The present application is based on PCT filing PCT/JP2019/039775, filed Oct. 9, 2019, which claims priority to JP 2018-191581, filed Oct. 10, 2018, the entire contents of each are incorporated herein by reference.
The present invention relates to an antenna, an antenna device, and an antenna device for vehicle.
As an antenna having broadband characteristics, there is a self-similar antenna having a self-similar shape. For example, a bow-tie antenna that is one of self-similar antennas is known as a broadband antenna that stably operates in a wide frequency band from about 600 MHz to 6 GHz.
Patent Literature 1 discloses an antenna device using the bow-tie antenna.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-43838
One of characteristics of the bow-tie antenna is non-directionality. Because of this, a bow-tie antenna can be one option at the time when an antenna having non-directionality and broadband characteristics is designed. However, when an antenna that has the broadband characteristics is to be designed while it is required to improve a gain in a desired direction, it is difficult to realize the antenna by simply applying a technology of a conventional self-similar antenna including a conventional bow-tie antenna, as it is.
An object of the invention is to provide a technology for realizing a broadband antenna, which can improve the gain in the desired direction.
According to a first aspect of the present invention, there is provided an antenna comprising:
a radiating element arranged in a standing state relative to an end portion connected to a feeding portion, and having an expanded shape in a predetermined expansion direction,
wherein the radiating element has a first radiating element portion and a second radiating element portion being plane-symmetric to each other across a predetermined virtual symmetric plane along the expansion direction, thereby forms the expanded shape, and has a self-similar shape with respect to the end portion.
According to the first aspect, the antenna can be structured such that the shape of the radiating element is a shape that expands in the predetermined expansion direction and is the self-similar shape with respect to the end portion that is connected to the feeding portion, and the radiating element is arranged in a standing state relative to the end portion. The antenna of the present aspect can increase the gain in the expansion direction. Accordingly, a broadband antenna can be realized that can control the directionality of the antenna by the orientation of the expansion direction, and improves the gain in the desired direction.
According to a second aspect of the present invention, in the antenna according to the first aspect, an opening degree of the expansion formed by the first radiating element portion and the second radiating element portion is 20 degrees or larger and 160 degrees or smaller.
According to the second aspect, the opening degree of the radiating element in the expansion direction according to the expanded shape can be controlled to 20 degrees or larger and 160 degrees or smaller.
According to a third aspect of the present invention, in the antenna according to the first or second aspect, the first radiating element portion and the second radiating element portion are integrally structured via a predetermined folded portion located on the virtual symmetric plane.
According to the third aspect, the antenna can be formed into a structure in which the first radiating element portion and the second radiating element portion that are integrally structured are folded at the folded portion, and the radiating element can be expanded at a predetermined opening degree.
According to a fourth aspect of the present invention, in the antenna according to the third aspect, the expanded shape is a V shape folded at the folded portion, when the first radiating element portion and the second radiating element portion are viewed from above.
According to the fourth aspect, the expanded shape can be the V shape that is folded at the folded portion when the first radiating element portion and the second radiating element portion are viewed from above.
According to a fifth aspect of the present invention, in the antenna according to the third or fourth aspect, the folded portion has a linear folding line, and a length of the radiating element in a direction of the folding line in a projection view onto the virtual symmetric plane is a length of ⅛ or longer of a wavelength of a radio wave at a lower limit of antenna band frequencies.
According to the fifth aspect, it is possible to set the length in the direction along the folding line of the radiating element in the projection view of the radiating element onto the virtual symmetric plane, at ⅛ or longer of the wavelength.
According to a sixth aspect of the present invention, in the antenna according to the first or second aspect, the first radiating element portion and the second radiating element portion are integrally structured without a part of a predetermined virtual folded portion located on the virtual symmetric plane.
According to the sixth aspect, the first radiating element portion and the second radiating element portion can be integrally structured so as to be folded without including a part of the virtual folded portion, and accordingly, the radiating element can be expanded at a predetermined opening degree.
According to a seventh aspect of the present invention, in the antenna according to the sixth aspect, the expanded shape is a V shape starting from the end portion as a base point, when the first radiating element portion and the second radiating element portion are viewed from above and are projected toward the end portion side.
