Antenna device

Abstract

The antenna device includes: a base attached to a metal object; an antenna disposed on a first surface side of the chassis; and a first protrusion extending from a second surface side opposite to the first surface of the base toward the object, the base includes a metal member having a shape having a long side and a wide side, and the first protrusion is disposed offset from a center line extending in the direction of the long side in the metal member.

Description

Technical Field

[0001] The present invention relates to an antenna device. Background Art

[0002] Patent Document 1 discloses an antenna device mounted on a vehicle. Prior Art Documents Patent Document

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018 - 113574 Summary of the Invention

[0004] However, if the antenna device is mounted on, for example, the roof of a vehicle, the antenna device may sometimes be affected by unwanted resonance generated between the floor of the antenna device and a metal base. In such a case, the frequency of the unwanted resonance is sometimes shifted by changing the capacitance between the floor and the metal base and the roof, thereby reducing the impact on the antenna device.

[0005] However, even when the capacitance between the floor of the antenna device and the metal base and the roof is changed, the impact of the unwanted resonance on the antenna device cannot sometimes be sufficiently suppressed.

[0006] An example object of the present invention is to suppress the impact of unwanted resonance on the antenna device. Other objects of the present invention will become apparent from the description of this specification.

[0007] An antenna device according to one aspect of the present invention includes: a base mounted on a metallic object; an antenna disposed on the first surface side of the base; and a first protrusion extending from the second surface side, opposite to the first surface of the base, toward the object. The base includes a metal member having a shape with a long side and a wide side, and the first protrusion is disposed offset from the center line extending in the direction of the long side in the metal member.

[0008] According to the above aspect of the present invention, the impact of unwanted resonance on the antenna device can be sufficiently suppressed. Brief Description of the Drawings

[0009] Figure 1 is a side view of the vehicle 1. Figure 2 is a diagram showing the configuration of the antenna device 10A. Figure 3 is a top view of the inside of the antenna device 10A. Figure 4 is a diagram for explaining the back surface of the metal base 30. Figure 5 is a diagram for explaining the mounting state of the antenna device 10A on the roof 2. Figure 6 It is a diagram showing the radiation characteristics of the patch antenna 50 in the antenna device 10A. Figure 7 It is a diagram for explaining the mounting state of the antenna device 10A on the vehicle roof 2. Figure 8 It is a diagram for explaining the parasitic capacitance between the metal base 30 and the vehicle roof 2. Figure 9 It is a diagram for explaining the parasitic capacitance between the metal base 32 and the vehicle roof 2. Figure 10 It is a diagram showing the radiation characteristics of the patch antenna 50 in the antenna device 10B. Figure 11 It is a diagram showing the voltage distribution of the metal base 30 in the antenna device 10A. Figure 12 It is a diagram showing the voltage distribution of the metal base 32 in the antenna device 10B. Figure 13 It is for explaining Figure 11 The schematic diagram of the voltage distribution of the A3 - A3 cross-section. Figure 14 It is a diagram showing an example of the voltage distribution of a general microstrip antenna. Figure 15 It is a schematic diagram for explaining the configuration for suppressing unwanted resonance. Figure 16 It is a diagram for explaining the leaf spring 210. Figure 17 It is a diagram for explaining the back surface of the metal base 30. Figure 18 It is a diagram showing the radiation characteristics of the patch antenna 50 in the antenna device 10C. Figure 19 It is a diagram showing the voltage distribution of the metal base 30 in the antenna device 10C. Figure 20 It is a diagram for explaining the back surface of the metal base 30 where the leaf springs 210a to 210d are arranged. Figure 21 It is a diagram showing the configuration of the antenna device 500. Figure 22 It is a diagram for explaining the back surface of the metal base 610. Detailed implementation mode

[0010] According to the description of this specification and the attached drawings, at least the following matters become clear.

[0011] Hereinafter, the preferred implementation mode of the present invention will be described with reference to the attached drawings. For the same or equivalent constituent elements, components, etc. shown in each drawing, the same reference numerals are assigned, and repeated explanations are appropriately omitted.

[0012] ===Definition of Vehicle 1 and Directions=== Figure 1 This is a side view of vehicle 1 equipped with antenna device 10A. In addition, Figure 1 an enlarged view showing the state after the installation of antenna device 10A is also shown. Here, antenna device 10A is installed on the roof 2 of vehicle 1. In addition, "vehicle" refers to wheeled transportation means such as motor vehicles and construction engineering machinery.

[0013] Hereinafter, the front-rear direction of vehicle 1 is set as the x direction, the left-right direction perpendicular to the x direction is set as the y direction, and the vertical direction perpendicular to the x direction and the y direction is set as the z direction. In addition, from the driver's seat of vehicle 1, the front side is set as the +x direction, the right side is set as the +y direction, and the roof direction (upward direction) is set as the +z direction. In addition, the front-rear, left-right, and up-down directions of antenna device 10A are described as being the same as those of vehicle 1.

[0014] ===Outline of Antenna Device 10A=== First, refer to Figure 2 to explain the outline of the configuration of a general antenna device 10A. Antenna device 10A is an antenna device for a vehicle (hereinafter, sometimes appropriately referred to as "vehicle antenna device"), and includes an antenna base 20, a housing 21, substrates 40 to 42, and a patch antenna 50.

[0015] Antenna base 20 is a plate-shaped member that forms the bottom surface of antenna device 10A, and includes a metal base 30 and a gasket 31. Metal base 30 is a "metal member" that functions as a ground part of antenna device 10A by being electrically connected to vehicle 1. In addition, metal base 30 is, for example, a casting made of aluminum alloy.

[0016] Gasket 31 is a waterproof member installed on metal base 30 so as to surround the outer periphery of metal base 30. Although it will be described in detail later, when antenna device 10A is installed on vehicle 1, gasket 31 is in close contact with roof 2 so that the gap between antenna device 10A and roof 2 disappears. As a result, gasket 31 can prevent water from entering the inside of antenna device 10A.

