Antenna Device

Abstract

To provide an antenna device that can be suppressed from being large-sized while guaranteeing the directivity of a beam.SOLUTION: An antenna device comprises a base plate 4 which is a flat plate-like conductor member and an element 2 which is a flat plate-like conductor member facing the base plate 4 and arranged apart from the base plate. The antenna device comprises a columnar short-circuit via 5 which electrically connects the element 2 and base plate 4 to each other, and a power feed via 6 which is in a columnar shape comprising a power feed end part electrically connected to the element and feeding electricity to the element. The element 2 is so formed that an arrangement-directional length which is a length in the arrangement direction of the short-circuit via 5 and power feed via 6 is larger than an orthogonal direction length which is a length in a direction orthogonal to the arrangement direction and also asymmetrically in the arrangement direction about the short-circuit via.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an antenna device. [Background technology]

[0002] Patent Document 1 discloses a planar antenna having unidirectionality. This planar antenna includes a ground plate, which is a conductor formed in a plate shape, a flat plate, which is a conductor arranged to face the ground plate at a distance, and at least one short-circuiting part that short-circuits between the ground plate and the flat plate, and includes multiple metamaterial elements that resonate at zero order. One of the metamaterial elements is a feed element having a feed part that is connected to the flat plate and supplies power, and the metamaterial elements other than the feed element are configured as parasitic elements having a parasitic part that short-circuits the flat plate to the ground plate. The feed element and the parasitic elements are arranged along the radiation direction of the beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-5663 A Summary of the Invention [Problem to be solved by the invention]

[0004] The planar antenna of Patent Document 1 requires that multiple elements, including fed elements and parasitic elements, be arranged along the beam radiation direction in order to form beam directivity. Therefore, in the technology of Patent Document 1, an array antenna is formed by arranging multiple sets of elements that maintain this arrangement, which may result in an increase in the size of the entire device.

[0005] An object of the present disclosure is to provide an antenna device that can prevent an increase in size while ensuring beam directivity. [Means for solving the problem]

[0006] The technical means of the present disclosure for solving the problems will be described below. Note that the claims and the reference characters in parentheses in this section indicate the corresponding relationship with the specific means described in the embodiments described later in detail, and do not limit the technical scope of the present disclosure.

[0007] The antenna device according to one aspect of the present disclosure includes a base plate (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) that electrically connects the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element and supplying power to the element; Equipped with The element is formed such that the length in the arrangement direction of the short-circuit via and the power supply via is greater than the length in the orthogonal direction perpendicular to the arrangement direction, and the length is asymmetric in the arrangement direction with the short-circuit via as the center. The short circuit via has a long portion (22) that is the side having a longer length in the arrangement direction with the short circuit via at the center, and a short portion (21) that is the side having a shorter length in the arrangement direction, the power supply vias are electrically connected at their long portions, and the short-circuit vias are electrically connected at their short portions on the power supply via side; The long portion is formed to have a tapered shape that tapers toward the power supply via. . According to another aspect of the present disclosure, an antenna device includes a base plate (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) that electrically connects the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element and supplying power to the element; Equipped with the element has an arrangement length, which is a length in a direction in which the short-circuiting via and the power supply via are arranged, that is greater than an orthogonal length, which is a length in a direction perpendicular to the arrangement direction, and is formed to have a length that is asymmetric in the arrangement direction with the short-circuiting via as a center, The extension direction of the power supply wiring connected to the end portion of the power supply via opposite to the power supply end portion is parallel to the arrangement direction. According to another aspect of the present disclosure, an antenna device includes a base plate (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) that electrically connects the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element and supplying power to the element; Equipped with the element has an arrangement length, which is a length in a direction in which the short-circuiting via and the power supply via are arranged, that is greater than an orthogonal length, which is a length in a direction perpendicular to the arrangement direction, and is formed to have a length that is asymmetric in the arrangement direction with the short-circuiting via as a center, If the distance between the representative positions of adjacent elements is d and the electrical length of one wavelength of the electromagnetic wave radiated from an element when power is supplied to the element is λe, then 1.1 λe <d<1.4λe Meet the following.