According to the seventh aspect, the expanded shape can be set at a V shape starting from the end portion as the base point, when the first radiating element portion and the second radiating element portion are viewed from above.
According to an eighth aspect of the invention, in the antenna according to the sixth or seventh aspect, the virtual folded portion has a virtual linear folding line, and a length of the radiating element in a direction of the virtual folding line in a projection view onto the virtual symmetric plane is a length of ⅛ or longer of a wavelength of a radio wave at a lower limit of antenna band frequencies.
According to the eighth aspect, it is possible to set the length in the direction along the virtual folding line of the radiating element in the projection view of the radiating element onto the virtual symmetric plane, at ⅛ or longer of the wavelength.
According to a ninth aspect of the invention, in the antenna according to the fifth or eighth aspect, the lower limit of the antenna band frequencies is 1 GHz or higher.
According to the ninth aspect, the antenna band frequency can be set at 1 GHz or higher.
According to a tenth aspect of the present invention, there is provided an antenna device comprising a plurality of antennas according to any one of the first to ninth aspects.
According to the tenth aspect, it is possible to realize an antenna device including a plurality of antennas according to any one of the first to ninth aspects.
According to an eleventh aspect of the present invention, there is provided an antenna device comprising a plurality of antennas according to any one of the first to ninth aspects, so as to face the expansion directions of the antennas toward different directions from each other.
According to the eleventh aspect, the antenna device can be structured in which the plurality of antennas according to any one of the first to ninth aspects are arranged such that the expansion directions thereof are faced toward different directions. Accordingly, each antenna can increase a gain of its expansion direction, and accordingly, for example, by adjusting the number of antennas or individual expansion directions so that the antennas cover all azimuth directions on a predetermined plane, it becomes possible to realize an antenna device having characteristics of high gain and non-directionality in a broad band.
According to a twelfth aspect of the present invention, there is provided an antenna device for vehicle comprising: the antenna according to any one of the first to ninth aspects; another antenna for radio receiving having an antenna band frequency lower than that of the antenna; and a case for accommodating the antenna and the other antenna.
According to the twelfth aspect, it is possible to realize the antenna device for vehicle that accommodates an antenna having a similar effect to that of any one of the first to ninth aspects, and another antenna for radio receiving, of which the antenna band frequency is lower than that of the antenna, in the case.
According to a thirteenth aspect of the present invention, there is provided an antenna comprising:
a radiating element arranged in a standing state relative to an end portion connected to a feeding portion, and having an expanded shape in a predetermined expansion direction,
According to the thirteenth aspect, an antenna can be structured such that the shape of the radiating element is a shape expanding in a predetermined expansion direction, an angle formed by the end portion and the first radiating element portion is set at an acute angle, an angle formed by the end portion and the second radiating element portion is set at an acute angle, and the radiating element is arranged in a standing state relative to the end portion. The antenna of the present aspect can increase the gain in the expansion direction. Accordingly, the antenna can control its directionality by the orientation of the expansion direction, and it becomes possible to realize a broadband antenna that improves a gain in a desired direction.
One example of preferred embodiments of the invention will be described below with reference to the drawings. Note that the invention is not limited by the embodiments that will be described below, and modes to which the invention can be applied are not also limited by the following embodiments. In addition, in the description of the drawings, the same portion is denoted by the same reference numeral.
Firstly, in the present embodiment, the direction is defined in the following way. Specifically, the antenna device for vehicle 1 of the present embodiment is used by being mounted on vehicles such as passenger automobiles, and the directions of front-rear, left-right and up-down of the device are defined to be the same as the directions of front-rear, left-right and up-down of vehicles at the time when the device is mounted on the vehicles. In addition, the front-rear direction is defined as a Y-axis direction, the left-right direction is defined as an X-axis direction, and the up-down direction is defined as a Z-axis direction. Reference directions that indicate directions parallel to the respective axial directions are added to the respective figures so that the directions of the three orthogonal axes can be easily understood. The intersection of the reference directions illustrated in each figure does not mean the coordinate origin. The added coordinate illustrates only reference directions. In addition, an appearance of the antenna device for vehicle 1 of the present embodiment is designed such that the front is tapered off and the width between right and left sides gradually decreases toward the upper side from the face attached on the vehicle, which can accordingly facilitate understanding the direction for the feature of the design.