[0017] In addition, here, antenna base 20 is composed of metal base 30 and gasket 31, but it is not limited thereto. For example, antenna base 20 may include a metal sheet (that is, a metal plate) instead of metal base 30.

[0018] In addition, the antenna base 20 can also be composed of either an insulating base made of resin and a metal base or a metal plate. Moreover, the antenna base 20 can also be composed of three components: an insulating base, a metal base, and a metal plate. In this case, the metal plate can also be equivalent to the "metal component".

[0019] The housing 21 is a component (so-called radome) that forms a housing space for accommodating the patch antenna 50 etc. together with the antenna base 20 by covering the antenna base 20. The housing 21 is a housing made of a synthetic resin (such as ABS resin) having electromagnetic wave permeability, and has a shark fin shape that is low in the front and becomes higher as it goes toward the rear.

[0020] The substrate 40 is a circuit board on which the patch antenna 50 described later is mounted, and is disposed on the surface (the upward-facing surface) of the metal base 30. The substrates 41 and 42 are also circuit boards for mounting antennas, similar to the substrate 40.

[0021] The patch antenna 50 is, for example, an antenna for receiving radio waves in the L1 band (center frequency: 1575.42 MHz) and the L5 band (center frequency: 1176.45 MHz) for the Global Navigation Satellite System (GNSS). The patch antenna 50 has a dielectric 60 formed of a dielectric material such as ceramic, and a radiation element 61 for handling radio waves in the L1 band and the L5 band.

[0022] In addition, in the antenna device 10A, the patch antenna 50 is only mounted on the substrate 40 among the substrates 40 to 42, but antennas can also be mounted on the substrates 41 and 42. For example, an antenna for handling radio waves for long-distance communication such as LTE (Long Term Evolution) and an antenna for receiving AM / FM broadcast radio waves can be mounted on the substrate 41. In addition, an antenna for receiving radio waves in the DAB (Digital Audio Broadcast) band can be mounted on the substrate 41. In addition, the LTE antenna, for example, handles radio waves in the 700 MHz to 5.0 GHz band.

[0023] In addition, on the substrate 42, for example, an antenna for handling radio waves for V2X (Vehicle-to-Everything) and a keyless antenna for a keyless entry system can be mounted. In addition, the keyless entry system is also called a smart entry system, and the operating frequency of the keyless antenna is, for example, 925 MHz. In this way, Figure 2 For simplicity, it is assumed that only one patch antenna 50 is included, but the antenna device 10A is a composite antenna device capable of accommodating multiple antennas.

[0024] Here, the surface (or upper surface) of the antenna base 20 corresponds to the "first surface", and the back surface (or lower surface) of the antenna base 20 corresponds to the "second surface". The directions on the surface side of the antenna base 20 and on the surface side of the metal base 30 are both upward directions, and the directions on the back side of the antenna base 20 and on the back side of the metal base 30 are both downward directions.

[0025] ===Details of the internal structure of the antenna device 10A and the installation state on the vehicle roof 2=== Next, with reference to Figures 3 to 5 the details of the internal structure of the antenna device 10A and the state in which the antenna device 10A is installed on the vehicle roof 2 of the vehicle 1 will be described. In addition, Figure 3 is a view for explaining the surface side of the antenna base 20, Figure 4 is a view for explaining the back side of the metal base 30. Figure 5 is a view for explaining the state in which the antenna device 10A is installed on the vehicle roof 2.

[0026] In addition, Figure 3 , Figure 4 in order to simplify, some components (for example, Figure 3 the substrate 41 in Figure 4 the gasket 31 in Figure 5 Although what is shown in Figure 3 is a side view observed from the left direction in the state where the antenna device 10A is installed on the vehicle roof 2, for simplicity, only the vehicle roof 2 is shown as the

[0027] As shown in Figure 3 , Figure 4 the metal base 30 has a shape with a long side extending in the front-rear direction and a wide side extending in the left-right direction when viewed from above. Therefore, hereinafter, the front-rear direction may sometimes be referred to as the "long side direction (or long side direction)", and the left-right direction may be referred to as the "wide side direction (or wide side direction)". In addition, here, the center line extending in the direction of the long side of the metal base 30 is set as the "center line CL".

[0028] The resin member 70 is inserted into the opening 35 near the center of the metal base 30 from the surface side of the metal base 30 (refer to the enlarged view in Figure 4 ). In addition, as shown in Figure 3 , a concave portion 71 and an opening 72 are formed on the member 70. In addition, in the enlarged view in Figure 4 , for simplicity, the opening 35 formed in the metal base 30 and the mounting portion 36 (described later) are shown, and the member 70 and the like are omitted.

[0029] The recess 71 is, for example, a depression for determining the configuration of a feeder line (not shown) of the patch antenna 50, and the feeder line is embedded in the recess 71. The opening 72 is a through-hole formed in the member 70 for taking out the feeder line from the front surface side to the back surface side of the metal base 30.

[0030] In addition, as Figure 4 the enlarged view of Figure 5 and the enlarged view of Figure 5 show, an installation portion 36 for use when the metal base 30 is mounted on the vehicle roof 2 is formed on the back surface side of the metal base 30. In addition, Figure 5 the enlarged view shows a state in which a capture fastener 80 and a bolt 81 (described later) are disassembled.

[0031] The installation portion 36 is a protruding portion extending downward from the back surface of the metal base 30 and is inserted into a through-hole provided in the vehicle roof 2 of the vehicle 1. When the installation portion 36 is inserted into the through-hole of the vehicle roof 2, a metal capture fastener 80 for fixing the metal base 30 to the vehicle roof 2 is mounted on the installation portion 36.

