1. Field of the Invention
The present disclosure relates to an antenna device to be installed inside a room of a vehicle, and a vehicle antenna in which the antenna device is installed.
2. Description of the Related Art
Usually, an antenna for receiving a radio broadcast or an antenna for receiving a television broadcast is installed in a vehicle. Recently, however, a demand has been growing for installing an antenna for transmitting and receiving vertically polarized radio waves, which have been used for inter-vehicle communication and road-to-vehicle communication in the ITS (Intelligent Transport System: Intelligent Transportation System).
As the antennas for transmitting and receiving the vertically polarized radio waves, there are disclosed a vehicle antenna (Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-44730)) provided with an antenna pattern that is installed to be parallel to a surface of a window glass at a position at an upper part of the interior side of the window glass of the vehicle, to which a rear-view mirror pedestal is to be bonded; and an antenna (Patent Document 2(Japanese Unexamined Patent Publication No. 2009-188912)) formed of a first radiation conductor and a second radiation conductor, where the first radiation conductor is formed on a vehicle interior side surface of the window glass of the vehicle, and the second radiating conductor is bent toward inside the vehicle so as to form a predetermined angle.
For a case of the vehicle antenna disclosed in Patent Document 1, which is related art, however, there is a problem that, since the antenna pattern is formed that is parallel to the glass surface of the vehicle, transmission and reception sensitivity with respect to vertically polarized waves arriving in a direction horizontal to the ground is affected by an installation angle of the window glass of the vehicle.
For a case of the vehicle antenna disclosed in Patent Document 2, there is also a problem that, since the first radiation conductor is formed on the window glass surface of the vehicle, transmission and reception sensitivity with respect to vertically polarized waves arriving in the direction horizontal to the ground is affected by an installation angle of the window glass of the vehicle.
There is a need for an antenna device that can enhance transmission and reception characteristics with respect to vertically polarized waves arriving in the direction horizontal to the ground, without depending on an installation angle of an window glass of a vehicle.
According to an aspect of the present invention, there is provided an antenna device to be installed in a vehicle, wherein the antenna device includes a first element; a second element; and a feeding part, and wherein an angle formed between an electric field plane generated at the first element and the second element and a direction of a long side of the vehicle is within a range of ±45 degrees.
According to another aspect of the present invention, there is provided a vehicle antenna including an antenna device, wherein the antenna device includes a first element; a second element; and a feeding part, and wherein an angle formed between an electric field plane generated at the first element and the second element and a direction of a long side of the vehicle is within a range of ±45 degrees.
According to the present invention, since it does not depend on an installation angle of the window glass of the vehicle, and an antenna conductor is not to be bent toward inside the vehicle, transmission and reception characteristic with respect to vertically polarized waves arriving in a direction horizontal to the ground can be enhanced, compared to an antenna device according to related art.
An embodiment is described below by referring to the drawings. In the drawings for describing the embodiments, when a direction is not particularly described, the direction refers to the direction on the drawing, and the orientation of each drawing corresponds to the direction of the symbols and the numbers.
As illustrated in
By using
The feeding part 13 is a part for coupling the antenna device 10 to a signal processing circuit, which is not depicted. In
As illustrated in
In the first element 11, a first electric current vector 41 is generated that is determined by the electric current distribution flowing from the edge of the first element 11 to the feeding part 13, and an extending direction from the edge of the first element 11 to the feeding part 13. Furthermore, in the second element 12, a second electric current vector 42 is generated that is determined by the electric current distribution flowing from the feeding part 13 to the edge of the second element 12, and an extending direction from the feeding part 13 to the edge of the second element 12.
At this time, as illustrated in
Since an antenna operates in an alternating-current manner, a generated electric current also flows in the reverse direction, namely, from the open end of the second element 12 to the open end of the first element 11. Consequently, the directions of the first electric current vector 41, the second electric current vector 42, and the combined electric current vector 40 vary in the alternating-current manner.
Here, a case is described where an electric current is generated from the open end of the first element 11 to the open end of the second element 12; however, as described above, since the situation is the same for the case where the direction in which the electric current flows is reversed, the angle formed by the combined electric current vector 40 with respect to the ground includes, not only the angle formed upward with respect to the ground, but also the angle formed downward. Furthermore, the combined electric current vector 40 is determined by an electric current vector at a moment at which the strength of the first electric current vector 41 and the second electric current vector 42, which vary in an alternating-current manner, becomes the strongest, namely, at a moment at which the electric current flows through one end to the other end.
As illustrated in
The support member 20 is preferably formed of an insulating material, such as a resin; however, it is not limited to this, as long as the antenna device 10 is formed and functions as the antenna.
The support member 20 may be provided with the side surface part 23 that is formed to face the side surface part 22; and may be provided with a front surface part 21 that is approximately parallel to the surface to which the support member is to be attached.
It suffices if the shape of the support member 20 is such that, when it is viewed from the front of the support member 20, it has side surfaces such that the antenna device 10 can be installed in one of the side surfaces in the left-right direction, such as a rectangular parallelepiped; however, it is not limited to this, as long as it can be installed in the vehicle without difficulty.
