Antenna and radio communication system

Abstract

An antenna and a radio communication system capable of improving the design quality of an antenna at low cost are provided. According to an example embodiment, an antenna (20) includes a parasitic antenna element (21) formed using a transparent conducting film, wherein the parasitic antenna element (21) is not in contact with a feed point (13) and is arranged in the vicinity of a feed antenna element (11) of a radio communication device (10) configured to function as a radio communicator, and an induced current is generated in the parasitic antenna element (21) by a driving current of the feed antenna element.

Description

TECHNICAL FIELD

[0001] The present application relates to an antenna and a radio communication system. BACKGROUND

[0002] A parasitic antenna element has an effect of improving the performance of a feed antenna element to which radio waves are fed. The improvement in performance includes improvement in the efficiency and bandwidth of the antenna, multiple polarizations, and directivity.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent No. 6412059

[0006] Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-072645

[0007] Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-318571 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] In the case where metal such as a metal sheet, a printed circuit board, or an aluminum sheet is used as a material of a parasitic antenna element that does not contact a feed point, there is a problem in the design quality of the antenna because the material is metal.

[0010] Further, in the case where a transparent conductive film is used as a feed antenna element, it is possible to design the antenna so that its appearance becomes simple. However, since the transparent conductive film has to be processed, there is a disadvantage that the antenna becomes expensive. The transparent conductive film is soft and fragile. Therefore, at a feed point where a radio circuit is connected to the transparent conductive antenna, a process for adding a reinforcing plate and a paste of, for example, gold or silver, and the like to an electrode contact portion is required, so the antenna becomes very expensive.

[0011] In view of the above, an object of the present application is to provide an antenna and a radio communication system that can improve the design quality of the antenna at low cost.

[0012] SOLUTION TO PROBLEM

[0013] An antenna according to an example embodiment includes a parasitic antenna element formed using a transparent conductive film, wherein the parasitic antenna element does not contact a feed point and is disposed in the vicinity of a feed antenna element of a radio communication device configured to function as a radio communicator, and an induced current is generated in the parasitic antenna element by a drive current of the feed antenna element.

[0014] A radio communication system according to another example embodiment includes a radio communication device including a feed antenna element, the radio communication device being configured to function as a radio communicator; and an antenna including a parasitic antenna element formed using a transparent conductive film, wherein the parasitic antenna element is not in contact with a feed point and is disposed in the vicinity of the feed antenna element, and an induced current is generated in the parasitic antenna element by a driving current of the feed antenna element.

[0015] Effects of Invention

[0016] According to example embodiments, it is possible to provide an antenna and a radio communication system capable of improving the design quality of an antenna at low cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a perspective view showing an antenna and a radio communication system according to Comparative Example 1;

[0018] Figure 2 is a structural diagram showing an antenna and a radio communication system according to Comparative Example 1;

[0019] Figure 3 is a perspective view showing an antenna and a radio communication system according to a first example embodiment;

[0020] Figure 4 is a structural diagram showing an antenna and a radio communication system according to a first example embodiment;

[0021] Figure 5 is a graph showing antenna performance of a radio communication device and a radio communication system according to a first example embodiment, the upper portion of which shows a case where the radio communication device is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication device;

[0022] Figure 6 is a graph showing antenna performance of a radio communication device and a radio communication system according to a first example embodiment, the upper portion of which shows a case where the radio communication device is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication device;

[0023] Figure 7 is a graph showing antenna performance of a radio communication device and a radio communication system according to a first example embodiment, the upper portion of which shows a case where the radio communication device is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication device;

[0024] Figure 8 is a graph showing antenna performance of a radio communication device and a radio communication system according to a first example embodiment, the upper portion of which shows a case where the radio communication device is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication device;

[0025] Figure 9is a structural diagram illustrating a radio communication system according to Comparative Example 2;

[0026] Figure 10 is a structural diagram illustrating an antenna and a radio communication system according to a second example embodiment;

[0027] Figure 11 is a structural diagram illustrating an antenna and a radio communication system according to a second example embodiment;

[0028] Figure 12 is a diagram illustrating an antenna and a radio communication system according to a third example embodiment;

[0029] Figure 13 is a diagram illustrating an antenna and a radio communication system according to a third example embodiment;

[0030] Figure 14 is a diagram illustrating another shape of an antenna according to a third example embodiment;

[0031] Figure 15 is a diagram illustrating another shape of an antenna according to a third example embodiment;

[0032] Figure 16 is a diagram illustrating a number of radio waves emitted to the outside of a vehicle of a radio communication system according to a third example embodiment;

[0033] Figure 17 is a diagram illustrating an antenna and a radio communication system according to a fourth example embodiment; and

[0034] Figure 18 is a diagram illustrating a state in which an antenna according to a fourth example embodiment is attached to and detached from a roof of a vehicle. DETAILED DESCRIPTION

[0035] An antenna and a radio communication system according to example embodiments will be described below with reference to the accompanying drawings. Note that, for convenience, the reference numerals added in each drawing for each component are added as examples to aid understanding, and it is needless to say that these reference numerals are not added in order to limit the present application to the example embodiments illustrated in the drawings.