More specifically, the antenna case 11 has a shape protruding upward at the central portion. In other words, the antenna case 11 has a shark fin shape. Then, the protruding portion above the internal space has a capacitance loading element 23 of the radio antenna 20 arranged in its inside, and has a helical element 21 arranged below the capacitance loading element 23. In addition, the internal space has two antennas 100-1 and 100-2 of the antenna device 10 arranged in a rear side of the bottom, and the internal space has the satellite radio antenna 30 and the GNSS antenna 40 arranged in a front side of the bottom. Length of the antennas 100-1 and 100-2 from the antenna base 13 to the highest position toward the upside, which are the overall height of the antennas 100-1 and 100-2 that are arranged in the antenna device for vehicle 1, are each lower than the overall height of the radio antenna 20. It can also be said that the antennas 100-1 and 100-2 are arranged at positions lower than the radio antenna 20. In addition, the antennas 100-1 and 100-2 are arranged at positions behind the radio antenna 20.
The radio antenna 20 is, for example, a radio receiving antenna for receiving broadcast waves of AM radio broadcasting and FM radio broadcasting. The radio antenna 20 includes a helical element 21 in which a conductor is spirally wound and a capacitance loading element 23 for adding a ground capacitance to the helical element 21, resonates with an FM wave band by the capacitance loading element 23 and the helical element 21, and receives an AM wave band by the capacitance loading element 23. The antenna band frequencies of the radio antenna 20 are lower than the antenna band frequencies of the antenna device 10. Accordingly, it can be said that interference is unlikely to occur between the antenna 100 and the radio antenna 20 (another antenna from the antenna 100), in view of the arrangement position and the frequency band as well.
The satellite radio antenna 30 is an antenna for receiving broadcast waves of satellite radio broadcasting such as Sirius (Sirius) XM radio. For example, as is illustrated in
The GNSS antenna 40 is an antenna for receiving satellite signals that are transmitted from a satellite for positioning such as a GPS satellite.
Next, the antenna 100 will be described.
As is illustrated in
The ground plate 110 has an insertion hole 111 that penetrates vertically (in the Z-axis direction). The feeding line is inserted through the insertion hole 111. The end portion 135 of the radiating element 130 that is directed toward the ground plate 110 is connected to the feeding line 150 that serves as a feeding portion, at a position directly above the insertion hole 111. When the feeding line 150 is formed of a coaxial cable, the inner conductor 151 of the coaxial cable is connected to the end portion 135, and the outer conductor is connected to the ground plate 110.
The radiating element 130 has a self-similar shape with respect to the end portion 135. When the opening degree δ is 180 degrees as is illustrated in
Here, fundamental characteristics of the antenna 100, particularly characteristics originating in the self-similar shape will be described. For ease of understanding, a bow-tie antenna that is well known as an antenna having the self-similar shape will be described as an example. First of all, as a premise, when the antenna size and the frequency keep an inversely proportional relationship, the electrical characteristics of the antenna show the same characteristics in principle even if the antenna size or the frequency changes. For example, when the current distribution in a monopole antenna behaves in a resonating way, the antenna size (height) L and the frequency f can be expressed by the relational expression (1) illustrated in
Subsequently, as is illustrated in
The antenna size that can be actually produced is limited, and accordingly, a limited range of the self-similar shape results in being cut out and used. For example, as is illustrated by a broken line in
In addition, in actual design, there is a case where the shape of the radiating element is deformed from the isosceles triangle, for adjustment of impedance, or the like. For example, the isosceles triangle shape can be changed to a semi-elliptical shape such as the radiating element 130 of the antenna 100 of the present embodiment. In this case as well, it is possible to utilize the constant electrical characteristics that are obtained by the self-similar shape.
The antenna 100 according to the present embodiment includes a ground plate 110 and one radiating element 130 having a self-similar shape, in place of two radiating elements that are arranged so as to face each other so that the apexes butt against each other as in a bow-tie antenna. Then, the antenna 100 is structured by arranging the radiating element 130 in such a state that the end portion 135 that serves as a reference of the self-similar shape stands toward the ground plate 110. Due to this structure, the antenna 100 of the present embodiment can spuriously obtain an operational effect substantially similar to that of a bow-tie antenna. Although the radiating element 130 is one, such an operational effect as if another radiating element is virtually arranged on the opposite side is obtained due to the ground plate 110.
