Patent Publication Number: US-11024940-B2

Title: Vehicle antenna and window glass for vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2018/016352 filed on Apr. 20, 2018 and designating the U.S., which claims priority of Japanese Patent Application No. 2017-085478 filed on Apr. 24, 2017. The entire contents of the foregoing applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The disclosure herein generally relates to a vehicle antenna and a window glass for vehicle. 
     2. Description of the Related Art 
     In the related art, L-shaped vehicle antennas, U-shaped vehicle antennas (including J-shaped vehicle antennas) have been known (See, for example, WO 2016/052709). 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     A telematics service that transmits information between a communication device installed in a vehicle and a vehicle outside has been known. In a vehicle antenna used in the telematics service, in order to accommodate a vertically polarized electromagnetic wave that propagates in a direction parallel to the horizontal plane (i.e. horizontal direction), a directivity of the antenna in the horizontal direction is desired to be enhanced. 
     Moreover, a wireless communication used in the Intelligent Transport Systems (ITS), includes, for example, a Dedicated Short Range Communication (DSRC). The DSRC is used for a road-vehicle communication, a vehicle-to vehicle communication, or the like. In a vehicle antenna used in the ITS, such as the DSRC, a directivity of the antenna in the horizontal direction is desired to be enhanced, taking into account the positional relationship between the own vehicle and the communication partner. 
     With an L-shaped antenna or a U-shaped antenna, as in the related art, the directivity in the horizontal direction is enhanced. However, because the L-shaped antenna greatly protrudes from a vehicle interior surface of the window glass for vehicle, it is difficult to reduce the height of the antenna. In the U-shaped antenna, an impedance matching deteriorates easily. 
     Thus, the disclosure of the present application provides a vehicle antenna and a window glass for vehicle, in which a directivity in the horizontal direction is enhanced, the height of the antenna is reduced, and an excellent impedance matching is maintained. 
     Solution to Problem 
     According to an aspect of the disclosure of the present application, a vehicle antenna arranged on a window glass for vehicle including an element portion having a shape of a crank and being famed by a first element, a second element and a third element; and a feeding portion configured to feed power to the element portion, the first element having a first upper end portion and a first lower end portion, and extending in an up-down direction of the window glass, the second element having a second upper end portion and a second lower end portion, and extending in the up-down direction of the window glass, the third element extending between the first lower end portion and the second upper end portion, and a first distance between the first lower end portion and the window glass being different from a second distance between the second upper end portion and the window glass, is provided. 
     According to another aspect of the disclosure of the present application, a window glass for vehicle provided with the vehicle antenna is provided. 
     Effect of Invention 
     According to an aspect of the present invention, the directivity in the horizontal direction is enhanced, the height of the antenna is reduced, and an excellent impedance matching is obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view schematically depicting an example of a configuration of a vehicle antenna and a window glass for vehicle according to an embodiment; 
         FIG. 2  is a perspective view schematically depicting a configuration of a vehicle antenna and a window glass for vehicle according to a first practical example; 
         FIG. 3  is a side view schematically depicting the configuration of the vehicle antenna and the window glass for vehicle according to the first practical example; 
         FIG. 4  is a perspective view schematically depicting a configuration of a vehicle antenna and a window glass for vehicle according to a first comparative example; 
         FIG. 5  is a side view schematically depicting the configuration of the vehicle antenna and the window glass for vehicle according to the first comparative example; 
         FIG. 6  is a perspective view schematically depicting a configuration of a vehicle antenna and a window glass for vehicle according to a second comparative example; 
         FIG. 7  is a side view schematically depicting the configuration of the vehicle antenna and the window glass for vehicle according to the second comparative example; 
         FIG. 8  is a diagram depicting an example of return loss characteristics of the vehicle antenna according to the first practical example; 
         FIG. 9  is a diagram depicting an example of actual gains of the vehicle antenna according to the first practical example; 
         FIG. 10  is a perspective view schematically depicting a configuration of a vehicle antenna according to a second practical example; 
         FIG. 11  is a perspective view schematically depicting a configuration of a vehicle antenna according to a third comparative example; 
         FIG. 12  is a diagram depicting an example of return loss characteristics of the vehicle antenna according to the second practical example; and 
         FIG. 13  is a diagram depicting an example of actual gains of the vehicle antenna according to the second practical example. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings for describing the embodiment, in the absence of a specific description with respect to a direction, the direction refers to a direction indicated in the drawings. Reference directions in the respective drawings correspond to directions of symbols or numerals. Moreover, a direction, such as parallel, orthogonal or the like allows for deviations so long as the effects of the present invention are maintained. Moreover, a window glass, to which the present invention can be applied, includes, for example, a windshield (front glass) arranged in a front part of a vehicle. The window glass may be a rear windshield arranged in a rear part of the vehicle, or a side windshield arranged in a side part of the vehicle. 