[0036] (First Example Embodiment)

[0037] First, a summary of the antenna according to the first example embodiment will be described. The antenna according to the present example embodiment includes a parasitic antenna element using a transparent conducting film. The parasitic antenna element does not contact a feed point and is disposed in the vicinity of a feed antenna element of a radio communication apparatus serving as a radio communicator, and an induced current is generated in the parasitic antenna element by a drive current of the feed antenna element. By the above structure, the pressure effect of the antenna according to the present example embodiment can be reduced, and the quality of a simple exterior design of the antenna can be improved. Further, since the antenna according to the present example embodiment has a non-contact structure, additional processing for connecting the transparent conducting film, which is difficult to handle, to the feed point is not required. Therefore, the antenna having an improved design quality can be provided at a low cost.

[0038] Next, the antenna and the radio communication system according to the present example embodiment will be described in detail. In order to more clearly understand the antenna and the radio communication system according to the present example embodiment, a comparison between the antenna and the radio communication system according to the present example embodiment and the antenna and the radio communication system according to Comparative Example 1 will be described. Figure 1 is a perspective view showing the antenna and the radio communication system according to Comparative Example 1. Figure 2 is a structural view showing the antenna and the radio communication system according to Comparative Example 1. Figure 3 is a perspective view showing the antenna and the radio communication system according to the first example embodiment. Figure 4 is a structural view showing the antenna and the radio communication system according to the first example embodiment.

[0039] As shown in Figure 1 and 2 , the radio communication system 101 according to Comparative Example 1 includes the radio communication apparatus 10 and the antenna 120.

[0040] The radio communication apparatus 10 serves as a radio communicator. For example, the radio communication apparatus 10 is a mobile Wi-Fi router. Note that if the radio communication apparatus 10 serves as a radio communicator, it is not limited to a mobile Wi-Fi router. The radio communication apparatus 10 includes a feed antenna element 11, a substrate 12, and a feed point 13 inside a cuboid housing 19. The substrate 12 is, for example, a printed circuit board on which components of the radio communication apparatus 10 are mounted. The feed point 13 is disposed in the substrate 12. For example, the feed antenna element 11 is connected to the substrate 12 via the feed point 13. The substrate 12 includes, for example, a rectangular substrate surface 12a.

[0041] Here, in order to describe the radio communication system 101, an XYZ orthogonal coordinate system is introduced. A direction perpendicular to the substrate surface 12a of the substrate 12 is defined as the Y-axis direction. Two orthogonal directions parallel to the substrate surface 12a are defined as the X-axis direction and the Z-axis direction. For example, each edge of the substrate 12 extends along the X-axis and Z-axis directions.

[0042] The feed antenna element 11 has, for example, an inverted L shape in which a thin metal sheet having one end 14 and the other end 15 is bent at a right angle in a bent portion 16. A portion of the feed antenna element 11 from the one end 14 to the bent portion 16 extends in the -Z axis direction. A portion of the feed antenna element 11 from the bent portion 16 to the other end 15 extends in the +X axis direction. For example, the length of the feed antenna element 11 from the one end 14 to the bent portion 16 is longer than the length thereof from the other end 15 to the bent portion 16. Note that the shape of the feed antenna element 11 is not limited to the inverted L shape, but may, for example, be an L shape or an F shape. Further, the feed antenna element 11 can be a single element, and it can be formed on a chip or the like, or it can be formed on the substrate 12.

[0043] The other end 15 of the feed antenna element 11 is connected to the feed point 13 of the substrate 12. A drive current is supplied from the feed point 13 to the feed antenna element 11. The drive current is, for example, a high-frequency current, and the feed antenna element 11 emits radio waves by the current. The feed antenna element 11 is arranged, for example, in an end portion of the housing 19. Note that the structure of the radio communication apparatus 10 according to Comparative Example 1 is the same as that of the radio communication apparatus 10 according to the first example embodiment described later.

[0044] The antenna 120 is attached to the mounting portion 29. The mounting portion 29 is, for example, a charging cradle that is an accessory of the mobile Wi-Fi router. Note that the mounting portion 29 is not limited to the charging cradle. The mounting portion 29 includes a cuboid base 29a provided with a recess 28 to which the radio communication apparatus 10 is fitted from above, and support portions 29b that support the base 29a from both sides in the direction in which the recess 28 extends. The antenna 120 is arranged in the support portions 29b of the mounting portion 29. For example, the antenna 120 is arranged inside the support portions 29b including a transparent member. The antenna 120 is arranged in the vicinity of the feed antenna element 11 of the radio communication apparatus 10.

[0045] The antenna 120 includes a parasitic antenna element 121. Therefore, the parasitic antenna element 121 is arranged in the charger of the radio communication apparatus 10. The parasitic antenna element 121 is formed using a metal film. For example, the parasitic antenna element 121 is formed using an aluminum film. The parasitic antenna element 121 has conductivity. Note that the parasitic antenna element 121 can be formed using other conductive members having conductivity other than aluminum. The parasitic antenna element 121 enhances the antenna performance of the feed antenna element 11 in the radio communication apparatus 10.

