Antenna device

Abstract

This antenna device (100) comprises: an antenna element (120); a housing (110); a radome (130) that covers the antenna element placed in the housing; and a fixture (140) for fixing the radome to the housing, the fixture having a front plate-shaped part (142) that is disposed so as to face an antenna element surface part (111) on which the antenna element is placed in the housing. The front plate-shaped part has a periodic structure part (150) composed of a material that reflects electromagnetic waves.

Description

Antenna device

[0001] The disclosed technology relates to an antenna device.

[0002] Some antenna devices are configured by assembling a radome that covers the antenna elements mounted on a housing and a fixture that secures the radome. The "planar antenna" described in Patent Document 1 is configured as follows: "A planar antenna in which the radiating elements 15 shown in FIG. 1 are arrayed is housed in a plastic case 19 as shown in FIG. 5, and a radome 21 made of a plastic such as polycarbonate, ABS, or AAS and having a thickness of approximately 1 mm is provided on the surface of the radiating elements 15 via a spacer 20 made of expanded polystyrene and having a thickness of approximately λ / 4. In this state, a frame 10 is installed on top of the radome 21 in the same manner as above" (0038). "In this case, the frame 10 can also serve as a clamp that secures the case 19 and the radome 21" (0039). The "planar antenna" in Patent Document 1 is configured by assembling a "radome 21" that covers the "radiating elements 15" mounted on the "case 19" and a "frame 10" that serves as a clamp that secures the "radome 21."

[0003] Japanese Utility Model Application Laid-Open Publication No. 4-121110

[0004] However, conventional antenna devices configured as described above have the problem that each configuration tends to reflect electromagnetic waves arriving from outside, which can cause the reflected scattered waves to be erroneously observed by an external antenna device.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to reduce the observability of an antenna device compared to conventional devices.

[0006] The antenna device of the present disclosure comprises an antenna element, a housing, a radome that covers the antenna element placed on the housing, and a fixture that fixes the radome to the housing, the fixture having a front plate-like portion that is arranged to face the antenna element surface portion on which the antenna element is placed on the housing, and is characterized in that the front plate-like portion has a periodic structure portion made of a material that reflects electromagnetic waves.

[0007] According to the present disclosure, it is possible to achieve an effect of reducing the observability of an antenna device compared to conventional methods.

[0008] FIG. 1 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100 according to a first embodiment of the present disclosure. FIG. 2 is an exploded perspective view schematically illustrating the exemplary configuration of the antenna device 100 according to the first embodiment of the present disclosure. FIG. 3 is a schematic diagram illustrating a first exemplary cross-sectional structure of a fixture 140. FIG. 4 is a schematic diagram illustrating a second exemplary cross-sectional structure of a fixture 140. FIG. 5 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100A that is a modified example of the antenna device 100. FIG. 6 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100B according to a second embodiment of the present disclosure. FIG. 7 is an exploded perspective view schematically illustrating an exemplary configuration of the antenna device 100B according to the second embodiment of the present disclosure. FIG. 8 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100C according to a third embodiment of the present disclosure. FIG. 9 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100D according to a fourth embodiment of the present disclosure. FIG. 10 is a perspective view schematically illustrating an exemplary configuration of an antenna device 100E according to a fifth embodiment of the present disclosure. FIG. 11 is a front view schematically illustrating an exemplary configuration of an antenna device 100E according to a fifth embodiment of the present disclosure.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] First Embodiment In the first embodiment, a configuration example will be described in which a metasurface (periodic structure portion) is provided on a fixture to reduce the observability of an antenna device.

[0011] A configuration example of an antenna device according to a first embodiment of the present disclosure will be described. FIG. 1 is a perspective view schematically illustrating a configuration example of an antenna device 100 according to the first embodiment of the present disclosure. FIG. 2 is an exploded perspective view schematically illustrating a configuration example of the antenna device 100 according to the first embodiment of the present disclosure. The antenna device 100 is a device configured to transmit, receive, or transmit and receive electromagnetic waves. The antenna device 100 is not particularly limited as long as it functions as an antenna that transmits, receives, or transmits and receives electromagnetic waves. For example, the antenna device 100 is an antenna device for a radar device used to detect surrounding conditions such as obstacles in a mobile object. The antenna device 100 shown in FIGS. 1 and 2 includes a housing 110, an antenna element 120, a radome 130, a fixture 140, and a metasurface (periodic structure portion) 150.

[0012] The housing 110 houses the internal configuration (not shown) of the antenna device 100. An antenna element 120 is mounted on the front surface of the housing 110, which is located in the direction (direction a) in which the antenna device 100 outputs electromagnetic waves. The surface on which the antenna element 120 is mounted is also referred to as an antenna element surface 111. A radome 130 is fixed to the housing 110 by a fixing device 140. The housing 110 shown in FIGS. 1 and 2 has a cylindrical or approximately cylindrical shape.

[0013] Antenna element surface portion 111 is the front portion of housing 110, and is the surface of housing 110 on which antenna element 120 is placed.

[0014] The antenna element 120 is an element that outputs electromagnetic waves. The antenna element 120 shown in Figures 1 and 2 is mounted on the housing 110 and covered by a radome 130. The antenna element 120 shown in Figure 2 has a disk shape.

[0015] The radome 130 is provided to protect the antenna element 120 from wind, rain, dust, and damage, and covers the antenna element 120 mounted on the housing 110. The radome 130 shown in Figures 1 and 2 has a cylindrical or nearly cylindrical shape. The radome 130 may also have a hemispherical shape.