       FIG. 1  is a cross-sectional view schematically depicting an example of a configuration of a vehicle antenna and a window glass for vehicle according to an embodiment, and indicates a cross-section in a plane orthogonal to a vehicle width direction. In the following description of the embodiment, a Y-axis direction indicates an up-down direction of a window glass  70 . A Z-axis direction indicates a direction orthogonal to a surface of the window glass  70 . An X-axis direction indicates a vehicle width direction of a vehicle  80 . A left part of  FIG. 1  indicates a vehicle front, and a right part of  FIG. 1  indicates a vehicle rear. 
     An antenna  100 , shown in  FIG. 1 , is an example of a vehicle antenna arranged on a window glass for vehicle. The antenna  100  is mounted to the window glass  70  via a mounting member (not shown). The window glass  70  is an example of a window glass on which a vehicle antenna is arranged.  FIG. 1  shows the window glass  70  that is a windshield (front glass). The window glass  70  is mounted to a window frame of the vehicle  80  at an angle θ with respect to a horizontal plane  60 . The angle θ is greater than 0° and less than 90° (e.g. 30°). 
     The antenna  100  includes an element portion  50  having a shape, in cross-section (in side view), of a crank (as in a crank handle), and being famed by an element  10 , an element  20 , and an element  30 ; and a feeding portion  40  that feeds power to the element portion  50 . 
     The element  10  is an example of a first element, and is a conductor extending in the up-down direction of the window glass  70 . The element  10  is a rectangular shaped conductor formed so as to face a vehicle interior side surface of the window glass  70 . The element  10  extends from an upper side edge toward a lower side edge. The element  10  has an upper end portion  1  and a lower end portion  2  in the up-down direction of the window glass  70 . The upper end portion  1  is an example of a first upper end portion. The lower end portion  2  is an example of a first lower end portion. The upper end portion  1  indicates an upper edge of the element  10  and a periphery of the upper edge. The lower end portion  2  indicates a lower edge of the element  10  and a periphery of the lower edge. A shape of the element  10  and shapes of the other elements, which will be described later, are not limited to rectangular, and the shapes may be other shapes. 
     The element  30  is an example of a second element, and is a conductor extending in the up-down direction of the window glass  70 . The element  30  is a rectangular shaped conductor formed so as to face the vehicle interior side surface of the window glass  70 . The element  30  extends from the upper side edge toward the lower side edge. The element  30  has an upper end portion  3  and a lower end portion  4  in the up-down direction of the window glass  70 . The upper end portion  3  is an example of a second upper end portion. The lower end portion  4  is an example of a second lower end portion. The upper end portion  3  indicates an upper edge of the element  30  and a periphery of the upper edge. The lower end portion  4  indicates a lower edge of the element  30  and a periphery of the lower edge. 
     The element  20  is an example of a third element, and is a conductor extending between the lower end portion  2  and the upper end portion  3 . One end of the element  20  is connected to the lower end portion  2  and another end of the element  20  is connected to the upper end portion  3 . 
     A distance D 1  indicates a distance between the lower end portion  2  and the vehicle interior side surface of the window glass  70  (an example of a first distance). A distance D 2  indicates a distance between the upper end portion  3  and the vehicle interior side surface of the window glass  70  (an example of a second distance). Because the distance D 1  is different from the distance D 2 , the antenna  100  having a three-dimensional structure with the element  20  extending in the Z-axis direction is formed. 
