Patent Publication Number: US-8125392-B2

Title: Antenna and electronic apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an antenna and an electronic apparatus in which the antenna is mounted, and particularly relates to an antenna used in an apparatus such as a personal computer to construct a wireless LAN or the like. 
     BACKGROUND ART 
     In recent years, radio communication systems (wireless LAN) have been widely used and “HotSpots” have been increased at which mobile devices supporting this wireless LAN, for example, notebook personal computers can be connected to the Internet or other services in the public areas. As a plate-like antenna mountable in the notebook personal computer capable of using the wireless LAN at the HotSpot, a flat-plane antenna formed of a plate-like metal element has been known (for example, see Non-patent Document 1). 
     The metal element of the antenna is formed by a rectangular plate-like ground conductor and an “L” shaped radiation conductor extending in a long narrow form from the end portion of the ground conductor. The frequency used by the antenna is about 2.4 GHz and the radiation conductor extends by a length corresponding to about ¼ of a wavelength λ of the used frequency. 
     An inner conductor (center conductor) of a coaxial cable is electrically connected to the radiation conductor, and an outer conductor of the coaxial cable is electrically connected to the ground conductor. 
     Then, the antenna is designed to be supplied with power by using the coaxial cable.
     [Non-patent Document 1] “Built-in Film Antenna for Mobile Devices using 2.4. GHz Band,” Technical Journal of Hitachi Cable, Ltd., No. 21 issued in January, 2002). Meanwhile, an antenna is known which is configured to be entirely flexible by forming a conductor thinly on a surface of a film-like base (for example, see Patent Document 1).   [Patent Document 1] Japanese Patent Application Publication No. 2005-277897).   

     DISCLOSURE OF THE INVENTION 
     Recent further miniaturization and the like of personal computers (particularly, mobile personal computers) have reduced an antenna mounting space, and further miniaturization of the antenna has been demanded. Nevertheless, in the conventional antenna using the metal element, the ground conductor is required to have a certain large size so as to maintain antenna characteristics (frequency characteristic and directivity) in a good condition. This makes it difficult to miniaturize the antenna. 
     Therefore, there is a problem that the conventional antenna using the metal element cannot sufficiently achieve the object of reducing the mounting space while maintaining the antenna characteristics (frequency characteristic and directivity). 
     Additionally, in the conventional flexible antenna, the antenna can be, for example, inserted from a narrow space by being bent or somehow when being mounted. Meanwhile, there is a problem that, when the antenna is mounted while being bent, the antenna characteristics are changed, so that the antenna cannot be used sometimes. 
     The present invention has been made in view of the aforementioned problem. An object of the present invention is to provide an antenna which is mounted while being bent, and thereby which allows a mounting space to be made smaller than that of the conventional antenna, and to provide an electronic apparatus on which the antenna is mounted. 
     An invention according to a first aspect of the present invention is an antenna comprising: a plate-like base made of an insulating material; and a conductor in a predetermined shape, the conductor having a plurality of cut-out portions and being provided at a predetermined position of the base so as to obtain a predetermined antenna characteristic, wherein the antenna is configured to maintain the antenna characteristic mostly even when the base is deformed into a predetermined curved-surface shape or the base is bent along a predetermined straight line. 
     An invention according to a second aspect of the present invention is an antenna comprising: a plate-like base made of an insulating material and having flexibility; a first conductor formed into an approximately rectangular outer shape, and provided on a surface of the base, the first conductor having a first cut-out portion and a second cut-out portion; a second conductor having a first element and a second element provided so as to connect the first element and the first conductor to each other, the first element being formed in a long narrow rectangular shape with approximately the same length as that of the first conductor, the first element being provided on the base a predetermined distance away from the first conductor, at a side of one end portion of the first conductor in a width direction, in such a way that a longitudinal direction of the first element is aligned with a longitudinal direction of the first conductor, the second element having a short rectangular shape, and being provided on the surface of the base so as to extend from one end portion of the first element in a longitudinal direction toward a vicinity thereof between the first element and the first conductor; and a coaxial cable whose outer conductor is electrically connected to a first predetermined portion of the first conductor and whose inner conductor is electrically connected to a second predetermined portion of the second conductor; wherein the first predetermined portion where the outer conductor of the coaxial cable is connected extends from the one end portion of the first conductor in the width direction to a vicinity thereof, at the side of the one end portion of the first conductor in the longitudinal direction thereof; the second predetermined portion where the inner conductor of the coaxial cable is connected extends in the width direction of the first element, at a side of the one end portion of the first element of the second conductor in the longitudinal direction; the first cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to an approximately center portion of the first conductor from the other end portion of the first conductor in the longitudinal direction, at the side of the one end portion of the first conductor in the width direction, in such a way that a longitudinal direction of the first cut-out portion is aligned with the longitudinal direction of the first conductor; and the second cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to an approximately center portion of the first conductor from the one end portion of the first conductor in the longitudinal direction, at a side of the other end portion of the first conductor in the width direction in such a way that a longitudinal direction of the second cut-out portion is aligned with the longitudinal direction of the first conductor; or alternatively, wherein the first cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to an approximately center portion of the first conductor from the one end portion of the first conductor in the longitudinal direction, at the side of the one end portion of the first conductor in the width direction, in such a way that the longitudinal direction of the first cut-out portion is aligned with the longitudinal direction of the first conductor; and the second cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to an approximately center portion of the first conductor from the other end portion of the first conductor in the longitudinal direction, at a side of the other end portion of the first conductor in the width direction in such a way that the longitudinal direction of the second cut-out portion is aligned with the longitudinal direction of the first conductor. 
     An invention according to a third aspect of the present invention is An antenna comprising: a plate-like base made of an insulating material and having flexibility; a first conductor formed into an approximately rectangular outer shape, and provided on a surface of the base, the first conductor having a first cut-out portion and a second cut-out portion; a second conductor having a first element and a second element provided so as to connect the first element and the first conductor to each other, the first element being formed in a long narrow rectangular shape with approximately the same length as that of the first conductor, the first element being provided on the base a predetermined distance away from the first conductor, at a side of one end portion of the first conductor in a width direction, in such a way that a longitudinal direction of the first element is aligned with a longitudinal direction of the first conductor, the second element having a short rectangular shape, and being provided on the surface of the base so as to extend from one end portion of the first element in a longitudinal direction toward a vicinity thereof between the first element and the first conductor; and a coaxial cable whose outer conductor is electrically connected to a first predetermined portion of the first conductor and whose inner conductor is electrically connected to a second predetermined portion of the second conductor; wherein the first predetermined portion where the outer conductor of the coaxial cable is connected extends from the one end portion of the first conductor in the longitudinal direction thereof to a vicinity thereof, at the side of the one end portion of the first conductor in the longitudinal direction thereof; the second predetermined portion where the inner conductor of the coaxial cable is connected extends in a width direction of the first element, at a side of the one end portion of the first element of the second conductor in the longitudinal direction of the first element; the first cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the one end portion of the first conductor in the longitudinal direction from the other end portion of the first conductor in the longitudinal direction, at the side of the one end portion of the first conductor in the width direction, in such a way that the longitudinal direction of the first cut-out portion is aligned with the longitudinal direction of the first conductor; and the second cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the other end portion of the first conductor in the longitudinal direction from the one end portion of the first conductor in the longitudinal direction, at a side of the other end portion of the first conductor in the width direction in such a way that the longitudinal direction of the second cut-out portion is aligned with the longitudinal direction of the first conductor. 
