Antenna device

Abstract

This antenna device comprises: an antenna housing that forms a hollow in the interior thereof; an antenna that is located in the interior and that performs at least one of transmission and reception of radio waves; and a scatterer that scatters, at a predetermined part of the antenna housing, the radio waves propagating in the hollow.

Description

Antenna device

[0001] The present invention relates to an antenna device that can be mounted on a moving object such as a vehicle or a robot.

[0002] With the recent increase in demand for vehicle-related applications, development of applications using V2X (Vehicle-to-everything) communication is progressing. V2X communication is a collective term for V2I (Vehicle-to-Infrastructure) communication, V2V (Vehicle-to-vehicle) communication, V2P (Vehicle-to-Pedestrian) communication, V2D (Vehicle-to-device) communication, and V2G (Vehicle-to-grid) communication. In V2X communication, when two V2X-compatible communication devices come within communication range of each other's antennas, an ad hoc network is formed including the vehicles equipped with the communication devices and antennas.

[0003] Patent Literature 1 discloses an in-vehicle wireless system that enables V2X communication in a vehicle. This in-vehicle wireless system includes, for example, a rooftop antenna housing attached to the roof of the vehicle and an interior antenna housing disposed in the vehicle cabin. The rooftop antenna housing has a hollow portion that houses a V2X antenna and a GNSS (Global Navigation Satellite System) antenna. The interior antenna housing houses a telephone antenna that can communicate with a smartphone or the like running an application. Because the position of a communication partner relative to an antenna device mounted on a vehicle is often uncertain, an antenna mounted on a vehicle is ideally isotropic.

[0004] Japanese Patent Application Laid-Open No. 2019-216342

[0005] The rooftop antenna housing described in Patent Document 1 is molded from a resin material. While it is well known that resin materials allow radio waves to pass through, in reality, radio waves propagate through various paths within the hollow portion of the antenna housing. As a result, even if the antenna is isotropic, a phenomenon called ripple occurs, which disrupts the directional characteristics. The ripple often reaches its maximum value in an area adjacent to an area where the ripple in the directional characteristics is at its minimum. If, as viewed from the antenna, a communication partner is located in the direction of the area where the ripple in the directional characteristics is at its minimum value, communication with that communication partner will be hindered.

[0006] One example of an object of the present invention is to reduce ripples in the directional characteristics during transmission or reception. Other objects of the present invention will become apparent from the disclosure of this specification.

[0007] One aspect of the present invention is an antenna device comprising an antenna housing that forms a hollow space inside, an antenna that is located inside the housing and that transmits and receives radio waves, and a scatterer that scatters the radio waves propagating through the hollow space at a predetermined location in the antenna housing.

[0008] According to the above aspect, the scatterer scatters radio waves propagating through the hollow portion of the antenna housing at a predetermined location, so that ripples in the directional characteristics during transmission or reception can be reduced.

[0009] 11 is a structural explanatory diagram of an antenna device according to a first embodiment; FIG. 12 is a diagram of directional characteristics in a horizontal plane of the antenna device according to the first embodiment; FIG. 13 is a graph of level deviations of the antenna device according to the first embodiment and an antenna device of a comparative example; FIG. 14 is a graph showing the effect of the length of a conductor rod on level (gain) deviation; FIG. 15 is a graph showing the effect of the size of a conductor rod in a horizontal plane on level deviation; FIG. 16 is an explanatory diagram of an area that is a candidate for a location where a conductor rod can be arranged; FIG. 17 is an explanatory diagram of multiple areas that are candidate locations for conductor rod arrangement; FIG. 18 is a graph showing level deviations in the area of ​​FIG. 7; FIG. 19 is an explanatory diagram of multiple areas showing differences in the spacing between two conductor rods; FIG. 19 is a graph showing level deviations in the area shown in FIG. 20; FIG. 21 is a structural explanatory diagram of an antenna device with different numbers of conductor rods; FIG. 22 is a graph showing level deviations for the number of conductor rods in the aspect shown in FIG. 21; FIG. 10 is a top view of the antenna device according to the fourth embodiment. FIG. 11 is a rear perspective view of the antenna device according to the fourth embodiment. FIG. 12 is a left side view of the antenna portion of the antenna device according to the fourth embodiment. FIG. 13 is a diagram of directional characteristics in the horizontal plane of the antenna device according to the fourth embodiment. FIG. 14 is a front perspective view of the antenna device according to the fifth embodiment. FIG. 15 is a top view of the antenna device according to the fifth embodiment. FIG. 16 is a left side view of the antenna device according to the fifth embodiment. FIG. 17 is a perspective view of the antenna device according to another embodiment. FIG. 18 is a perspective view of the antenna device according to another embodiment. FIG. 19 is a diagram of directional characteristics in the horizontal plane of the antenna device according to another embodiment.

[0010] Below, an embodiment of the present invention will be described in which it is applied to an antenna device equipped with an antenna housing that can be attached to the roof or the like of a vehicle. In this specification, directions are defined as x, y, and z directions, representing front, rear, left, right, top, and bottom as viewed from the driver's seat of the vehicle. The z direction is normal to the bottom surface of the antenna device. The x direction is one of the horizontal directions perpendicular to the z direction. The y direction is one of the horizontal directions perpendicular to the z and x directions. In this specification, the x direction is described as the front-to-back direction (front is +, rear is -), the y direction is the left-to-right direction (left is +, right is -), and the z direction is the up-and-down direction (up is +, down is -). In addition, in the drawings, the directions indicated by the arrows on the x-axis, y-axis, and z-axis may be referred to as the forward, leftward, and upward directions, respectively. Furthermore, the plane containing the x-axis and y-axis may be referred to as the xy plane or horizontal plane. In addition, viewing the antenna device from above is sometimes called a top view, viewing the antenna device from the left / right is sometimes called a side view, and viewing the antenna device from the upper left / upper right / lower left / lower right / front left / front right / rear left / rear right is sometimes called an oblique view.

[0011] [First Embodiment] FIG. 1 is an explanatory diagram of the structure of an antenna device according to a first embodiment. The antenna device 1 of the first embodiment includes an antenna housing 10. The antenna housing 10 has a hollow space therein. The hollow space accommodates an antenna and antenna components. The antenna housing 10 includes, for example, an antenna base 11 that is approximately elliptical in top view and an antenna case 12 that defines a space together with the antenna base. The antenna base 11 is a conductive base having a certain level of strength, such as aluminum die-cast. However, the antenna base 11 may also be formed from one or more metal plates made of sheet metal. Alternatively, the antenna base 11 may be formed from one or more metal plates and a conductive base. Alternatively, the antenna base 11 may be formed from an insulating base made of resin or the like and at least one of a conductive base and one or more metal plates. The antenna case 12 is made of a hollow, three-dimensional resin that seals the antenna base 11. However, for convenience, the antenna case 12 is omitted in the top view of FIG. 1, and the antenna case 12 is shown by a broken line in the side view.

[0012] The antenna 13 and two conductor rods 14a and 14b, which are examples of scatterers, are located on the upper surface of the antenna base 11. The antenna 13 is a linear, rod-like, planar, spiral, or zigzag resonant element extending from its feed point in the +z direction. The resonant frequency (hereinafter sometimes referred to as the "operating frequency") of the antenna 13 in the first embodiment is, for example, the 5.9 GHz band (wavelength λ: approximately 50 mm), which is one of the V2X bands. The antenna 13 may be an antenna known as a monopole antenna, a dipole antenna, a sleeve antenna, a collinear antenna, a slot antenna, a slit antenna, or a patch antenna.