The support member 20 including the antenna device 10 may be installed above the window glass 30 of the vehicle; for example, in the vicinity of an inner surface of the window glass 30 of the vehicle, such as a front glass or a rear glass.
Here, the “vicinity of the inner surface of the window glass 30 of the vehicle” specifies a range that does not depart from the effect of the present invention; specifically, it refers to interior material inside the room of the vehicle that is usually within 1 m from the surface of the window glass 30 and a fringe of the window glass 30. Furthermore, for a case where the support member 20 including the antenna device 10 is formed on the inner surface of the window glass 30, the antenna device 10 may be in contact with the window glass 30, or may not be in contact with it.
The support member 20 including the antenna device 10 may preferably be located on the inner surface of the window glass 30 and at the fringe of the window glass 30, so that reception characteristics and transmission characteristics can be enhanced with respect to vertically polarized waves arriving in the direction horizontal to the ground. Furthermore, it is preferable because the antenna device is not formed to spread on the surface of the window glass 30, and the appearance and a visual field of a passenger are not damaged.
For a case where the support member 20 including the antenna device 10 is formed within an inner surface of a windshield of the vehicle, various types of in-vehicle sensors, such as a rain sensor, in-vehicle cameras, and so forth may be arranged inside the support member 20 or in the vicinity of the support member 20. Furthermore, the support member 20 may be provided inside a bracket for storing various types of in-vehicle sensors, in-vehicle cameras, and so forth. Furthermore, the support member 20 may be an attachment base of a rear-view mirror.
The support member 20 may include a plurality of antenna devices 10. Furthermore, the antenna devices 10 may be formed not only at the side surface part 22, but also at the side surface part 23. Furthermore, a plurality of support members 20 respectively including the antenna devices 10 may be formed in the vehicle.
For a case where the antenna devices 10 are separated from each other and are arranged in the vehicle width direction, it can operate as a diversity antenna exhibiting favorable transmission and reception characteristics with respect to vertically polarized waves arriving from any of the right and left directions relative to the traveling direction of the vehicle. Furthermore, by providing the plurality of antenna devices 10, it may be operated as a MIMO (Multiple Input-Multiple Output) antenna.
In the antenna device 10 illustrated in
In
As illustrated in
When the first element 14 is the wide conductor, at least a part of an edge side of the wide conductor is preferably formed along an edge side of the side surface part 22 on which the second element 12 is formed. Furthermore, when at least a part of the first element 14 is the wide conductor and is formed along the edge side of the side surface part 22 on which the second element 12 is formed, and when the first element 14 is a ground conductor, power can be fed to the antenna device 10 with a more simple configuration.
As illustrated in
Accordingly, as illustrated in
For a case where the antenna device 10 is installed in the support member 20, if the direction of the combined electric current vector 40 generated in the antenna device 10 is an angle within a range from 90 degrees ±45 degrees with respect to the ground, transmission and reception characteristics for the vertically polarized waves arriving in the direction horizontal to the ground are enhanced, so that the transmission and reception characteristics for the vertically polarized waves arriving in the direction horizontal to the ground can be enhanced, regardless of shifts in the position and the angle for attaching the antenna device 10, and positional robustness can be enhanced. Note that the high positional robustness implies that, even if the arranged positions and so forth of the first element 11 and the second element 12 are shifted, a small effect is caused on the operation and the directivity of the antenna device 10. Furthermore, since the degree of freedom on determining the arranged positions of the first element 11 and the second element 12 is high, it is advantageous in a point that the installation position, the attachment angle of the antenna device 10, and so forth can be freely designed.
When at least a part of the first element 14 is the wide conductor, wide-band characteristics of the antenna device 10 can be achieved.
The antenna device 10A includes the second element 12 having an inverted F shape. The inverted F shaped second element 12 includes a feed element 81; and a radiating element 82 connected to the feed element 81 at a connecting point 101. The feed element 81 contacts the radiating element 82 to feed power. The feed element 81 is, for example, a linear element including one end coupled to the feeding part 13; and the other end connected to the radiating element 82 at the connecting point 101. The radiating element 82 is, for example, an L-shaped element including one edge 102 connected to the first element 14 to be used as the ground conductor; and the other edge 103 that is at the opposite side of the one edge 102.
The combined electric current vector generated in the antenna device 10A is determined by a first electric current 91 from the end portion 15 of the first element 14 toward the edge 102; a second electric current 92 from the feeding part 13 toward the connecting point 101; and a third electric current 93 from the edge 102 toward the edge 103.
The second element 12 includes a feed element 83; and a radiating element 84. The feed element 83 feeds power to the radiating element 84 in a contactless manner. The feed element 83 is, for example, an L-shaped element including one end coupled to the feeding part 13; and an open end 109 at the side opposite to the one end. The feed element 83 is provided with a part that extends parallel to the radiating element 84 while being separated by a distance with which power can be fed to the radiating element 84 in a contactless manner. The radiating element 84 is, for example, an L-shaped element including one edge 104 connected to the first element 14, which is used as the ground conductor; and the other edge 105 at the side opposite to the one edge 104.