     A directivity of an antenna having a planar structure without a part extending in the Z-axis direction is liable to be greater in the normal direction to the surface of the window glass  70 . The antenna  100  according to the embodiment includes the element  20  extending in the Z-axis direction, and a directivity of the antenna  100  according to the embodiment becomes greater in a direction that approaches the horizontal surface with respect to the normal direction to the surface of the window glass  70 . Thus, with the antenna  100  according to the embodiment, a directivity in a direction parallel to the horizontal surface  60  (i.e. horizontal direction) is enhanced, and an antenna gain (actual gain) in the horizontal direction is increased. 
     Moreover, the antenna  100  according to the embodiment is provided with the element portion  50  having a shape of a crank. Compared with an L-shaped antenna having the same antenna length as the antenna  100 , the height of the element portion  50  having the shape of a crank in the antenna  100 , bent at two points, is easily made lower than the L-shaped antenna, bent at one point. The height of an element portion in the L-shaped antenna is a sum of a length of the element  20  and a length of the element  30 . The L-shaped antenna greatly protrudes from the vehicle interior surface of the window glass  70 , and forms an obstacle for a driver. In the antenna  100  according to the embodiment having the element portion  50  with a shape of a crank, a height of the element portion  50  (difference between the distances D 2  and D 1 ) is easily made smaller. 
     The length of the Z-axis direction component of the element  20  (the length component that is normal to the surface of the window glass  70 , the actual length of the element  20  being taken as the hypotenuse) is preferably small from the viewpoint of decreasing the height of the antenna. Moreover, the length of the Z-axis direction component of the element is preferably determined according to frequencies of electromagnetic waves that are transmitted or received by the antenna. For example, the length of the Z-axis direction component of the element  20  may be 30 mm or less from the viewpoint of decreasing the height of the antenna, is preferably 23 mm or less, and is more preferably 15 mm or less. When the length of the element  20  in the Z-axis direction component is extremely small, the configuration of the antenna becomes close to that of the planar antenna without the Z-axis direction component. Thus, the length of the Z-axis direction component of the element  20  may be 4 mm or more, is preferably 7 mm or more, and is more preferably 10 mm or more. The length of the element  20  in the Z-axis direction corresponds to the height of the element  20 , when both the bending angles α and β, that form the antenna in the shape of a crank are 90°. 
     When the frequency used for LTE is, for example, 0.96 GHz, the length of the Z-axis direction component of the element  20 , normalized by a wavelength λ of electromagnetic waves at an operation frequency of the antenna, may be 0.096λ or less, is preferably 0.074λ or less, and is more preferably 0.048λ or less. In this case, the length of the Z-axis direction component of the element  20  may be 0.013λ or more, is preferably 0.022λ or more, and more preferably 0.032λ or more. 
     In a U-shaped antenna, a capacitive coupling between elements facing each other is liable to increase. Thus, an impedance matching easily degrades. However, in the element portion  50  according to the embodiment, the lower end portion  2  of the element  10  is connected to the upper end portion  3  of the element  30  via the element  20 . Because the lower end portion  2  of the element  10  is connected to the upper end portion  3  of the element  30 , the element  10  and the element  30  do not face each other, or the areas of the conductor portions of the elements  10  and  30  that face each other are small (narrow). Thus, the capacitive coupling between the element  10  and the element  30  is less likely to increase. According to the antenna  100  of the embodiment, compared with the U-shaped antenna, more excellent impedance matching is obtained. 
     From a viewpoint of enhancing the directivity of the antenna in the horizontal direction, as illustrated in  FIG. 1 , the distance D 1  is preferably less than the distance D 2 . The distance D 1  may be zero. When the distance D 1  is zero, the element  10  is brought into contact with the vehicle interior side surface of the window glass  70 . 
     Even for an antenna provided with an element portion having a shape of a crank, in which the distance D 2  is less than the distance D 1 , a height is reduced, and an excellent impedance matching is obtained. In the antenna provided with the element portion having the shape of a crank, in which the distance D 2  is less than the distance D 1 , the element  30  is closer to the window glass  70  than the element  10 . 