[0046] The parasitic antenna element 121 has a curved shape. For example, the parasitic antenna element 121 has a U shape in which a thin metal sheet having one end 124 and the other end 125 is bent at a right angle in a bending portion 126, and is bent at a right angle at a bending portion 127. A portion of the parasitic antenna element 121 from the one end 124 to the bending portion 126 extends in the +Z-axis direction. A portion of the parasitic antenna element 121 from the bending portion 126 to the bending portion 127 extends in the -Y-axis direction. A portion of the parasitic antenna element 121 from the bending portion 127 to the other end 125 extends in the -Z-axis direction. For example, a length of the parasitic antenna element 121 from the bending portion 126 to the bending portion 127 is longer than a length thereof from the one end 124 to the bending portion 126 and a length thereof from the bending portion 127 to the other end 125. Note that the shape of the parasitic antenna element 121 is not limited to the U shape, but can be, for example, a rod shape.

[0047] The parasitic antenna element 121 does not contact the feeding point 13 of the substrate 12, and also does not contact the other feeding points. The parasitic antenna element 121 is spatially coupled to the feeding antenna element 11. For example, a length of the parasitic antenna element 121 from the one end 124 to the other end 125 is about 1 / 2 of a wavelength of radio waves emitted by the feeding antenna element 11. Further, the parasitic antenna element 121 is located in the vicinity of the feeding antenna element 11 of the radio communication apparatus 10. For example, one end 14 of the feeding antenna element 11 and the one end 124 of the parasitic antenna element 121 are spatially coupled to each other at a spatial coupling portion SC. By the above, an induced current is generated in the parasitic antenna element 121 by a drive current of the feeding antenna element 11. The induced current generated in the parasitic antenna element 121 can have a current component having a direction different from that of the drive current. The induced current generated in the parasitic antenna element 121 is a resonance current.

[0048] The above-described radio communication system 101 according to the comparative example 1 can improve the antenna performance of the radio communication apparatus 10. However, the parasitic antenna element 121 of the antenna 120 is formed using an aluminum film. Therefore, there is a problem in the design quality of the antenna because the appearance of the antenna is not simple.

[0049] Next, a radio communication system according to the present example embodiment will be described. As shown in Figure 3 and 4 The radio communication apparatus 10 according to the first example embodiment has the same structure as that of the radio communication apparatus 10 according to the comparative example. In Figure 3 and 4 The same XYZ orthogonal coordinate system as that used in Figure 1 and 2 is used.

[0050] Further, the structure in which the antenna 20 according to the first example embodiment is attached to the mounting portion 29 is the same as the structure in which the antenna 120 according to Comparative Example 1 is attached to the mounting portion 29. That is, the antenna 20 is arranged in the support portion 29b of the mounting portion 29, and is arranged in the vicinity of the feed antenna element 11 of the radio communication apparatus 10.

[0051] The antenna 20 according to the first example embodiment includes a parasitic antenna element 21. The parasitic antenna element 21 is formed using a transparent conductive film. The transparent conductive film has conductivity. Further, the transparent conductive film is transparent, and thus one side of the transparent conductive film can be seen from the other side through the transparent conductive film. As described above, the antenna 20 according to the first example embodiment uses the transparent conductive film as the non-contact parasitic antenna element 21.

[0052] Like the parasitic antenna element 121 according to Comparative Example 1, the parasitic antenna element 21 has a curved shape. For example, the parasitic antenna element 21 has a U shape in which a thin metal sheet having one end 24 and the other end 25 is bent at a right angle in a curved portion 26, and is bent at a right angle at a curved portion 27. A portion of the parasitic antenna element 21 from the one end 24 to the curved portion 26 extends in the +Z-axis direction. A portion of the parasitic antenna element 21 from the curved portion 26 to the curved portion 27 extends in the -Y-axis direction. A portion of the parasitic antenna element 21 from the curved portion 27 to the other end 25 extends in the -Z-axis direction. For example, the length of the parasitic antenna element 21 from the curved portion 26 to the curved portion 27 is longer than the length of the parasitic antenna element 21 from the one end 24 to the curved portion 26 and the length of the parasitic antenna element 21 from the curved portion 27 to the other end 25. The length of the parasitic antenna element 21 from the one end 24 to the other end 25 is about 1 / 2 of the wavelength of the radio wave radiated by the feed antenna element 11. The parasitic antenna element 21 does not contact the feed point 13 of the substrate 12, and also does not contact other feed points.

[0053] The parasitic antenna element 21 is spatially coupled to the feed antenna element 11. For example, the parasitic antenna element 21 is located in the vicinity of the feed antenna element 11 of the radio communication apparatus 10. Further, the one end 14 of the feed antenna element 11 and the one end 24 of the parasitic antenna element 21 are spatially coupled to each other at a spatial coupling portion SC. In the above manner, an induced current is generated in the parasitic antenna element 21 by a drive current of the feed antenna element 11. The induced current generated in the parasitic antenna element 21 can have a current component having a direction different from the direction of the drive current. The induced current generated in the parasitic antenna element 21 is a resonant current.

[0054] Next, the operation of the radio communication system 1 according to the first example embodiment will be described. As described above, the radio communication system 1 according to the first example embodiment includes the radio communication apparatus 10 and the antenna 20. Figure 4As shown, the other end 15 of the feed antenna element 11 having an inverted L shape is connected to the feed point 13. The one end 14 of the feed antenna element 11 is located at the space coupling portion SC at which the one end 14 of the feed antenna element 11 is coupled to the parasitic antenna element 21. At the space coupling portion SC, the one end 14 of the feed antenna element 11 and the one end 24 of the parasitic antenna element 21 are coupled to each other with a high-frequency voltage. By doing so, a high-frequency voltage is induced in the non-fed non-contact parasitic antenna element 21. Thus, a high-frequency current as a radio wave source flows through the parasitic antenna element 21. Further, the parasitic antenna element 21 emits an antenna, that is, a radio wave.