[0032] And, after the capture fastener 80 is mounted on the installation portion 36, the bolt 81 is inserted into a threaded hole (not shown) formed in the lower end portion of the installation portion 36. As a result, fixing is performed in a state where a part of the metal capture fastener 80 is in contact with the back surface (lower surface) of the vehicle roof 2, whereby the metal base 30 and the vehicle roof 2 are electrically connected. Therefore, in the antenna device 10A, the metal base 30 functions as a grounding member.

[0033] In addition, when the antenna device 10A is mounted on the vehicle roof 2, the gasket 31 is in close contact with the surface (upper surface) of the vehicle roof 2 so that the gap between the gasket 31 and the vehicle roof 2 disappears. Therefore, it is possible to prevent water from entering the inside of the vehicle 1 between the antenna device 10A and the vehicle roof 2.

[0034] ===Radiation efficiency of the patch antenna 50=== Figure 6 is a diagram showing the radiation efficiency of the patch antenna 50 in the antenna device 10A. In addition, Figure 6 the horizontal axis of is the operating frequency of the patch antenna 50, and the vertical axis is the radiation efficiency of the patch antenna 50. Here, for simplicity, the antenna device 10A is mounted on a metal plate (not shown) having the same shape as the vehicle roof 2, and the radiation efficiency of the patch antenna 50 is measured. In addition, hereinafter, the metal plate having the same shape as the vehicle roof 2 is referred to as "metal plate X".

[0035] As can be seen from Figure 6As described above, when the patch antenna 50 operates at 1700 MHz, the radiation efficiency of the patch antenna 50 deteriorates to -1.29 dB. The patch antenna 50 is an antenna for the L1 band of GNSS. Therefore, it is speculated that when the antenna device 10A is installed on the actual vehicle 1, the reception characteristics of the radio waves in the L1 band of GNSS will deteriorate. Here, the reason for the deterioration of the radiation efficiency of the patch antenna 50 will be described.

[0036] ===Regarding unwanted resonance=== Figure 7 Similar to Figure 5 is a side view for explaining the installation state of the antenna device 10A on the roof 2, and the gasket 31 is omitted. Here, the actual roof 2 of the vehicle 1 is curved, and thus, as Figure 6 shown, a gap 100 is formed between the back surface of the metal base 30 and the surface of the roof 2. As a result, as Figure 8 illustrated, a parasitic capacitance (hereinafter referred to as "parasitic capacitance C0") is generated between the metal base 30 and the roof 2. In addition, Figure 8 in, the distance between the metal base 30 and the roof 2 in the cross-section of A2 - A2 is set as "distance d0".

[0037] In this case, generally, a voltage at the resonance frequency corresponding to the parasitic capacitance C0 and the inductance of the metal base 30 (i.e., unwanted resonance) is generated in the metal base 30. Assuming that in the case where the radiation characteristics of the patch antenna 50 deteriorate due to the unwanted resonance corresponding to the parasitic capacitance C0 and the inductance of the metal base 30, if the parasitic capacitance C0 is changed, the frequency at which the radiation characteristics deteriorate will also change.

[0038] ===Deformation example of the metal base and change in radiation characteristics=== Figure 9 is a diagram for explaining the parasitic capacitance generated in the metal base 32 and the roof 2. In the front part of the back surface of the metal base 32, a concave portion 110 (so-called "counterbore") that is recessed compared to the outer peripheral side portion of the metal base 32 is formed. In addition, the metal base 30 and the metal base 32 have the same shape except for the concave portion 110.

[0039] Therefore, as shown in the cross-sectional view of A2 - A2 of the metal base 32, the "distance d1" between the surface of the metal base 32 where the concave portion 110 is formed and the surface of the roof 2 is longer than the above-mentioned Figure 8 distance d0.

[0040] As a result, the parasitic capacitance C1 generated between the metal base 32 and the roof 2 is larger than Figure 8The parasitic capacitance C0 is small, and it is thus speculated that the resonance frequency caused by the parasitic capacitance C1 (i.e., the frequency of unwanted resonance) will become higher.

[0041] The antenna device 10B is a vehicle antenna device that uses the metal base 32 instead of the metal base 30 (see Figure 2 ). In addition, the configuration of the antenna device 10B other than the metal base 32 is the same as that of the antenna device 10A. Therefore, the detailed description of the antenna device 10B is omitted here.

[0042] Here, the antenna device 10B is mounted on a metal plate X having the same shape as the vehicle roof 2, and the radiation efficiency of the patch antenna 50 in the antenna device 10B is measured. Figure 10 is a graph showing the radiation efficiency (solid line) of the patch antenna 50 of the antenna device 10B. In addition, Figure 10 for reference, the radiation efficiency of the patch antenna 50 of the antenna device 10A is also shown by a dotted line.

[0043] As can be seen from Figure 10 , when the patch antenna 50 of the antenna device 10B operates at 1550 MHz, the radiation efficiency of the patch antenna 50 deteriorates and becomes -1.83 dB. That is, the frequency fb (1550 MHz) of the unwanted resonance in the antenna device 10B is lower than the frequency fa (1700 MHz) of the unwanted resonance in the antenna device 10A.

[0044] As described above, assuming that the frequencies fa and fb of the unwanted resonances of the antenna devices 10A and 10B are caused by the parasitic capacitances C0 and C1 respectively, the frequency fb would be higher than the frequency fa. However, as Figure 6 and Figure 10 show, the frequency fb is lower than the frequency fa, and thus it is considered that the unwanted resonances of the antenna devices 10A and 10B are generated based on physical phenomena not caused by the parasitic capacitances C0 and C1.

[0045] ===Verification of the cause of the unwanted resonance in the antenna devices 10A and 10B === Figure 11 is a graph showing the voltage distribution on the back surface of the metal base 30 in the antenna device 10A (simulation result). Figure 11 In this figure, the parts with large voltage amplitudes are shown in light colors. In the metal base 30, the voltage amplitude becomes large in the front and right-end region 120a and the front and left-end region 120b.