[0016] The fixing device 140 fixes the radome 130 to the housing 110. The fixing device 140 fixes the radome 130 to the housing 110 and also fixes the antenna element 120. The fixing device 140 is made of a dielectric, a metal, and a dielectric and a metal. The fixing device 140 shown in FIGS. 1 and 2 includes an opening 141 and a front plate portion 142. The fixing device 140 has the front plate portion 142 arranged in the housing 110 so as to face the antenna element surface portion 111 on which the antenna element 120 is mounted. The fixing device 140 has an opening 141 to expose the radome 130. The fixing device 140 shown in FIGS. 1 and 2 has a cylindrical or approximately cylindrical shape. It is only necessary that the fixing device 140 have the front plate portion 142 and be configured to be able to fix the radome 130. The fixture 140 shown in FIGS. 1 and 2 is ring-shaped, but may be a rectangular plate or the like as long as it is configured to be able to fix the radome 130.

[0017] The opening 141 is formed in the center of the front plate portion 142 so as not to cover the radome 130 in the normal direction (direction a) of the antenna element surface portion 111. The opening 141 shown in Figures 1 and 2 has a circular or nearly circular shape when viewed toward the front of the antenna device 100 (when viewed toward direction α).

[0018] The front plate portion 142 has a metasurface (periodic structure portion) 150 made of a material that reflects electromagnetic waves. The front plate portion 142 has an opening 141 formed therein that does not cover the radome 130 in the normal direction (direction a) of the antenna element surface portion 111. The front plate portion 142 shown in Figures 1 and 2 has a ring shape or a nearly ring shape when viewed from the front of the antenna device 100 (when viewed in direction α).

[0019] The metasurface (periodic structure) 150 is made of a material that reflects electromagnetic waves and is, for example, a two-dimensional periodic arrangement of structures that are small relative to the wavelength of light. The metasurface (periodic structure) 150 shown in FIGS. 1 and 2 is arranged in a grid pattern on the plate-like surface of the front plate portion 142 of the fixture 140. The structures of the metasurface (periodic structure) 150 shown in FIGS. 1 and 2 are rectangular, but may also be circular or have other shapes. The arrangement of the metasurface (periodic structure) 150 or the shape of each structure is appropriately designed depending on the frequency band of the electromagnetic waves to be reflected, etc. Here, an example of the cross-sectional structure of the front plate portion 142 having the metasurface (periodic structure) 150 will be described.

[0020] 3 is a schematic diagram showing a first example of the cross-sectional structure of fixing device 140. Front plate portion 142 of fixing device 140 is composed of a layer of metal portion 143 and a layer of dielectric portion 144, and patches constituting metasurface (periodic structure portion) 150 are attached or embedded on the side of dielectric portion 144 facing the front of antenna device 100 (direction a).

[0021] 4 is a schematic diagram showing a second example of the cross-sectional structure of fixing device 140. Front plate portion 142 of fixing device 140 is composed of metal portion 143, and each patch constituting metasurface (periodic structure portion) 150 is attached or embedded on the side of metal portion 143 facing the front of antenna device 100.

[0022] Next, a configuration example of a modified example of the antenna device according to the first embodiment of the present disclosure will be described. Fig. 5 is a perspective view schematically illustrating a configuration example of an antenna device 100A, which is a modified example of the antenna device 100. The antenna device 100A shown in Fig. 5 includes a housing 110A, an antenna element 120, a radome 130A, a fixing member 140A, and a metasurface (periodic structure portion) 150A.

[0023] The housing 110A is configured similarly to the housing 110 already described, with the difference being that the housing 110A shown in FIG. 7 has a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape.

[0024] The radome 130A is configured similarly to the radome 130 already described, with the difference being that the radome 130A shown in FIG. 7 has a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape.

[0025] Fixture 140A has a similar configuration to fixture 140 already described, with the difference being that fixture 140A shown in Fig. 7 has a rectangular parallelepiped or substantially rectangular parallelepiped shape. Fixture 140A shown in Fig. 7 includes opening 141A and front plate-like portion 142A.

[0026] The opening 141A shown in FIG. 7 has a rectangular or nearly rectangular shape when viewed from the front of the antenna device 100 (when viewed in the direction α).

[0027] The front plate portion 142A shown in FIG. 7 has a rectangular frame shape or a substantially rectangular frame shape when viewed from the front of the antenna device 100 (when viewed in the direction α).

[0028] The metasurface (periodic structure portion) 150A is configured in the same manner as the metasurface (periodic structure portion) 150 already described. The structures of the metasurface (periodic structure portion) 150A shown in Figure 7 are each rectangular, but may also be circular or have other shapes. The arrangement of the metasurface (periodic structure portion) 150A or the shape of each structure is designed appropriately depending on the frequency band of the electromagnetic waves to be reflected, etc.

[0029] With the configuration according to this embodiment, for an antenna device that requires a fixture to be attached to a radome, by arranging a metasurface on the fixture, it is possible to achieve low observability by canceling out the scattering of the metasurface arranged on the fixture and other structures. In other words, it is possible to make it less likely for the antenna device to be erroneously observed by other antenna devices.

[0030] This embodiment has shown an example embodiment including the following configuration: an antenna device comprising: an antenna element (120); a housing (110); a radome (130) covering the antenna element (120) mounted on the housing (110); and a fixture (140) for fixing the radome to the housing (110), the fixture (140) having a front plate-shaped portion (142) arranged to face an antenna element surface portion (111) on which the antenna element (120) is mounted in the housing (110), the front plate-shaped portion (142) having a periodic structure portion (150) made of a material that reflects electromagnetic waves. This makes it possible to provide an antenna device that can reduce observability compared to conventional devices.