[0013] The two conductor rods 14a, 14b are arranged, for example, in front of the antenna 13 at predetermined positions that scatter radio waves propagating in the hollow portion of the antenna housing 10, and are arranged at a predetermined height and substantially parallel to the antenna 13. Each conductor rod 14a, 14b is electrically connected to the conductive antenna base 11 to form a grounded scatterer. In the first embodiment, each conductor rod 14a, 14b is a rectangular prism conductor with a length (height) of L [mm] in the z direction from the antenna base 11 and a side dimension of W [mm]. However, their cross-sectional shape and size may be arbitrary. Furthermore, each conductor rod 14a, 14b is not limited to a rectangular prism or rod shape, and may also be a cylindrical, elliptical cylinder, oblong cylinder, polygonal prism, headed cylinder, cylindrical, elliptical cylinder, oblong cylinder, polygonal cylinder, cone, elliptical cone, oblong cone, polygonal pyramid, planar, spiral, or zigzag shape.

[0014] The predetermined portion is a portion in the antenna housing 10 where deviation in the intensity distribution of radio waves becomes relatively small. Alternatively, the predetermined portion is a portion that affects interference, etc., of traveling waves, reflected waves, etc. propagating within the antenna housing 10, and can relatively reduce the difference (level deviation) between the maximum and minimum values ​​of ripple in the directional characteristics in the antenna housing 10. For example, the predetermined portion is a portion where the difference between the maximum and minimum values ​​of ripple in the directional characteristics becomes relatively small by arranging structures such as the conductor rods 14a and 14b in the first embodiment.

[0015] The specified length (height) is, for example, the distance in the upward direction (z direction) when the antenna device 1 is installed on the vehicle roof between the highest point of the structure existing in the hollow portion of the antenna housing 10, excluding the inner surface of the antenna case 12 and the antenna 13, and the mounting location on the vehicle roof.

[0016] 1, the shape of the antenna base 11 is symmetrical across a horizontal plane bounded by the x-axis. The x-axis here refers to the central axis connecting the long ends of the antenna base 11. The distance between the long ends on the x-axis connecting the center point of the antenna 13 and the geometric center 110 of the antenna base 11 is approximately 220 mm, and the distance between the short ends in the y-direction passing through the geometric center 110 is approximately 90 mm.

[0017] The antenna 13 is disposed on a central axis (x-axis) connecting the long ends of the antenna base 11 in the x-direction, at a position 90 mm in the negative x-direction from the geometric center 110. The two conductor rods 14a, 14b are disposed parallel to the antenna 13, one each at equal distances in the positive y-direction and the negative y-direction from the central axis connecting the long ends of the antenna base 11, with the position 90 mm in the positive x-direction from the geometric center 110 as the base point.

[0018] The shortest distance (spacing) between the two opposing conductor rods 14a and 14b is 35 mm, for example, in the 5.9 GHz band. The length (height) of the antenna 13 in the z direction is approximately 12.5 mm, which is the resonant wavelength λ of the operating frequency. In this case, the length L of the two conductor rods 14a and 14b in the z direction is approximately 11 mm.

[0019] The directional characteristics in the horizontal plane (xy plane) of the antenna device 1 according to the first embodiment are shown by a solid line in Fig. 2. The directional characteristics in the horizontal plane (xy plane) of the comparative antenna device R, which is a comparative example, are also shown by a thick dashed line in Fig. 2. The comparative antenna device R differs from the antenna device 1 according to the first embodiment in that it does not have any conductor rods, i.e., the number of conductor rods is zero. The shape, structure, and size of the comparative antenna device R are the same as those of the antenna device 1 according to the first embodiment.

[0020] In FIG. 2 , the forward direction (+x direction) of the antenna 13 is set to 0 degrees, and this angle (0 degrees) is set as the reference angle. FIG. 2 shows the horizontal plane directivity characteristics at measurement points from the reference angle, shifted counterclockwise by 30 degrees each time, up to 360 degrees (=0 degrees). The radial direction indicates level (gain on the antenna 13 side), measured in units of dBi, but will be expressed as dB in the drawings and the following description. Furthermore, in the drawings and the following description, level (gain) will be expressed as "level" and level (gain) deviation will be expressed as "level deviation." The angular range in which the level deviation between the antenna device 1 of the first embodiment and the comparative antenna device R becomes significant is indicated by a shaded area in FIG. 2 . The angular range is 45 degrees and 315 degrees relative to the reference angle, i.e., ±45 degrees relative to the reference angle. FIG. 3 shows a graph of the level deviation of the antenna device 1 with two conductor rods and the comparative antenna device R with no conductor rods within this angular range.

[0021] In the directional characteristic diagram of Fig. 2, the level at the reference angle (0 degrees) of the comparative example antenna device R is 2.59 dB. In contrast, the level at the reference angle of the antenna device 1 of the first embodiment is 8.15 dB, which is an increase of 5.56 dB. Furthermore, the level deviation of the comparative example antenna device R in the above angle range is 13.63 dB as shown in Fig. 3, while that of the antenna device 1 of the first embodiment is 7.37 dB, which is a reduction of 6.26 dB.

[0022] In the case of the comparative example antenna device R, although it is configured only with the antenna base 11 and the antenna case 12 in addition to the antenna 13, there are portions (null points) where the gain drops sharply at approximately 15 degrees and approximately 345 degrees from the reference angle (approximately ±15 degrees from the reference angle), as shown by the dashed lines in Figure 2. This phenomenon occurs mainly because the radio waves radiated from the antenna 13 are scattered as they pass through the antenna case 12.

[0023] However, by arranging the two conductive rods 14a and 14b at predetermined locations on the antenna base 11 as in the first embodiment, the scattering pattern of radio waves in the hollow portion of the antenna housing 10 changes from that observed when only the antenna case 12 is used. In other words, the scattering pattern according to the first embodiment includes scattering by the antenna case 12 and scattering by the conductive rods 14a and 14b. As a result, the null points at approximately 15 degrees and approximately 345 degrees from the reference angle (approximately ±15 degrees from the reference angle) are alleviated, and the level at the reference angle is also increased. Furthermore, the ripple within the above angle range is significantly reduced. In other words, adding the conductive rods 14a and 14b to an antenna housing 10 that has already been designed and manufactured not only reduces ripple but also allows the directional characteristics of the antenna 13 to be changed after the fact.

[0024] <Modification 1> The effect of the length L of the conductive rods 14a and 14b on the level deviation is shown by a solid line in the graph of FIG. 4 . As a comparative example, the level deviation of the comparative antenna device R described above is also shown by a dotted line in the graph of FIG. 4 . The level deviation of the comparative antenna device R, which does not have conductive rods, is 13.63 dB. In contrast, in the case of the antenna device 1 of the first embodiment, the level deviation was 12.04 dB when the length L of the two conductive rods 14a and 14b was 5 mm, 7.81 dB when it was 8 mm, 6.46 dB when it was 11 mm, 7.07 dB when it was 14 mm, 8.68 dB when it was 17 mm, 9.55 dB when it was 20 mm, and 9.16 dB when it was 23 mm. In other words, by setting the length L of the conductive rods 14a and 14b to 1 / 10 or more of the wavelength λ of the operating frequency of the antenna 13 (5 mm or more for the operating frequency of the first embodiment), a ripple reduction effect can be obtained. In particular, when the length L is about ¼ of the wavelength λ (11 mm in the case of the operating frequency of the first embodiment), the effect of reducing ripples becomes significant.