[0046] Figure 12 is a graph showing the voltage distribution on the back surface of the metal base 32 in the antenna device 10B. Figure 12In this case, the color of the part with a large voltage amplitude is shown lightly. The same applies to the metal base 32, where the voltage amplitude increases in the regions 121a at the front and right end and 121b at the front and left end. In this way, in both the metal bases 30 and 32, the voltage amplitude increases at the front and the end in the broadside direction. Therefore, hereinafter, the metal base 30 is used to verify the physical phenomenon that causes the unwanted resonance.

[0047] Figure 13 It is a schematic diagram Figure 11 showing the voltage distribution in the A3 - A3 cross-section of the metal base 30 for explanation. As Figure 13 shown, in the metal base 30, the voltage amplitude becomes the minimum at the position of the center line (center line CL) in the broadside direction of the metal base 30. And as it moves away from the center line CL of the metal base 30 towards the outside in the broadside direction, the voltage amplitude increases, and at the outer edge part of the metal base 30, the voltage amplitude becomes the maximum. Specifically, the voltage amplitude is almost zero (minimum value) at the center of the metal base 30, the voltage amplitude is the positive maximum at the outer edge part on the left side, and the voltage amplitude is the negative maximum at the outer edge part on the right side.

[0048] Therefore, in the metal base 30, a standing wave (hereinafter referred to as "standing wave S") with a half-wavelength of the length Lw in the broadside direction is generated. In addition, the length Lw in the broadside direction is the representative length in the broadside direction in the region (for example, Figure 11 the regions 120a, 120b) where the voltage amplitude is large and the standing wave S is generated (for example, the length at the part of the line where the A3 - A3 cross-section is recorded).

[0049] Here, if the wavelength of the standing wave S is set as "wavelength λs", then the following relational expression (1) holds between the length Lw and the wavelength λs. Lw = 1 / 2 × λs · · · (1)

[0050] In addition, here, although the wavelength λs of the standing wave S is set as Figure 11 the length in the broadside direction at the part of the line where the A3 - A3 cross-section is shown as above, it is not limited to this, and any length in the broadside direction within the regions 120a, 120b where the standing wave in the broadside direction is generated is acceptable.

[0051] The voltage distribution obtained based on this standing wave S is consistent with Figure 14 the voltage distribution of a two-end open type microstrip antenna (or open resonator) composed of a normal radiation element and a ground plane as shown. In addition, Figure 14 is a schematic diagram for observing the microstrip antenna from the side in a way that the relationship between the radiation element and the ground plane can be understood. Figure 14A radiation element having a length L1 and a width W1 (not shown) is equivalent to a part of the metal base 30, and the floor is equivalent to the vehicle roof 2.

[0052] Figure 14 shows the voltage distribution (solid line) and current distribution (dotted line) in the direction along the length L1 of the radiation element. As can be seen from Figure 14 As shown, at the left and right ends of the length L1 in the long side direction of the radiation element, the voltage amplitude becomes the maximum. Specifically, at the center in the length L1 direction of the radiation element, the voltage amplitude is almost zero (minimum value), at the left end (outer edge part), the voltage amplitude is the positive maximum value, and at the right end, the voltage amplitude is the negative maximum value.

[0053] Therefore, it is considered that the unwanted resonance generated in the metal base 30 of the antenna device 10A is caused by the metal base 30 and the vehicle roof 2 forming an open-ended microstrip antenna.

[0054] === Suppression of unwanted resonance === Figure 15 is a schematic diagram showing a configuration for suppressing the unwanted resonance generated on the metal base 30 (i.e., the standing wave S generated in the wide side direction of the metal base 30). In the metal base 30, at the outer edge in the wide side direction where the impedance becomes high, the voltage amplitude of the standing wave S becomes the maximum. Therefore, in order to suppress the standing wave S, it is only necessary to reduce the impedance in the region of the metal base 30 where the voltage amplitude of the standing wave S is large. Therefore, for example, it is only necessary to dispose a protrusion 200 on the back surface of the metal base 30 that extends from the back surface of the metal base 30 toward the vehicle roof 2 and contacts the surface of the vehicle roof 2.

[0055] Here, as the "protrusion 200", for example, a leaf spring 210 as shown in Figure 16 can be used. Figure 16 is a diagram for explaining the leaf spring 210, including a perspective view of the leaf spring 210 and a diagram showing the usage state of the leaf spring 210.

[0056] The leaf spring 210 is composed of a fixing portion 220, an extending portion 221, and a bending portion 222. The fixing portion 220 is a part fixed to the back surface of the metal base 30 by, for example, a conductive double-sided tape. The extending portion 221 extends obliquely downward from the end of the fixing portion 220, and the bending portion 222 is formed by bending the end of the extending portion 221 on the side opposite to the fixing portion 220. And when the metal base 30 is mounted on the vehicle roof 2, a part of the bending portion 222 is pressed by the vehicle roof 2.

[0057] In addition, here, the leaf spring 210 has been described as an example of the "protrusion 200", but it is not limited thereto, and any member that can reduce the impedance between the metal base 30 and the vehicle roof 2 is acceptable. For example, a part of the back surface of the metal base 30 may be processed into a protrusion shape to serve as the protrusion 200. Alternatively, instead of the leaf spring 210, a conductive washer may be used, for example.