[0031] Embodiment 2. In the above-described embodiment 1, a configuration example was described in which the observability of the antenna device was reduced by providing a metasurface (periodic structure portion) on the fixture. In embodiment 2, a configuration example is described in which the observability of the antenna device was reduced by the length of the gap between the front plate portion of the fixture and the antenna element surface of the housing, and the area of ​​the front plate portion of the fixture. In embodiment 2, duplicated descriptions of components according to embodiment 2 that are the same as those according to embodiment 1 already described will be omitted as appropriate.

[0032] Next, a configuration example of an antenna device according to a second embodiment of the present disclosure will be described. Fig. 6 is a perspective view schematically illustrating a configuration example of an antenna device 100B according to the second embodiment of the present disclosure. Fig. 7 is an exploded perspective view schematically illustrating a configuration example of the antenna device 100B according to the second embodiment of the present disclosure. The antenna device 100B shown in Figs. 6 and 7 includes a housing 110B, an antenna element 120B, a radome 130B, and a fixture 140B.

[0033] Similar to the housing 110 already described, the housing 110B houses the internal configuration (not shown) of the antenna device 100B. The antenna element 120 is mounted on the front surface of the housing 110B, which is located in the direction (direction a) in which the electromagnetic waves of the antenna device 100B are output. The surface on which the antenna element 120 is mounted is also referred to as the antenna element surface 111B. A radome 130B is fixed to the housing 110B by a fixing member 140B. The housing 110B shown in FIGS. 6 and 7 has a cylindrical or approximately cylindrical shape.

[0034] Antenna element surface portion 111B is the front surface of housing 110B, and is the surface of housing 110B on which antenna element 120 is placed.

[0035] The antenna element 120B is an element that outputs electromagnetic waves, similar to the antenna element 120 already described. The antenna element 120B shown in Figures 6 and 7 is mounted on a housing 110B and covered by a radome 130B. The antenna element 120B shown in Figure 7 has a disk shape.

[0036] Similar to the radome 130 already described, the radome 130B is provided to protect the antenna element 120B from wind, rain, dust, and damage, and covers the antenna element 120B mounted on the housing 110B. The radome 130B shown in Figures 6 and 7 has a cylindrical or nearly cylindrical shape. The radome 130B may also have a hemispherical shape.

[0037] The fixture 140B, like the fixture 140 already described, fixes the radome 130B to the housing 110B. The fixture 140B fixes the radome 130B to the housing 110B and also fixes the antenna element 120. The fixture 140B shown in FIGS. 6 and 7 includes an opening 141B and a front plate portion 142B. The fixture 140B has the front plate portion 142B arranged in the housing 110B so as to face the antenna element surface portion 111B on which the antenna element 120 is mounted. The fixture 140B has an opening 141B so as to expose the radome 130B. The fixture 140B shown in FIGS. 6 and 7 has a cylindrical or approximately cylindrical shape.

[0038] The opening 141B is formed in the center of the front plate portion 142B so as not to cover the radome in the normal direction (direction a) of the antenna element surface portion 111B. The opening 141B shown in Figures 6 and 7 has a circular or nearly circular shape when viewed from the front of the antenna device 100B (when viewed in direction α).

[0039] The front plate portion 142B has an opening 141B formed therein that does not cover the radome 130 in the normal direction of the antenna element surface portion 111B. The front plate portion 142B shown in Figures 6 and 7 has a ring shape or a nearly ring shape when viewed from the front of the antenna device 100B.

[0040] Here, the distance between the front plate portion 142B of the fixing device 140B and the antenna element surface portion 111B of the housing 110B in the antenna device 100B according to the second embodiment of the present disclosure will be described. When designing the antenna device 100B, the frequency or frequency band for which reflection is to be suppressed is determined in advance. The distance between the front plate portion 142B and the antenna element surface portion 111B is designed and configured to be a length such that, in the predetermined frequency band, the reflection phase characteristics of the antenna element 120B, the radome 130B, and the housing 110B are in opposite phase to the reflection phase characteristics of the fixing device. The area of ​​the surface of the front plate portion 142B facing the antenna element surface portion 111B is designed and configured to be an area such that, in the predetermined frequency band, the reflection amplitude characteristics of the antenna element 120B, the radome 130B, and the housing 110B are equal to the reflection amplitude characteristics of the fixing device 140B.

[0041] More specifically, for example, when the normal direction (direction a), which is the direction in which electromagnetic waves travel, is taken as positive, the distance δ between the front plate portion 142B and the antenna element surface portion (111B) is configured to be within the range shown in the following formula (1): 180-90<abs|P ｔａｒｇｅｔ -P ｃａｎｃｅｌｌｅｒ |+(δ*2π / λ)*(180 / π)<180+90 (1) where, in the above formula (1), abs| | is an absolute function, and P ｔａｒｇｅｔ is the reflection phase characteristic of the fixture 140B, and P ｃａｎｃｅｌｌｅｒis the reflection phase characteristic of the antenna element 120B, the radome 130B, and the housing 110B, and λ is a frequency in a predetermined frequency band. This makes it possible to provide an antenna device 100B that can reduce observability compared to conventional devices by adjusting the range of the distance δ between the front plate portion 142B and the antenna element surface portion 111B. In other words, it is possible to make it less susceptible to false observation by other antenna devices. Furthermore, the configuration according to this embodiment allows the distance δ to be a design element, thereby expanding the degree of freedom in design.