     In order to enhance a gain of vertically polarized waves, as illustrated in  FIG. 1 , the element portion  50  having a shape of a crank is preferably formed so that the long-side direction of the element portion  50  is parallel to the up-down direction of the window glass  70  (i.e. the short-side direction of the element portion  50  is parallel to the vehicle width direction). In addition, the element portion  50  may be famed so that the short-side direction of the element portion  50  is parallel to the up-down direction of the window glass  70  (i.e. the long-side direction of the element portion  50  is parallel to the vehicle width direction). 
     A feeding portion  40  is located at the upper end portion  1 . Thus, a feeding cable arranged from a roof side of the vehicle  80  is easily connected to the feeding portion  40 , and the length of the feeding cable is reduced. 
     The element portion  50  may function as a dipole antenna by arranging the feeding portion  40  on the element  20 . That is, with the element  10  and the element  30  being separated from each other by the feeding portion  40 , one of the element  10  and the element  30  is connected to a core wire of a coaxial cable, and another one of the element  10  and the element  30  is connected to a ground wire of the coaxial cable. In order to adjust the input impedance, the position of the feeding portion  40  may be offset. 
     In the embodiment shown in  FIG. 1 , the antenna  100  is arranged in an upper part on the vehicle interior side of the window glass  70  so that the element  10  and the element  30  are parallel to the vehicle interior side surface of the window glass  70 . Moreover, the angle α indicates an angle formed by the element  10  and the element  20 , and the angle β indicates an angle formed by the element  20  and the element  30 . The angle α is greater than 0° and less than 180° (e.g. 90°), and the angle β is greater than 0° and less than 180° (e.g. 90°). 
     The arrangement positions of the element  10  and the element  30  are not limited to the above-described positions, i.e. with respect to the element  10  and the element  30  being arranged so as to be parallel to the vehicle interior side surface of the window glass  70 , respectively. The element  10  and the element  30  may be arranged so that the element  10  and the element  30  are not parallel to the surface. The angle α may be the same as the angle β, and may be different from the angle β. 
     The antenna  100  according to the embodiment is suitable for transmitting and receiving electromagnetic waves of the UHF (Ultra High Frequency) band. For example, the antenna  100  is suitable for transmitting and receiving electromagnetic waves of three frequency bands (0.698 GHz to 0.96 GHz, 1.71 GHz to 2.17 GHz, and 2.4 GHz to 2.69 GHz) among the plurality of frequency bands used for LTE (Long Term Evolution) communication. 
     Furthermore, the antenna  100  is also suitable for transmitting and receiving electromagnetic waves of the ISM (Industry Science Medical) band. The ISM band includes the communication bands of 0.863 GHz to 0.870 GHz (Europe), 0.902 GHz to 0.928 GHz (US), and 2.4 GHz to 2.5 GHz (worldwide). A communication standard using the 2.4 GHz band, one of the ISM bands, includes a wireless LAN (Local Area Network) of DSSS (Direct Sequence Spread Spectrum) system, conforming to the IEEE 802.11b; Bluetooth (trademark registered); a part of the FWA (Fixed Wireless Access) system; and the like. The electromagnetic waves the antenna  100  transmits and receives are not limited to the above-described frequency bands. 
     First Practical Example 
       FIG. 2  is a perspective view depicting a configuration of a vehicle antenna and a window glass for vehicle according to a first practical example, from a vehicle interior side viewpoint.  FIG. 3  is a side view depicting the configuration of the vehicle antenna and the window glass for vehicle according to the first practical example. In  FIGS. 2 and 3 , an antenna  101  is an example of the antenna  100  illustrated in  FIG. 1 , and a window glass  71  is an example of the window glass  70  illustrated in  FIG. 1 . 
     The antenna  101  includes an element portion  51  having a shape of a crank and configured of an element  11 , an element  12  and an element  13 ; and a feeding portion  14  for feeding power to the element portion  51 . The element portion  51  is an example of the element portion  50  illustrated in  FIG. 1 , and the feeding portion  14  is an example of the feeding portion  40  illustrated in  FIG. 1 . 