[0025] <Modification 2> The effect of the size (thickness) W of the conductor rods 14a, 14b in the horizontal plane on the level deviation is shown by a solid line and a long-dashed line in the graph of Fig. 5. As a comparative example, the level deviation of the comparative antenna device R described above is also shown by a dotted line in the graph of Fig. 5. As described above, the level deviation of the comparative antenna device R is 13.63 dB. In contrast, in the antenna device 1 of the first embodiment, when the length L is 6 mm, the level deviation was 13.28 dB when the size W of one side of the conductor rods 14a, 14b was 0.5 mm, 13.27 dB when it was 1 mm, 12.89 dB when it was 3 mm, and 12.58 dB when it was 5 mm.

[0026] Furthermore, in the antenna device 1 of the first embodiment, when the length L was 11 mm, the impedance was 11.65 dB when the size W of one side of the conductive rods 14a, 14b was 0.5 mm, 11.23 dB when it was 1 mm, 10.87 dB when it was 3 mm, and 10.79 dB when it was 5 mm. In other words, even if the length L of the conductive rods 14a, 14b cannot be sufficiently secured, the ripple reduction effect can be obtained by making the size W in the horizontal plane of the conductive rods 14a, 14b larger than that of the antenna 13. Furthermore, when the length L of the conductive rods 14a, 14b is about ¼ of the wavelength λ of the operating frequency of the antenna 13 (11 mm in the case of the operating frequency of the first embodiment), the ripple reduction effect can be significantly obtained by making the size W larger.

[0027] <Modification 3> The locations where the conductive rods 14a and 14b are arranged may be locations other than those shown in Fig. 1. Here, candidate areas where the conductive rods 14a and 14b can be arranged will be described with reference to Figs. 6 to 10. Fig. 6 is an explanatory diagram of candidate areas where the conductive rods can be arranged, and is a top view of the antenna base 11.

[0028] Here, for convenience in explaining the above-mentioned regions, a first circle 15 and a second circle 16 are defined. The first circle 15 is a circle having its center on the x-axis connecting the feed position 130 of the antenna 13 and the geometric center 110 of the antenna base 11. Furthermore, the first circle 15 has a radius of ½ the wavelength λ of the operating frequency and passes through the feed position 130 of the antenna 13. The second circle 16 is a circle obtained by moving the first circle 15 on the x-axis from the feed position 130 of the antenna 13 by a distance of 2 times the length (height) L [mm] when the conductor rods 14a and 14b are grounded to the antenna base 11.

[0029] Although not shown in FIG. 6 , the second circle 16 when the conductor rods 14a and 14b are not grounded to the antenna base 11 is a circle obtained by moving the first circle 15 on the x-axis from the feed position 130 of the antenna 13 by a distance equal to 1 times the length (height) L [mm]. Two tangents that pass through the feed position 130 of the antenna 13 and touch the second circle 16 are defined as tangents 17 and 18, respectively. Furthermore, the points where the second circle and the two tangents 17 and 18 touch are defined as tangent points 151 and 152, respectively. Furthermore, the intersections of the two tangents 17 and 18 with the inner edge of the antenna base 11 are defined as intersections 111 and 112, respectively. Furthermore, the intersections of a line 19 connecting the tangent points 151 and 152 of the second circle 16 in the y-direction with the inner edge of the antenna base 11 are defined as intersections 113 and 114, respectively.

[0030] A first candidate area Ar1, which is a candidate for a location where the conductive rods 14a and 14b can be arranged, can be an area on the rear side of the x-axis inside the antenna base 11, connecting the intersection 113, the contact point 151, the feed position 130 of the antenna 13, the contact point 152, the intersection point 114, and the intersection point 113. A second candidate area Ar2, which is a candidate for a location where the conductive rods 14a and 14b can be arranged, can be an area on the front side of the x-axis inside the antenna base 11, connecting the intersection point 111, the contact point 151, the feed position 130 of the antenna 13, the contact point 152, the intersection point 112, and the intersection point 111.

[0031] 7 is an explanatory diagram of multiple areas that are candidates for placement of two conductor rods 14a and 14b in the first candidate area Ar1 and the second candidate area Ar2 defined in FIG. 6. The first area A is an area behind the antenna 13 in the first candidate area Ar1. The second area B is an area in front of the antenna 13 in the first candidate area Ar1, and is farther from the antenna 13 than the first area A. The third area C is an area inside the antenna base 11, and is an area in front of the antenna 13 in the first candidate area Ar1, and is farther from the antenna 13 than the second area B. The fourth area D is an area in the second candidate area Ar2 that is closer to the antenna 13 than the area shown in FIG. 1.

[0032] The distance between the conductor bars 14a and 14b is 12.5 mm in area A, 17.5 mm in area B, 27.5 mm in area C, and 15 mm in area D. The height of each of the conductor bars 14a and 14b is 11 mm.

[0033] Fig. 8 is a graph showing the level deviation in areas A to D shown in Fig. 7. As a comparative example, the level deviation of the above-mentioned comparative antenna device R is also shown in the graph of Fig. 8. As described above, the level deviation of the comparative antenna device R is constant at 13.63 dB. In contrast, in the case of the antenna device 1 of the first embodiment, the level deviation is 9.38 dB in area A, 6.46 dB in area B, 11.15 dB in area C, and 8.54 dB in area D. Therefore, the ripple reduction effect can be obtained in both the first candidate area Ar1 and the second candidate area Ar2.

[0034] 9 is an explanatory diagram of a plurality of areas showing differences in the spacing between the two conductor rods, and in particular, an explanatory diagram of a plurality of areas roughly classified according to the arrangement of the two conductor rods 14a, 14b in the second candidate area Ar2. When the antenna 13 is located behind the antenna device 1, the effect of reducing the level deviation can be obtained by arranging the two conductor rods 14a, 14b roughly in front of the antenna device 1. In particular, the effect of reducing the level deviation becomes more pronounced by arranging them at a constant interval, approximately 1 / 2 the wavelength λ, with the x-axis as the boundary.

[0035] In the example of FIG. 9 , the conductive rods 14a and 14b are arranged equidistant from each other in the +y and -y directions, with the central axis (x-axis) of the antenna base 11 as the boundary. Area #3 is an area roughly in front of the antenna device 1, where the two conductive rods 14a and 14b are arranged at a fixed interval, approximately half the wavelength λ, with the x-axis as the boundary. Area #2 is roughly in front of the antenna device 1, but the two conductive rods 14a and 14b are arranged slightly farther or closer to the interval of approximately half the wavelength λ. Area #1 is roughly in front of the antenna device 1, but the interval between the two conductive rods 14a and 14b is even farther than in Area #2. The length L in the z direction of the conductive rods 14a and 14b is 11 mm. Here, Area #4 does not belong to either candidate area Ar1 or Ar2, and is an area close to the periphery of the antenna base 11.