     An invention according to a fourth aspect of the present invention is an antenna comprising: a plate-like base made of an insulating material and having flexibility; a first conductor formed into an approximately rectangular outer shape, and provided on a surface of the base, the first conductor having a first cut-out portion and a second cut-out portion; a second conductor having a first element and a second element provided so as to connect the first element and the first conductor to each other, the first element being formed in a long narrow rectangular shape with approximately the same length as that of the first conductor, the first element being provided on the base a predetermined distance away from the first conductor, at a side of one end portion of the first conductor in a width direction, in such a way that a longitudinal direction of the first element is aligned with a longitudinal direction of the first conductor, the second element having a short rectangular shape, and being provided on the surface of the base so as to extend from one end portion of the first element in a longitudinal direction toward a vicinity thereof between the first element and the first conductor; a first connection section formed into a rectangular shape, and provided on the surface of the base to be connected to the first element, the first connection section being located, in the width direction of the first conductor, at the side of the first element of the second conductor between the first conductor and the first element, and being located, in the longitudinal direction of the first conductor, at the side of the second element of the second conductor; a second connection section formed into a rectangular shape, and provided on the surface of the base to be connected to the first conductor, the second connection section being located, in the width direction of the first conductor, at the side of the first conductor between the first conductor and the first element of the second conductor, and being located, in the longitudinal direction of the first conductor, between the first connection section and the second element of the second conductor; and a coaxial cable whose inner conductor is electrically connected to the first connection section and whose outer conductor is electrically connected to the second connection section; wherein the first cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the one end portion of the first conductor in the longitudinal direction from the other end portion of the first conductor in the longitudinal direction, at the side of the one end portion of the first conductor in the width direction, in such a way that the longitudinal direction of the first cut-out portion is aligned with the longitudinal direction of the first conductor; and the second cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the other end portion of the first conductor in the longitudinal direction from the one end portion of the first conductor in the longitudinal direction, at a side of the other end portion of the first conductor in the width direction in such a way that the longitudinal direction of the second cut-out portion is aligned with the longitudinal direction of the first conductor. 
     An invention according to a fifth aspect of the present invention is an antenna comprising: a plate-like base made of an insulating material and having flexibility; a first conductor formed into an approximately rectangular outer shape, and provided on a surface of the base, the first conductor having a first cut-out portion and a second cut-out portion; a second conductor having a first element and a second element provided so as to connect the first element and the first conductor to each other, the first element being formed in a long narrow rectangular shape with approximately the same length as that of the first conductor, the first element being provided on the base a predetermined distance away from the first conductor, at a side of one end portion of the first conductor in a width direction, in such a way that a longitudinal direction of the first element is aligned with a longitudinal direction of the first conductor, the second element having a short rectangular shape, and being provided on the surface of the base so as to extend from one end portion of the first element in a longitudinal direction toward a vicinity thereof between the first element and the first conductor; and a coaxial cable whose inner conductor is electrically connected to a first predetermined portion of the first conductor and whose outer conductor is electrically connected to a second predetermined portion of the second conductor; wherein the first predetermined portion where the inner conductor of the coaxial cable is connected is located at a side of the one end portion of the first conductor in the width direction and at a side of the one end portion of the first conductor in the longitudinal direction; the second predetermined portion where the outer conductor of the coaxial cable is connected is located between the first predetermined portion and the second element of the second conductor, at a side of the one end portion of the first element of the second conductor in the longitudinal direction; the first cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the one end portion of the first conductor in the longitudinal direction from the other end portion of the first conductor in the longitudinal direction, at the side of the one end portion of the first conductor in the width direction, in such a way that the longitudinal direction of the first cut-out portion is aligned with the longitudinal direction of the first conductor; and the second cut-out portion is formed into a long narrow rectangular shape with approximately the same width as that of the first element of the second conductor, and extends to a portion on the side of the other end portion of the first conductor in the longitudinal direction from the one end portion of the first conductor in the longitudinal direction, at a side of the other end portion of the first conductor in the width direction in such a way that the longitudinal direction of the second cut-out portion is aligned with the longitudinal direction of the first conductor. 
     An invention according to a sixth aspect of the present invention is an electronic apparatus comprising the antenna according to any one of the first to fifth aspects of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating a schematic configuration of an antenna according to a first embodiment of the present invention. 
         FIG. 2  is a view illustrating a state in which the antenna is deformed. 
         FIG. 3  is a view illustrating a frequency characteristic of the antenna. 
         FIG. 4  is a view illustrating directivity of a main polarized wave of the antenna at the time when the antenna is deformed as illustrated in  FIG. 2 . 
         FIG. 5  is a view illustrating directivity of the main polarized wave of the antenna at the time when the antenna is deformed as illustrated in  FIG. 2 . 
         FIG. 6  is a view illustrating directivity of the main polarized wave of the antenna at the time when the antenna is deformed as illustrated in  FIG. 2 . 
         FIG. 7  is a view illustrating a relationship between a bending radius R of the antenna and an average gain. 
         FIG. 8  is a view illustrating a schematic configuration of an antenna according to a second embodiment of the present invention. 
         FIG. 9  is a view illustrating the frequency characteristics of the antenna according to the first embodiment and the antenna according to the second embodiment, respectively. 
         FIG. 10  is a view illustrating directivity of the main polarized waves of the antenna according to the first embodiment and the antenna according to the second embodiment, respectively, in the arrangement as illustrated in  FIG. 2 . 
         FIG. 11  is a view illustrating directivity of the main polarized waves of the antenna according to the first embodiment and the antenna according to the second embodiment, respectively, in the arrangement as illustrated in  FIG. 2 . 
         FIG. 12  is a view illustrating directivity of the main polarized waves of the antenna according to the first embodiment and the antenna according to the second embodiment, respectively, in the of arrangement as illustrated in  FIG. 2 . 
         FIG. 13  is a view illustrating a relationship between a bending radius R of the antenna and an average gain. 
         FIG. 14  is a view illustrating an average gain at the time when each antenna is mounted in a plane shape. 
         FIG. 15  is a view illustrating a schematic configuration of an antenna according to a third embodiment of the present invention. 
         FIG. 16  is a view illustrating a state in which the antenna is deformed. 
         FIG. 17  is a view illustrating a frequency characteristic of the antenna at the time when a distance S in  FIG. 16  is set to “0 mm.” 
         FIG. 18  is a view illustrating a frequency characteristic of the antenna at the time when the distance S in  FIG. 16  is set to “16 mm.” 
         FIG. 19  is a view illustrating directivity (directivity of an xy plane) of the antenna at the time when the distance S in  FIG. 16  is set to “0 mm.” 
         FIG. 20  is a view illustrating directivity (directivity of the xy plane) of the antenna at the time when the distance S in  FIG. 16  is set to “16 mm.” 
         FIG. 21  illustrates an average gain in each of the distance S and an angle α in the antenna. 
         FIG. 22  is a view illustrating an average gain at the time when the antenna is deformed into a cylinder side surface shape and showing a gain based on a bending radius R. 
