (described later) and between antenna  106  and connecting part  402  (described later). In the closed state of  FIG. 4 , area r 2  of circuit board  103  functions as a passive element by coupling electromagnetically with circuit board  104 . The slit is not mandatory, and, as the above embodiment 1, as long as an insulation section is provided it is possible to gain the effect of the present embodiment. 
         [0038]    Circuit board  104  is provided in second casing  102 , and power feeding section  105  and antenna  106  are provided. Circuit board  104  has connecting part  402 . 
         [0039]    Connecting part  401  is, for example, a connector and is provided in area r 2  in circuit board  103 . Also, connecting part  401  electrically connects a ground section of circuit board  103  and connecting cable section  403 . 
         [0040]    Connecting part  402  is, for example, a connector, and is provided in circuit board  104 . Also, connecting part  402  electrically connects a ground section of circuit board  104  and connecting cable section  403 . 
         [0041]    Connecting cable section  403  is made from a flexible material, and electrically connects connecting part  401  and connecting part  402 . Connecting cable section  403  connects electrically a ground section of circuit board  103  and a ground section of circuit board  104 , and that, for example, transmits a signal which is processed in a radio circuit (not shown) provided in circuit board  104  to a display section (not shown) provided in circuit board  103 . A front view of portable radio device  400  in an open state is the same as  FIG. 2  except that connecting section  401 , connecting section  402 , and connecting cable section  403  are provided, and a plane view of first casing  101  are the same as  FIG. 3 , so that overlapping descriptions will be omitted. 
         [0042]    In portable radio device  400  which has the above configuration, a ground section of circuit board  103 , connecting cable section  403 , and a ground section of circuit board  104  are electrically connected, so that they function as a bottom board of antenna  106 . In this case, area r 1  of circuit board  103  can be electrically separated by slit  108 . 
         [0043]    Therefore, according to the present embodiment, in addition to the effect of the above embodiment 1, by electrically connecting circuit boards with each other by using a connecting cable, it is possible to gain high antenna performance even if the power of electromagnetic coupling between the circuit boards is large. According to the present embodiment, it is possible to form an antenna which has a given electrical length without deteriorating antenna performance, with a ground section of an area which does not face a circuit board of the first casing, a connecting cable section, and a ground section of a circuit board of the second casing. 
         [0044]    Although with the present embodiment the slit is formed to penetrate a circuit board in a thickness direction, the present embodiment is not limited to this, and it is equally possible to form an insulation section instead of the slit by removing a conductive section in the location to form the slit on a circuit board. 
       Embodiment 3 
       [0045]      FIG. 5  is a front view of portable radio device  500  in a closed state according to embodiment 3 of the present invention. 
         [0046]    Portable radio device  500  shown in  FIG. 5  adds reactance element  501  to portable radio device  400  according to embodiment 2 shown in  FIG. 4 . Also, parts in  FIG. 5  that are the same as in  FIG. 1  and  FIG. 4  will be assigned the same reference numerals as in  FIG. 1  and  FIG. 4  and overlapping descriptions will be omitted. 
         [0047]    Circuit board  103  is provided in first casing  101  and operates as a passive element, and also a display section such as LCD (not shown) is attached. In the closed state of  FIG. 5  when first casing  101  and second casing  102  overlap, circuit board  103  has slit  108  in the boundary part between area r 1  which faces to antenna  106  in a vertical direction (a vertical direction of  FIG. 5 ) and area r 2  which includes the rest area. Circuit board  103  has connecting part  401 . Circuit board  103  has slit  108  between antenna  106  and connecting part  401  (described later) and between antenna  106  and connecting part  402 . In the closed state of  FIG. 5 , area r 2  of circuit board  103  functions as a passive element by coupling electromagnetically with circuit board  104 . Circuit board  103  has reactance element  501  which is attached over slit  108 . 
         [0048]    Reactance element  501  connects between end parts which oppose each other and which form slit  108  of a circuit board, and adjusts an electrical length of an antenna of circuit board  103 . For example, reactance element  501  optimizes circuit constant to let area r 1  of circuit board  103  function as a passive element in a closed state, and adjusts an electrical length in circuit board  103 . 
         [0049]    Next, slit  108  provided in circuit board  103  will be described by using  FIG. 6 .  FIG. 6  is a plane view of first casing  101 . Antenna  106  is provided in second casing  102  but in  FIG. 6  is drawn using a broken line to compare with the location of slit  108 . Also, parts in  FIG. 6  that are the same as in  FIG. 3  will be assigned the same reference numerals as in  FIG. 3  and overlapping descriptions will be omitted. Also, in  FIG. 6 , as the above embodiment 1, in the closed state of  FIG. 5  when first casing  101  and second casing  102  overlap, there are cases where area r 1 , which includes as a part an area facing antenna  106  in a vertical direction (a vertical direction of  FIG. 5 ), includes an area facing antenna  106  in a vertical direction (a vertical direction of  FIG. 5 ). 
         [0050]    Reactance element  501  connects a ground section of end part  601  and a ground section of end part  602  which oppose each other and which form slit  108  of circuit board  103 . 
         [0051]    Therefore, according to the present embodiment, in addition to the effect of the above embodiment 1, it is possible to optimize antenna performance by providing a reactance element which connects between end parts forming the slit of a circuit board and adjusting an electrical length of a circuit board. 
         [0052]    With the present embodiment, the reactance can be changed by using variable reactive elements, or by switching between multiple reactive elements with a switch. For example, it is possible to detect an open state and a closed state to change the reactance of a reactance element based on the detected state, or the designer may adjust a reactance element each time to provide the given reactance. 
         [0053]    Although with the above embodiment 1-embodiment 3 the slit is formed to extend from one end part of a circuit board in a perpendicular direction to a slide direction of first casing  101 , the present invention is not limited to this, and it is equally possible to extend and form the slit in an arbitrary direction from one end part of a circuit board as long as it is in a direction to cross the slide direction of first casing  101 . Although with the above embodiment 1-embodiment 3 the slit is formed from one end part of a circuit board, the present invention is not limited to this, and it is possible to extend and form the slit in a direction to cross the slide direction from an arbitrary location of a circuit board. Although with the above embodiment 1-embodiment 3 the slit is formed in a circuit board, the present invention is not limited to this, and it is equally possible to form the slit in a metal chassis for maintaining strength, in a metal case, or in an arbitrary conductive section which is close to an antenna other than a circuit board such as a sheet metal. 
         [0054]    The disclosure of Japanese Patent Application No. 2008-334010, filed on Dec. 26, 2008 including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0055]    A portable radio device of the present invention is especially suitable for a portable radio device which connects a plurality of casings in a mutually slidable fashion and which is placed in an open state and a closed state in accordance with slide operations.