[0036] FIG. 10 is a graph showing the level deviation in areas #1 to #4 shown in FIG. 9. As a comparative example, the level deviation of the above-mentioned comparative antenna device R is also shown in the graph of FIG. 10. As mentioned above, the level deviation of the comparative antenna device R is 13.63 dB. In contrast, in the case of the antenna device 1 of the first embodiment, the level deviation is 11.99 dB in area #1, 11.47 dB in area #2, 10.95 dB in area #3, and 14.02 dB in area #4. Furthermore, a ripple reduction effect is obtained in all areas #1 to #3. However, the level deviation is larger in area #4.

[0037] In this way, when the antenna 13 is located behind the antenna base 11, arranging the two conductor rods 14a and 14b roughly in front of the antenna base 11 has the effect of reducing the level deviation of the antenna device 1. In particular, it can be seen that arranging the conductor rods 14a and 14b at a fixed interval, approximately 1 / 2 the wavelength λ, around the x-axis can effectively reduce the ripple. On the other hand, it can be seen that the ripple cannot be sufficiently improved in areas other than the candidate areas Ar1 and Ar2.

[0038] <Modification 4> The number of conducting rods used as scatterers is not limited to two. Fig. 11 is a diagram showing a structural example of an antenna device according to Modification 4 of the first embodiment, and is an explanatory diagram of the structure of an antenna device in which the number of conducting rods is changed. When there is one conducting rod, for example, one conducting rod 14 is arranged on the x-axis, which is the central axis of the antenna base 11. The distance between the antenna 13 and the conducting rod 14 may be a distance that allows the conducting rod 14 to act as a director of the antenna 13.

[0039] In the case of four conductor rods, for example, two of the conductor rods 14a and 14b may be arranged in the same positions as in FIG. 1 , and the remaining two conductor rods 14c and 14d may be arranged closer to the antenna 13 than the conductor rods 14a and 14b, with a greater distance between them than the conductor rods 14a and 14b, at the same distance from the x-axis. In the case of six conductor rods, for example, four of the conductor rods 14a, 14b, 14c, and 14d may be arranged in the same manner as in the case of four conductor rods, and the remaining two conductor rods 14e and 14f may be arranged in the first candidate area Ar1 at the same distance from the x-axis. However, in the case of six conductor rods, the positions of the conductor rods do not have to be as shown in FIG. 11 . Furthermore, the number of conductor rods is not limited to an even number, and an odd number, such as three or five, may also be used, and the arrangement does not necessarily have to be symmetrical.

[0040] FIG. 12 is a graph showing the level deviation for each number of conductor rods in the configuration shown in FIG. 11 . As a comparative example, the level deviation of the comparative antenna device R described above is also plotted in the graph in FIG. 12 . As mentioned above, the level deviation of the comparative antenna device R was 13.63 dB, and 7.37 dB when two conductor rods were used. In contrast, in the antenna device 1 of the first embodiment, the level deviation was 9.80 dB when one conductor rod was used, 7.27 dB when four conductor rods were used, and 9.93 dB when six conductor rods were used. Thus, a ripple reduction effect was achieved even with one or more conductor rods. However, the ripple reduction effect was greater with two or four conductor rods than with one. Increasing the number of conductor rods to three or more can suppress the level deviation more effectively than with two conductor rods. However, it should be noted that simply increasing the number of conductor rods may result in a convergence of the level deviation reduction effect.

[0041] <Modification 5> The conductor rods 14a, 14b may be insulated from the antenna base 11. In this case, the conductor rods 14a, 14b are each non-grounded. Therefore, at least the length L in the z direction of each conductor rod 14a, 14b differs from that of a grounded conductor rod in which the conductor rods are electrically connected to the antenna base 11.

[0042] Fig. 13 is a graph showing the relationship between the length in the z direction and the level deviation when the two conductor rods are grounded and ungrounded. Specifically, the graph shows the relationship between the length L in the z direction and the level deviation for each length L when the conductor rods 14a and 14b are grounded type G and ungrounded type UG. Referring to Fig. 13, when the conductor rods 14a and 14b are grounded type G, the level deviation is 12.25 dB when the length L is 6 mm, 6.46 dB when the length L is 11 mm, and 9.16 dB when the length L is 23 mm. In contrast, when the conductor rods 14a and 14b are ungrounded type UG, the level deviation is 12.87 dB when the length L is 6 mm, 11.07 dB when the length L is 11 mm, and 5.39 dB when the length L is 23 mm.

[0043] Therefore, when the conductive rods 14a and 14b are of the grounded type G, the ripple reduction effect can be achieved if the z-direction length L of each conductive rod 14a and 14b is approximately 1 / 4 or more of the wavelength λ of the radio wave at the operating frequency of the antenna 13. On the other hand, when the conductive rods 14a and 14b are of the ungrounded type UG, the ripple reduction effect can be achieved if the z-direction length L of each conductive rod 14a and 14b is approximately 1 / 2 or more of the wavelength λ of the radio wave at the operating frequency of the antenna 13. Furthermore, in the case of the grounded type G, the z-direction length of the conductive rods 14a and 14b can be shorter than in the case of the ungrounded type UG, so the vertical height of the antenna case 12 can be reduced compared to the case of the ungrounded type UG. In other words, ripple can be reduced without compromising the antenna design. Furthermore, in the case of the grounded type G, the conductive rods 14a and 14b can be directly fixed to the antenna base 11, which has the advantage of eliminating the need for separate holding parts for the conductive rods 14a and 14b.

[0044] <Other Modifications> The scatterer is not limited to a conductive conductor rod, but may also be a non-conductive material, or a combination of a conductive material and a non-conductive material. The connecting screws used to connect the antenna case 12 to the antenna base 11, the positioning guides for cables and circuit boards present in the hollow portion of the antenna housing 10, other antenna units packaged in the hollow portion of the antenna housing 10, or metal screws or feed pins used to attach those antenna units to the antenna base 11, can also be used as scatterers. The connecting screws and the antenna base 11 are electrically connected by physical contact or capacitive coupling. This eliminates the need for additional components to achieve ripple reduction in existing antenna devices, resulting in the advantages of miniaturization and cost reduction. Furthermore, the connecting screws used to connect the antenna base 11 to the antenna case 12 are generally arranged symmetrically with respect to the x-z plane of the antenna base 11 from the standpoints of waterproofing and fitting strength, so they can be used as scatterers as they are. The scatterer may be detachably attached to the inner wall of the antenna case 12, or may be integrally formed as a protrusion protruding at a predetermined angle from the inner wall of the antenna case 12, other than the antenna base 11. The antenna 13 may be positioned closer to the geometric center 110 rather than rearward of the antenna base 11. The antenna 13 may be positioned further forward of the geometric center 110 rather than rearward of the antenna base 11.

[0045] [Second Embodiment] A second embodiment of the present invention will be described. In the second embodiment, an example in which the antenna device 1 of the first embodiment is applied to a specific antenna device will be described with reference to Figs. 14 to 16. Fig. 14 is a perspective view of the antenna device 2 of the second embodiment. Fig. 15 is a top view of the antenna device 2 of the second embodiment. Fig. 16 is a side view of the antenna device 2 of the second embodiment. In Figs. 14 to 16, components having the same functions as those of the antenna device 1 of the first embodiment are denoted by the same reference numerals for convenience. Also shown is a structural example in which the antenna case 12 shown in Fig. 1 is removed.