     The element  11  is an example of the first element, and is a planar conductor extending in the up-down direction of the window glass  71 . The element  11  has an upper end portion  1   a  and a lower end portion  2   a  in the up-down direction of the window glass  71 . The upper end portion  1   a  is an example of the first upper end portion, and the lower end portion  2   a  is an example of the first lower end portion. The element  11  is brought into contact with the vehicle interior side surface of the window glass  71 . Thus, the distance D 1  is zero (0 mm). 
     The element  13  is an example of the second element, and is a planar conductor extending in the up-down direction of the window glass  71 . The element  13  has an upper end portion  3   a  and a lower end portion  4   a  in the up-down direction of the window glass  71 . The upper end portion  3   a  is an example of the second upper end portion, and the lower end portion  4   a  is an example of the second lower end portion. 
     A support member for supporting the antenna  101  may be arranged between the window glass  71  and at least one of the element  11  and the element  13 . At least one of the element  11 , the element  12 , and the element  13  may be installed in a camera bracket mounted to the window glass  71 . 
     The element  12  is an example of the third element, and is a planar conductor extending between the lower end portion  2   a  and the upper end portion  3   a . An end of the element  12  is connected to the lower end portion  2   a , and the other end of the element  12  is connected to the upper end portion  3   a.    
     The element portion  51  includes a conductor portion  15 , a conductor portion  16 , and a loop slot  17 . The conductor portion  15  is an example of a first conductor portion, and is formed so as to range over the element  11 , the element  12  and the element  13 . The conductor portion  16  is an example of a second conductor portion, and is formed inside the slot  17 . That is, the conductor portion  16  is located inward in an in-plane direction with respect to the conductor portion  15  spaced by the slot  17 . The conductor portion  16  is formed so as to range over the element  11 , the element  12  and the element  13 . The slot  17  is formed inside the conductor portion  15  so as to range over the element  11 , the element  12  and the element  13 . The element portion  51  includes the conductor portion  15 ; the slot  17  formed inside the conductor portion  15  so as to range over the element  11 , the element  12  and the element  13 ; and the conductor portion  16  formed inside the slot  17 , and thereby the bandwidth of the antenna  101  can be increased. 
     A shape of an inner contour of the conductor portion  15  and a shape of a contour of the conductor portion  16  are not particularly limited. The shapes may include a polygon including a quadrangle, a circle, a half circle, an ellipse, a fan-shape, and a shape including straight lines and curves. The shape of the inner contour of the conductor portion  15  and the shape of the contour of the conductor portion  16  may be a combination of the above-described shapes. However, the slot  17  formed by the conductor portion  15  and the conductor portion  16  preferably has a part in which a width gradually increases from the upper end portion of the element  11  toward the element  13 . Thus, the bandwidth of the antenna  101  can be easily increased. The shape of the inner contour of the conductor portion  15  and the shape of the contour of the conductor portion  16  refer to shapes viewed on the elements in a planar shape obtained by unbending the bending portions of the elements. 
     In the example illustrated in  FIG. 2 , the shape of the inner contour of the conductor portion  15  is an ellipse on a bent plane, bent in a shape of a crank. That is, when the conductor portion  15  is unbent at the lower end portion  2   a  and the upper end portion  3   a , the shape of the inner contour of the conductor portion  15  is an ellipse. The shape of the contour of the conductor portion  16  is an ellipse on a bent plane with a perimeter that is less than the perimeter of the inner contour of the conductor portion  15 . The slot width of the slot  17  gradually increases from the upper end portion  1   a  of the element  11  toward the element  13 . The feeding portion  14  is located at a position having a minimum slot width of the slot  17  (In  FIG. 2 , in an upper portion of the element  11  in the Y-axis direction). The feeding portion  14  is a dipole-type feeding portion. A core wire of a coaxial cable that is a feeding wire is connected to the upper portion of the conductor portion  16  and a ground wire of the coaxial cable is connected to the upper portion of the conductor portion  15 , so as to interpose the slot  17 . The ground wire of the coaxial cable may be connected to the upper portion of the conductor portion  16 , and the core wire of the coaxial cable may be connected to the upper portion of the conductor portion  15 . Moreover, when an AV line is used for the feeding wire, a connector for electrically connecting the AV line to the feeding portion  14  is mounted to the feeding portion  14 , and thereby the AV line can be easily connected to the feeding portion  14 . The letter “A” of the AV line represents low voltage cables for automobiles, and the letter “V” represents vinyl coating. 