         FIG. 23  is a view illustrating a frequency characteristic at the time when the antenna is deformed into a cylinder side surface shape. 
         FIG. 24  is a view illustrating directivity (directivity of an xy plane) of the antenna at the time when the antenna is deformed into a cylinder side surface shape. 
         FIG. 25  is a view illustrating a schematic configuration of an antenna according to a fourth embodiment of the present invention. 
         FIG. 26  is a view illustrating a frequency characteristic of the antenna. 
         FIG. 27  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna in a frequency of 2.43 GHz. 
         FIG. 28  is a view illustrating a schematic configuration of an antenna according to a fifth embodiment of the present invention. 
         FIG. 29  is a view illustrating a frequency characteristic of the antenna 
         FIG. 30  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) in connection with the antenna in a frequency of 2.43 GHz. 
         FIG. 31  is a view illustrating a state in which a flat plate-like conductive member is brought into contact with the plate-like antenna according to the fourth embodiment. 
         FIG. 32  is a view illustrating a frequency characteristic of the antenna at the time when a distance dz is changed. 
         FIG. 33  is a view illustrating a frequency characteristic of the antenna after a length of a second conductor  7   c  and that of one end portion  33  are appropriately changed where dz=0 mm and frequency adjustment is performed. 
         FIG. 34  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna in a frequency of 2.43 GHz after the length of the second conductor  7   c  and that of one end portion  33  are appropriately changed where dz=0 mm and frequency adjustment is performed. 
         FIG. 35  is a view illustrating a state in which a flat plate-like conductive member is placed upright on the flat plate-like antenna. 
         FIG. 36  is a view illustrating a frequency characteristic of the antenna at the time when the distance dz is changed. 
         FIG. 37  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna in a frequency of 2.43 GHz where dz=0 mm. 
         FIG. 38  is a view illustrating a state in which the antenna is mounted in an electronic apparatus. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     First Embodiment 
       FIG. 1  is a view illustrating a schematic configuration of an antenna  1  according to a first embodiment of the present invention. 
     The antenna  1  is used in a frequency band of 2.4 GHz to construct a radio LAN or the like by being mounted in an apparatus, for example, a personal computer or the like, and includes a thin (for example, a thickness of about 35 μm) plate-like base  3 , which is made of an insulating material (a dielectric constant of about 3.0) such as synthetic resin (for example, polyimide) and which has flexibility. 
     A conductor  5  having a predetermined shape (for example, copper having a thickness of about 10 μm to 35 μm) is thinly formed integrally on one surface of the base  3  in a thickness direction of the base  3 . The conductor  5  is generated by etching or the like, has multiple cut-out portions  10 ,  13  and  15  to obtain predetermined antenna characteristics (a VSWR characteristic (frequency characteristic), a radiation characteristic (directivity) and the like), and is provided at a predetermined position on the surface of the base  3 . 
     Then, even when the base  3  and the conductor  5  are deformed into predetermined curved surface shapes, the antenna  1  is designed to be capable of mostly maintain the antenna characteristics. Moreover, the conductor  5  is thinly provided, thereby durability against bending of the antenna  1  is improved and skin effect of copper can be obtained. 
     In more detail explanation, the base  3  is formed rectangularly, for example. The conductor  5  includes a first conductor (ground conductor)  6  having multiple cut-out portions (for example, two cut-out portions)  13  and  15  and a second conductor (radiation conductor)  7  projected from the first conductor  6 , and is formed to have an approximately rectangular outer shape. That is, if neither the cut-out portions  13  and  15  of the first conductor  6  nor the cut-out portion  10  formed between the first conductor  6  and the second conductor  7  (cut-out portion formed between the first conductor  6  and the second conductor  7  by projection of the second conductor  7 ) is present, the conductor  5  is rectangularly formed. Further, the conductor  5  is provided on one surface of the base  3  in the thickness direction of the base  3  so that a longitudinal direction of the conductor  5  and a longitudinal direction of the base  3  match each other. 
     The predetermined curved-surface shape has a cylindrical side-surface shape where a radius is R as illustrated in  FIG. 2 , for example, and the conductor  5  is used by being deformed so that one side (long side) and another side (the other long side) opposite to the one side can form a circular-arc shape and the other sides (short sides) are linearly shaped. However, the antenna  1  does not always have to be used in the aforementioned deformed state and there is a case that the base  3  and the conductor  5  are used in a plane shape without being deformed. 
     The antenna  1  has a coaxial cable  17  as an example of a feeder line, and an inner conductor (center conductor)  21  of the coaxial cable  17  is electrically connected to a predetermined position of the second conductor  7  and an outer conductor (external conductor)  19  of the coaxial cable  17  is electrically connected to a predetermined position of the first conductor  6 . It is noted that the coaxial cable  17  having an outer diameter of 0.75 mm to 1.15 mm is used. Moreover, the conductor  5  and the base  3  are used in a deformed state in such a way that a straight line CL, which connects the predetermined position (portion), where the inner conductor  21  of the coaxial cable  17  is connected, to the predetermined position (portion) where the outer conductor  19  of the coaxial cable  17  is connected, extends (extends in a z-axis direction in  FIG. 2 ) in parallel with a center axis of the cylinder (center axis connecting the center of an upper surface of the cylinder to the center of a bottom surface thereof) and that the center axis of the cylinder is parallel to each linear side (each short side) of the base  3 . 
     It is noted that an x-axis illustrated in  FIG. 2  is an axis which is perpendicular to the z-axis and extends in a diameter direction of the cylinder. In addition, a z-axis is an axis which is perpendicular to the x-axis and the y-axis. 
     When the antenna  1  is described in more detail, the first conductor  6  includes the first cut-out portion  13  and the second cut-out portion  15  and is formed to have an approximately rectangular outer shape. In other words, if no cut-out portions  13  and  15  are present, the first conductor  6  is rectangularly shaped. 
     The second conductor  7  is formed in an “L” shape by a first element  9  and a second element  11 . 
     The first element  9  is formed to have approximately the same length as that of the first conductor  6  and a long narrow rectangular shape, and is provided to be separated away from the first conductor  6  by a predetermined distance (distance approximately the same as the width of the first element  9 ) at a side of one end portion of the first conductor  6  in a width direction in such a way that a longitudinal direction of the first element  9  is aligned with a longitudinal direction of the first conductor  6  and both end portions of the first element  9  in the longitudinal direction are aligned with both end portions of the first conductor  6  in the longitudinal direction. 
     The second element  11  is provided so as to electrically connect the first element  9  and the first conductor  6  to each other. Specifically, the second element  11  is formed to have approximately the same width as that of the first element  9 , the same length as a distance between the first element  9  and the first conductor  6  and a short rectangular shape, and is provided between the first element  9  and the first conductor  6  and from one end portions of the first element  9  and the first conductor  6  in the longitudinal directions thereof, respectively, to the vicinity of the one end portions. 
     A first predetermined portion where the outer conductor  19  of the coaxial cable  17  is connected is separated away from the second element  11  of the second conductor  7  by a predetermined distance (distance slightly larger than the width of the second element  11 ) at the side of the one end portion of the first conductor  6  in the longitudinal direction and extends from one end portion of the first conductor  6  in the width direction to the vicinity of the one end portion. 
