Antenna device

Abstract

This antenna device comprises a radiation element and a ground part disposed facing the radiation element. At least one first opening is formed in the ground part. The first opening has a non-radiative structure and has a shape for adjusting the electrical characteristics of the radiation element.

Description

Antenna device

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

[0002] An antenna device including a radiation element and a ground portion is known (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2025-172993

[0004] By the way, when miniaturizing an antenna device including a radiation element and a ground portion, it may affect the characteristics of the antenna included in the antenna device.

[0005] An object of the present invention is to provide an antenna device capable of suppressing the influence on the characteristics of the antenna. Other objects of the present invention will become apparent from the description herein.

[0006] One aspect of the present invention includes a radiation element and a ground portion disposed opposite to the radiation element, the ground portion has at least one first opening formed therein, the first opening has a non-radiating structure, and has a shape for adjusting the electrical characteristics of the radiation element. It is an antenna device.

[0007] According to the above aspect of the present invention, an antenna device capable of suppressing the influence on the characteristics of the antenna can be provided.

[0008] This is a diagram illustrating antenna device 10. This is a diagram illustrating the relationship between a dipole antenna and the ground plate. This is a diagram illustrating antenna device 11. This is a diagram illustrating the frequency characteristics of antenna device 11. This is a diagram illustrating antenna device 12. This is a diagram illustrating the frequency characteristics of antenna device 12. This is a diagram illustrating antenna device 13. This is a diagram illustrating the frequency characteristics of antenna device 13. This is a diagram illustrating antenna device 14. This is a diagram illustrating a modified version of the ground plate. This is a diagram illustrating antenna device 100. This is a diagram illustrating the gain of antenna device 100. This is a diagram illustrating the radiation characteristics of antenna device 100. This is a diagram illustrating antenna device 110. This is a diagram illustrating the characteristics of antenna device 110. This is a diagram illustrating a modified version of the slit. This is a diagram illustrating a modified version of the ground plate. This is a diagram illustrating an antenna device including a patch antenna. This is a diagram illustrating the frequency characteristics of antenna devices 150 to 152. This is a diagram illustrating a modified version of the ground plate. This is a diagram illustrating a ground plate with ribs.

[0009] The following matters become clear from this specification and the accompanying drawings:

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0011] <<Antenna Device 10>> Figure 1 is a diagram illustrating an antenna device 10 that includes a typical cross dipole antenna. First, with reference to Figure 1, we define the direction and other parameters of the antenna device 10 using a cross dipole antenna.

[0012] ==Definition of Directions, etc.== As shown in Figure 1, the direction from the arm portion 61B of the element 50 (described later) formed on the front surface of the substrate 40 (described later) toward the arm portion 61A is defined as the +X direction. The direction from the element 50 on the front surface of the substrate 40 toward the element 51 is defined as the +Y direction. The direction from the base plate 20 toward the substrate 40 is defined as the +Z direction.

[0013] The opposite directions of the +X, +Y, and +Z directions are defined as the -X, -Y, and -Z directions, respectively. Here, the +Z direction is defined as the upward or zenith direction, and the -Z direction is defined as the downward direction.

[0014] The +X, -X, +Y, -Y, +Z, and -Z directions are all unidirectional (directions with a fixed orientation). Furthermore, directions that are not unidirectional, such as both the +X and -X directions, are sometimes simply referred to as the "X direction." Similarly, directions that are both the +Y and -Y directions are sometimes simply referred to as the "Y direction." Also, directions that are both the +Z and -Z directions are sometimes simply referred to as the "Z direction."

[0015] In Figure 1, the +X, +Y, and +Z directions are represented by line segments with arrows to facilitate understanding of the directions in the antenna device 10. Note that the intersection of these arrowed line segments does not represent the coordinate origin. Unless otherwise specified, the definitions of directions described above are the same in other diagrams of antenna devices, including cross dipole antennas.

[0016] The antenna device 10 in Figure 1 is a device that corresponds to radio waves in the frequency band used for, for example, the Global Navigation Satellite System (GNSS). Furthermore, the antenna device 10 is a so-called multi-band device that corresponds to radio waves in multiple frequency bands. For example, the antenna device 10 corresponds to radio waves in the L1 band (1560 MHz to 1606 MHz band) and the L5 band (1164 MHz to 1189 MHz band).

[0017] Here, the wavelength λ for a typical frequency in the L1 band (e.g., f = 1575 MHz) is approximately 190 mm, and the wavelength λ for a typical frequency in the L5 band (e.g., f = 1176 MHz) is approximately 255 mm. Furthermore, one-quarter of the wavelength λ for a typical frequency in the L1 band (e.g., f = 1575 MHz) (hereinafter referred to as λ / 4) is approximately 48 mm, and λ / 4 for a typical frequency in the L5 band (e.g., f = 1176 MHz) is approximately 64 mm. Hereafter, the wavelength of the frequency to which an antenna device or antenna corresponds may be simply referred to as "λ".

[0018] Furthermore, the frequency bands of radio waves that the antenna device 10 supports may be, for example, the L2 band and the L6 band, and the communication standard is not limited to GNSS, but may be other communication standards and frequency bands. The antenna device 10 may support, for example, radio waves in the frequency band for Satellite Digital Audio Radio Service (SDARS) or radio waves in the frequency band for V2X. In other words, the antenna device 10 can support both circular polarization and linear polarization (vertical polarization and horizontal polarization).