[0042] This embodiment shows an example of an embodiment including the following configuration: an antenna element (120B), a housing (110B), a radome (130) covering the antenna element (120B) mounted on the housing (110B), and a fixture (140B) for fixing the radome (130B) to the housing (110B), the fixture (140B) having a front plate-like portion (142B) arranged to face an antenna element surface portion (111B) on which the antenna element (120B) is mounted in the housing (110B), wherein in a predetermined frequency band, the distance between the front plate-like portion (142B) and the antenna element surface portion (111B) is such that the reflection phase characteristics of the antenna element (120B), the radome (130B) and the housing (110B) are in opposite phase to the reflection phase characteristic of the fixture, an antenna device configured such that the area of ​​the surface of the front plate portion (142B) facing the antenna element surface portion (111B) is an area that equalizes the reflection amplitude characteristics of the antenna element (120B), the radome (130B), and the housing (110B) with the reflection amplitude characteristics of the fixing device (140B). As a result, the present disclosure has an effect of providing an antenna device that enables reduced observability compared to conventional devices.

[0043] This embodiment further shows an example of a configuration including the following: An antenna device characterized in that the distance δ between the front plate portion (142B) and the antenna element surface portion (111B) is configured to be within the range shown in the following formula (1): 180-90<abs|P ｔａｒｇｅｔ -P ｃａｎｃｅｌｌｅｒ |+(δ*2π / λ)*(180 / π)<180+90 (1) where, in the above formula (1), abs| | is an absolute function, and P ｔａｒｇｅｔ is the reflection phase characteristic of the fixture (140B), and P ｃａｎｃｅｌｌｅｒ is the reflection phase characteristic of the antenna element (120), the radome (130B), and the housing (110B), and λ is a frequency in a predetermined frequency band. This further clarifies the range of the distance δ between the front plate portion and the antenna element surface portion, thereby providing an antenna device that can reduce observability compared to conventional devices. Furthermore, the present disclosure achieves the same effect as the above by applying the above configuration to a system or the like that includes the antenna device.

[0044] Embodiment 3. In the above-described embodiments, a configuration has been described in which a metasurface (periodic structure portion) is provided on the fixture, or a configuration in which the observability of the antenna device is reduced by adjusting the length of the gap between the front plate portion of the fixture and the antenna element surface of the housing, and the area of ​​the front plate portion of the fixture. In embodiment 3, a configuration example will be described in which a metasurface (periodic structure portion) is provided on the fixture, and the observability of the antenna device is reduced by adjusting the length of the gap between the front plate portion of the fixture and the antenna element surface of the housing, and the area of ​​the front plate portion of the fixture. In embodiment 3, duplicated descriptions of components according to embodiment 3 that are the same as those according to embodiment 1 or embodiment 2 already described will be omitted as appropriate.

[0045] Next, a configuration example of an antenna device according to a third embodiment of the present disclosure will be described. Fig. 8 is a perspective view schematically illustrating a configuration example of an antenna device 100C according to the third embodiment of the present disclosure. The antenna device 100C illustrated in Fig. 8 includes a housing 110C, a radome 130C, a fixture 140C, and a metasurface (periodic structure portion) 150C.

[0046] The housing 110C, like the housing 110 already described, houses the internal configuration (not shown) of the antenna device 100C. An antenna element (120) is mounted on the front surface of the housing 110C, which is located in the direction (direction a) in which the electromagnetic waves of the antenna device 100C are output. The surface on which the antenna element (120) is mounted is also referred to as the antenna element surface 111C. A radome 130C is fixed to the housing 110C by a fixing device 140C. The housing 110C shown in FIG. 8 has a cylindrical or approximately cylindrical shape.

[0047] The antenna element surface 111C is the front surface of the housing 110C, and is the surface of the housing 110C on which the antenna element (120) is placed.

[0048] The antenna element (120) is an element that outputs electromagnetic waves, similar to the already described antenna element 120. Although not shown in Fig. 8, the antenna element (120) is mounted on the housing 110C and covered by the radome 130C.

[0049] Similar to the radome 130 already described, the radome 130C is provided to protect the antenna element (120) from wind, rain, dust, and damage, and covers the antenna element (120) mounted on the housing 110C. The radome 130C shown in Fig. 8 has a cylindrical or nearly cylindrical shape. The radome 130C may also have a hemispherical shape.

[0050] The fixture 140C, like the fixture 140 already described, fixes the radome 130C to the housing 110C. The fixture 140C shown in FIG. 8 is configured to include an opening 141C and a front plate-like portion 142C. The fixture 140C has the front plate-like portion 142C arranged to face the antenna element surface portion (111) on which the antenna element (120) is mounted in the housing 110C. The fixture 140C has an opening 141C to expose the radome 130C. The fixture 140C shown in FIG. 8 is cylindrical or approximately cylindrical.

[0051] The opening 141C is formed in the center of the front plate portion 142C so as not to cover the radome 130C in the normal direction of the antenna element surface portion (111). The opening 141C shown in Fig. 8 has a circular or nearly circular shape when viewed toward the front of the antenna device 100C (when viewed toward the direction α).

[0052] The front plate portion 142C has a metasurface (periodic structure portion) 150C made of a material that reflects electromagnetic waves. The front plate portion 142C has an opening 141C formed therein that does not cover the radome 130C in the normal direction of the antenna element surface portion 111. The front plate portion 142C shown in Figure 8 has a ring shape or a nearly ring shape when viewed from the front direction of the antenna device 100 (when viewed in direction α).