[0055] Figure 5 is a graph showing the antenna performance of a radio communication apparatus and a radio communication system according to the first example embodiment, the upper portion of which shows a case where the radio communication apparatus is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication apparatus. Figure 6 is a graph showing the antenna performance of a radio communication apparatus and a radio communication system according to the first example embodiment, the upper portion of which shows a case where the radio communication apparatus is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication apparatus. Figure 7 is a graph showing the antenna performance of a radio communication apparatus and a radio communication system according to the first example embodiment, the upper portion of which shows a case where the radio communication apparatus is a single unit, and the lower portion of which shows a case where an antenna is added to the radio communication apparatus. The radio communication apparatus 10 is, for example, a single mobile WiFi router, and the antenna 20 is mounted on a mounting portion 29 such as a charging cradle or the like.

[0056] As shown in the upper portion of Figure 5 , in a case where the radio communication apparatus 10 is a single unit, both the horizontally polarized wave and the vertically polarized wave propagate in all directions in the XZ plane centered on the front direction (Y-axis direction). However, the intensity of the vertically polarized wave is smaller than that of the horizontally polarized wave. As shown in the lower portion of Figure 5 , even in a case where the antenna 20 is added, both the horizontally polarized wave and the vertically polarized wave propagate in all directions in the XZ plane centered on the front direction (Y-axis direction). However, compared to the case where the radio communication apparatus 10 is a single unit, the intensity of the vertically polarized wave increases in all directions and is equal to that of the horizontally polarized wave.

[0057] As shown in the upper portion of Figure 6 , in a case where the radio communication apparatus 10 is a single unit, the vertically polarized wave propagates in all directions in the XY plane centered on the upper surface direction (Z-axis direction). However, as for the horizontally polarized wave, its intensity decreases and is recessed in the side surface direction (X-axis direction) when viewed from the upper surface direction. As shown in the lower portion of Figure 6As shown in the lower part, with the antenna 20 added, both horizontally polarized and vertically polarized waves propagate in all directions within the XY plane centered on the direction above the surface (Z-axis direction). As described above, the charging base with the antenna 20 mounted is designed to radiate radio waves in all directions to eliminate radio waves radiated in weak directions.

[0058] like Figure 7 As shown in the upper part, when the radio communication device 10 is a single unit, vertically polarized waves propagate in all directions within the YZ plane centered on the side surface direction (X-axis direction). However, regarding horizontally polarized waves, when viewed from the side surface direction, their intensity decreases and dips in the upper and lower surface directions (Z-axis direction). Figure 7 As shown in the lower part, with the antenna 20 added, both the horizontally polarized wave and the vertically polarized wave propagate in all directions within the YZ plane centered on the side surface direction (X-axis direction).

[0059] Next, the effects of this example embodiment will be explained.

[0060] In the antenna 20 according to the first example embodiment, the parasitic antenna element 21 is formed using a transparent conductive film. Therefore, the antenna design quality can be improved due to its simple appearance.

[0061] Furthermore, since the parasitic antenna element 21 is a non-contact antenna element, it is not necessary to connect it to the feed point 13. Therefore, the process of adding reinforcing plates and conductive adhesives to the soft and brittle transparent conductive film to connect the parasitic antenna element 21 to the feed point 13 can be eliminated, thus allowing the antenna to be manufactured at low cost.

[0062] The radio communication system 1 according to the first example embodiment includes an antenna 20 comprising a parasitic antenna element 21 in the radio communication device 10 used alone as a radio communicator. This structure can improve the antenna performance of the radio communication device 10. That is, the antenna efficiency and bandwidth, multipolarization, and directivity in all directions can be improved.

[0063] (Second Embodiment)

[0064] Next, an antenna and radio communication system according to a second example embodiment will be described. The parasitic antenna element of the antenna according to the second example embodiment is suspended from the ceiling. A radio communication device is mounted on the ceiling. To better understand the antenna and radio communication system according to the second example embodiment, a comparison with the radio communication system according to Comparative Example 2 will be explained. Figure 8 This is a diagram illustrating a radio communication system according to Comparative Example 2. Figure 9 This is a structural diagram showing the radio communication system according to Comparative Example 2.Figure 10 and 11 Each is a structural diagram showing an antenna and a radio communication system according to a second example embodiment.

[0065] As Figure 8 and 9 shown, the radio communication system 102 according to Comparative Example 2 includes a radio communication device 130. The radio communication device 130 functions as a radio communicator. The radio communication device 130 is, for example, a ceiling-mounted radio router. Note that the radio communication device 130 is not limited to a ceiling-mounted radio router. The radio communication device 130 includes a feed antenna element 131, a substrate 132, and a feed point 133. The feed point 133 of the substrate 132 includes a connector 138 attached to the feed point 133 for connecting the feed point 133 to the feed antenna element 131. The substrate 132 and the feed point 133 are arranged within a disc-shaped housing 39. The housing 39 is attached to a ceiling of a building. The feed antenna element 131 is suspended from an end of the housing 39 attached to the ceiling.