The combined electric current vector generated in the antenna device 10B is determined by a first electric current 95 from the end portion 15 of the first element 14 toward the edge 104; a second electric current 94 from the feeding part 13 toward the open end 109; and a third electric current 96 from the edge 104 toward the edge 105.
The second element 12 includes a feed element 85; and a radiating element 86. The feed element 85 feeds power to the radiating element 86 in a contactless manner. The feed element 85 is, for example, an L-shaped element including one end coupled to the feeding part 13; and an open end 106 at the side opposite to the one end. The feed element 85 is provided with a part that extends parallel to the radiating element 86 while being separated by a distance with which power can be fed to the radiating element 86 in a contactless manner. The radiating element 86 is, for example, a U-shaped element including a first open end 107 that is far from the open end 106; and second open end 108 that is close to the open end 106. The second open end 108 is the edge at the side at which it is electrically coupled to the feed element 85.
The combined electric current vector generated in the antenna device 10C is determined by a first electric current 97 from the end portion 15 of the first element 14 toward the open end 106 of the feed element 85; and a second electric current 98 from the second open end 108 toward the first open end 107.
Furthermore, when, in
For example,
The feeding part 13 is formed on the short edge 14a. The conductor portion 12a is an L-shaped element whose one end is coupled to the feeding part 13; and is formed parallel to the XY plane. The conductor portion 12b is a linear element connected to the other end of the conductor portion 12a; and is formed parallel to the ZX plane.
The conductor portion 12a is arranged along the short edge 14a; and the conductor portion 12b is arranged along the long edge 14b. Consequently, an electric current that flows in the first element 14, which is the ground conductor, from the feeding part 13 flows to correspond to an electric current that flows in the second element 12, so that it flows along the long edge 14b after flowing along the short edge 14a. As a result, an electric current path 16 in the diagonal direction of the first element 14, which is the ground conductor, is achieved, so that various electric current path lengths toward the diagonal direction can be obtained, and broad-band characteristics of the antenna device is developed.
In contrast,
For a case of
As illustrated in
By using
The feeding part 53 is a part for coupling the antenna device 50 to a signal processing circuit, which is not depicted. In
As illustrated in
In the element 54, a first electric current vector 61 is generated that is determined by the electric current distribution flowing from the edge of the element 54 to the part connected to the element 55; and an extending direction from the edge of the element 54 to the part connected to the element 55.
In the part formed of the element 55, the feeding part 53, and the element 56, a second electric current vector 62 is generated that is determined by the electric current distribution flowing, to the part at which the element 56 and the element 57 are connected, from the part at which the element 54 and the element 55 are connected; and an extending direction, to the part at which the element 56 and the element 57 are connected, from the part at which the element 54 and the element 55 are connected.
In the element 57, a third electric current vector 63 is generated that is determined by the electric current distribution flowing, to the open end of the element 57, from the part at which the element 56 and the element 57 are connected; and an extending direction, to the open end of the element 57, from the part at which the element 56 and the element 57 are connected.
When the element 54 and the element 57 are arranged in parallel, the first electric current vector 61 and the third electric current vector 63 are vectors having opposite directions, as illustrated in
As illustrated in
Note that, in
As described in the first embodiment and the second embodiment, when the antenna device according to the embodiment is to be attached to a vehicle, it is not necessary to form the first element and the second element on the surface of the window glass of the vehicle, so that the transmission and reception characteristics of the vertically polarized waves arriving in the direction horizontal to the ground do not depend on the installation angle of the window glass of the vehicle, and the transmission and reception characteristics of the vertically polarized waves arriving in the direction horizontal to the ground can be enhanced.
Furthermore, for the antenna device according to the embodiment, as in Patent Document 2, it is not necessary to bend the first element or the second element toward the vehicle interior, so that it can be attached to the vehicle with a simple method.
The preferred embodiments of the present invention are described above; however, the present invention is not limited to the above-described embodiments, and various modifications, improvements, and substitutions can be added to the above-described embodiments without departing from the scope of the present invention.
The sizes of the elements of the antenna device 50 illustrated in
Table 1 and
As shown in Table 1 and
Namely, even if the direction of the combined electric current vector 60 generated in the antenna device 50 is tilted with respect to the ground, not only in the +Y axis direction and the −Y axis direction, but also in the +X axis direction and in the −X axis direction, if the tilt angle is less than or equal to 45 degrees, the gain decreases only by 3.00 dB at most.
From the above, it can be seen that if the direction of the combined electric current vector 60 generated in the antenna device 50 is an angle within a range of 90 degrees ±45 degrees, favorable transmission and reception characteristics can be obtained with respect to vertically polarized waves arriving in the direction horizontal to the ground.
Number | Date | Country | Kind |
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2014-204635 | Oct 2014 | JP | national |
The present application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2015/077971 filed on Oct. 1, 2015 and designating the U.S., which claims priority of Japanese Patent Application No. 2014-204635 filed on Oct. 3, 2014. The entire contents of the foregoing applications are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2015/077971 | Oct 2015 | US |
Child | 15458629 | US |