[0053] The metasurface (periodic structure) 150C is made of a material that reflects electromagnetic waves, and is, for example, a two-dimensional periodic arrangement of structures that are small relative to the wavelength of light. The metasurface (periodic structure) 150C shown in FIG. 8 is arranged in a lattice pattern on the plate-like surface of the front plate-shaped portion 142C of the fixture 140C. The structures of the metasurface (periodic structure) 150C shown in FIG. 8 are each rectangular, but may also be circular or have other shapes. The arrangement of the metasurface (periodic structure) 150C or the shape of each structure is designed appropriately depending on the frequency band of the electromagnetic waves to be reflected, etc.

[0054] Here, the distance between the front plate portion 142C of the fixing device 140C and the antenna element surface portion 111C of the housing 110C in the antenna device 100C according to the third embodiment of the present disclosure will be described. When designing the antenna device 100C, the frequency or frequency band for which reflection is to be suppressed is determined in advance. The distance between the front plate portion 142C and the antenna element surface portion (111) is designed and configured to a length such that, in the predetermined frequency band, the reflection phase characteristics of the antenna element (120), the radome 130C, and the housing 110C are in opposite phase to the reflection phase characteristics of the fixing device 140C. The area of ​​the surface of the front plate portion 142C facing the antenna element surface portion (111) is designed and configured to an area such that, in the predetermined frequency band, the reflection amplitude characteristics of the antenna element (120), the radome 130C, and the housing 110C are equal to the reflection amplitude characteristics of the fixing device 140C.

[0055] More specifically, for example, the distance δ between the front plate portion 142C and the antenna element surface portion (111) is set to be within the range shown in the following formula (1): 180−90<abs|P ｔａｒｇｅｔ -P ｃａｎｃｅｌｌｅｒ |+(δ*2π / λ)*(180 / π)<180+90 (1) where, in the above formula (1), abs| | is an absolute function, and P ｔａｒｇｅｔ is the reflection phase characteristic of the fixture 140C, and P ｃａｎｃｅｌｌｅｒ is the reflection phase characteristic of the antenna element (120), the radome 130C, and the housing 110C, and λ is a frequency in a predetermined frequency band. This makes it possible to reduce observability compared to conventional methods by adjusting the range of the distance δ between the front plate portion 142C and the antenna element surface portion (111). In other words, it is possible to make it less likely for other antenna devices to make erroneous observations.

[0056] Furthermore, in the antenna device according to this embodiment, the metasurface placed on the surface of the fixture is designed so that the reflection phase characteristics of the portion consisting of the radome, antenna element, and housing are in opposite phase to the reflection phase characteristics of the fixture. Furthermore, in the antenna device according to this embodiment, the fixture is designed so that the reflection amplitude characteristics of the fixture and the portion consisting of the radome, antenna element, and housing are approximately the same. This reduces the reflection amplitude characteristics, which addresses the problem of large reflection amplitude characteristics. Furthermore, it is possible to reduce the reflection amplitude characteristics over a wide band including the antenna's operating band, which addresses the problem of the reflection amplitude characteristics not being able to be reduced within the antenna's operating band. Furthermore, it is possible to prevent the reflection pattern from being affected. Furthermore, it is possible to reduce the reflection amplitude characteristics even when the fixture is installed, which addresses the problem of large reflection amplitude characteristics.

[0057] This embodiment shows an example of an embodiment including the following configuration: an antenna element (120), a housing (110C), a radome (130C) covering the antenna element (120) mounted on the housing (110C), and a fixture (140C) for fixing the radome (130C) to the housing (110C), the fixture (140C) having a front plate-shaped portion (142C) arranged to face an antenna element surface portion (111) on which the antenna element (120) is mounted in the housing (110C), the front plate-shaped portion (142C) having a periodic structure portion (150C) made of a material that reflects electromagnetic waves, and in a predetermined frequency band, the distance between the front plate-shaped portion (142C) and the antenna element surface portion (111) is an antenna device configured such that: the interval is such a length that the reflection phase characteristics of the antenna element (120), the radome (130C), and the housing (110C) are in opposite phase to the reflection phase characteristic of the fixing device (140C), and the area of ​​the surface of the front plate-shaped portion (142C) on which the periodic structure portion (150C) is arranged is such an area that the reflection amplitude characteristics of the antenna element (120), the radome (130C), and the housing (110C) are equal to the reflection amplitude characteristics of the fixing device (140C). As a result, the present disclosure has the effect of providing an antenna device that enables a reduction in observability compared to conventional devices.

[0058] This embodiment further shows an example of a configuration including the following: An antenna device characterized in that the distance δ between the front plate portion (142C) and the antenna element surface portion (111) is configured to be within the range shown in the following formula (1): 180-90<abs|P ｔａｒｇｅｔ -P ｃａｎｃｅｌｌｅｒ |+(δ*2π / λ)*(180 / π)<180+90 (1) where, in the above formula (1), abs| | is an absolute function, and P ｔａｒｇｅｔ is the reflection phase characteristic of the fixture (140C), and P ｃａｎｃｅｌｌｅｒis the reflection phase characteristic of the antenna element (120), the radome (130C), and the housing (110C), and λ is a frequency in a predetermined frequency band. This further provides an antenna device that can reduce observability compared to conventional devices by adjusting the range of the distance δ between the front plate portion and the antenna element surface portion. Furthermore, the present disclosure provides the same effect as above by applying the above configuration to a system or the like that includes the antenna device.