[0066] The substrate 132 is, for example, a printed circuit board on which components of the radio communication device 130 are mounted. The substrate 132 includes, for example, a rectangular substrate surface 132a.

[0067] Here, for the purpose of explaining the radio communication system 102, an XYZ orthogonal coordinate system is introduced. A direction perpendicular to the substrate surface 132a of the substrate 132 is defined as a Z-axis direction. For example, a direction downward from the ceiling is defined as a -Z-axis direction. Two orthogonal directions parallel to the substrate surface 132a are defined as an X-axis direction and a Y-axis direction. For example, each side of the substrate 132 extends along the X-axis direction and the Y-axis direction.

[0068] The feed antenna element 131 has a thin strip shape formed so as to extend in one direction. The feed antenna element 131 has, for example, one end 134 and the other end 135. For example, a portion of the feed antenna element 131 from the one end 134 to the other end 135 extends in the -Z-axis direction. That is, the feed antenna element 131 is suspended downward from the ceiling.

[0069] The feed antenna element 131 is formed using a transparent conductive film. The transparent conductive film has conductivity. In addition, the transparent conductive film is transparent, so that one side of the transparent conductive film can be seen from the other side through the transparent conductive film. Since the transparent conductive film is thin, the feed antenna element 131 can be fixed to, for example, an acrylic antenna element support 136.

[0070] One end 134 side of the feed antenna element 131 is fixed to a reinforcing plate 137. A connector 138 is connected to a surface of the feed antenna element 131 opposite to the surface to which the reinforcing plate 137 is fixed, by using a conductive adhesive 139 such as silver paste. In this way, the feed antenna element 131 is connected to the feed point 133 of the substrate 132 via the connector 138.

[0071] In the radio communication system 102 according to the comparative example, in order for the radio communication device 130 to function as a radio communicator, a drive current is transmitted through the feed antenna element 131 so that it radiates radio waves. Further, the feed antenna element 131 is formed using a transparent conductive film.

[0072] In the radio communication system 102 described above, the feed antenna element 131 formed using an aluminum film can have a pressure effect. This is because the feed antenna element 131 is suspended from a ceiling, and thus is within the line of sight of a person passing below the feed antenna element 131. On the other hand, when a transparent conductive film is used for the feed antenna element 131, the pressure effect of the antenna is reduced, and the appearance of the antenna can be simple, and thus the design quality of the antenna can be improved.

[0073] However, the feed antenna element 131 is of a contact type, and is in contact with the substrate 132 via the connector 138. Thus, the radio communication system 102 physically supplies a current from the substrate 132 for generating radio waves to the feed antenna element 131 via the connector 138. Thus, the feed antenna element 131 needs to be processed using the reinforcing plate 137, the conductive adhesive 139, and the like. The reinforcing plate 137 is used to enhance the connection strength, and the conductive adhesive 139 is used to ensure the connection of the feed antenna element 131 to the connector 138. Thus, the manufacturing cost is increased.

[0074] Next, an antenna and a radio communication system according to a second example embodiment will be described. As shown in Figure 10 and 11 , the radio communication system 2 according to the second example embodiment includes a radio communication device 30 and an antenna 40. In Figure 10 and 11 , the same XYZ orthogonal coordinate system as that used in Figure 8 and 9 is used. The radio communication device 30 functions as a radio communicator. The radio communication device 30 is, for example, a radio router installed on a ceiling. Note that the radio communication device 30 is not limited to a radio router installed on a ceiling. The radio communication device 30 is installed on a ceiling in Figure 8The disk-shaped housing 39 shown includes the feed antenna element 31, the substrate 32, and the feed point 33. The substrate 32 is, for example, a printed circuit board on which components of the radio communication apparatus 30 are mounted. The feed point 33 is arranged in the substrate 32. The feed antenna element 31 is connected to the substrate 32 via the feed point 33, for example. The substrate 32 includes a rectangular substrate surface 32a, for example.

[0075] The feed antenna element 31 has, for example, an inverted L shape in which a thin metal sheet having one end 34 and the other end 35 is bent at a right angle at a bend 36. A portion of the feed antenna element 31 from the one end 34 to the bend 36 extends in the -X axis direction. A portion of the feed antenna element 31 from the bend 36 to the other end 35 extends in the +Y axis direction. The length of the feed antenna element 31 from the one end 34 to the bend 36 is longer than the length of the feed antenna element 31 from the other end 35 to the bend 36, for example. Note that the shape of the feed antenna element 31 is not limited to the L shape, but can be an inverted L shape or an F shape, for example. Furthermore, the feed antenna element 31 can be formed on the substrate 32, or it can be formed on a chip or the like, and it can be a single element.

[0076] The other end 35 of the feed antenna element 31 is connected to the feed point 33 of the substrate 32. A drive current is supplied to the feed antenna element 31 from the feed point 33. In the above manner, the feed antenna element 31 radiates radio waves. The feed antenna element 31 is arranged in an end portion of the housing 39, for example.