[0008] According to this embodiment, since the length of the elements in the arrangement direction is greater than the length in the orthogonal direction and the elements are formed to have lengths asymmetric in the arrangement direction with the short-circuit via as the center, the distribution of the electric field generated in the elements is also asymmetric with the short-circuit via as the center. Therefore, the beam radiated from the element can have directivity toward the side with the longer length in the arrangement direction with the short-circuit via as the center. Therefore, it is possible to form the directivity of the beam with only a single element. As described above, an antenna device can be provided that can suppress the size increase while ensuring the directivity of the beam. [Brief description of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating examples of mounting an antenna device. [Diagram 2] 4A and 4B are diagrams illustrating an example of wiring of the antenna device. [Diagram 3] 1A and 1B are diagrams illustrating a structure of an antenna device. [Figure 4] FIG. 2 is a top view of the antenna device. [Diagram 5] FIG. 2 is a cross-sectional view of the antenna device. [Figure 6] 1 is a graph showing the relationship between element spacing and FB ratio. [Figure 7] FIG. 13 is a diagram showing a simulation result of a current distribution. [Figure 8] FIG. 2 is a diagram showing the directivity of an antenna device. [Figure 9] FIG. 13 is a diagram showing a change in gain depending on the power supply direction. [Figure 10] 13A and 13B are diagrams illustrating modified examples of elements in the antenna device. [Figure 11] 13A and 13B are diagrams illustrating modified examples of elements in the antenna device. [Figure 12] 13A and 13B are diagrams illustrating modified examples of the laminated structure in the antenna device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. In addition, by assigning the same reference numerals to corresponding components in each embodiment, duplicated descriptions may be omitted. In addition, when only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other parts of the configuration. Furthermore, in addition to the combination of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments can be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0011] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings.

[0012] First embodiment The antenna device 1 of the first embodiment is mounted on a vehicle A shown in Fig. 1. The antenna device 1 is configured to be capable of transmitting and receiving radio waves belonging to a frequency band (so-called ISM band) allocated for general-purpose use in fields such as industry and science, as defined by the International Telecommunication Union. In this embodiment, the antenna device 100 is used to transmit radio waves. The antenna device 100 may also be used to receive radio waves. Since radio wave transmission and reception is reversible, a configuration capable of transmitting radio waves of a certain frequency is also a configuration capable of receiving radio waves of that frequency.

[0013] The antenna device 1 is configured as a so-called metamaterial antenna. A metamaterial antenna is an antenna that utilizes zero-order resonance, which is a phenomenon in which a metamaterial resonates at a frequency where the phase constant is zero, among the dispersion characteristics of the metamaterial. The metamaterial antenna operates by LC parallel resonance between the capacitance formed between the ground plate 4 and the element 2 and the inductance of the short-circuit via 5.

[0014] A plurality of antenna devices 1 are mounted on vehicle A. For example, at least one of the antenna devices 1 is installed so as to have directivity toward the front of vehicle A, and at least one of the antenna devices 1 is set so as to have directivity toward the rear of vehicle A. The directivity of the antenna device 1 is configured by a configuration described later. The antenna device 1 may be configured integrally with an external camera that monitors the outside world.

[0015] The antenna device 1 includes a plurality of antenna elements 10. The antenna elements 10 are formed in a power of two (for example, 16×16) for one antenna device 1. A power feed wiring 11 is connected to the antenna elements 10. The power feed wiring 11 is arranged so as to perform so-called tournament power feeding (see FIG. 2). Of the power feed wiring 11, a connection portion 11a connected to a power feed via 6 described below is arranged so as to extend substantially parallel to the arrangement direction of the short-circuit vias 5 and the power feed vias 6. As a result, the power feeding direction to the power feed vias 6 is parallel to the above-mentioned arrangement direction.

[0016] As shown in Figs. 3 to 5, the antenna element 10 includes a ground plate 4, a support plate 3, a short-circuit via 5, a power feed via 6, and an element 2. The ground plate 4 is a conductor plate that provides a ground potential in the antenna device 1. The ground plate 4 is made of a conductor material such as copper. The ground plate 4 is electrically connected to a ground cable such as the outer conductor of a coaxial cable. The ground plate 4 is provided on the back surface of the support plate.

[0017] The support plate 3 is a support member that supports the base plate 4 and the element 2 in a state where they face each other and are spaced apart from each other. The support plate 3 is made of an insulating material such as glass epoxy resin. The support plate 3 is formed, for example, as a substantially rectangular flat plate.