       FIG. 4  is a perspective view depicting a configuration of a vehicle antenna and a window glass for vehicle according to a first comparative example, from a vehicle interior side viewpoint.  FIG. 5  is a side view depicting the configuration of the vehicle antenna and the window glass for vehicle according to the first comparative example. An antenna  201  having an I-shape in a side view, as shown in  FIGS. 4 and 5 , is an example of an antenna that does not include an element portion having a shape of a crank. That is, the antenna  201  has a configuration in which the element portion  51  in the antenna  101 , shown in  FIGS. 2 and 3 , is unbent. The antenna  201  is arranged on a window glass  72 . 
     The antenna  201  includes an I-shaped element portion  52  configured of a conductor portion  25 , a conductor portion  26 , and a slot  27 ; and a feeding portion  24  for feeding power to the element portion  52 . A shape of an inner contour of the conductor portion  25  is an ellipse. A shape of the conductor portion  26  is an ellipse with a perimeter that is less than the perimeter of the inner contour of the conductor portion  25 . The feeding portion  24  is located at a position having a minimum slot width of the slot  27  (In  FIG. 4 , in the upper portion of the element portion  52  in the Y-axis direction). A core wire of a coaxial cable is connected to the upper portion of the conductor portion  26 , and a ground wire of the coaxial cable is connected to the upper portion of the conductor portion  25 . 
       FIG. 6  is a perspective view depicting a configuration of a vehicle antenna and a window glass for vehicle according to a second comparative example, from a vehicle interior side viewpoint.  FIG. 7  is a side view depicting the configuration of the vehicle antenna and the window glass for vehicle according to the second comparative example. An antenna  301  having a U-shape in a side view, as shown in  FIGS. 6 and 7 , is an example of an antenna that does not include an element portion having a shape of a crank. The antenna  301  is arranged on a window glass  73 . 
     The antenna  301  includes a U-shaped element portion  53  formed by a conductor portion  35 , a conductor portion  36 , and a slot  37 ; and a feeding portion  34  for feeding power to the element portion  53 . A shape of an inner contour of the conductor portion  35  is an ellipse on a bent plane, bent in a U-shape or in a J-shape. A shape of a contour of the conductor portion  36  is an ellipse on a bent plane, bent in a U-shape or in a J-shape, with a perimeter that is less than the perimeter of the inner contour of the conductor portion  35 . The feeding portion  34  is located at a position having a minimum slot width of the slot  37  (In  FIG. 6 , in an upper portion of the element portion  53  in the Y-axis direction). A core wire of a coaxial cable is connected to an upper portion of the conductor portion  36 , and a ground wire of the coaxial cable is connected to the upper portion of the conductor portion  35 . 
     The lower portion of the antenna  301  (that is to say, the portion including a widest width portion of the slot  37 ) is different from the element  13  of the antenna  101 , shown in  FIGS. 2 and 3 . The lower portion of the antenna  301  (including the widest width portion of the slot  37 ) extends parallel to the window glass  73  in a direction from a lower side toward an upper side of the window glass  73 , and faces the upper portion of the antenna  301  (including a narrow width portion of the slot  37 ). 
       FIG. 8  is a diagram depicting an example of a result of simulation for return loss characteristics of the vehicle antennas  101 ,  201 , and  301  according to the first practical example. For the simulations for electromagnetic fields, Microwave Studio (trademark registered) by CST—Computer Simulation Technology AG was used. In  FIG. 8 , “Band A” indicates the frequency band for LTE (0.698 GHz to 0.96 GHz), “Band B” indicates the frequency band for LTE (1.71 GHz to 2.17 GHz), and “Band C” indicates the frequency band for LTE (2.4 GHz to 2.69 GHz). The vertical axis indicates a reflection coefficient S 11  for each of the antennas. 