[0077] The antenna 40 includes a parasitic antenna element 41. The parasitic antenna element 41 is formed using a transparent conductive film. The transparent conductive film has conductivity. Furthermore, the transparent conductive film is transparent, so that one side of the transparent conductive film can be seen from the other side through the transparent conductive film. The parasitic antenna element 41 enhances the antenna performance of the feed antenna element 31 in the radio communication apparatus 30.

[0078] The parasitic antenna element 41 has a thin strip shape formed so as to extend in one direction. The parasitic antenna element 41 has, for example, one end 44 and the other end 45. A portion of the parasitic antenna element 41 from the one end 44 to the other end 45 extends in the -Z axis direction, for example. That is, the parasitic antenna element 41 hangs down from the ceiling. Therefore, in addition to the feed antenna element 31, the parasitic antenna element 41 also radiates radio waves. Figure 8 The appearance of the radio communication system according to the present example embodiment is the same as that of the radio communication system according to the comparative example, except that the feed antenna element 131 is replaced by the parasitic antenna element 41 shown. However, the parasitic antenna element 41 does not come into contact with the feed point 33 of the substrate 32, and also does not come into contact with other feed points. Since the transparent conductive film is thin, the parasitic antenna element can be fixed to, for example, the acrylic antenna element holder 136.

[0079] The parasitic antenna element 41 is spatially coupled to the feed antenna element 31. For example, the parasitic antenna element 41 is located in the vicinity of the feed antenna element 31 of the radio communication apparatus 30. In addition, the length of the parasitic antenna element 41 from the one end 44 to the other end 45 is about 1 / 2 of the wavelength of the radio wave radiated by the feed antenna element 31. Thus, the one end 34 of the feed antenna element 31 and the one end 44 of the parasitic antenna element 41 are spatially coupled to each other at the spatial coupling portion SC. By the above, an induced current is generated in the parasitic antenna element 41 by the driving current of the feed antenna element 31. The induced current generated in the parasitic antenna element 41 can have a current component having a direction different from that of the driving current. The induced current generated in the parasitic antenna element 41 is a resonant current.

[0080] Since the parasitic antenna element 41 and the feed antenna element 31 are spatially coupled to each other, the need for treating the parasitic antenna element 41 with the reinforcing plate 137, the conductive adhesive 139, and the like, and including the connector 138 can be eliminated. Thus, the design quality of the antenna can be improved at low cost. However, the feed antenna element 31 needs to be provided in the substrate 32 of the radio communication apparatus 30 compared to the radio communication system 102 according to the comparative example 2. The structures and effects other than the above are the same as those described with reference to the first example embodiment.

[0081] (Third Example Embodiment)

[0082] Next, the antenna and the radio communication system according to the third example embodiment will be described. In the antenna according to the third example embodiment, the parasitic antenna element is arranged, for example, in a window of a conveyance tool, and the radio communication apparatus is arranged in the conveyance tool. Figure 12 and 13 Each is a diagram showing the antenna and the radio communication system according to the third example embodiment. In Figure 12 , the vehicle 70 exemplified as a conveyance tool is shown in its state of facing forward, and in Figure 13 , the vehicle 70 exemplified as a conveyance tool is shown in its state of facing in a horizontal direction. Figure 14 and 15 Each is a diagram showing other shapes of the antenna according to the third example embodiment. As Figure 12 and 13 indicated, the radio communication system 3 includes the radio communication apparatus 50 and the antenna 60.

[0083] The radio communication device 50 is, for example, an in-vehicle radio communicator called a data communication module (DCM). In the event of an accident, the DCM can make an emergency call and transmit information about the vehicle to a mobile phone network. Note that the radio communication device 50 is not limited to a DCM. The radio communication device 50 is mounted on, for example, an instrument panel. The radio communication device 50 includes a feed antenna element 51 therein. The function of the feed antenna element 51 of the radio communication device 50 is the same as that of the feed antenna elements 11 and 31 described above.

[0084] The antenna 60 includes a parasitic antenna element 61 formed using a transparent conducting film. The antenna 60 is mounted to a window 71 (e.g., a windshield) of the vehicle 70. The parasitic antenna element 61 of the antenna 60 is spatially coupled to the feed antenna element 51 of the radio communication device 50. In the above manner, the antenna 60 increases the amount of radio waves emitted by the radio communication device 50 to the outside of the vehicle.

[0085] When the transmittance of the transparent conducting film is equal to or higher than a specified transmittance, it does not violate the safety standards established by the Ministry of Land, Infrastructure, Transport and Tourism. Thus, the antenna can be attached to the window without posing a danger to the driver. Note that when there is a risk that the driver's field of view will be obstructed, the antenna element can be changed to a T-shaped non-contact parasitic antenna element 61a as shown in FIG. 6B, or can be changed to an L-shaped non-contact parasitic antenna element 61b as shown in FIG. 6C. Figure 14 Figure 15

[0086] In the case where the transparent conducting film is used as the feed antenna element 131 as in the radio communication system 102 according to Comparative Example 2, when the window glass is broken due to the vehicle 70 encountering an accident or the like, the radio communication device stops the function of the radio communicator.

[0087] On the other hand, in the radio communication system 3 according to the third example embodiment, even when the window glass is broken due to the vehicle 70 encountering an accident or the like, and thus the antenna 60 is broken, since the radio communication device 50 includes the feed antenna element 51 therein, the radio communication device 50 does not stop functioning as a radio communicator even if the antenna performance is slightly reduced.