[0018] The short-circuiting via 5 and the power supply via 6 are columnar (e.g., cylindrical) conductor members. The short-circuiting via 5 and the power supply via 6 are shaped to extend in a direction substantially perpendicular to the ground plate 4 and the element 2. The short-circuiting via 5 is provided between the element 2 and the ground plate 4, and electrically connects the element 2 and the ground plate 4. The short-circuiting via 5 provides a current path from the element 2 to the ground plate 4. An element side end 5a, which is the end of the short-circuiting via 5 on the element 2 side, is in contact with or bonded to the element 2. An opposite end 5b, which is the end of the short-circuiting via 5 opposite to the element side end 5a, is in contact with or bonded to the ground plate 4.

[0019] A power supply end 6a, which is an end of the power supply via 6 on the element 2 side, is in contact with or bonded to the element 2. This electrically connects the power supply end 6a to the element 2. An opposite end 6b, which is an end of the power supply via 6 opposite to the power supply end 6a, is electrically connected to the power supply unit 7 via a power supply wiring 11 shown in FIG. 2. The power supply via 6 provides a current path for supplying current from the power supply unit 7 to the element 2 via the power supply wiring 11.

[0020] 2, an end of the connection portion 11a of the power supply wiring 11 is connected to the opposite end portion 6b. The connection portion 11a is connected to the opposite end portion 6b such that the extension direction of the connection portion 11a is parallel to the direction in which the power supply vias 6 and the short-circuit vias 5 are arranged.

[0021] If the diameter of the cylindrical power supply via 6 is φa and the diameter of the short-circuit via 5 is φb, these diameters are set to satisfy, for example, the following conditional expressions (1) and (2): In the following, λe is the electrical length of one wavelength in the electromagnetic wave radiated from the element 2 when power is supplied to the element 2.

[0022] (Number 1) 0.05λe<φa<0.3λe (1)

[0023] (Number 2) 0.2λe<φb<0.4λe (2)

[0024] The element 2 is a radiating element that radiates radio waves into space. The element 2 is formed from a flat conductive material. The element 2 faces the ground plate 4 across the support plate 3. The element 2 is disposed so as to be substantially parallel to the ground plate 4. The opposing arrangement of the element 2 and the ground plate 4 forms a capacitance according to the area of ​​the element 2 and the distance between the element 2 and the ground plate 4.

[0025] The shape of the element 2 will be described in detail. In the following, the direction in which the short-circuit vias 5 and the power supply vias 6 are arranged is referred to as the arrangement direction. Also, the direction perpendicular to the arrangement direction is referred to as the perpendicular direction. Note that the arrangement direction can also be said to be the direction in which the element side end 5a and the power supply end 6a are arranged.

[0026] 4, the element 2 is formed in a shape in which the length in the arrangement direction is greater than the length in the perpendicular direction. The element 2 is formed in a shape that is asymmetric in the arrangement direction with the short-circuit via 5 as the center. More specifically, the element 2 is formed in a shape in which the lengths divided in the arrangement direction at the center of the short-circuit via 5 are different.

[0027] When the short-circuiting via 5 has a cylindrical shape, the central axis position of the cylindrical shape at the element side end 5a is the center of the short-circuiting via 5. When the shape of the short-circuiting via 5 is other than cylindrical, the center of a circumscribing circle circumscribing the shape of the element side end 5a is the center of the short-circuiting via 5. Alternatively, the center of the short-circuiting via 5 may be a position that equally divides the area of ​​the element side end 5a in orthogonal directions.

[0028] In addition, the element 2 is formed so as to have a symmetrical shape in the orthogonal direction with the power supply via 6 in between. More specifically, the element 2 is formed so as to have a symmetrical shape in the orthogonal direction with the power supply via 6 as the center. More specifically, the element 2 is formed so as to have a symmetrical shape in the orthogonal direction with a virtual line passing through the center of the power supply via 6 and parallel to the arrangement direction in between. Here, the center of the power supply via 6 may be set to the central axis position of the cylindrical shape of the power supply end 6a, similarly to the center of the short-circuit via 5, when the power supply via 6 has a cylindrical shape. Alternatively, when the shape of the power supply via 6 is other than cylindrical, the center of the circumscribing circle circumscribing the shape of the power supply end 6a may be set to the center of the power supply via 6.

[0029] If the orthogonal length is a and the alignment length is b, these lengths are set so as to satisfy, for example, the following conditional expressions (3) and (4).