     It is found that in any of the Bands A, B and C for the U-shaped antenna  301 , an excellent impedance matching was not obtained. However, it is found that in each of the Bands A, B and C (especially Band A) for the antenna  101  having the shape of a crank and the I-shaped antenna  201 , an excellent impedance matching was obtained. 
       FIG. 9  is a diagram depicting an example of actual gains of the respective antennas  101  and  201 , according to the first practical example. In  FIG. 9 , the vertical axis indicates an average value of antenna gains (actual gains) obtained by averaging 0° to 360° of azimuthal angles of the direction of the antenna, which is parallel to the horizontal plane. As shown in  FIG. 9 , it is found that the antenna gain in the horizontal direction of the antenna having a shape of a crank  101  is superior to the antenna gain in the horizontal direction of the I-shaped antenna  201 . 
     In the simulations of the reflection coefficient and the antenna gain, as shown in  FIGS. 8 and 9 , dimensions of the respective members of the antenna, illustrated in  FIGS. 2 to 7 , are as follows (in units of mm), 
     L1: 150, 
     L2: 200, 
     L11: 80, 
     L12: 15, 
     L13: 50, 
     L18: 40, 
     L20: 120 (long diameter of ellipse of outer conductor), 
     L21: 38 (short diameter of ellipse of outer conductor), 
     L22: 96 (long diameter of ellipse of inner conductor), 
     L23: 30 (short diameter of ellipse of inner conductor), 
     L24: 145, 
     L25: 1 (narrowest portion of slot (feeding point)), 
     L28: 40, 
     L31: 80, 
     L32: 15, 
     L33: 50, and 
     L38: 40. 
     Moreover, the angles θ, α and β (See  FIG. 1 ) are 30°, 90°, and 90°, respectively. The dimensions of the respective members of the element portion  51  having a shape of a crank, shown in  FIG. 2 , in the state where the element portion  51  is unbent, and the dimensions of the respective members of the U-shaped element portion  53 , shown in  FIG. 6 , in the state where the element portion  53  is unbent, are the same as the dimensions of the corresponding members of the I-shaped element portion  52 , shown in  FIG. 4 , respectively. 
     Second Practical Example 
       FIG. 10  is a perspective view depicting a configuration of a vehicle antenna according to a second practical example. An antenna  102  is an example of the antenna  100 , illustrated in  FIG. 1 . The antenna  102  is a dipole antenna in which a feeding portion  114  is arranged on an element  112 . In  FIG. 10 , a window glass is not illustrated, but the antenna  102  is mounted to the window glass in the same attaching form as that shown in  FIGS. 2 and 3 . 
     The vehicle antenna according to the second practical example is not limited to the dipole antenna having the shape illustrated in  FIG. 10 . For example, the vehicle antenna may be a dipole antenna in which shapes of two elements on both sides of the feeding portion  114 , in the state where the lower end portion  2   b  and the upper end portion  3   b  are unbent, are ellipses. Moreover, the vehicle antenna may be a dipole antenna in which shapes of two elements on both sides of the feeding portion  114 , in the state where the lower end portion  2   b  and the upper end portion  3   b  are unbent, are triangles, i.e. a bow tie antenna. Furthermore, the vehicle antenna may be a folded dipole antenna having a loop shape with the feeding portion  114  as a starting point in the state where the lower end portion  2   b  and the upper end portion  3   b  are unbent. 
     The antenna  102  includes an element portion  151  having a shape of a crank and configured of an element  111 , an element  112  and an element  113 ; and a feeding portion  114  for feeding power to the element portion  151 . The element portion  151  is an element of the element portion  50  illustrated in  FIG. 1 , and the feeding portion  114  is an example of the feeding portion  40  illustrated in  FIG. 1 . 
     The element  111  is an example of the first element, and is a planar conductor extending in the up-down direction of the window glass. The element  111  has an upper end portion  1   b  and a lower end portion  2   b  in the up-down direction of the window glass. The upper end portion  1   b  is an example of the first upper end portion, and the lower end portion  2   b  is an example of the first lower end portion. 
     The element  113  is an example of the second element, and is a planar conductor extending in the up-down direction of the window glass. The element  113  has an upper end portion  3   b  and a lower end portion  4   b  in the up-down direction of the window glass. The upper end portion  3   b  is an example of the second upper end portion, and the lower end portion  4   b  is an example of the second lower end portion. 