[0059] Embodiment 4. In the above-described embodiments, a configuration has been described in which the fixing device does not have a specific configuration between the front plate portion of the fixing device and the antenna element surface of the housing. In embodiment 4, a configuration example will be described in which the observability of the antenna device is reduced by having a configuration in which the internal configuration is enclosed between the front plate portion of the fixing device and the antenna element surface of the housing. In embodiment 4, duplicated descriptions of components according to embodiment 4 that are the same as components according to embodiment 1, embodiment 2, or embodiment 3 already described will be omitted as appropriate.

[0060] A configuration example of an antenna device according to a fourth embodiment of the present disclosure will be described. Fig. 9 is a perspective view schematically illustrating a configuration example of an antenna device 100D according to the fourth embodiment of the present disclosure. The antenna device 100D illustrated in Fig. 9 includes a housing 110D, a radome 130D, a fixture 140D, and a metasurface (periodic structure portion) 150D.

[0061] The housing 110D may have the same configuration as any one of the housings 110, 110A, 110B, and 110C already described, and a detailed description thereof will be omitted. The radome 130D may have the same configuration as any one of the radomes 130, 130A, 130B, and 130C already described, and a detailed description thereof will be omitted. The metasurface (periodic structure portion) 150D may have the same configuration as any one of the metasurfaces (periodic structure portion) 150, 150A, 150B, and 150C already described, and a detailed description thereof will be omitted.

[0062] The fixture 140D is configured to appear ring-shaped when the antenna device 100D is viewed from the front (in the direction α). The fixture 140D shown in FIG. 9 includes an opening 141D, a front plate-like portion 142D, and an outer peripheral surface portion 145D. The opening 141D secures the radome 130D to the housing 110D. The fixture 140D shown in FIG. 9 includes an opening 141D, a front plate-like portion 142D, and an outer peripheral surface portion 145D. The fixture 140D has a front plate-like portion 142D arranged to face the antenna element surface portion (111) on which the antenna element (120) is mounted in the housing 110D. The fixture 140D has an opening 141D to expose the radome 130D. The fixture 140D shown in FIG. 9 is cylindrical or approximately cylindrical.

[0063] The opening 141D is formed in the center of the front plate portion 142D so as not to cover the radome 130D in the normal direction of the antenna element surface portion (111). The opening 141D shown in Fig. 9 has a circular or nearly circular shape when viewed toward the front of the antenna device 100D (when viewed toward the direction α).

[0064] The front plate portion 142D has a metasurface (periodic structure portion) 150D made of a material that reflects electromagnetic waves. The front plate portion 142D has an opening 141D that does not cover the radome 130D in the normal direction of the antenna element surface portion 111. The front plate portion 142D shown in Figure 9 has a ring shape or a nearly ring shape when viewed from the front direction of the antenna device 100D (when viewed in direction α).

[0065] The outer peripheral surface portion 145D extends from the front plate-like portion 142D to the antenna element surface portion (111) and surrounds the outer periphery of the radome 130D that covers the antenna element (120) on the antenna element surface portion (111). That is, the fixing device 140D has the outer peripheral surface portion 145D that extends from the front plate-like portion 142D to the antenna element surface portion (111) and surrounds the outer periphery of the antenna element (120) on the antenna element surface portion (111). By configuring it in this way, it is possible to suppress deterioration of the reflection amplitude characteristics of electromagnetic waves arriving from outside due to electromagnetic waves that are incident at angles other than frontal incidence.

[0066] The metasurface (periodic structure) 150D is made of a material that reflects electromagnetic waves, and is, for example, a two-dimensional periodic arrangement of structures that are small relative to the wavelength of light. The metasurface (periodic structure) 150D shown in FIG. 9 is arranged in a lattice pattern on the plate-like surface of the front plate-shaped portion 142D of the fixture 140D. The structures of the metasurface (periodic structure) 150D shown in FIG. 9 are each rectangular, but may also be circular or have other shapes. The arrangement of the metasurface (periodic structure) 150D or the shape of each structure is designed appropriately depending on the frequency band of the electromagnetic waves to be reflected, etc.

[0067] This embodiment further illustrates an example embodiment including the following configuration: the fixing device (140D) has an outer peripheral surface portion (145D) extending from the front plate portion (142D) to the antenna element surface portion (111) and surrounding the outer periphery of the antenna element (120) on the antenna element surface portion (111). This provides an antenna device that can suppress deterioration of reflection amplitude characteristics of electromagnetic waves arriving from outside due to electromagnetic waves incident at angles other than frontal incidence. Furthermore, the present disclosure provides similar effects to those described above by applying the above configuration to a system or the like including the antenna device.

[0068] Embodiment 5. In the above-described embodiment 4, in addition to the embodiments 1 to 3, a configuration has been described in which a ring-shaped configuration that surrounds the internal configuration is provided between the front plate portion of the fixture and the antenna element surface of the housing. In embodiment 5, a configuration example will be described in which the fixture is configured to have a regular ring shape when the antenna device is viewed from the front, thereby reducing the observability of the antenna device. In embodiment 5, duplicated descriptions of components according to embodiment 5 that are the same as components according to embodiment 1, embodiment 2, embodiment 3, or embodiment 4 that have already been described will be omitted as appropriate.

[0069] A configuration example of an antenna device according to a fifth embodiment of the present disclosure will be described. Fig. 10 is a perspective view schematically illustrating a configuration example of an antenna device 100E according to the fifth embodiment of the present disclosure. Fig. 11 is a front view schematically illustrating a configuration example of an antenna device 100E according to the fifth embodiment of the present disclosure. The antenna device 100E shown in Figs. 10 and 11 differs from the antenna device 100D already described in that the fixture has a regular ring shape when viewed from the front. The antenna device 100E shown in Figs. 10 and 11 includes a housing 110E, a radome 130E, a fixture 140E, and a metasurface (periodic structure portion) 150E.