[0030] (Number 3) 0.4λe <a<0.6λe ···(3)

[0031] (Number 4) 0.5λe <b<0.9λe ···(4)

[0032] The element 2 having the above-mentioned shape has a short portion 21 and a long portion 22. The short portion 21 is a portion of the element 2 whose length dimension in the arrangement direction centered on the short-circuiting via 5 is shorter than that of the long portion 22. The boundary between the short portion 21 and the long portion 22 is, for example, a virtual boundary line extending in an orthogonal direction passing through the central axis of the short-circuiting via 5. The short portion 21 is, for example, rectangular.

[0033] The long portion 22 is a portion of the element 2 whose length dimension in the arrangement direction centered on the short-circuit via 5 is longer than that of the short portion 21. For example, the long portion 22 is a portion extending from the short-circuit via 5 toward the power supply via 6, and is a portion electrically connected to the power supply via 6. In other words, the long portion 22 is a portion of the element 2 that covers the power supply via 6.

[0034] The long portion 22 is formed to have an equal-width portion 22a and a tapered portion 22b. The equal-width portion 22a is a portion directly connected to the short portion 21, and is formed so that its width in the perpendicular direction is substantially the same as that of the short portion 21. The equal-width portion 22a is, for example, rectangular with sides parallel to the arrangement direction. The length of the equal-width portion 22a in the arrangement direction is, for example, substantially the same as that of the short portion 21. The equal-width portion 22a and the short portion 21 form a rectangular portion (a square portion in this embodiment) with the short-circuit via 5 at its center.

[0035] The tapered portion 22b is a portion that extends from the uniform width portion 22a to the opposite side of the short via 5. The tapered portion 22b is formed so that the width in the orthogonal direction becomes smaller as it extends to the opposite side of the short portion 21 in the arrangement direction. The tapered portion 22b has, for example, a portion that is connected to the uniform width portion 22a and linearly tapered, and a semicircular end portion that is connected to the portion. Due to the tapered portion 22b, the area of ​​the element 2 in the first embodiment is smaller than the product of the length in the arrangement direction and the length in the orthogonal direction. Here, the area of ​​the element 2 is defined as the area in a plan view from the thickness direction of the element 2. The thickness direction of the element 2 is defined as a direction perpendicular to the arrangement direction and the orthogonal direction.

[0036] The distance d between the elements 2 in adjacent antenna elements 10 is set so as to satisfy, for example, the following conditional formula (5). Note that the distance d here is the distance between representative positions PR common to each of the elements 2 having substantially the same shape. The representative position PR may be, for example, a position corresponding to the center of the short-circuit via 5, or may be the center of gravity of the element 2, or may be another position. By setting the distance within this range, the feedback ratio is improved as shown in FIG. 6.

[0037] (Number 5) 1.1 λe <d<1.4λe ···(5)

[0038] The lengths of the elements 2 are asymmetrical with respect to the short-circuit via 5, so that bias occurs in the current distribution when current is passed through them (see FIG. 7). Specifically, the electric field generated on the longer side, i.e., on the long portion 22, is stronger. As a result, a directional electromagnetic wave is irradiated as a beam toward the long portion 22 of the element 2.

[0039] Fig. 8 is a graph showing the directivity of antenna device 1 with the top of the page being the long portion 22 side of element 2. In Fig. 8, the up-down direction of the page coincides with the arrangement direction of short-circuit vias 5 and power feed vias 6. As shown in Fig. 8, antenna device 1 is capable of emitting a beam having directivity toward the long portion 22 side.

[0040] 9 also shows the difference in gain between the case where the extension direction of the power feed lines connected to the power feed vias 6 is perpendicular to the arrangement direction (left side of the page) and the case where it is parallel to the arrangement direction (right side of the page). As shown above, the gain is improved (6.9 dB improvement in FIG. 9) when the extension direction of the power feed lines is parallel to the arrangement direction.

[0041] According to the above first embodiment, since the length of the elements 2 in the arrangement direction is greater than the length in the orthogonal direction and the elements 2 are formed to have lengths asymmetric in the arrangement direction with the short-circuit via 5 as the center, the distribution of the electric field generated in the elements 2 is also asymmetric with the short-circuit via 5 as the center. Therefore, the beam radiated from the elements 2 can have directivity toward the side with the longer length in the arrangement direction with the short-circuit via 5 as the center. Therefore, it may be possible to form the beam directivity with only a single element 2. As described above, an antenna device 1 can be provided that can suppress an increase in size while ensuring beam directivity.

[0042] (Other embodiments) Although one embodiment has been described above, the present disclosure should not be construed as being limited to the embodiment described above, and can be applied to various embodiments within the scope not departing from the gist of the present disclosure.