The description shall return to
Then, in the radiating element 130, an opening degree δ of expansion of the radiating element 130 (an angle formed by the first radiating element portion 131 and the second radiating element portion 133) is set by a folding angle of the folded portion 137.
For example, as is illustrated in
Specifically, when the opening degree δ is 180 degrees (when the folding angle θ is 0 degree) in 6.0 GHz, both gains in the azimuth direction of the Y-axis positive direction (the forward direction, a direction at which the azimuth angle is 180 degrees) and of the Y-axis negative direction (the backward direction, a direction at which the azimuth angle is 0 degree) appear equally high compared to those in the direction in the X-axis (the left-right direction); and show the directionality of a limited azimuth angle range of about 60 degrees (in total of an azimuth angle of 0 degree to an azimuth angle of 30 degrees and an azimuth angle of 330 degrees to an azimuth angle of 360 degrees, in the case of the backward direction) as the azimuth angle range, in each of the forward direction and the backward direction. On the other hand, when the opening degree δ is set to be smaller than 180 degrees (the folding angle θ is set to be larger than 0 degree), a higher gain than the gain at the time when the opening degree δ is 180 degrees (when the folding angle θ is 0 degree) appears in the azimuth direction of the backward direction (Y-axis negative direction) that is the expansion direction. In addition, as the opening degree δ is decreased (as the folding angle θ is increased), an azimuth angle range in which a high gain appears gradually expands from the azimuth direction in the backward direction (Y-axis negative direction) that is the expansion direction, to the azimuth direction close to the left-right direction. On the other hand, the gain in the forward direction (Y-axis positive direction) opposite to the expansion direction decreases as the opening degree δ is decreased (as the folding angle θ is increased). As described above, the antenna 100 of the present embodiment shows such operational effects that as the frequency is increased, the directionality in the expansion direction appears and the difference in the directionality according to the opening degree δ is exhibited, and that as the opening degree δ is decreased (the folding angle θ is increased), the azimuth angle range in which a high gain is obtained gradually expands around the azimuth direction of the expansion direction.
In a case where the antenna band frequencies of the antenna 100 include 5 to 6 GHz, a high gain is obtained on the expansion direction side when the opening degree δ is set in a range of one degree or more and 179 degrees or smaller, but it can be said that preferably by setting the opening degree δ in a range of 20 degrees or larger and 160 degrees or smaller, an azimuth angle range in which a high gain can be obtained can be obtained on the expansion direction side including the azimuth direction of the expansion direction. At this time, when the lower limit of the antenna band frequencies is determined to be 1 GHz, even in a case where the usable frequency is 1 GHz, the gains become a high state in all azimuth directions as is estimated from
However, in the case where the antenna 100 singly uses frequencies exceeding 4 GHz, a high gain can be obtained in the expansion direction by setting the opening degree δ in a range of 20 degrees or larger and 160 degrees or smaller, but, for example, the gain in the direction opposite to the expansion direction becomes low. For this reason, it is possible to realize a broadband antenna that has a high gain as a whole and is non-directional or nearly non-directional, by arranging a plurality of antennas so that the expansion directions are faced toward different orientations, on the basis of the characteristics exhibited by a single antenna 100. For example, in addition to the antenna 100 illustrated in
As described with reference to
In order that the antenna device for vehicle 1 is miniaturized and the antenna device for vehicle 1 accommodates a lot of antennas therein, it is desirable that the size of the antenna 100 is as small as possible, but a certain size is required in order that the antenna 100 obtains desired antenna characteristics. Then, in the antenna 100 of the present embodiment, the height of the radiating element 130 is set to be ⅛ or higher of a wavelength of the radio wave at a lower limit of the antenna band frequencies. The height of the radiating element 130 is defined in the following way. The height of the radiating element 130 is defined as a length of the radiating element 130 along a direction of the folding line of the folded portion 137 in the case where the radiating element 130 is projected onto the virtual symmetric plane A1 and viewed. The radiating element 130 has such a shape as to be folded at the folded portion 137. In the case of an antenna 100, in which the radiating element 130 is not folded and the opening degree δ is set at 180 degrees, has a shape illustrated in
In the case of the antenna 100 that is illustrated in
In
As described above, the antenna 100 of the present embodiment can increase the gain in the expansion direction. Accordingly, the directionality of the antenna 100 can be controlled by an orientation of the radiating element 130 that is arranged on the ground plate 110 (toward which orientation the expansion direction is arranged), and it is possible to realize a broadband antenna of which the gain in a desired direction is improved.