[0058] In addition, here, although it is assumed that the protrusion 200 is in contact with the vehicle roof 2, as long as the impedance between the metal base 30 and the vehicle roof 2 is reduced, the protrusion 200 does not necessarily have to be in contact with the vehicle roof 2. In addition, as Figure 15 shown, preferably, the protrusion 200 is arranged, for example, at a position offset by 1 / 4×Lw (i.e., 1 / 8×λs) or more in the broadside direction from the central axis CL. In addition, Figure 15 in, an example in which the protrusion 200 is arranged at a position offset by 1 / 8×λs or more from the central axis CL has been described, but it is not limited thereto. As long as the protrusion 200 is offset and arranged from the central axis CL in the broadside direction, the amplitude of the standing wave S can be suppressed.

[0059] <<<<<<Regarding the antenna device 10C>>>>>> Here, the antenna device 10C of the present embodiment that can suppress unnecessary resonance will be described (refer to Figure 2 ). The antenna device 10C is the same vehicle-mounted antenna device as the antenna device 10A. The antenna device 10C has the same structure as the antenna device 10A except that a protrusion 200 is arranged on the back side of the metal base 30. Therefore, here, the protrusion 200 arranged on the back of the metal base 30 will be described. In addition, in the present embodiment, the leaf spring 210 is used as the protrusion 200, but other members (such as washers) may be used as described above.

[0060] ===Region on the back of the metal base 30=== Figure 17 is a diagram for explaining the region on the back of the metal base 30. In the present embodiment, the front end of the metal base 30 is set as the end 37, and the rear end is set as the end 38. In addition, the mounting portion 36 used when mounting the antenna base 20 to the vehicle roof 2 is arranged on the center line CL.

[0061] On the back of the metal base 30, the mounting portion 36 is arranged, and Figure 17The region surrounded by the solid-line quadrilateral (the region of the mounting portion 36) is set as the "central region 300". In addition, in the back surface of the metal base 30, the region overlapping with the dashed-line quadrilateral drawn outside to the right direction of the central region 300 is set as the "outer region 310a", and the region overlapping with the dashed-line quadrilateral drawn outside to the left direction of the central region 300 is set as the "outer region 310b".

[0062] Therefore, the outer regions 310a and 310b are regions located outside in the direction of the wide side of the central region 300 and extending along the direction of the long side.

[0063] In addition, the outer region 310a of the present embodiment includes the adjacent region 320a, and the regions 321a and 322a. The adjacent region 320a is the region in the outer region 310a adjacent to the central region 300. In addition, the region 321a is the region in the outer region 310a located on the end 37 side starting from the adjacent region 320a, and the region 322a is the region in the outer region 310a located on the end 38 side starting from the adjacent region 320a.

[0064] Similarly to the outer region 310a, the outer region 310b also includes the adjacent region 320b, and the regions 321b and 322b. The adjacent region 320b is the region in the outer region 310b adjacent to the central region 300. In addition, the region 321b is the region in the outer region 310b located on the end 37 side starting from the adjacent region 320b, and the region 322b is the region in the outer region 310b located on the end 38 side starting from the adjacent region 320b.

[0065] ===Configuration of the leaf spring in the antenna device 10C === As Figure 11 shown, on the metal base 30, in the front of the metal base 30 and at the end in the wide side direction, a region where the voltage amplitude becomes higher is generated. Then, as Figure 17 shown, on the metal base 30 of the antenna device 10C, the leaf spring 210a is disposed in the region 321a, and the leaf spring 210b is disposed in the region 321b. In addition, the leaf springs 210a and 210b have the same configuration as the leaf spring 210 Figure 16 described above.

[0066] In addition, Figure 17In the figure, the distances da from the center line CL to the leaf spring 210a and db from the center line CL to the leaf spring 210b are shown. In addition, the distance da is, for example, the distance from the center line CL to the geometric center of the leaf spring 210a when viewed from above, and the distance db is, for example, the distance from the center line CL to the geometric center of the leaf spring 210b when viewed from above. Further, the distances da and db in the present embodiment are longer than the above-mentioned 1 / 4×Lw (i.e., 1 / 8×λs).

[0067] ===Radiation characteristics of the patch antenna 50 in the antenna device 10C=== Figure 18 This is a diagram showing the radiation characteristics of the patch antenna 50 in the antenna device 10C. In addition, Figure 18 in this figure, the radiation characteristics of the patch antenna 50 in the antenna device 10C are represented by solid lines, and the radiation characteristics of the patch antenna 50 in the antenna device 10A obtained Figure 6 in this figure are represented by dotted lines. As can be seen from Figure 18 this figure, the reduction in the radiation characteristics of the patch antenna 50 in the antenna device 10A is improved.

[0068] ===Voltage distribution of the metal base 30 of the antenna device 10C=== Figure 19 This is a diagram showing the voltage distribution in the metal base 30 in which the leaf springs 210a and 210b are arranged. As can be seen by comparing Figure 17 this figure with the voltage distribution of the metal base 30 in which no leaf spring is arranged (refer to Figure 19 ) as known, unnecessary resonance is suppressed and the voltage amplitude is reduced over the entire range of the metal base 30. Figure 11 In this way, in the antenna device 10C, by arranging the leaf springs 210a and 210b in the metal base 30, unnecessary resonance can be suppressed.

[0069]

[0070] <<<<<<Regarding the arrangement, number, etc. of the leaf springs>>>>>>

[0071] ===Symmetry=== In the antenna device 10C, as shown Figure 17 in this figure, the leaf springs 210a and 210b are arranged symmetrically with respect to the center line CL, but it is not limited to this. For example, the distance da to the leaf spring 210a may be longer than the distance db to the leaf spring 210b. The leaf spring 210a may also be arranged on the end portion 37 side of the front end as compared with the leaf spring 210b.

[0072] ​In addition, the leaf spring 210a is arranged such that the axis in the long side direction of the leaf spring 210a is substantially parallel to the center line CL in the long side direction of the metal base 30, but it is not limited thereto. For example, the axis in the long side direction of the leaf spring 210a and the central axis CL may be substantially perpendicular, or may have a specified angle (e.g., 30°). In addition, here, the leaf spring 210a is described, but the same applies to the leaf spring 210b.