[0070] The housing 110D may have the same configuration as the housing 110C already described, and a detailed description thereof will be omitted. The radome 130D may have the same configuration as the radome 130C already described, and a detailed description thereof will be omitted. The metasurface (periodic structure portion) 150D may have the same configuration as the metasurface (periodic structure portion) 150C already described, and a detailed description thereof will be omitted.

[0071] The fixing device 140E is configured to appear as a regular ring when the antenna device 100E is viewed from the front (when viewed in the direction α). The fixing device 140E shown in Figures 10 and 11 includes an opening 141E, a front plate-shaped portion 142E, and an outer peripheral surface portion 145E.

[0072] The opening 141E fixes the radome 130E to the housing 110E. The fixing device 140E shown in Figures 10 and 11 includes an opening 141E, a front plate-like portion 142E, and an outer peripheral surface portion 145E. The fixing device 140E has the front plate-like portion 142E arranged in the housing 110E so as to face the antenna element surface portion (111) on which the antenna element (120) is mounted. The fixing device 140E has an opening 141E so as to expose the radome 130E. The fixing device 140E shown in Figures 10 and 11 has a cylindrical or approximately cylindrical shape.

[0073] The opening 141E is formed in the center of the front plate portion 142E so as not to cover the radome 130E in the normal direction (direction a) of the antenna element surface portion (111). The opening 141E shown in Figures 10 and 11 has a circular or nearly circular shape when viewed toward the front of the antenna device 100E (when viewed toward direction α).

[0074] The front plate portion 142E has a metasurface (periodic structure portion) 150E made of a material that reflects electromagnetic waves. The front plate portion 142E has an opening 141E formed therein that does not cover the radome 130E in the normal direction (direction a) of the antenna element surface portion (111). The front plate portion 142E shown in Figures 10 and 11 has a regular ring shape or a nearly regular ring shape when viewed from the front of the antenna device 100E (when viewed in direction α).

[0075] The outer peripheral surface portion 145D extends from the front plate-like portion 142E to the antenna element surface portion (111) and surrounds the outer periphery of the radome 130E covering the antenna element (120) on the antenna element surface portion (111). That is, the fixing device 140E has the outer peripheral surface portion 145E that extends from the front plate-like portion 142E to the antenna element surface portion (111) and surrounds the outer periphery of the antenna element (120) on the antenna element surface portion (111). With this configuration, it is possible to suppress deterioration of the reflection amplitude characteristics of electromagnetic waves arriving from outside due to electromagnetic waves incident at angles other than frontal incidence.

[0076] Here, the features of this embodiment will be described. The front plate portion 142E has an opening 141E that does not cover the radome 130E in the normal direction of the antenna element surface portion (111). The front plate portion 142E has a regular ring shape in which the central axis of the outer diameter of the front plate portion 142E is the same as the central axis of the inner diameter, which is the diameter of the opening 141E. By configuring it in this way, it is possible to further suppress deterioration of the reflection amplitude characteristics of electromagnetic waves arriving from the outside due to electromagnetic waves incident from angles other than frontal incidence. Specifically, such an antenna device 100E is designed, for example, as follows. The outer diameter r of the front plate portion 142E １ and the inner radius r ２ are configured to have values ​​shown in the following equations (2) and (3). However, in the formula (2) and the formula (3), r ＡＮＴ is the outer diameter of the antenna element (120), and RCS ｔａｒｇｅｔ are the reflection amplitude characteristics of the antenna element (120), the radome 130E, and the housing 110E. With this configuration, the shape of the fixing tool can be formulated using the reflection amplitude characteristics of the antenna element, the radome, and the housing, which makes it easier to design the antenna device 100E of the present disclosure.

[0077] This embodiment further illustrates an example embodiment including the following configuration: The antenna device is characterized in that the front plate portion (142E) has an opening (141E) that does not cover the radome (130E) in the normal direction of the antenna element surface portion, and has a regular ring shape in which the central axis of the outer diameter of the front plate portion (142E) is equal to the central axis of the inner diameter, which is the diameter of the opening (141E). This further provides an advantage of providing an antenna device that can further suppress deterioration of reflection amplitude characteristics due to electromagnetic waves incident from angles other than frontal incidence, with respect to electromagnetic waves arriving from outside. Furthermore, the present disclosure achieves the same advantage as the above by applying the above configuration to a system or the like including the antenna device.

[0078] This embodiment further shows an example of a configuration including the following: １ and the inner radius r ２ The antenna device is configured so that r is a value shown in the above-mentioned formula (2) and formula (3). ＡＮＴ is the outer diameter of the antenna element (120), and RCS ｔａｒｇｅｔ is the reflection amplitude characteristic of the antenna element (120), the radome (130E), and the housing (110E). As a result, the present disclosure further provides the effect of facilitating the design of the antenna device of the present disclosure, since the shape of the fixing tool can be formulated using the reflection amplitude characteristics of the antenna element, the radome, and the housing. Furthermore, the present disclosure provides the same effect as the above by applying the above configuration to a system including an antenna device, etc.

[0079] It should be noted that, within the scope of this disclosure, the embodiments may be freely combined, any component of each embodiment may be modified, or any component of each embodiment may be omitted.

[0080] The present disclosure can reduce the observability of an antenna device compared to conventional methods, thereby preventing other antenna devices from making erroneous observations, and is suitable for use in, for example, antenna devices mounted on mobile objects.