[0046] The antenna device 2 of the second embodiment is a composite antenna device in which the antenna 13 and the satellite signal support unit 33 are packaged in a single antenna housing. The antenna 13 is a V2X collinear antenna that includes a radiating element 131 and a resin support 132 that supports the radiating element 131, and extends in the z direction from the position of the antenna 13 shown in FIG. 1 . The radiating element 131 has a first linear portion that extends linearly in the z direction from a base end that serves as a power feed portion, a loop-shaped portion, a second linear portion that extends linearly again in the z direction from the loop-shaped portion, and a third linear portion that is bent rearward just before the tip of the second linear portion. The support 132 has a framework structure and includes a pair of pillar portions that extend in the z direction relative to the antenna base 11 and multiple connecting portions that connect these pillar portions. The connecting portions have holes or notches formed therein for fixing the radiating element 131.

[0047] The satellite signal processing unit 33 includes a dielectric 331, an electrode 332 mounted on the top surface of the dielectric 331, and a power feed pin (not shown) that electrically connects the electrode 332 to a circuit board on the back side of the dielectric 331. The dielectric 331 is substantially quadrilateral in top view and has a thickness (length L) in the z-direction near the geometric center of the conductive antenna base 11. In this embodiment, the dielectric 331 is ceramic, but other dielectrics with different dielectric constants and hardness, such as Teflon (registered trademark), may also be used. The electrode 332 is a four-feed electrode with, for example, slits formed in a size adjusted for satellite signal reception, and is mounted approximately parallel to the plate-like surface of the antenna base 11. To avoid interference with the antenna 13, the satellite signal processing unit 33 employs a planar antenna that is at least half the wavelength λ of the radio wave of the operating frequency of the antenna 13 and whose height in the z-direction can be reduced so that its thickness in the z-direction does not affect the operation of the antenna 13.

[0048] The antenna base 11 is not approximately elliptical in top view as shown in Figures 1, 6, 7, 9, and 11, but is not rounded in the +x and -x directions. Furthermore, the edges of the antenna base 11 in the +y and -y directions that sandwich the dielectric of the satellite signal compatible unit 33 are bulged outward in a non-streamlined manner relative to the elliptical shape. The antenna device 2 having this structure inevitably has more locations where ripples occur in the directional characteristics than the antenna device 1 of the first embodiment, in which the antenna base 11 is approximately elliptical in top view and no other antenna components are present in the antenna housing. Furthermore, the number of joining screws (one type of joining device) for watertightly joining the antenna case 12 to the antenna base 11 is also greater than that of the antenna device 1 of the first embodiment, which has an approximately elliptical antenna base 11 in top view.

[0049] Therefore, in the antenna device 2 of the second embodiment, in order to reduce ripples, in addition to the two conductor rods 14a and 14b whose length in the z direction is 11 mm or more, metal joining screws for watertightly joining the antenna case 12 to the antenna base 11 are used as scatterers. The joining screws are respectively referred to as conductor rods 14c to 14j. Furthermore, these conductor rods 14c to 14j may be shorter than the conductor rods 14a and 14b. As a result, similar to the first embodiment, it is possible to achieve a greater ripple reduction effect than when these conductor rods 14a to 14j are not used as scatterers.

[0050] A feed pin (not shown) for connecting the electrodes of the satellite signal unit 33 to the circuit board for satellite signals can also be used as a conductor rod. The feed pin is a columnar conductor with a length approximately equal to the thickness of the dielectric base on which the patch electrode is mounted. The length of the feed pin is approximately 10 mm, and it serves as a ground conductor grounded to the antenna base 11 at frequencies in the V2X band. Therefore, it can achieve the same operation and effect as other conductor rods that function as scatterers.

[0051] In the antenna device 2 of the second embodiment, resin mounting bosses capable of adjusting the insertion depth (threading depth) of joining screws (conductor rods 14a to 14j) are provided at corresponding locations on the antenna base 11. The mounting bosses have mounting holes or mounting apertures with threads threaded in the z-direction on their inner walls. The mounting holes are bosses with bottoms, and the mounting apertures are bosses through which joining screws pass. In one aspect, the mounting holes or mounting apertures in the mounting bosses are formed longer than the design value, and the directional characteristics of the antenna 13 can be adjusted in any direction by changing the length of the joining screws, which function as scatterers, or their insertion depth (threading depth). For example, by adjusting the screwing depth of any of the conductor rods 14c to 14j after assembling the antenna device 2, the length in the z-direction functioning as a scatterer can be freely changed. The lengths of the conductor rods 14c to 14j may be within a range that ensures the holding force between the antenna case 12 and the antenna base 11, and may all be the same length, or may be adjustable to different lengths according to the directional characteristics.

[0052] Alternatively, an extra mounting boss may be formed in advance, and if necessary, a metal screw or a screw made of a non-conductive material may be attached to this mounting boss so that it can be removed and the amount of exposure can be adjusted after assembling the antenna device 2. This makes it possible to adjust the amount of ripple reduction and control or fine-tune the directional characteristics of the antenna 13 in any direction.

[0053] [Third Embodiment] A third embodiment of the present invention will be described. In the third embodiment, an example in which the antenna device 1 of the first embodiment is applied to another antenna device will be described with reference to Figs. 17 to 19. Fig. 17 is a perspective view of the antenna device 3 of the third embodiment. Fig. 18 is a top view of the antenna device 3 of the third embodiment. Fig. 19 is a side view of the antenna device 3 of the third embodiment. In Figs. 17 to 19, components having the same functions as those of the antenna device 1 of the first embodiment and the antenna device 2 of the second embodiment are denoted by the same reference numerals for convenience. Also shown is a structural example in which the antenna case 12 shown in Fig. 1 is removed.

[0054] In the antenna device 3 of the third embodiment, a conductive parasitic element 334 is disposed on the upper surface of the electrode 332 of the satellite signal corresponding unit 33 included in the antenna device 2 of the second embodiment. In this embodiment, the parasitic element 334 has a plate-like surface and is supported by a resin support material so as to be substantially parallel to the surface of the plate-like electrode at a predetermined distance. This parasitic element 334 can be made to function as a director for the satellite signal corresponding unit 33. The resonant frequency can also be changed by forming holes, slits, or slots in the parasitic element 334.

[0055] [Fourth Embodiment] A fourth embodiment of the present invention will be described. Fig. 20 is a front perspective view of an antenna device 4 according to the fourth embodiment. Fig. 21 is a top view of the antenna device 4 according to the fourth embodiment. Fig. 22 is a rear perspective view of the antenna device 4 according to the fourth embodiment. Fig. 23 is a left side view of the antenna portion of the antenna device 4 according to the fourth embodiment, specifically, a side view of the antenna 13 as seen from the front left side. In Figs. 20 to 23, for convenience, components having the same functions as those of the antenna devices 1, 2, and 3 described so far are denoted by the same reference numerals. Furthermore, all of these figures show structural examples in which the antenna case 12 shown in Fig. 1 has been removed.