[0073] For example, as long as the leaf spring 210a and the leaf spring 210b are respectively arranged in the regions 321a, 321b that are symmetric with respect to the center line CL, the voltage amplitude of the standing wave S can be made very small, and unwanted resonance can be suppressed. ===Arrangement region of leaf spring=== In the antenna device 10C, the leaf springs 210a, 210b are respectively arranged in the regions 321a, 321b, but it is not limited thereto. The leaf springs 210a, 210b may also be respectively arranged in the adjacent regions 320a, 320b or the regions 322a, 322b that are symmetric with respect to the center line CL. Even in this case, the impedance between the metal base 30 and the vehicle roof 2 can be reduced, thereby suppressing unwanted resonance.

[0074] ===Number of leaf springs=== In the antenna device 10C, two leaf springs 210a, 210b are arranged on the back surface of the metal base 30, but the number of the arranged leaf springs is not limited thereto. For example, depending on the shape of the vehicle roof on which the antenna device 10C is installed and the installation position of the antenna device 10C on the vehicle roof, there is a case where a gap is formed between only one of the outer regions 310a, 310b, i.e., the outer region 310a and the vehicle roof. In this case, by arranging only one leaf spring in the outer region 310a, the unwanted resonance caused by the gap between the metal base 30 and the vehicle roof can be suppressed.

[0075] In addition, here, it is assumed that one leaf spring is arranged in the outer region 310a, but it may also be that multiple leaf springs are arranged in the outer region 310a. That is, as long as at least one leaf spring is arranged in the outer region 310a, the unwanted resonance can be suppressed.

[0076] Generally, when the shape of the vehicle roof on which the antenna device 10C is installed and the installation position of the antenna device 10C on the vehicle roof are known, it is possible to predict what kind of gap will be generated between the metal base 30 and the vehicle roof. However, sometimes, for example, due to the accuracy during the installation of the antenna device 10C, the predicted gap may change.

[0077] Therefore, it is difficult to correctly predict the region of the standing wave S generated on the metal base. Thus, for example, as Figure 20As shown, it can also be that leaf springs 210a and 210b are respectively arranged in regions 321a and 321b, and leaf springs 210c and 210d are respectively arranged in regions 322a and 322b. In addition, the leaf springs 210c and 210d are arranged in a symmetric manner with respect to the center line CL.

[0078] By adopting such a configuration, even if standing waves S are generated in any region of the metal base 30, the voltage amplitude of the standing waves S can be reduced. Therefore, as Figure 20 shown, four leaf springs 210a to 210d are arranged on the metal base 30, whereby unwanted resonance can be reliably suppressed.

[0079] ===Correspondence relationship=== Figure 20 In the metal base 30 of , when the end 37 corresponds to the "first end" and the end 38 corresponds to the "second end", the regions 321a and 321b correspond to the "first region", and the regions 322a and 322b correspond to the "second region".

[0080] Figure 20 In the metal base 30 of , when the end 38 corresponds to the "first end" and the end 37 corresponds to the "second end", the regions 322a and 322b correspond to the "first region", and the regions 321a and 321b correspond to the "second region".

[0081] In addition, for example, the leaf spring 210a corresponds to the "first protrusion", the leaf spring 210b corresponds to the "second protrusion", the leaf spring 210c corresponds to the "third protrusion", and the leaf spring 210d corresponds to the "fourth protrusion". The roof 2 of the vehicle 1 corresponds to the "metal object".

[0082] In addition, Figure 20 in , the distances of the leaf springs 210a and 210b from the center line CL are distances da and db, and the distances of the leaf springs 210c and 210d from the center line CL are distances dc and dd. Figure 20 In as well as in Figure 17 similarly, the distances da to dd are respectively set to be longer than the above-mentioned 1 / 4×Lw (i.e., 1 / 8×λs).

[0083] <<<<<<Symmetry other than vehicles>>>>>> The antenna device 10C of the present embodiment is assumed to be used for a wheeled vehicle, that is, a "vehicle", but is not limited thereto. For example, it can also be used for moving bodies such as aircraft, detectors, wheel-less construction machinery, agricultural machinery, and ships. In addition, the antenna device 10C is assumed to be installed on the roof 2 of the vehicle 1, but it can also be carried into the vehicle and installed on, for example, a metal part inside the vehicle.

[0084] Even in this case, the antenna device 10C can suppress the unwanted resonance that may occur by mounting the antenna device 10C on the metal part.

[0085] === Antenna device 500 === Figure 21 The antenna device 500 is the same device as the Figure 2 antenna device 10A, and is composed of an antenna base 600, a housing 601, a substrate 602, and a patch antenna 603.

[0086] The antenna base 600 is a plate-shaped member that forms the bottom surface of the antenna device 500, and is composed of a metal base 610, a metal plate 611, and a gasket 612. In addition, the metal base 610 and the gasket 612 are the same as the metal base 30 and the gasket 31 of the antenna device 10A, respectively.

[0087] The metal plate 611 is electrically connected to the metal base 610 and forms a "metal member" together with the metal base 610.

[0088] The housing 601 is a member that covers the antenna base 600 and forms a housing space together with the antenna base 600 for accommodating the patch antenna 603 and the like.

[0089] The substrate 602 is a circuit board on which the patch antenna 603 described later is mounted, and is disposed on the surface of the metal base 610.

[0090] Similar to the patch antenna 50, the patch antenna 603 is an antenna that responds to radio waves in the L1 band and the L5 band for GNSS. The patch antenna 603 has a radiation element 700 disposed on the surface of a dielectric (not shown), holding members 701, 702, and metal bodies 710, 711.

[0091] Here, the holding member 701 holds the metal body 710 in such a manner that the metal bodies 710, 711 having a surrounding shape that surrounds the center (geometric center) of the radiation element 700 are located above the radiation element 700, and the holding member 702 holds the metal body 711.