In addition, an antenna device 10 that includes a plurality of (for example, two) antennas 100 can increase the gains in the expansion directions by the respective antennas 100. Accordingly, by adjusting the number of antennas 100, each of the expansion directions thereof, and the opening degrees δ thereof so as to cover all azimuth directions, it is possible to realize an antenna device having a high gain and the non-directionality (or characteristics close to non-directionality) in a broad band.
In addition, each of the antennas 100 constituting the antenna device 10 is arranged at a position lower than the radio antenna 20 that is another antenna. In addition, the antenna band frequencies of the other antenna (in this case, the radio antenna 20) are lower than the antenna band frequencies (1 GHz or higher) of the antenna 100. Accordingly, it can be said that the antenna device 10 has a structure in which interference from another antenna (in this case, the radio antenna 20) with respect to the antenna 100 resists occurring.
The height of the radiating element 130 is ⅛ or higher of the wavelength. Accordingly, when the antenna band frequencies are 1 GHz or higher, the height can be particularly reduced, and the degree of freedom of arrangement in the antenna device for vehicle 1 increases.
One example of the embodiment has been described above. The mode to which the invention can be applied is not limited to the above embodiment; and addition, omission and modification of constituent elements can be appropriately made. For example, the invention can be applied to such examples of modification that the above embodiment is modified in the following ways.
For example, in the above embodiment, the radiating element 130 has been exemplified that has a semi-elliptical shape in a state where the opening degree δ is 180 degrees, but the shape of the radiating element is not limited thereto, and can be an isosceles triangle shape or shapes in which those designs are appropriately changed. It should be noted that also in this case, the angle formed by the end portion and the first radiating element portion is an acute angle, and that the angle formed by the end portion and the second radiating element portion is an acute angle. In addition, the angle formed by the end portion and the first radiating element portion is substantially the same as the angle formed by the end portion and the second radiating element portion.
In addition, the shape of the radiating element can also be such a shape as is illustrated in
In the above embodiment, as described with reference to
In addition, in the radiating element 130b, a linear shape portion along the center line on the virtual symmetric plane A2 is defined as a virtual folded portion 137b. The virtual folded portion 137b is a portion of a linear shape at which respective portions obtained by extending the first radiating element portion 131b and the second radiating element portion 133b toward the virtual symmetric plane A2 side intersect with the virtual symmetric plane A2. In other words, the first radiating element portion 131b and the second radiating element portion 133b are integrally structured without including a part of the predetermined virtual folded portion 137b that is located on the virtual symmetric plane A2. Note that, in the radiating element 130b, an angle formed by the end portion 135 and the first radiating element portion 131b is an acute angle, and an angle formed by the end portion 135 and the second radiating element portion 133b is an acute angle. The end portion 135 is arranged on the ground plate 110. For this reason, the angle formed by the end portion 135 and the first radiating element portion 131b corresponds to an angle formed by an outer portion of the first radiating element portion 131b that extends from the end portion 135 and the ground plate 110. Similarly, the angle formed by the end portion 135 and the second radiating element portion 133b corresponds to an angle formed by an outer portion of the second radiating element portion 132b that extends from the end portion 135 and the ground plate 110. Note that the angle formed by the end portion 135 and the first radiating element portion 131b is substantially the same as the angle formed by the end portion 135 and the second radiating element portion 133b.