     A second predetermined portion where the inner conductor  21  of the coaxial cable  17  is connected is separated away from the second element  11  of the second conductor  7  by a predetermined distance (approximately the same distance as that of the first predetermined portion; distance slightly larger than the width of the second element  11 ) at a side of one end portion of the first element  9  of the second conductor  7  in the longitudinal direction and extends in the width direction of the first element  9 . 
     The first cut-out portion  13  is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and a long narrow rectangular shape, and extends from the other end portion of the first conductor  6  in the longitudinal direction to an approximately center portion of the first conductor  6  at the side of the one end portion of the first conductor  6  in the width direction in such a way that a longitudinal direction of the first cut-out portion  13  is aligned with the longitudinal direction of the first conductor  6 . 
     The second cut-out portion  15  is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and a long narrow rectangular shape, and extends from the one end portion of the first conductor  6  in the longitudinal direction to approximately the center portion of the first conductor  6  at a side of the other end portion of the first conductor  6  in the width direction in such a way that the longitudinal direction of the second cut-out portion  15  is aligned with the longitudinal direction of the first conductor  6 . 
     The coaxial cable  17  connected to the conductor  5  extends in a direction of the first predetermined portion (portion where the outer conductor  19  is connected) with the second predetermined portion (portion where the inner conductor  21  is connected) being as a reference point. Further, as described above, the straight line which connects the first predetermined portion and the second predetermined portion to each other extends in the width direction of the first conductor  6  and that of the second conductor  7  (x-axis direction in  FIG. 2 ). Furthermore, seeing from a thickness direction of the base  3  (conductor  5 ), the conductor  5  (conductors  6  and  7 ) is present inside the rectangularly formed base  3 . 
     In addition, for example, the conductor  5  and the surface of the base  3 , on which the conductor  5  is provided, are covered with a thin insulating film  23 . 
     When the antenna  1  is used by being mounted (e.g., adhered) along the curved surface of the cylinder side surface shape as illustrated in  FIG. 2 , the respective short sides positioned at both sides of the base  3  in the longitudinal direction of the base  3  are linearly maintained and the respective long sides positioned at both sides of the base  3  in a width direction are deformed into arc shapes. Then, the antenna  1  (base  3  and conductor  5 ) is deformed into a cylinder side surface shape. 
     When power is fed to the antenna  1  through the coaxial cable  17 , the antenna  1  operates as a monopole antenna and current flows in an extending direction of the coaxial cable  17  and the current is strongly distributed in the vicinity of a feeding point (portions where the inner conductor  21  and the outer conductor  19  of the coaxial cable  17  is connected). Therefore, a main polarized wave is in a direction parallel to the extending direction of the coaxial cable  17 , and even when the antenna  1  is deformed as illustrated in  FIG. 2 , the characteristics of the antenna  1  (frequency characteristic, directivity, and the like) are almost unchanged. In other words, even when the antenna  1  is bent as illustrated in  FIG. 2 , the characteristics of the antenna  1  are almost unchanged since the current flowing direction remains parallel to the extending direction of the coaxial cable  17  and the current concentrates at the feeding point due to the coaxial cable  17 . 
     A test result of the characteristics of the antenna  1  will be next described. 
       FIG. 3  is a view illustrating a frequency characteristic of the antenna  1 . 
     In  FIG. 3 , a horizontal axis indicates a frequency and a vertical axis indicates a VSWR (Voltage Standing Wave Ratio) value. A range where an absolute value of VSWR is “not more than 2” corresponds to a resonance frequency band. 
     A graph G 31  illustrated in  FIG. 3  is a graph indicating a frequency characteristic at the time when the antenna  1  is deformed into a cylinder side surface shape as illustrated in  FIG. 2  and a radius R is 10 mm. When the radius R is 10 mm, the resonance frequency band having a VSWR absolute value of “not more than 2” corresponds to a range from 2.48 GHz to 2.59 GHz. 
     Likewise, graphs G 32  to G 37  illustrated in  FIG. 3  are graphs each indicating a frequency characteristic at the time when the antenna  1  is deformed into a cylinder side surface shape as illustrated in  FIG. 2  and each radius R is changed. Moreover, a graph G 38  illustrated in  FIG. 3  is a graph indicating a frequency characteristic at the time when the antenna  1  is plane-shaped. 
     In the graph G 32  (R=15 mm), the resonance frequency band ranges from 2.41 GHz to 2.59 GHz, but in the graphs G 33  to G 38 , the resonance frequency band ranges from 2.40 GHz to 2.59 GHz. Therefore, when a bending radius is 20 mm or more, it is possible to obtain the same frequency characteristic as that obtained when the antenna  1  is used in a plane shape. 
       FIG. 4  to  FIG. 6  are views each illustrating directivity of the main polarized wave of the antenna  1  at the time when the antenna  1  is deformed as illustrated in  FIG. 2 ,  FIG. 4  illustrates a characteristic of an xy plane,  FIG. 5  illustrates a characteristic of a yz plane, and  FIG. 6  illustrates a characteristic of a zx plane. 
     As is understood from graphs G 41  to G 48 , G 51  to G 58  and G 61  to G 68  in  FIG. 4  to  FIG. 6 , if the bending radius is 20 mm or more, it is possible to obtain the same directivity as that obtained when the antenna  1  is used in a plane shape as in the case of the frequency characteristic. 
       FIG. 7  is a view illustrating a relationship between a bending radius R of the antenna  1  and an average gain at the time when the antenna  1  is deformed as illustrated in  FIG. 2 . 
     As is understood from graphs G 71  to G 73  in  FIG. 7 , if the bending radius is 20 mm or more, it is possible to obtain the same average gain as that obtained when the antenna  1  is used in a plane shape as in the cases of the frequency characteristic and directivity. 
     Therefore, if the antenna  1  is mounted as illustrated in  FIG. 2  and the bending radius is set to 20 mm or more, it is possible to obtain the same antenna characteristic as that obtained when the antenna  1  is used in a plane shape. In other words, the antenna  1  can be used if the antenna  1  is mounted as illustrated in  FIG. 2  and the bending radius is 20 mm or more. 
     In the antenna  1 , the base  3  and the conductor  5  have flexibility, and therefore the antenna  1  can be mounted in an apparatus such as a personal computer by being deformed into a curved surface shape or bent as described later, and can be mounted in a setting space smaller than the conventional case. 
     Moreover, multiple cut-out portions  13  and  15  are formed in the first conductor  6 , thereby making it possible to miniaturize the first conductor  6 , and obtain good antenna characteristics (frequency characteristic, directivity, and average gain) as illustrated in  FIG. 3  to  FIG. 7  even when the antenna is deformed into a curved surface shape or bent. 
     Second Embodiment 
       FIG. 8  is a view illustrating a schematic configuration of an antenna  1   a  according to a second embodiment of the present invention. 
     The antenna  1   a  according to the second embodiment is configured in the same way as that of the antenna  1  according to the first embodiment and exhibits approximately the same effects except in that the positions of cut-out portions  13   a  and  15   a  formed in a first conductor  6   a  (conductor  5   a ) are reversed in a longitudinal direction of the first conductor  6   a.    