[0092] In the patch antenna 603, metal bodies 710, 711 are provided above the radiation element 700 serving as a wave source, whereby the axial ratio of the patch antenna 603 can be adjusted.

[0093] In addition, the metal bodies 710, 711 have a surrounding shape that surrounds the center of the radiation element 700, whereby the change in the impedance of the patch antenna 603 can be suppressed.

[0094] === Region on the back surface of the metal base 610 === Figure 22It is a diagram for explaining the area on the back side of the metal base 610 in the antenna base 600. In the present embodiment, the front end of the antenna base 600 is set as the end 650, and the rear end is set as the end 651. In addition, the mounting portion 740 used when mounting the antenna base 600 to the vehicle roof 2 is arranged on the center line CL. Moreover, the mounting portion 740 is the same as the mounting portion 36.

[0095] In the back side of the metal base 610, the area where the mounting portion 740 is arranged and Figure 17 the area (the area of the mounting portion 740) surrounded by the solid-line quadrilateral in it is set as the "central area 800". In addition, in the back side of the metal base 610, the area overlapping with the dotted-line quadrilateral drawn on the outer side to the right of the central area 800 is set as the "outer area 810a", and the area overlapping with the dotted-line quadrilateral drawn on the outer side to the left of the central area 800 is set as the "outer area 810b".

[0096] Therefore, the outer areas 810a and 810b are areas located outside the wide-side direction of the central area 800 and extending along the long-side direction.

[0097] In addition, the outer area 810a of the present embodiment includes the adjacent area 820a, and the areas 821a and 822a. The adjacent area 820a is the area in the outer area 810a adjacent to the central area 800. In addition, the area 821a is the area in the outer area 810a on the end 650 side starting from the adjacent area 820a, and the area 822a is the area in the outer area 810a on the end 651 side starting from the adjacent area 820a.

[0098] Similarly to the outer area 810a, the outer area 810b also includes the adjacent area 820b, and the areas 821b and 822b. The adjacent area 820b is the area in the outer area 810b adjacent to the central area 800. In addition, the area 821b is the area in the outer area 810b on the end 650 side starting from the adjacent area 820b, and the area 822b is the area in the outer area 810b on the end 651 side starting from the adjacent area 820b.

[0099] In the present embodiment, leaf springs 750a and 750b are respectively arranged in the areas 821a and 821b, and leaf springs 750c and 750d are respectively arranged in the areas 822a and 822b. In addition, the leaf springs 750a and 750b, and the leaf springs 750c and 750d are respectively arranged in a symmetric manner with respect to the center line CL. Moreover, the leaf springs 750a to 750d are the same as the leaf spring 210a and the like respectively.

[0100] In addition, the distances of the leaf springs 750a and 750b from the center line CL are distances da and db, respectively, and the distances of the leaf springs 750c and 750d from the center line CL are distances dc and dd, respectively. Figure 22 is also the same as Figure 17 Similarly, the distances da to dd are each longer than the above-mentioned 1 / 4 × Lw (i.e., 1 / 8 × λs).

[0101] With such a configuration, even if a standing wave S is generated in any region of the metal base 610, the voltage amplitude of the standing wave S can be reduced. Therefore, as Figure 22 shown, by disposing the four leaf springs 750a to 750d on the metal base 610, unwanted resonance can be reliably suppressed.

[0102] Figure 22 In the metal base 610 of Figure 22 , when the end portion 650 corresponds to the "first end portion" and the end portion 651 corresponds to the "second end portion", the regions 821a and 821b correspond to the "first region", and the regions 822a and 822b correspond to the "second region".

[0103] Figure 22 In the metal base 610 of Figure 22 , when the end portion 651 corresponds to the "first end portion" and the end portion 650 corresponds to the "second end portion", the regions 822a and 822b correspond to the "first region", and the regions 821a and 821b correspond to the "second region".

[0104] In addition, for example, the leaf spring 750a corresponds to the "first protrusion", the leaf spring 750b corresponds to the "second protrusion", the leaf spring 750c corresponds to the "third protrusion", and the leaf spring 750d corresponds to the "fourth protrusion".

[0105] ======Summary====== According to this specification, an antenna device is provided in the following manner.

[0106] (Mode 1) Mode 1 is an antenna device having: a base mounted on a metallic object; an antenna disposed on the first surface side of the base; and a first protrusion extending from the second surface side, opposite to the first surface of the base, toward the object. The base includes a metal member having a shape with a long side and a wide side, and the first protrusion is disposed offset from a center line extending in the direction of the long side in the metal member.

[0107] According to the above mode, the leaf spring 210a disposed offset from the center line CL can reduce the impedance between the metal base 30 and the vehicle roof 2, thereby suppressing unwanted resonance.

[0108] (Mode 2) The antenna device of Mode 2 further has a mounting portion used when mounting the base on the object. The mounting portion is disposed on the center line on the second surface side of the base. The area of the mounting portion located on the center line is the central area, and the first protrusion is disposed in an outer area which is located outside the wide side direction of the central area in the second surface of the base and extends along the long side direction.

[0109] According to the above mode, the leaf spring 210a is disposed in the outer area 310a of the metal base 30, thereby enabling the reduction of the amplitude of the standing wave S of the metal base 30. As a result, the unwanted resonance generated on the metal base 30 is suppressed.

[0110] (Mode 3) The antenna device of Mode 3 further has a second protrusion extending from the second surface side of the base toward the object. The second protrusion is disposed in the outer area.

[0111] According to the above mode, the leaf spring 210a is disposed in the outer area 310a, and the leaf spring 210b is disposed in the outer area 310b. Additionally, according to the above mode, the two leaf springs 210a and 210b may also be disposed in one of the two outer areas 310a and 310b (for example, the outer area 310a). According to this mode, the number of leaf springs disposed on the metal base 30 increases, thereby enabling a more significant reduction in the impedance between the metal base 30 and the vehicle roof 2.