[0056] The antenna device 4 of the fourth embodiment differs from the above-described antenna devices 2 and 3 mainly in the following configuration: (1) The satellite signal response unit 33 is a unit that receives signals for the High Definition Global Navigation Satellite System, and two parasitic elements 334, each made of a conductive plate, are arranged parallel to each other. (2) The attachment position of the base end of the radiating element 131 of the antenna 13 is shifted rearward by the length of the support body 132 in the x direction, the second straight portion 131-2 extending from the loop-shaped portion 131R of the radiating element 131 toward the tip is inclined forward with respect to the first straight portion 131-1, and the angle of the third straight portion 131-3 bending from the second straight portion 131-2 is larger than the angle of the third straight portion 131-3 in the antenna devices 2 and 3. (3) Instead of the two conductor rods 14a and 14b in front of the antenna devices 2 and 3, there is one conductor rod 14m on the central axis of the antenna base 11 forward of the satellite signal corresponding unit 33, a conductor rod 14AL behind the satellite signal corresponding unit 33 and in front of the radiating element 131, and a conductor rod 14BL behind the antenna 13. A metal plate 40 at ground potential is disposed between the front conductor rod 14m and the satellite signal corresponding unit 33. Note that the metal plate 40 may be integral with the metal base portion of the antenna base 11.

[0057] The configuration (1) described above allows for acquisition of position information with an error of one-tenth or less compared to a configuration that receives normal satellite signals, which have a limited number of receivable signals. Furthermore, the configuration (2) described above allows for suppression of a decrease in radiation gain in the horizontal plane. Furthermore, the configuration (3) described above allows for a reduction in radiation gain on the front side of the antenna 13, when an antenna unit that operates at a frequency within the V2X band, such as the satellite signal compatible unit 33, is present in front of the antenna 13, and allows for a stable and high radiation gain on the rear side in the azimuth angle range of 60° to 300°, particularly in the range of 90° to 270°. In other words, a rear-specialized antenna 13 can be realized. The configurations (2) and (3) described above are described in detail below.

[0058] For example, when mounting the antenna devices 2 and 3 on a vehicle roof, the mounting portion of the vehicle roof may be significantly tilted in the fore-and-aft direction depending on the vehicle model. For example, in the case of sedans, the vehicle roof is often tilted from the front to the rear by 10 degrees or more. If the antenna 13, which extends vertically relative to the antenna base 11, is mounted on such a vehicle, the radiation gain of the antenna 13 in the horizontal plane may decrease. On the other hand, if the antenna base 11 is left as is and the antenna 13 is simply tilted in advance in the opposite direction to the tilt of the vehicle roof by the amount of the tilt of the vehicle roof, the plane of polarization will be disrupted, and it will be impossible to suppress the decrease in radiation gain in the horizontal plane parallel to the ground.

[0059] Therefore, in the antenna device 4 of the fourth embodiment, when the mounting portion of the vehicle roof is tilted rearward by θ° with respect to the horizontal plane, a part of the radiating element 131 of the antenna 13, for example, the second straight portion 131-2, is tilted forward by approximately 2θ° with respect to the first straight portion 131-1, and the third straight portion 131-3 is made approximately parallel to the antenna base 11 (the configuration (2) above). In other words, when the antenna device 4 is mounted on such a vehicle roof, the first straight portion 131-1 and the second straight portion 131-2 of the radiating element 131 are made to have a substantially L-shape, each tilted by approximately equal θ° with respect to the horizontal plane. The third straight portion 131-3 has the effect of shortening the height of the radiating element 131 in the z direction and loading a predetermined capacitance on the radiating element 131. The portion inclined from the first straight portion 131-1 to the second straight portion 131-2 and the portion bent from the second straight portion 131-2 to the third straight portion 131-3 may be rounded.

[0060] By shaping the radiating element 131 of the antenna 13 in this way, even if the vehicle roof on which the antenna device 4 is mounted is inclined, the plane of polarization can be corrected to the horizontal direction, thereby suppressing a decrease in radiation gain in the horizontal plane of the antenna 13. Furthermore, by forming a plurality of holes or notches for fixing the radiating element 131 in advance in each of the connecting portions of the support body 132 and selecting the hole or notch for fixing the radiating element 131 according to the vehicle model, it may be possible to change the inclination θ° of the second straight portion 131-2 of the radiating element 131 relative to the first straight portion 131-1 after the antenna device 4 is mounted.

[0061] In the above configuration (3), first, a single conductor rod 14m can increase scattering in the 0° forward direction in the V2X band. Alternatively, a single conductor rod 14m can form a null point near 0° forward in the V2X band. Furthermore, the conductor rod 14AL operates as a reflecting element for the antenna 13 in the V2X band. More specifically, the front of the pair of pillars of the support 132 is relatively thicker than the rear, as shown in FIG. 23 , and its inner surface forms a mounting boss with a threaded hole. The conductor rod 14AL is screwed into the screw hole from the back side of the V2X circuit board, sandwiching the circuit board between them, to join the support 132 to the circuit board. In other words, the conductor rod 14AL also serves as a screw for joining the support 132 to the circuit board. A conductor pattern electrically connected to the power supply of the antenna 13 is formed on the back side of the circuit board, and the conductor rod 14AL is electrically connected to the conductor pattern when the support 132 is joined to the circuit board. The circuit board is fixed to the antenna base 11 by a conductive screw separate from the conductive rod 14AL, so that the conductive pattern and the antenna base 11 are electrically connected and function as a ground conductor.

[0062] The conductor rod 14AL is positioned approximately 12 mm forward of the first straight portion 131-1 of the antenna 13. The distance from the ground conductor is approximately 12 mm, which corresponds to approximately 1 / 4λ (wavelength) in the V2X band. Therefore, the conductor rod 14AL functions as a reflecting element for the antenna 13 in the V2X band. This allows the directional characteristics of the antenna 13 to be oriented in the y direction (vehicle width direction) and at an azimuth angle of 60° to 300° rearward. In the fourth embodiment, the distance of the conductor rod 14AL from the ground conductor is set to approximately 1 / 4λ. However, the azimuth angle range of radiation can be adjusted by setting the distance between 1 / 4λ and 1 / 2λ. Furthermore, even if the conductor rod 14AL is replaced with a non-grounded conductor rod, it can still be used as a reflecting element. In this case, the length of the conductor rod can be set to approximately 1 / 2λ.

[0063] The conductor rod 14BL will now be described. The conductor rod 14BL is disposed behind the support 132, i.e., behind the antenna 13, to reduce ripples in the directional characteristics in the y direction (vehicle width direction) and toward the rear. The shape of the conductor rod 14BL may be substantially conical, but may also be a solid shape of any other shape, such as a square prism, a rod, a cylinder, an elliptical cylinder, an oblong cylinder, a polygonal prism, a headed cylinder, a cylindrical shape, an elliptical cylinder, an oblong cylinder, a polygonal cylinder, an elliptical cone, an oblong cone, a polygonal pyramid, a plane, a spiral, or a zigzag. The length (height) of the conductor rod 14BL in the z direction is approximately 6 mm. The distance from the radiating element 131 in the x direction is approximately 6 mm.

[0064] In the fourth embodiment, as in the first to third embodiments, it is possible to reduce ripple in the directional characteristics by adjusting the length of the conductor rod 14BL and the distance of the conductor rod 14BL from the antenna 13 (radiating element 131). Also, by changing the shape and position of the conductor rod 14BL, it is possible to increase the radiation gain in a desired azimuth angle range, for example, 150° to 210° behind the antenna 13. Furthermore, the conductor rod 14BL can also function as a waveguide element.