     The element  112  is an example of the third element, and is a planar conductor extending between the lower end portion  2   b  and the upper end portion  3   b . An end of the element  112  is connected to the lower end portion  2   b , and the other end of the element  112  is connected to the upper end portion  3   b.    
     The element  112  is separated by a gap  112   c  into a first partial element  112   a  and a second partial element  112   b . The feeding portion  114  is a dipolar feeding portion. A core wire of a coaxial cable is connected to the partial element  112   a  and a ground wire of the coaxial cable is connected to the partial element  112   b  so as to interpose the gap  112   c . Alternatively, the ground wire of the coaxial cable is connected to the partial element  112   a  and the core wire of the coaxial cable is connected to the partial element  112   b.    
       FIG. 11  is a perspective view depicting a configuration of a vehicle antenna according to a third comparative example. An I-shaped antenna  202 , shown in  FIG. 11 , is an example of an antenna that does not include an element portion having a shape of a crank. The antenna  202  is a dipole antenna in which the feeding portion  224  is arranged at the gap  223 . That is, the antenna  202  has a configuration in which the element portion  151  in the antenna  102 , shown in  FIG. 10 , is unbent. In  FIG. 11 , a window glass is not illustrated, but the antenna  202  is mounted to the window glass in the same attaching form as that in  FIGS. 4 and 5 . 
     The antenna  202  includes an I-shaped element portion  152  configured of a planar conductor portion  221 , a planar conductor portion  222 , and a gap  223 ; and a feeding portion  224  for feeding power to the element portion  152 . A core wire of a coaxial cable is connected to a lower part of the conductor portion  221 , and a ground wire of the coaxial cable is connected to an upper part of the conductor portion  222 . 
       FIG. 12  is a diagram depicting an example of a result of measurement for return loss characteristics of the vehicle antenna  102  and  202  according to the second practical example. The vertical axis indicates a reflection coefficient S 11  for each of the antennas. 
     From the result of the measurement, shown in  FIG. 12 , it is found that an excellent impedance matching was obtained for both the antenna having a shape of a crank  102  and the I-shaped antenna  202  in the frequency band around 900 MHz. 
       FIG. 13  is a diagram depicting an example of actual gains of the vehicle antenna  102  and  202 , according to the second practical example. In  FIG. 13 , the vertical axis indicates an average value of antenna gains (actual gains) obtained by averaging 0° to 360° of azimuthal angles of the direction of the antenna, which is parallel to the horizontal plane. As shown in  FIG. 13 , it is found that the antenna gain in the horizontal direction of the antenna having a shape of a crank  102  is superior to the antenna gain in the horizontal direction of the I-shaped antenna  202 . 
     In the simulations of the reflection coefficient and the antenna gain, as shown in  FIGS. 12 and 13 , dimensions of the respective members of the antenna, illustrated in  FIGS. 12 and 13 , are as follows (in units of mm), 
     L111: 70, 
     L112: 12, 
     L113: 70, 
     L118: 40, 
     L214: 140, and 
     L228: 40. 
     Moreover, the angles θ, α and β (See  FIG. 1 ) are 30°, 90°, and 90°, respectively. Gap lengths of the gaps  112   c  and  223  were 0.5 mm. 
     As described above, the vehicle antenna and a window glass for vehicle have been described by the embodiments. The present invention is not limited to the embodiments. Various variations and enhancements, such as combination/replacement with/by a part or whole of another embodiment may be made without departing from the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1  upper end portion 
           2  lower end portion 
           10 ,  11 ,  111  first element 
           15  first conductor portion 
           16  second conductor portion 
           17  slot 
           20 ,  12 ,  112  third element 
           30 ,  13 ,  113  second element 
           14 ,  24 ,  34 ,  40 ,  114 ,  224  feeding portion 
           50 ,  51 ,  52 ,  53 ,  151 ,  152  element portion 
           60  horizontal plane 
           70 ,  71 ,  72 ,  73  window glass 
           80  vehicle 
           100 ,  101 ,  102 ,  201 ,  202 ,  301  antenna