     Specifically, the first cut-out portion  13   a  of the antenna  1   a  according to the second embodiment is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and a long narrow rectangular shape, and extends from one end portion of the first conductor  6   a  in the longitudinal direction to an approximately center portion of the first conductor  6   a  at a side of the one end portion of the first conductor  6   a  in the width direction in such a way that a longitudinal direction of the first cut-out portion  13   a  is aligned with the longitudinal direction of the first conductor  6   a.    
     Moreover, the second cut-out portion  15   a  of the antenna  1   a  according to the second embodiment is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and a long narrow rectangular shape, and extends from the other end portion of the first conductor  6   a  in the longitudinal direction to an approximately center portion of the first conductor  6   a  at a side of the other end portion of the first conductor  6   a  in the width direction in such a way that a longitudinal direction of the second cut-out portion  15   a  is aligned with the longitudinal direction of the first conductor  6   a.    
     A test result of the characteristics of the antenna  1   a  will be next described. 
       FIG. 9  is a view illustrating the frequency characteristics of the antenna  1  and the antenna  1   a , and a graph G 91  indicates a frequency characteristic of the antenna  1  and a graph G 92  indicates a frequency characteristic of the antenna  1   a . It is noted that the antennas  1  and  1   a  are plane-shaped. As is understood from  FIG. 9 , the antenna  1   a  can obtain approximately the same frequency characteristic as that of the antenna  1 . 
       FIG. 10  to  FIG. 12  are views each illustrating directivity of the main polarized wave of each of the antennas  1  and  1   a  at the time when the antenna  1  and the antenna  1   a  are placed as illustrated in  FIG. 2 ,  FIG. 10  illustrates a characteristic of an xy plane,  FIG. 11  illustrates a characteristic of a yz plane, and  FIG. 12  illustrates a characteristic of a zx plane. It is noted that the antennas  1  and  1   a  are plane-shaped. 
     Graphs G 101 , G 103  and G 105  in  FIG. 10  to  FIG. 12  indicate directivity of the antenna  1  according to the first embodiment and graphs G 102 , G 104  and G 106  in  FIG. 10  to  FIG. 12  indicate directivity of the antenna  1   a  according to the second embodiment. As is understood from  FIGS. 10 to 12 , in the frequency band of 2.4 GHz, the antenna  1   a  can obtain approximately the same directivity as that of the antenna  1 . 
       FIG. 13  is a view illustrating a relationship between a bending radius R and an average gain in the antenna  1   a.    
     As is understood from graphs G 131  to G 135  in  FIG. 13 , if the bending radius is 20 mm or more when the antenna  1   a  is mounted as illustrated in  FIG. 2 , it is possible to obtain the same average gain as that obtained when the antenna  1   a  is used in a plane shape as in the cases of the frequency characteristic and directivity. 
       FIG. 14  is a view illustrating average gains of the antennas  1  and  1   a  at the time when the antennas  1  and  1   a  are mounted in a plane shape. As is understood from  FIG. 14 , the antenna  1   a  can obtain approximately the same average gain as that of the antenna  1 . 
     Third Embodiment 
       FIG. 15  is a view illustrating a schematic configuration of an antenna  1   b  according to a third embodiment of the present invention. 
     The antenna  1   b  according to the third embodiment of the present invention is different from the antenna  1  according to the first embodiment in the points that a first conductor  6   b  is formed to have a slightly smaller width than the antenna  1  according to the first embodiment and cut-out portions  13   b  and  15   b  are formed to be slightly longer, but regarding the other points, the antenna  1   b  is configured in approximately the same way as that of the antenna  1  of the first embodiment. 
     Specifically, the antenna  1   b  according to the third embodiment includes a thin plate-like base  3   b  is made of insulating material, and conductor  5   b  of a predetermined shape, which has multiple cut-out portions  13   b  and  15   b  and is thinly formed at a predetermined position on a surface of the base  3  so as to obtain a predetermined antenna characteristics. The antenna  1   b  is designed to be mostly capable of maintaining antenna characteristics even when the base  3   b  and the conductor  5   b  are bent along a predetermined straight line L 1  (see  FIG. 16 ) 
     More specifically, similar to the antenna  1 , the base  3   b  is formed to have a thin rectangular plate shape, a first conductor  6   b  is also formed to have approximately a rectangular shape, the second conductor  7  is formed in an “L” shape, and the coaxial cable  17  is also provided as in the case of the antenna  1 . 
     The first cut-out portion  13   b  of the first conductor  6   b  is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and a long narrow rectangular shape, and extends to a portion at a side of one end portion of the first conductor  6   b  in a longitudinal direction from the other end portion of the first conductor  6   b  in the longitudinal direction at a side of the one end portion of the first conductor  6   b  in a width direction in such a way that a longitudinal direction of the cut-out portion  13   b  is aligned with the longitudinal direction of the first conductor  6   b.    
     The second cut-out portion  15   b  of the first conductor  6   b  is formed to have approximately the same width as that of the first element  9  of the second conductor  7  and extends from the one end portion of the first conductor  6   b  in the longitudinal direction to a portion at a side of the other end portion of the first conductor  6   b  in the longitudinal direction at a side of the other end portion of the first conductor  6   b  in the width direction in such a way that a longitudinal direction of the second cut-out portion  15   b  is aligned with the longitudinal direction of the first conductor  6   b.    
     A test result of the characteristics of the antenna  1   b  will be next described. 
     The antenna  1   b  may be used in a bent state as illustrated in  FIG. 16 . It is noted that, in  FIG. 16 , an extending direction of the coaxial cable  17  is a z-axis direction as in the case of  FIG. 2 , and a thickness direction of the antenna  1   b  (thickness direction of the base  3   b  and that of the conductor  5 ) is an x-axis direction. Moreover, a bent line (straight line) L 1  in  FIG. 16  extends in a z-axis direction. “S” illustrated in  FIG. 16  indicates a distance from the center of the coaxial cable  17  to the bent line L 1  and “α” indicates a bending angle of the antenna  1   b.    
       FIG. 17  is a view illustrating a frequency characteristic of the antenna  1   b  at the time when the distance S in  FIG. 16  is set to “0 mm.” 
     In  FIG. 17 , a graph G 171  indicates a frequency characteristic at the time when the angle α is “0°,” a graph G 172  indicates a frequency characteristic at the time when the angle α is “45°,” a graph G 173  indicates a frequency characteristic at the time when the angle α is “90°,” and a graph G 174  indicates a frequency characteristic at the time when the angle α is “135°.” 
       FIG. 18  is a view illustrating a frequency characteristic of the antenna  1   b  at the time at the time when the distance S in  FIG. 16  is set to “16 mm.” 
     In  FIG. 18 , a graph G 181  indicates a frequency characteristic at the time when the angle α is “0°,” a graph G 182  indicates a frequency characteristic at the time when the angle α is “45°,” a graph G 183  indicates a frequency characteristic at the time when the angle α is “90°,” and a graph G 184  indicates a frequency characteristic at the time when the angle α y is “135°.” 
     As is understood from  FIG. 17  and  FIG. 18 , in the antenna  1   b , if the bending angle α c is an acute angle which is 90° or less, it is possible to obtain a good frequency characteristic (resonance frequency band of 2.40 GHz). 
       FIG. 19  is a view illustrating directivity (directivity of an xy plane) of the antenna  1   b  at the time when the distance S in  FIG. 16  is set to “0 mm.” 