[0065] When the conductive rods 14AL and 14BL are not present (for example, when the support 132 is simply fixed with adhesive or the like), the ripple level deviation at 135° to 225° behind the antenna 13 is 3.7 dB. However, when only the conductive rod 14AL is added, the level deviation becomes 2.5 dB, a reduction of 1.2 dB. The length of the conductive rod 14AL in this case was 11 mm. Furthermore, when the conductive rod 14BL is added from this state, the gain on the rear side of the antenna 13 increases and the ripple level deviation is also reduced. The length of the conductive rod 14BL in this case was 8 mm. In this way, by appropriately changing the length of the conductive rod 14BL, it is possible to adjust the radiation gain and level deviation on the rear side of the antenna 13.

[0066] FIG. 24 shows the horizontal plane directivity characteristics of the antenna device 4 of the fourth embodiment, which has two of the above-described conductive rods 14AL and 14BL, and the comparative antenna device 4', which has only the conductive rod 14AL. In the figure, the solid line represents the antenna device 4, and the dashed line represents the comparative antenna device 4'. In the comparative antenna device 4', the radiation gain at 180° behind the antenna 13 is 8.2 dB, while in the antenna device 4, the radiation gain at 180° behind the antenna 13 is 9.9 dB. Therefore, simply by adding the conductive rod 14BL, the radiation gain of the antenna 13 improved by about 1.7 dB. Furthermore, in the comparative antenna device 4', the level deviation from 135° to 225° behind the antenna 13 was 2.5 dB, while the level deviation of the antenna device 4 was 1.3 dB. Therefore, simply by adding the conductive rod 14BL, the level deviation and the ripple in the directivity characteristic were reduced.

[0067] In this example, the distance in the x direction from the center of the z-direction length of the conductor rod 14AL to the radiating element 131 of the antenna 13 is 11.9 mm, and the distance in the x direction from the center of the z-direction length (height) of the conductor rod 14BL to the radiating element 131 of the antenna 13 is 6.2 mm, but these distances may be set arbitrarily and the radiation gain may be adjusted to obtain the desired directional characteristics.

[0068] In the above description, the length and position of the conductor rod 14BL are set to reduce ripple. However, in order to change the directional characteristics afterward, the length and position of the conductor rod 14BL may be set to increase ripple at a certain position.

[0069] The structure of the portion of the antenna case 12 that secures the joining screws (conductor rods 14c to 14j) will now be described in detail. As explained in the second embodiment, the antenna case 12 is provided with mounting bosses (resin) for attaching the joining screws. Ribbed pads 50 are provided around the mounting bosses to sandwich the antenna base 11 and the antenna case 12 together to waterproof the inside of the antenna case 12. Here, the pads 50 are made of resin and have elasticity.

[0070] The rib-like structure of the mounting boss and the pad 50 may affect the scattering behavior of the conductive rods 14i and 14j near the antenna 13. In other words, since the scattering behavior differs from that of the conductive rods 14i and 14j alone, it is desirable to set the length and position of the conductive rods 14i and 14j taking into consideration the influence of these structures. For example, if the presence of the conductive rods 14i and 14j has a large effect on the directional characteristics, the conductive rods 14i and 14j can be positioned closer to the radiating element 131, as in the case of the conductive rod 14AL, so that the scattering effect of the conductive rod 14AL becomes more dominant than that of the conductive rods 14i and 14j, thereby adjusting the directional characteristics.

[0071] In this way, in the fourth embodiment, an example of the antenna device 4 that covers the width direction (y direction) of the vehicle on which it is mounted and the range of 60° to 300° on the rear side has been described, but the ranges of 0° to 60° and 300° to 0° on the front side of the vehicle may be covered by, for example, a separate V2X antenna attached to the windshield of the vehicle. That is, a configuration may be adopted in which the entire periphery of the vehicle is covered by a V2X antenna separate from the antenna 13 of the fourth embodiment.

[0072] [Fifth Embodiment] A fifth embodiment of the present invention will be described. Fig. 25 is a front perspective view of an antenna device 5 according to the fifth embodiment. Fig. 26 is a top view of the antenna device 5 according to the fifth embodiment. Fig. 27 is a side view of the antenna device 5 according to the fifth embodiment, viewed from the front left side. In Figs. 25 to 27, functional components similar to those of the antenna device 4 according to the fourth embodiment are designated by the same reference numerals, and redundant description will be omitted. For example, the satellite signal compatible unit 33 includes two parasitic elements, each of which has a hollowed-out central portion. Furthermore, all of the figures show an example structure in which the antenna case 12 shown in Fig. 1 has been removed.

[0073] The antenna device 5 of the fifth embodiment differs from the antenna device 4 of the fourth embodiment in that an SXM (SiriusXM digital radio) compatible unit 34 is located on the surface of a metal plate 40 in front of the satellite signal compatible unit 33 and behind the conductive rod 14m. The SXM compatible unit 34 includes a base 341 made of ceramic or the like fixed to a substrate, a patch antenna 342 provided on the surface of the base 341 in the z-direction, and a conductive parasitic element 344. The SXM compatible unit 34 is positioned to reduce the effect of scattered waves on signals transmitted and received by the antenna 13. An antenna mounting portion 18 is fixed to the rear side of the antenna base 11, i.e., the side that is pointed toward the vehicle roof when the antenna device 5 is installed. Note that, although the example shown in FIGS. 25 to 27 does not include the conductive rod 14BL of the antenna device 4 of the fourth embodiment, the antenna device 5 may include the conductive rod 14BL.

[0074] [Other Embodiments] In the fourth embodiment, the shape and structure of the antenna case 12 are not described, but the case design including the antenna case 12 may affect the directional characteristics of the antenna 13. For example, Fig. 28 shows an antenna device 6 with a first case design (shark-fin-shaped antenna case 12), and Fig. 29 shows an antenna device 7 with a second case design (rocket-shaped antenna case 12). The antenna structure within the case of these antenna devices 6 and 7 is the same as that of the fourth embodiment. Fig. 30 is a diagram showing the horizontal plane directional characteristics of these antenna devices 6 and 7.

[0075] In this way, differences in case design may cause the adjustment of the radiation gain of the antenna 13 and the ripple level deviation to differ from the design values, but by applying the technology of the fourth embodiment and arranging the conductor rods 14m, 14c to 14i, 14AL, 14BL, etc. in appropriate locations with appropriate sizes, the adjustments can be corrected to match the design values.

[0076] The above describes examples of antenna devices 1 to 7 mounted on vehicles in multiple embodiments, but the present invention can also be implemented as an antenna device for other mobile objects, such as drones and robots, where it is desirable for the antenna housed in the antenna housing to be isotropic.

[0077] In the above-described embodiments, the conductor rods may be fixed or may be configured to be removable. When the conductor rods are configured to be removable, it becomes easy to adjust the directional characteristics to the desired level by attaching and detaching the conductor rods, thereby increasing the degree of freedom in design. Furthermore, when the conductor rods are configured to be removable, there is no need to use a dedicated antenna base, so various antenna bases can be used, further reducing costs and increasing the degree of freedom in design. Furthermore, by using removable conductor rods, it is possible to eliminate the need to place conductor rods in unnecessary positions, thereby reducing costs.