If the opening degree δ between the first radiating element portion 131b and the second radiating element portion 133b is set at 180 degrees as in the radiating element 100 of
In the antenna 100b having a shape in which a part thereof is cut out in this way, when the frequency is increased, a difference in directionality for each opening degree δ (folding angle θ) appears similarly to the case illustrated in
More specifically,
For example, as is illustrated in
In addition, it is also possible to structure an antenna device including a plurality of antennas 100b in the present example of modification. For example, as illustrated in
The electrical characteristics of the antenna device 10b will be specifically described below with reference to
Note that
In addition, in the antenna device 10b, the two antennas 100b-1 and 100b-2 may not share a ground plate 110, and a ground plate may be disposed for each antenna. Similarly, in the structure of the above embodiment, the two antennas 100-1 and 100-2 in the antenna device 10 do not share the ground plate 110, but may be disposed on different ground plates (specifically, ground wiring of a substrate, a metallic base, a roof of a vehicle, or the like), respectively.
In addition, in the above embodiment, the antenna device 10 including two antennas 100 has been exemplified, but the number of antennas 100 constituting the antenna device 10 is not limited to two, and the antenna device 10 can also be structured so as to include three or more antennas 100. For example, the number of antennas 100 may be four, and expansion directions of the radiating elements 130 may be arranged so as to be faced toward four directions of forward, backward, leftward and rightward directions, respectively.
In addition, the opening degree δ of each of the plurality of antennas 100 included in the antenna device 10 does not need to be the same with each other, and the angles may be different. As for the height as well, the heights of the antennas 100 may be set at different heights by adjusting each of the heights, so as to improve the gain in a frequency band to be used or a plurality of frequency bands, because the higher is the height, the higher is the gain at a low frequency.
In addition, in the above embodiment, in the case where the plurality of antennas 100 are arranged, the radiating elements 130 are determined to be arranged such that the expansion directions are faced toward different directions. On the other hand, the radiating elements 130 may be arranged such that the expansion directions are faced toward the same direction. Thereby, it becomes possible to increase the gain in a direction in which the radiating element 130 faces. In addition, in this case, the opening degree δ of each of the radiating elements 130 may be changed.
In the antenna device for vehicle 1 in the above embodiment, the plurality of antennas 100 have been described so as to be arranged behind the radio antenna 20, as illustrated in
In addition, when one or more antennas 100 are arranged in front of or behind the radio antenna 20 in the antenna device for vehicle 1, at least a part of region of the one or more antennas 100 may be arranged on a substantially center line between the front and rear directions of the capacitance loading element 23. In addition, when the plurality of antennas 100 are arranged in such a positional relationship interposing the radio antenna from the front and rear directions in the antenna device for vehicle 1, at least a part of region of the one or more antennas 100 may be arranged on a substantially center line between the front and rear directions of the capacitance loading element 23.
In addition, the height of the antenna 100 can be designed to be lower for operation in a higher frequency band. As a result, it becomes possible to enhance the degree of freedom in design of the antenna 100.
In addition, in the above embodiment, the antenna 100 has been described so as to be accommodated in the antenna case 11, but the antenna 100 may be accommodated in a housing other than the antenna case 11. In other words, the antenna 100 may be accommodated in a housing other than the antenna case 11 having the shark fin shape. In addition, in this case, the shape of the housing can be arbitrarily changed.
In addition, in the above embodiment, the antenna device for vehicle that is mounted on a vehicle has been exemplified, but the invention is not limited to the above embodiment. For example, the invention can also be similarly applied to an antenna device mounted on an aircraft, a ship or the like, to an antenna device that is used in a base station of wireless communication, and to the like.
Number | Date | Country | Kind |
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JP2018-191581 | Oct 2018 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2019/039775 | 10/9/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2020/075744 | 4/16/2020 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5872546 | Ihara | Feb 1999 | A |
8217850 | Jennings et al. | Jul 2012 | B1 |
Number | Date | Country |
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1 249 893 | Oct 2002 | EP |
2002-43838 | Feb 2002 | JP |
2002-164731 | Jun 2002 | JP |
2006-121643 | May 2006 | JP |
2008-228165 | Sep 2008 | JP |
Entry |
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Extended European Search Report dated May 11, 2022 in corresponding European Application 19871891.8, 14 pp. |
Office Action dated Oct. 11, 2022, in corresponding Japanese patent Application No. 2020-551188, 14 pages. |
Number | Date | Country | |
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20210328332 A1 | Oct 2021 | US |