     In  FIG. 19 , a graph G 191  indicates directivity at the time when the angle α is “0°,” a graph G 192  indicates a frequency characteristic at the time when the angle α is “45°,” a graph G 193  indicates a frequency characteristic at the time when the angle α“90°,” and a graph G 194  indicates a frequency characteristic at the time when the angle α is “135°.” 
       FIG. 20  is a view illustrating directivity (directivity of an xy plane) of the antenna  1   b  at the time when the distance S in  FIG. 16  is set to “16 mm.” 
     In  FIG. 20 , a graph G 201  indicates directivity at the time when the angle α is “0°,” a graph G 202  indicates a frequency characteristic at the time when the angle α is “45°,” a graph G 203  indicates a frequency characteristic at the time when the angle α is “90°,” and a graph G 204  indicates a frequency characteristic at the time when the angle α is “135°.” 
     As is understood from  FIG. 19  and  FIG. 20 , in the antenna  1   b , if the bending angle α is an acute angle which is 90° or less, it is possible to obtain an approximately favorable directivity. Further, as is understood from  FIG. 17  to  FIG. 20 , in a case where the distance S is larger, it is possible to maintain the favorable directivity even if the angle α is increased. 
       FIG. 21  illustrates an average gain in each of the distance S and the angle α. 
     Meanwhile, the antenna  1   b  may be used not only in the bent state but also by being deformed into a cylinder side surface shape as illustrated in  FIG. 2 . 
       FIG. 22  is a view illustrating an average gain at the time when the antenna  1   b  is deformed into a cylinder side surface shape and a gain based on a bending radius R (infinite; including the case of the plane shape). 
       FIG. 23  is a view illustrating a frequency characteristic at the time when the antenna  1   b  is deformed into a cylinder side surface shape. 
     In  FIG. 23 , a graph G 231  indicates a frequency characteristic at the time when the bending radius R of the antenna  1   b  is set to 10 mm, a graph G 232  indicates a frequency characteristic at the time when the bending radius R of the antenna  1   b  is set to 20 mm, a graph G 233  indicates a frequency characteristic at the time when the bending radius R of the antenna  1   b  is set to 30 mm, a graph G 234  indicates a frequency characteristic at the time when the bending radius R of the antenna  1   b  is set to 40 mm, and a graph G 235  indicates a frequency characteristic at the time when the antenna  1   b  is plane-shaped. 
     As is understood from  FIG. 23 , when the bending radius R of the antenna  1   b  is 10 mm or more, it is found that the frequency characteristic of the antenna  1   b  is maintained in a good state. 
       FIG. 24  is a view illustrating directivity (directivity of an xy plane) of the antenna  1   b  at the time when the antenna  1   b  is deformed into a cylinder side surface shape. 
     In  FIG. 24 , a graph G 241  indicates directivity at the time when the bending radius R of the antenna  1   b  is set to 10 mm, a graph G 242  indicates directivity at the time when the bending radius R of the antenna Ibis is set to 20 mm, a graph G 243  indicates directivity at the time when the bending radius R of the antenna  1   b  is set to 30 mm, a graph G 244  indicates directivity at the time when the bending radius R of the antenna  1   b  is set to 40 mm, and a graph G 245  indicates directivity at the time when the antenna  1   b  is plane-shaped. 
     As is understood from  FIG. 24 , if the bending radius R is 20 mm or more, it is found that the directivity of the antenna  1   b  is maintained in a good state. 
     It is noted that, the cut-out portions  13   b  and  15   b  of the first conductor  6   b  of the antenna  1   b  are formed to be longer than the cut-out portions  13  and  15  of the antenna  1 , and thereby, the width size can be reduced to be smaller than that of the antenna  1  of the first embodiment. 
     Fourth Embodiment 
       FIG. 25  is a view illustrating a schematic configuration of an antenna  1   c  according to a fourth embodiment of the present invention. Part (b) of  FIG. 25  is a view illustrating an enlarged peripheral portion where connection sections  25  and  27  are provided, and display of the coaxial cable is omitted to facilitate understanding of this embodiment. 
     The antenna  1   c  according to the fourth embodiment of the present invention is different from the antenna  1   b  according to the third embodiment in the points that connection sections  25  and  27  projecting from a first conductor  6   c  and a second conductor  7   c  are provided and the inner conductor  21  and the outer conductor  19  of the coaxial cable  17  are electrically connected to the connection sections  25  and  27 , respectively, but regarding the other points, the antenna  1   c  is configured in approximately the same way as that of the antenna  1   b  of the third embodiment. 
     That is to say, the antenna  1   c  according to the fourth embodiment of the present invention is configured to include a base  3   c , the first conductor  6   c , the second conductor  7   c , the connection sections  25  and  27 , and the coaxial cable  17 . 
     The first conductor  6   c  is approximately rectangularly shaped and formed on one surface of the base  3   c . It is noted that a first cut-out portion  13   c  and a second cut-out portion  15   c  are formed on the first conductor  6   c.    
     The second conductor  7   c  includes a first element  9   c  and a second element  11   c  and is formed in an “L” shape. The first element  9   c  is formed to have approximately the same length as that of the first conductor  6   c  and a long narrow rectangular shape. Then, the first element  9   c  is provided to be separated away from the first conductor  6   c  by a predetermined distance at a side of the one end portion of the first conductor  6   c  in a width direction in such a way that a longitudinal direction of the first element  9   c  is aligned with a longitudinal direction of the first conductor  6   c.    
     The second element  11   c  is formed to have a short rectangular shape, and is provided on one surface of the base  3   c  between the first element  9   c  and the first conductor  6   c  and from one end portion of the first element  9   c  in the longitudinal direction to the vicinity of the one end portion so as to connect the first element  9   c  and the first conductor  6   c  to each other. It is noted that a distance (for example, 1 mm) between the first element  9   c  and the first conductor  6   c  is smaller than a width (for example, 2 mm) of the first element  9   c.    
     Moreover, although the lengths of the first conductor  6   c  and the first element  9   c  are 30 mm, they may be changed as appropriate within the range of 26 mm to 30 mm if a value of VSWR is “2” or less in the range from 2.2 GHz to 2.6 GHz. 
     The first connection section  25  is thinly provided on one surface of the base  3   c  similar to the conductors  6   c  and  7   c , and is formed rectangularly to have a width (for example, 0.7 mm) slightly smaller than the distance (for example, 1 mm) between the first conductor  6   c  and the first element  9   c  and a length (for example, 1.5 mm) slightly larger than the width. Further, the first connection section  25  is located between the first conductor  6   c  and the first element  9   c  and on the first element  9   c  side in the width direction of the first conductor  6   c , and is located on the second element  11   c  side in the longitudinal direction of the first conductor  6   c.    
     Furthermore, in the first connection section  25 , one long side is separated away from the first conductor  6   c  by a predetermined slight distance (for example, 0.3 mm; 1 mm to 0.7 mm) and the other long side is electrically connected to the first element  9   c . Note that, as is already understood, the first connection section  25  is formed of conductors, and is thinly provided on the surface where the conductors  6   c  and  7   c  of the base  3   c  are provided integrally with a conductor  5   c  (conductors  6   c ,  7   c ). 