[0078] According to the disclosure of this specification, for example, the following antenna devices are provided. [Aspect 1] The antenna device of Aspect 1 includes an antenna housing having a hollow space therein, an antenna located inside the antenna housing for transmitting and / or receiving radio waves, and a scatterer that scatters the radio waves propagating through the hollow space at a predetermined location in the antenna housing. The scatterer is, for example, a passive component that scatters radio waves in response to the action of external radio waves or the like. According to the above aspect, the scatterer scatters the radio waves propagating through the hollow space in the antenna housing. This reduces ripple in the directional characteristics during transmission or reception. In particular, it is possible to mitigate the effect of the null point, where the ripple is at its minimum value. Furthermore, the directional characteristics can be arbitrarily changed by the scatterer.

[0079] [Aspect 2] In aspect 2, at least one scatterer is present in a location where the ripple in the directional characteristic of the radio wave is smaller than in other locations. Alternatively, there are two or more scatterers, and in the antenna housing, at least one first scatterer is located at the predetermined location, and at least one second scatterer is located in a location where the deviation in the intensity distribution of the radio wave near the predetermined location is relatively small. Alternatively, there are two or more scatterers, and in the antenna housing, at least one first scatterer is located at the predetermined location, and at least one second scatterer is located in a location where a ripple in the directional characteristic occurs. Alternatively, two or more scatterers are present in locations symmetrical with respect to an axis connecting the antenna feed point and the geometric center of the antenna housing. Alternatively, the scatterer is present on the axis connecting the antenna feed point and the geometric center of the antenna housing. According to the above aspect, ripples in the directional characteristic of the antenna are mitigated. As a result, the directional characteristic of the antenna in the antenna housing can be made closer to isotropy.

[0080] [Aspect 3] In aspect 3, the scatterer is made of a non-grounded conductive material. Alternatively, the scatterer is made of a grounded conductive material. Alternatively, the scatterer is made of a non-conductive material. Alternatively, the antenna is an isotropic element extending vertically from a ground plane, and the scatterer is arranged parallel to the antenna with a length of 0.1 to 1 wavelength λ of the operating frequency of the antenna. According to the above aspect, the size and arrangement of the scatterer can be changed depending on the structure of the antenna device. This increases the degree of freedom in designing the antenna device.

[0081] [Aspect 4] Aspect 4 includes an antenna housing having a hollow space therein, an antenna located within the housing for transmitting and / or receiving radio waves, and a scatterer for scattering the radio waves propagating through the hollow space at a predetermined location within the antenna housing. The antenna housing has an antenna base and an antenna case that forms the hollow space on the antenna base. The scatterers are two or more and are located in locations within the antenna base and the antenna case where the strength of the propagating radio waves is relatively low. According to the above aspect, the scatterers scatter the radio waves propagating through the hollow space within the antenna housing. This reduces ripples in the directional characteristics during transmission or reception. Furthermore, the directional characteristics can be arbitrarily changed by the scatterers.

[0082] Furthermore, in the past, for example, in the case of V2V communication, which is one type of V2X, one antenna with a forward and one backward directional characteristic was required, but by using a scatterer, for example, it is possible to increase the strength of radio waves in the forward and backward directions with a single antenna, so that one antenna is sufficient. Furthermore, by using a scatterer, it is possible to change the directional characteristics not only in the forward and backward directions but also in the left and right directions. This allows for the miniaturization and cost reduction of the antenna device.

[0083] [Aspect 5] In aspect 5, the scatterer is detachably attached to the antenna base or the antenna case. Alternatively, the antenna base is formed with a resin mounting boss that allows the insertion amount of the scatterer to be adjusted. Alternatively, a connector for joining the antenna bases also serves as the scatterer. According to the above aspect, the size and arrangement of the scatterer can be changed depending on the structure of the antenna device. This increases the degree of freedom in designing the antenna device.

[0084] [Aspect 6] In Aspect 6, an antenna component other than the antenna is present in the hollow portion, and a connector for connecting the antenna component to the antenna housing also serves as the scatterer. According to the above aspect, when the antenna component is provided in the antenna housing, the connector functions as the scatterer, eliminating the need to provide a separate scatterer.

[0085] [Aspect 7] In aspect 7, the antenna is a V2X antenna, and one of the antenna components is a satellite signal supporting unit. Alternatively, the satellite signal supporting unit has a patch electrode that is lower in height from its mounting location than the antenna. Alternatively, the satellite signal supporting unit is provided with a parasitic element that covers the patch electrode in a non-contact manner. Alternatively, the parasitic element has a wave-guiding function for the patch electrode. According to the above aspect, ripple mitigation is easy even when a V2X antenna and a satellite signal supporting unit are both present in an antenna housing.

[0086] [Aspect 8] In aspect 8, a portion of the radiating element of the antenna is inclined in a predetermined direction, for example, in a direction opposite to the inclination angle when the mounting portion is inclined. The inclination angle of the portion of the radiating element can be approximately twice the inclination angle of the mounting portion. According to the above aspect, it is possible to suppress a decrease in gain in the horizontal plane of the radiating element caused by the inclination of the mounting portion.

[0087] [Aspect 9] In aspect 9, a conductor rod that functions as a reflector is located in front of the antenna, and another conductor rod that functions as a scatterer is located behind the antenna. According to the above aspect, the directional characteristics of the antenna can be changed after the fact. In addition, the level deviation of the ripple can be reduced.

[0088] 1, 2, 3, 4, 5, 6, 7 Antenna device 10 Antenna housing 11 Antenna base 12 Antenna case 13 Antenna 131 Radiating element 132 Support 14, 14a to 14j, 14m, 14AL, 14BL Conductor rod 33 Satellite signal compatible unit 331 Dielectric 332 Electrode 334 Parasitic element 34 SXM compatible unit 341 Base 342 Patch antenna 344 Parasitic element

Claims

1. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with At least one scatterer is present in a region where the ripple of the directional characteristic of the radio wave is smaller than in other regions. Antenna device.

2. The scatterers are two or more, In the antenna housing, at least one first scatterer is located at the predetermined location; At least one second scatterer is located in a portion where the ripple of the directional characteristic is relatively small. The antenna device according to claim 1 .

3. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with The scatterers are two or more, In the antenna housing, at least one first scatterer is located at the predetermined location; At least one second scatterer is located in a region where the deviation of the intensity distribution of the radio wave in the vicinity of the predetermined region is relatively small. Antenna device.

4. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with two or more scatterers are present at locations that are approximately symmetrical with respect to an axis connecting a feed point of the antenna and a geometric center point of the antenna housing; Antenna device.

5. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with the scatterer is present on an axis connecting a feed point of the antenna and a geometric center point of the antenna housing; Antenna device.

6. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with the antenna is a resonant element extending vertically from a ground plane; the scatterer is arranged in parallel with the antenna, with a length of 0.1 to 1 times the wavelength λ of the operating frequency of the antenna; Antenna device.

7. The scatterer is made of a non-grounded conductive material.

7. An antenna device according to claim 1.

8. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with The scatterer is made of a grounded conductive member. Antenna device.

9. An antenna housing having a hollow space therein; an antenna located inside the device and configured to transmit and / or receive radio waves; a scatterer that scatters the radio waves propagating through the hollow portion at a predetermined location of the antenna housing; Equipped with The scatterer is made of a non-conductive material. Antenna device.