[0043] In the modified example, the shape of the element is not limited to the shape of the first embodiment. For example, the element may be formed in a polygonal shape as shown in Fig. 10. Or, the element may be formed in an elliptical shape as shown in Fig. 11. Or, the element may be formed in a circular shape. The element may be in any shape as long as it has a long part and a short part.

[0044] In a modified example, the antenna device 1 may have a ground layer 8 (see FIG. 12). The ground layer 8 is formed in two or more layers as shown in FIG. 12, for example. Alternatively, in a modified example, the antenna device 1 may have a phase shifter layer. For example, a phase shifter layer may be provided instead of the lower ground layer 8 in FIG. 12.

[0045] In a variant, the antenna device 1 may be powered by capacitive coupling. [Explanation of symbols]

[0046] 1: antenna device, 2: element, 4: ground plane, 5: short via, 6: power feed via, 6a: power feed end, 21: short portion, 22: long portion

Claims

1. A ground plane (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) electrically connecting the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element, which supplies power to the element; Equipped with The element has an arrangement length, which is a length in the arrangement direction of the short-circuit via and the power supply via, that is greater than an orthogonal length, which is a length in a direction perpendicular to the arrangement direction, and is formed to have a length that is asymmetric in the arrangement direction with the short-circuit via as a center, and has a long portion (22) that is the side on which the length in the arrangement direction is longer with respect to the short-circuit via as a center, and a short portion (21) that is the side on which the length in the arrangement direction is shorter, the power supply vias are electrically connected to each other at the long portion, and the short-circuiting vias are electrically connected to each other on a side closer to the short portion than the power supply vias are, The antenna device, wherein the long portion is formed to have a tapered shape that tapers toward the power feed via.

2. The antenna device according to claim 1 , wherein a direction in which a feed line connected to an end of the feed via opposite to the feed end portion extends is parallel to the arrangement direction.

3. If the distance between the representative positions of adjacent elements is d and the electrical length of one wavelength of electromagnetic waves radiated from the elements when power is supplied to the elements is λe, then 1.1λe<d<1.4λe 3. The antenna device according to claim 1, wherein the above-mentioned condition is satisfied.

4. A ground plate (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) electrically connecting the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element, which supplies power to the element; Equipped with the element has an arrangement length, which is a length in a direction in which the short-circuit via and the power feed via are arranged, that is greater than an orthogonal length, which is a length in a direction orthogonal to the arrangement direction, and is formed to have a length that is asymmetric in the arrangement direction with the short-circuit via as a center, The antenna device has a feed line connected to an end of the feed via opposite to the feed end, the feed line extending in a direction parallel to the arrangement direction.

5. Let d be the distance between the representative positions of adjacent elements, and λe be the electrical length of one wavelength of electromagnetic waves radiated from the elements when power is supplied to the elements, 1.1λe<d<1.4λe The antenna device according to claim 4, which satisfies the following:

6. A ground plate (4) which is a flat conductive member; An element (2) which is a flat conductive member disposed opposite to the ground plane and spaced apart from the ground plane; A columnar short-circuit via (5) electrically connecting the element and the ground plane; A columnar power supply via (6) having a power supply end (6a) electrically connected to the element, which supplies power to the element; Equipped with the element has an arrangement length, which is a length in a direction in which the short-circuit via and the power feed via are arranged, that is greater than an orthogonal length, which is a length in a direction orthogonal to the arrangement direction, and is formed to have a length that is asymmetric in the arrangement direction with the short-circuit via as a center, If the distance between the representative positions of adjacent elements is d and the electrical length of one wavelength of electromagnetic waves radiated from the elements when power is supplied to the elements is λe, then 1.1λe<d<1.4λe An antenna device that meets the needs of our customers.

7. The element has a long portion (22) that is a side having a longer length in the arrangement direction with the short-circuit via as a center, and a short portion (21) that is a side having a shorter length in the arrangement direction, The antenna device according to claim 4 , wherein the power supply vias are electrically connected at the long portion, and the short-circuiting vias are electrically connected on the short portion side of the power supply vias.

8. An antenna device described in any one of claims 1 to 7, wherein the element does not have an opening, and the area of ​​the element is smaller than the product of the arrangement direction length and the orthogonal direction length.

9. The antenna device according to claim 1 , wherein the shape of the element is symmetrical across the power feed via in the orthogonal direction.

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