[0088] Figure 16 is a graph showing the amount of radio waves emitted to the outside of the vehicle by the radio communication system according to the third example embodiment. As Figure 16 ​​As shown, in a case where the antenna 60 is gradually moved under the vehicle 70 in a manner such that it is at the antenna position Al, then at the antenna position A2, and then at the antenna position A3, the number of radio waves emitted to the outside of the vehicle becomes Al > A2 > A3. This is because the vehicle body of the vehicle 70 is made of metal and blocks radio waves. Radio waves mainly pass through the window 71. Therefore, radio waves of the antenna 60 installed under the vehicle 70 are difficult to radiate to the outside of the vehicle.

[0089] The antenna 60 according to the present example embodiment is attached to the window 71, and thus it is possible to increase the number of radio waves emitted to the outside of the vehicle. Furthermore, the antenna 60 is formed using a transparent conductive film, and thus it is possible to reduce the obstruction to the driver's view.

[0090] An antenna called a shark fin antenna or a rod antenna installed on the roof of the vehicle 70 is likely to fall off in a case of rollover. Therefore, the radio communication apparatus 50 is preferably installed inside the vehicle 70. However, this causes the disadvantage that radio waves emitted from the radio communication apparatus 50 installed inside the vehicle 70 are hardly emitted to the outside of the vehicle.

[0091] In the radio communication system 3 according to the present example embodiment, the antenna 60 is attached to the window 71, and thus it is possible to increase the number of radio waves emitted to the outside of the vehicle. Therefore, it is possible to reduce the risk of the antenna falling off and breaking in a case of rollover, while it is possible to increase the number of emitted radio waves. Structures and effects other than the above are the same as those described with reference to the first example embodiment and the second example embodiment.

[0092] (Fourth Embodiment)

[0093] Next, the antenna and the radio communication system according to the fourth example embodiment will be described. In the antenna according to the fourth example embodiment, a parasitic antenna element is arranged, for example, on the roof of a conveyance, and a radio communication apparatus is arranged inside the conveyance so as to be located on the inner side of the roof. Figure 17 is a view showing an antenna and a radio communication system according to the fourth example embodiment. In Figure 17 In FIG. 4A, a vehicle 70, which is an example of a conveyance, is shown in a state in which it faces a horizontal direction. Figure 18 is a view showing a state in which an antenna according to the fourth example embodiment is attached to and detached from the roof of a vehicle. As Figure 17 and 18 As shown, the radio communication system 4 includes a radio communication apparatus 50 and an antenna 80.

[0094] As in the third example embodiment, the radio communication apparatus 50 is, for example, a DCM. In the present example embodiment, instead of being arranged on the instrument panel, the radio communication apparatus 50 is arranged within the vehicle 70 so as to be located on the inner side of the roof 72 of the vehicle 70. The radio communication apparatus 50 includes the feed antenna element 51 therein. The function of the feed antenna element 51 of the radio communication apparatus 50 is the same as that of the feed antenna elements 11 and 31 described above.

[0095] The antenna 80 includes the parasitic antenna element 81 formed using a transparent conductive film. The parasitic antenna element 81 can be reinforced by being bonded to the transparent acrylic plate 140. The antenna 80 protrudes upward from the roof 72 of the vehicle 70. For example, the parasitic antenna element 81 is arranged on the roof 72. Specifically, the parasitic antenna element 81 is arranged on the roof 72 except for one end, and the one end of the parasitic antenna element 81 is arranged in the vicinity of the feed antenna element 51 via a through-hole formed in the roof 72. The parasitic antenna element 81 of the antenna 80 is spatially coupled to the feed antenna element 51 of the radio communication apparatus 50. By the above means, the antenna 80 increases the amount of radio waves emitted by the radio communication apparatus 50 to the outside of the vehicle.

[0096] An antenna mounted on the top of the roof 72 is called a shark fin, a dolphin, or the like. From the viewpoint of a vehicle designer, the aforementioned antenna mounted on the top of the roof 72 spoils the body line of the vehicle.

[0097] In the present example embodiment, the radio communication apparatus 50 such as a DCM is mounted on the inner side of the roof 72, and the non-contact parasitic antenna element 81 is mounted on the top of the roof. By doing so, it is possible to improve the design quality of the antenna by giving the antenna a simple appearance. Further, since the antenna element is transparent, it is possible to eliminate color matching. Further, since the antenna can be easily replaced with another antenna by inserting the antenna into the through-hole of the roof 72, it is possible to reduce costs.

[0098] In the radio communication system 4 according to the fourth example embodiment, even when the antenna 80 is broken, since the radio communication apparatus 50 includes the feed antenna element 51 therein, the radio communication apparatus 50 does not stop functioning as a radio communicator even if the antenna performance is slightly reduced.

[0099] Note that the present application is not limited to the example embodiments described above, and can be appropriately changed without departing from the spirit of the present application. For example, a combination of the structures of the first example embodiment to the fourth example embodiment is within the scope of the technical idea of the present application. All or a part of the example embodiments disclosed above can be described as, but are not limited to, the following supplementary notes.

[0100] (Supplementary Note 1)

[0101] A radio communication system, comprising:

[0102] A radio communication device, comprising a fed antenna element, said radio communication device being configured to function as a radio communicator; and

[0103] The antenna includes a parasitic antenna element formed using a transparent conductive film, wherein...