     The second connection section  27  is also thinly provided on one surface of the base  3   c , similar to the conductors  6   c  and  7   c , and is rectangularly formed similar to the first conductor  6   c . Further, the second connection section  27  is located between the first conductor  6   c  and the first element  9   c  and on the first conductor  6   c  side in the width direction of the first conductor  6   c.    
     Furthermore, in the second connection section  27 , one long side is separated away from the first element  9   c  by a predetermined slight distance and the other long side is electrically connected to the first conductor  6   c . Note that, as is already understood, the second connection section  27  is also formed of conductors, and is thinly provided on the surface where the conductor  5   c  of the base  3   c  is provided integrally with the conductor  5   c.    
     In the coaxial cable  17 , the inner conductor  21  is electrically connected to the first connection section  25  and the outer conductor  19  is electrically connected to the second connection section  27 . Note that the coaxial cable  17  extends to the one end portion side of the first conductor  6   c  in the longitudinal direction (side where the second element  11   c  is provided; right side in  FIG. 25 ). 
     Note that, in the antenna  1   c , a mounting form of the coaxial cable  17  may be reversely set. Specifically, the inner conductor may be connected to the second connection section  27  where the outer conductor  19  is connected, and the outer conductor  19  may be connected to the first connection section  25  where the inner conductor  21  is connected so that the coaxial cable  17  can extend to the left side in  FIG. 25 . 
     In the antenna  1   c , the coaxial cable  17  extends to the one end portion side of the first conductor  6   c  in the longitudinal direction (longitudinal direction of the antenna  1   c ), and therefore can be easily mounted in a location where it is difficult to handle coaxial cable  17  wiring in the antennas  1 ,  1   a ,  1   b  according to the first to third embodiments. 
     A test result of the characteristics of the antenna  1   c  will be next described. 
       FIG. 26  is a view illustrating a frequency characteristic of the antenna  1   c.    
     As is understood from  FIG. 26 , in the antenna  1   c , the range from 2.4 GHz to 2.4835 GHz (range illustrated by an arrow in  FIG. 26 ) corresponds to a resonance frequency band. 
       FIG. 27  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna  1   c  in a frequency of 2.43 GHz. 
     Part (a) of  FIG. 27  indicates directivity on an xy plane, a graph G 271  in Part (a) of  FIG. 27  indicates directivity of E_θ, and a graph G 272  in Part (a) of  FIG. 27  indicates directivity of E_φ. Part (b) of  FIG. 27  indicates directivity on a yz plane, a graph G 273  in Part (b) of  FIG. 27  indicates directivity of E_θ, and a graph G 274  in Part (b) of  FIG. 27  indicates directivity of E_φ. Part (c) of  FIG. 27  indicates directivity on a zx plane, a graph G 275  in Part (c) of  FIG. 27  indicates directivity of E_θ, and a graph G 276  in Part (c) of  FIG. 27  indicates directivity of E_φ. 
     It is understood from  FIG. 27  that the antenna  1   c  has approximately favorable directivity. In sum, judging from the maximum gain, a gain of about −0.5 dBi is obtained. 
     Here, description will be given of a case in which a conductor is placed close to the antenna  1   c  as a mounting form of the antenna  1   c.    
       FIG. 31  is a view illustrating a state in which a flat plate-like conductive member (copper plate of, for example, 40 mm×70 mm×0.035 mm)  31  is brought into contact with the plate-like antenna  1   c.    
     In a state that the copper plate  31  is thus placed, the thickness direction, the longitudinal direction and the width direction of each of the antenna  1   c  and the copper plate  31  match each other. Further, in the thickness direction, the flat plate-like copper plate  31  comes in contact with a back surface (surface where no conductor  5   c  is provided) of the antenna  1   c  (base  3   c ). In the longitudinal direction, the center of the copper plate  31  and that of the antenna  1   c  approximately match each other. In the width direction, the copper plate  31  is positioned on the other end portion side of the antenna  1   c  in the width direction, and a distance between one end portion  33  of the first conductor  6   c  of the antenna  1   c  in the width direction and one end portion  35  of the copper plate  31  in the width direction is dz. 
       FIG. 32  is a view illustrating a frequency characteristic of the antenna  1   c  at the time when the distance dz is changed. 
     In Part (a) of  FIG. 32 , a graph G 321  indicates a frequency characteristic at the time when dz=0 mm, a graph G 322  indicates a frequency characteristic at the time when dz=2 mm, and a graph G 323  indicates a frequency characteristic at the time when dz=4 mm. 
     Moreover, in Part (b) of  FIG. 32 , a graph G 324  indicates a frequency characteristic at the time when dz=6 mm, a graph G 325  indicates a frequency characteristic at the time when dz=8 mm, and a graph G 326  indicates a frequency characteristic at the time when dz=10 mm. 
       FIG. 33  is a view illustrating a frequency characteristic of the antenna  1   c  after the length of the second conductor  7   c  and that of one end portion  33  are appropriately changed where dz=0 mm and then frequency adjustment is performed. In this state, in the antenna  1   c , the range from 2.4 GHz to 2.4835 GHz corresponds to a resonance frequency band. 
       FIG. 34  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna  1   c  at a frequency of 2.43 GHz after the length of the second conductor  7   c  and that of one end portion  33  are appropriately changed where dz=0 mm and then frequency adjustment is performed. 
     Part (a) of  FIG. 34  indicates directivity on an xy plane, a graph G 341  in Part (a) of  FIG. 34  indicates directivity of E_θ, and a graph G 342  in Part (a) of  FIG. 34  indicates directivity of E_φ. Part (b) of  FIG. 34  indicates directivity on a yz plane, a graph G 343  in Part (b) of  FIG. 34  indicates directivity of E_θ, and a graph G 344  in Part (b) of  FIG. 34  indicates directivity of E_φ. Part (c) of  FIG. 34  indicates directivity on a zx plane, a graph G 345  in Part (c) of  FIG. 34  indicates directivity of E_θ, and a graph G 346  in Part (c) of  FIG. 34  indicates directivity of E_φ. 
     As is understood from  FIG. 33  and  FIG. 34 , if frequency adjustment is performed, it is possible to obtain approximately favorable frequency characteristic and directivity even when the almost entire surface of the first conductor (ground conductor)  6   a  is covered with the conductor in a plan view (when seeing from an x-axis direction.) In other words, judging from the maximum gain, a gain of about −1 dBi is obtained. 
       FIG. 35  is a view illustrating a state in which a flat plate-like conductive member (copper plate of, for example, 40 mm×70 mm×0.035 mm)  31  is placed upright in the flat plate-like antenna  1   c.    
     In the state that the copper plate  31  is thus mounted, the longitudinal directions of the antenna  1   c  and the copper plate  31  match each other and the center of the copper plate  31  and that of the antenna  1   c  approximately match each other. Further, the copper plate  31  is upright approximately perpendicular to the surface (surface where the conductor  5   c  is provided) of the antenna  1   c  (upright in a direction perpendicular to the paper plane of  FIG. 35  and on the front side of the paper plane) and one end portion of the copper plate  31  in the width direction thereof comes in contact with the surface of the antenna  1   c . Furthermore, a distance between the copper plate  31  and one end portion  33  of the first conductor  6   c  in the width direction is dz. 
       FIG. 36  is a view illustrating a frequency characteristic of the antenna  1   c  at the time when the distance dz is changed. 