[0081] 100, 100A, 100B, 100C, 100D, 100E Antenna device, 110, 110A, 110B, 110C, 110D, 110E Housing, 111, 111B Antenna element surface portion, 120, 120B Antenna element, 130, 130A, 130B, 130C, 130D, 130E Radome, 140, 140A, 140B, 140C, 140D, 140E Fixing device, 141, 141A, 141B, 141C, 141D, 141E Opening, 142, 142A, 142B, 142C, 142D, 142E Front plate portion, 143 Metal portion, 144 Dielectric portion, 145D, 145E Outer surface portion, 150, 150A, 150B, 150C, 150D, 150E metasurface (periodic structure portion).

Claims

1. An antenna device comprising: an antenna element; a housing; a radome that covers the antenna element placed on the housing; and a fixture that fixes the radome to the housing, the fixture having a front plate portion that is arranged to face the antenna element surface portion on which the antenna element is placed on the housing, wherein the front plate portion has a periodic structure portion made of a material that reflects electromagnetic waves.

2. An antenna device comprising: an antenna element; a housing; a radome covering the antenna element placed on the housing; and a fixture for fixing the radome to the housing, the fixture having a front plate portion arranged to face the antenna element surface portion on which the antenna element is placed on the housing; wherein, in a predetermined frequency band, the distance between the front plate portion and the antenna element surface portion has reflection phase characteristics in which the reflection phase characteristics of the antenna element, the radome, and the housing are in opposite phase to the reflection phase characteristic of the fixture, and the area of ​​the surface of the front plate portion facing the antenna element surface portion is an area that makes the reflection amplitude characteristics of the antenna element, the radome, and the housing equal to the reflection amplitude characteristic of the fixture.

3. An antenna device comprising: an antenna element; a housing; a radome covering the antenna element placed on the housing; and a fixture for fixing the radome to the housing, the fixture having a front plate-like portion arranged to face the antenna element surface portion on which the antenna element is placed on the housing; wherein the front plate-like portion has a periodic structure portion made of a material that reflects electromagnetic waves, and in a predetermined frequency band, the distance between the front plate-like portion and the antenna element surface portion has reflection phase characteristics such that the reflection phase characteristics of the antenna element, the radome, and the housing are in opposite phase to the reflection phase characteristic of the fixture, and the area of ​​the surface of the front plate-like portion on which the periodic structure portion is arranged is an area that makes the reflection amplitude characteristics of the antenna element, the radome, and the housing equal to the reflection amplitude characteristic of the fixture.

4. The antenna device according to any one of claims 1 to 3, characterized in that the distance δ between the front plate portion and the antenna element surface portion is configured to be within the range shown in the following formula (1): 180-90<abs|P ｔａｒｇｅｔ -P ｃａｎｃｅｌｌｅｒ |+(δ*2π / λ)*(180 / π)<180+90 (1) where, in the above formula (1), abs| | is an absolute function, and P ｔａｒｇｅｔ is the reflection phase characteristic of the fixture, and P ｃａｎｃｅｌｌｅｒ is the reflection phase characteristic of the antenna element, the radome, and the housing, and λ is a frequency in a predetermined frequency band.

5. An antenna device according to any one of claims 1 to 3, characterized in that the fixing device has an outer peripheral surface portion that extends from the front plate portion to the antenna element surface portion and surrounds the outer periphery of the antenna element.

6. The antenna device according to claim 4, wherein the fixing device has an outer peripheral surface portion that extends from the front plate portion to the antenna element surface portion and surrounds the outer periphery of the antenna element.

7. An antenna device as claimed in any one of claims 1 to 3, characterized in that the front plate-shaped portion has an opening that does not cover the radome in the normal direction of the antenna element surface portion, and is a regular ring-shaped portion in which the central axis of the outer diameter of the front plate-shaped portion is the same as the central axis of the inner diameter, which is the diameter of the opening.

8. The antenna device according to claim 4, characterized in that the front plate portion has an opening that does not cover the radome in the normal direction of the antenna element surface portion, and is a regular ring shape in which the central axis of the outer diameter of the front plate portion is the same as the central axis of the inner diameter which is the diameter of the opening.

9. The antenna device described in claim 5, characterized in that the front plate portion has an opening that does not cover the radome in the normal direction of the antenna element surface portion, and is a regular ring shape in which the central axis of the outer diameter of the front plate portion is the same as the central axis of the inner diameter which is the diameter of the opening.

10. The outer diameter r of the front plate-shaped portion １ and the inner radius r ２ The antenna device according to claim 7, characterized in that is configured so that values ​​shown in the following formulas (2) and (3) are obtained. However, in the formula (2) and the formula (3), r ＡＮＴ is the outer diameter of the antenna element, and RCS ｔａｒｇｅｔ is the reflection amplitude characteristic of the antenna element, the radome and the housing.

11. The outer diameter r of the front plate-shaped portion １ and the inner radius r ２ The antenna device according to claim 8, characterized in that is configured so that values ​​shown in the following equations (2) and (3) are obtained. However, in the formula (2) and the formula (3), r ＡＮＴ is the outer diameter of the antenna element, and RCS ｔａｒｇｅｔ is the reflection amplitude characteristic of the antenna element, the radome and the housing.

12. The outer diameter r of the front plate-shaped portion １ and the inner radius r ２ The antenna device according to claim 9, wherein is configured so that values ​​shown in the following formulas (2) and (3) are obtained. However, in the formula (2) and the formula (3), r ＡＮＴ is the outer diameter of the antenna element, and RCS ｔａｒｇｅｔ is the reflection amplitude characteristic of the antenna element, the radome and the housing.

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