[0104] The parasitic antenna element does not contact the feed point and is arranged near the feed antenna element.

[0105] The driving current of the fed antenna element generates an induced current in the parasitic antenna element.

[0106] (Supplementary Note 2)

[0107] According to Supplementary Note 1, in the radio communication system, the induced current is a resonant current.

[0108] (Supplementary Explanation 3)

[0109] According to Supplementary Note 1 or 2, in the radio communication system, the parasitic antenna element is arranged in the charger of the radio communication device.

[0110] (Supplementary Note 4)

[0111] According to the radio communication system described in Supplementary Note 1 or 2, wherein,

[0112] The radio communication equipment is installed on the ceiling, and

[0113] The parasitic antenna element is suspended from the ceiling.

[0114] (Supplementary Note 5)

[0115] According to the radio communication system described in Supplementary Note 1 or 2, wherein,

[0116] The radio communication equipment is arranged inside the transport vehicle, and

[0117] The parasitic antenna element is arranged inside the window of the transport vehicle.

[0118] (Supplementary Note 6)

[0119] According to any one of Supplementary Notes 1 to 5, in the radio communication system, the parasitic antenna element has a curved shape.

[0120] (Supplementary Note 7)

[0121] The radio communication system according to any one of Supplementary Notes 1 to 6, wherein the feed antenna element has an inverted L shape.

[0122] (Supplementary Note 8)

[0123] The radio communication system according to any one of Supplementary Notes 1 to 7, wherein the parasitic antenna element has one end and another end, and a length from the one end to the another end is about 1 / 2 of a wavelength of radio waves emitted by the feed antenna element.

[0124] (Supplementary Note 9)

[0125] The radio communication system according to any one of Supplementary Notes 1 to 8, wherein,

[0126] the feed antenna element has one end and another end connected to a feed point,

[0127] the parasitic antenna element has one end and another end, and

[0128] the one end of the feed antenna element is spatially coupled to the one end of the parasitic antenna element.

[0129] Although the present application has been described with reference to example embodiments, the present application is not limited to the above example embodiments. Various changes which can be understood by those skilled in the art can be made to the configuration and details of the present application within the scope of the present application.

[0130] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-195862, filed on October 29, 2019, the entire contents of which are incorporated herein by reference.

[0131] List of reference numerals

[0132] 1, 2, 3, 4, 101, 102 Radio communication system

[0133] 10, 30, 50, 130 Radio communication device

[0134] 11, 31, 51, 131 Feed antenna element

[0135] 12, 32, 132 Substrate

[0136] 12a Substrate surface

[0137] 13, 33, 133 Feed point

[0138] 14, 34, 134 One end

[0139] 15, 35, 135 Another end

[0140] 16, 36 curved portion

[0141] 19, 39 housing

[0142] 20, 40, 60, 80, 120 antenna

[0143] 21, 41, 61, 61a, 61b, 81, 121 parasitic antenna element

[0144] 24, 44, 124 one end

[0145] 25, 45, 125 other end

[0146] 26, 27, 126, 127 curved portion

[0147] 28 recess

[0148] 29 mounting portion

[0149] 29a base

[0150] 29b support portion

[0151] 70 vehicle

[0152] 71 window

[0153] 72 roof

[0154] 136 antenna element holder

[0155] 137 reinforcing plate

[0156] 138 connector

[0157] 139 conductive adhesive

[0158] 140 acrylic plate

Claims

1. An antenna comprising a parasitic antenna element formed using a transparent conducting film, wherein, the parasitic antenna element is not in contact with a feed point, and is arranged in the vicinity of a feed antenna element of a radio communication apparatus configured to function as a radio communicator, and an induced current is generated in the parasitic antenna element by a drive current of the feed antenna element, wherein the parasitic antenna element is arranged within a window of a conveyance, the radio communication apparatus internally includes the feed antenna element, and the radio communication apparatus is mounted on an instrument panel inside the conveyance.

2. The antenna of claim 1, wherein, The induced current is a resonant current.

3. The antenna according to claim 1 or 2, wherein, The parasitic antenna element has a curved shape.

4. The antenna of claim 1 or 2, wherein, The feed antenna element has an inverted L shape.

5. The antenna according to claim 1 or 2, wherein, The parasitic antenna element has one end and another end, and a length from the one end to the other end is 1 / 2 of a wavelength of radio waves emitted by the feed antenna element.

6. The antenna according to claim 1 or 2, wherein, the feed antenna element has one end and another end connected to a feed point, the parasitic antenna element has one end and another end, and the one end of the feed antenna element is spatially coupled to the one end of the parasitic antenna element.

7. A radio communication system comprising: a radio communication apparatus including a feed antenna element, the radio communication apparatus being configured to function as a radio communicator; and an antenna comprising a parasitic antenna element formed using a transparent conducting film, wherein, the parasitic antenna element is not in contact with a feed point, and is arranged in the vicinity of the feed antenna element, and an induced current is generated in the parasitic antenna element by a drive current of the feed antenna element, wherein the parasitic antenna element is arranged within a window of a conveyance, the radio communication apparatus internally includes the feed antenna element, and the radio communication apparatus is mounted on an instrument panel inside the conveyance.

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