     In  FIG. 36 , a graph G 361  indicates a frequency characteristic at the time when dz=0 mm, a graph G 362  indicates a frequency characteristic at the time when dz=−5 mm, and a graph G 363  indicates a frequency characteristic at the time when dz=−10 mm. 
       FIG. 37  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna  1   c  in a frequency of 2.43 GHz where dz=0 mm. 
     Part (a) of  FIG. 37  indicates directivity on an xy plane, a graph G 371  in Part (a) of  FIG. 37  indicates directivity of E_θ, and a graph G 372  in Part (a) of  FIG. 37  indicates directivity of E_φ. Part (b) of  FIG. 37  indicates directivity on a yz plane, a graph G 373  in Part (b) of  FIG. 37  indicates directivity of E_θ, and a graph G 374  in Part (b) of  FIG. 37  indicates directivity of E_φ. Part (c) of  FIG. 37  indicates directivity on a zx plane, a graph G 375  in Part (c) of  FIG. 37  indicates directivity of E_θ, and a graph G 376  in Part (c) of  FIG. 37  indicates directivity of E_φ. 
     It is understood from  FIG. 36  and  FIG. 37  that approximately favorable frequency and directivity can be obtained even when the copper plate  31  of the antenna  1   c  is placed upright. 
       FIG. 38  is a view illustrating a state in which the antenna  1   c  is mounted in an electronic apparatus (for example, a display device of a car navigation system). 
     A display device  41  of the car navigation system includes an image display section  43  formed of a LCD or the like, a frame body  45  which is provided around the image display section  43  and has a rectangular outer shape, and a housing  47  which has a rectangular outer shape and stores inside a drive circuit or the like of the image display section  43  and is provided on the inner sides of the image display section  43  and the frame body  45  to be integral with the frame body  45 . Note that the frame body  45  is made of an insulating material and the housing  47  is made of a conductor such as a copper plate. 
     In a state that the antenna  1   c  is mounted on an circumference of the frame body  45  as illustrated in  FIG. 38 , the antenna  1   c  is separated away from the housing  47 , but the mounting position of the antenna  1   c  may be moved to the housing  47  side as illustrated by an arrow in  FIG. 38 . Even when such movement is made, it is possible to obtain favorable frequency characteristic and directivity as illustrated in  FIG. 33  and  FIG. 34  and improve a degree of freedom of the mounting form of the antenna  1   c.    
     Moreover, the antenna  1   c  may be mounted so as to be bent at an angle of 90° across the corner part of the frame body  45 . 
     Fifth Embodiment 
       FIG. 28  is a view illustrating a schematic configuration of an antenna  1   d  according to a fifth embodiment of the present invention. 
     The antenna  1   d  according to the fifth embodiment of the present invention is different from the antenna  1   c  according to the fourth embodiment in the points that the connection sections  25  and  27  are deleted and the end portion of the coaxial cable  17  (portion of the end portion side where the inner conductor  21  and the outer conductor  19  are electrically connected to the antenna  1   d ) is obliquely placed, but regarding the other points, the antenna  1   d  is configured in approximately the same way as that of the antenna  1   c  of the fourth embodiment. 
     In other words, the antenna  1   d  according to the fifth embodiment of the present invention is configured to include the base  3   c , the first conductor  6   c , the second conductor  7   c , and the coaxial cable  17 . 
     The inner conductor  21  of the coaxial cable  17  is electrically connected to a first predetermined portion of the first conductor  6   c  and the outer conductor  19  is electrically connected to a second predetermined portion of the second conductor  7   c.    
     The first predetermined portion where the inner conductor  21  of the coaxial cable  17  is connected is located at a side of one end portion of the first conductor  6   c  in a width direction, and at a side of the one end portion of the first conductor  6   c  in a longitudinal direction. Further, the second predetermined portion where the outer conductor  19  of the coaxial cable  17  is connected is located between the first predetermined portion and the second element  11   c  of the second conductor  7   c  at a side of one end portion of the first element  9   c  of the second conductor  7   c  in a longitudinal direction. Furthermore, the second predetermined portion is positioned on the first conductor  6   c  side (lower side of the first element  9   c  in  FIG. 28 ) in a width direction of the first element  9   c.    
     In addition, the coaxial cable  17  is obliquely provided between the first portion and the second portion, but is bent afterward and thereby extends to a side of the one end portion of the first conductor  6   c  (side where the second element  11   c  is provided; right side in  FIG. 28 ) in the longitudinal direction. Moreover, the coaxial cable  17  is bent, and therefore a portion  51  in the vicinity of the outer conductor  19  of the coaxial cable  17  (portion opposite to the center conductor  21  with the outer conductor  19  disposed in-between) is fixed to an insulating film  23  (base  3   c ) of the antenna  1   d  by adhesion, for example. Further, the coaxial cable  17  may be obliquely extended without being bent. 
     Furthermore, in the antenna  1   d , the mounting form of the coaxial cable  17  may be reversely set as in the case of the antenna  1   c  according to the fourth embodiment. 
     A test result of the characteristics of the antenna  1   d  will be next described. 
       FIG. 29  is a view illustrating a frequency characteristic of the antenna  1   d.    
     As is understood from  FIG. 29 , in the antenna  1   d , the range from 2.4 GHz to 2.4835 GHz (range illustrated by an arrow in  FIG. 29 ) corresponds to a resonance frequency band. 
       FIG. 30  is a view illustrating directivity of a main polarized wave (E_θ) and directivity of a cross-polarization (E_φ) of the antenna  1   c  at a frequency of 2.43 GHz where dz=0 mm. 
     Part (a) of  FIG. 30  indicates directivity on an xy plane, a graph G 301  in Part (a) of  FIG. 30  indicates directivity of E_θ, and a graph G 302  in Part (a) of  FIG. 30  indicates directivity of E_φ. Part (b) of  FIG. 30  indicates directivity on a yz plane, a graph G 303  in Part (b) of  FIG. 30  indicates directivity of E_θ, and a graph G 304  in Part (b) of  FIG. 30  indicates directivity of E_φ. Part (c) of  FIG. 30  indicates directivity on a zx plane, a graph G 305  in Part (c) of  FIG. 30  indicates directivity of E_θ, and a graph G 306  in Part (c) of  FIG. 30  indicates directivity of E_φ. 
     It is understood from  FIG. 30  that the antenna  1   d  has approximately favorable directivity. 
     Meanwhile, in the antenna  1  according to the first embodiment illustrated in  FIG. 1 , the mounting form of the coaxial cable  17  may be reversely set. Specifically, the inner conductor  21  may be connected to the portion where the outer conductor  19  is connected, and the outer conductor  19  is connected to the portion where the inner conductor  21  is connected so that the coaxial cable  17  can be extended upward in  FIG. 1 . 
     Further, the antenna  1   c  according to the third embodiment and the antenna  1   d  according to the fourth embodiment may be used by being bent and mounted as illustrated in  FIG. 2  and  FIG. 16 . 
     Furthermore, in the antenna  1  according to the first embodiment, the antenna  1   a  according to the second embodiment and the antenna  1   b  according to the third embodiment, the mounting form of the coaxial cable  17  may be changed as in the antenna  1   c  according to the third embodiment and the antenna  1   d  according to the fourth embodiment.