[0112] (Mode 4) In the antenna device of Mode 4, the first protrusion and the second protrusion are disposed with the center line therebetween.

[0113] According to the above mode, the leaf spring 210a and the leaf spring 210b are disposed with the center line CL therebetween. According to this mode, the amplitude of the standing wave S of the metal base 30 can be further reduced, thereby suppressing the unwanted resonance.

[0114] (Mode 5) In the antenna device of Mode 5, the base has a first end in the long side direction and a second end located on the opposite side of the first end. The outer area has: an adjacent area adjacent to the central area in the wide side direction; a first area on the first end side of the adjacent area; and a second area on the second end side of the adjacent area. The first protrusion and the second protrusion are disposed in the first area.

[0115] According to the above method, the leaf spring 210a is disposed in the region 321a, and the leaf spring 210b is disposed in the region 321b. That is, the leaf spring 210a and the leaf spring 210b are disposed in regions on the end 37 side of the metal base 30 with the center line CL therebetween. According to this method, the amplitude of the standing wave S of the metal base 30 can be further reduced, thereby suppressing unnecessary resonance.

[0116] (Method 6) The antenna device of Method 6 further includes a third protrusion and a fourth protrusion extending from the second surface side of the base toward the object, and the third protrusion and the fourth protrusion are disposed in the second region with the center line therebetween.

[0117] According to the above method, the leaf spring 210a is disposed in the region 321a, and the leaf spring 210b is disposed in the region 321b. In addition, the leaf spring 210c is disposed in the region 322a, and the leaf spring 210d is disposed in the region 322b. According to this method, regardless of where the standing wave S is generated in the metal base 30, the amplitude of the standing wave S can be reduced, thereby suppressing unnecessary resonance.

[0118] (Method 7) In the antenna device of Method 7, the first protrusion and the second protrusion are disposed symmetrically with respect to the center line, and the third protrusion and the fourth protrusion are disposed symmetrically with respect to the center line.

[0119] According to the above method, the distances da and db of the leaf springs 210a and 210b from the center line CL are equal, and the distances dc and dd of the leaf springs 210c and 210d from the center line CL are equal. Therefore, the amplitude of the standing wave S can be reliably reduced, thereby suppressing unnecessary resonance.

[0120] (Method 8) In the antenna device of Method 8, the first protrusion is disposed offset from the center line by more than 1 / 8 of the wavelength of the standing wave generated in the direction of the wide side of the metal member.

[0121] According to the above method, for example, as Figure 15 shown, the amplitude of the standing wave S generated on the metal base 30 can be reduced, thereby also suppressing unnecessary resonance.

[0122] (Method 9) In the antenna device of Method 9, the object is the roof of a vehicle.

[0123] According to the above method, when the antenna device 10C is mounted on the roof 2 of the vehicle 1, unnecessary resonance generated on the antenna device 10C can be suppressed.

[0124] The above embodiments are used to facilitate the understanding of the present invention and are not used for a limiting interpretation of the present invention. In addition, the present invention can be changed and improved without departing from its gist, and the present invention naturally includes its equivalents. Description of Reference Numerals

[0125] 1 Vehicle 2 Roof 10A to 10C, 500 Antenna Device 20, 600 Antenna Base 21, 601 Housing 30, 32, 610 Metal Base 36, 740 Mounting Portion 37, 38, 650, 651 End 50, 603 Patch Antenna 210a to 210d, 750a to 750d Leaf Spring 300, 800 Central Region 310a, 310b, 810a, 810b Outer Region 320a, 320b, 820a, 820b Adjacent Region 321a, 321b, 322a, 322b, 821a, 821b, 822a, 822b Region.

Claims

1. An antenna device, wherein, comprising: a base mounted on a metallic object; an antenna disposed on the first surface side of the base; and a first protrusion extending from the second surface side, opposite to the first surface of the base, toward the object, the base includes a metallic member, the metallic member has a shape with a long side and a wide side, the first protrusion is disposed offset from the center line extending in the direction of the long side in the metallic member.

2. The antenna device according to claim 1, wherein it further has a mounting portion used when mounting the base to the object, the mounting portion is disposed on the center line on the second surface side of the base, the region of the mounting portion located on the center line is a central region, the first protrusion is disposed in an outer region that is outside the central region in the direction of the wide side of the second surface of the base and extends along the direction of the long side.

3. The antenna device according to claim 2, wherein it further has a second protrusion extending from the second surface side of the base toward the object, the second protrusion is disposed in the outer region.

4. The antenna device according to claim 3, wherein the first protrusion and the second protrusion are disposed with the center line therebetween.

5. The antenna device according to claim 4, wherein the base has a first end in the direction of the long side and a second end located on the opposite side of the first end, the outer region has: an adjacent region adjacent to the central region in the direction of the wide side; a first region located on the first end side of the adjacent region; and a second region located on the second end side of the adjacent region, the first protrusion and the second protrusion are disposed in the first region.

6. The antenna device according to claim 5, wherein it further has a third protrusion and a fourth protrusion extending from the second surface side of the base toward the object, the third protrusion and the fourth protrusion are disposed with the center line therebetween in the second region.

7. The antenna device according to claim 6, wherein the first protrusion and the second protrusion are disposed symmetrically with respect to the center line, the third protrusion and the fourth protrusion are disposed symmetrically with respect to the center line.

8. The antenna device according to claim 1, wherein the first protrusion is disposed offset from the center line by more than 1 / 8 of the wavelength of the standing wave generated in the direction of the wide side of the metallic member.

9. The antenna device according to any one of claims 1 to 8, wherein the object is the roof of a vehicle.

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