[0019] The antenna device 10 includes a ground plate 20, a cross dipole antenna 30, a support member 31, and a circuit board 32.

[0020] (Ground Plate 20) The ground plate 20 is a conductive member that functions as a reflector to improve the directivity of the cross dipole antenna 30 toward the zenith. The ground plate 20 is a metal plate-like member that has a circular shape when viewed in a plan view from the Z direction perpendicular to the ground plate 20. The ground plate 20 corresponds to the "ground section".

[0021] In this case, in order for the ground plate 20 to function as a reflector, it is preferable that the electrical length of the ground plate 20 be approximately 0.4 times or more the wavelength λ of the frequency corresponding to the antenna device 10.

[0022] In the antenna device 10, the diameter φ of the ground plate 20 is set to 150 mm so that the electrical length of the ground plate 20 is equal to or greater than the wavelength of the corresponding frequency of the antenna device 10, which is 0.4λ (for example, 255 mm × 0.4 = 102 mm). Hereafter, unless otherwise specified, the explanation will assume that the diameter φ = 150 mm.

[0023] Here, we have mainly described the size of the ground plate 20 when it functions as a reflector, but the distance between the ground plate 20 and the cross dipole antenna 30 will be discussed later. In addition, although the shape of the ground plate 20 is circular, it may be other shapes such as a quadrilateral, and it may have irregularities formed on its outer edge.

[0024] (Cross dipole antenna 30) The cross dipole antenna 30 is an antenna that corresponds to circular polarization and has a substrate 40 and two dipole antennas 41 and 42.

[0025] The substrate 40 is a dielectric material having a square shape in plan view. While the substrate 40 is described as square here, it is not limited to this shape; for example, it may be rectangular or circular, and may have notches or other features formed on its outer edge. Hereafter, the length La of one side of the square substrate 40 will be, for example, 60 mm.

[0026] The dipole antenna 41 is formed on the +Z side surface (hereinafter referred to as the "front surface") of the substrate 40 and has elements 50, 51 and a feed point 52. Element 50 is, for example, an inner conductor side element connected to the inner conductor (i.e., core wire) of a feed line (not shown). Element 51 is, for example, an outer conductor side element connected to the outer conductor of a feed line (not shown). Elements 50 and 51 are conductive patterns formed on the front surface of the substrate 40.

[0027] The external shapes of element 50 and element 51 are symmetrical with respect to axis A1, which passes through the power supply section 52 and is parallel to the X-axis. Here, the external shapes of one element and the external shapes of the other element are said to be "symmetrical" with respect to axis A1 if one element is inverted along axis A1, then the external shapes of the other element coincide. However, the external shapes of element 50 and element 51 do not have to be perfectly symmetrical with respect to axis A1. For example, the external shape of element 50 may have a shape that is partially different from the external shape of element 51.

[0028] The power supply unit 52 is located between element 50 and element 51. Specifically, the power supply unit 52 is located in the center of the line segment connecting the end of element 50 closest to element 51 and the end of element 51 closest to element 50. Note that "center" is not limited to the exact center, but also includes a position shifted by a predetermined distance from the center.

[0029] Element 50 has extensions 60A, 60B and arms 61A, 61B. Extension 60A is a portion that curves and extends in the -Y direction as it moves away from the power supply 52 in the +X direction. The width of extension 60A gradually increases as it moves away from the power supply 52. ​​Arms 61A extending in the -X direction are formed from the -Y end of extension 60A. The width of extension 60A may increase gradually, in steps (e.g., in a stepped shape), or in a combination thereof as it moves away from the power supply 52.

[0030] Since the external shapes of the extension portion 60B and the arm portion 61B are symmetrical with respect to the axis A2 that passes through the power supply portion 52 and is parallel to the Y-axis, a detailed explanation of the extension portion 60B and the arm portion 61B will be omitted.

[0031] Element 51 has extensions 62A, 62B and arms 63A, 63B. As described above, the outer shape of element 50 and the outer shape of element 51 are symmetrical with respect to axis A1 which passes through the power supply section 52 and is parallel to the X-axis. For this reason, the extensions 62A, 62B and arms 63A, 63B are the same as the extensions 60A, 60B and arms 61A, 61B, so a detailed explanation of element 51 is omitted here.

[0032] Here, the electrical length from the feed point 52 to the -X end (open end) of the arm 61A is approximately λ / 4, and the electrical length from the feed point 52 to the +X end (open end) of the arm 63B is approximately λ / 4. In other words, the electrical length from the -X end of the arm 61A to the +X end of the arm 63B via the feed point 52 is approximately λ / 2. Also, the electrical length from the +X end of the arm 61B to the -X end of the arm 63A via the feed point 52 is approximately λ / 2. Therefore, the dipole antenna 41 is a so-called half-wavelength dipole antenna.

[0033] The dipole antenna 42 is formed on the -Z side surface (hereinafter referred to as the "back surface") of the substrate 40 and has elements 53, 54 and a feed point 55. Comparing elements 53, 54 with elements 50, 51, the positions of elements 53, 54 on the back surface of the substrate 40 are different from the positions of elements 50, 51 on the front surface of the substrate 40. Specifically, the positions of elements 53, 54 in a plan view are the positions obtained by rotating elements 50, 51 90° clockwise or counterclockwise around the feed point 52. Aside from the positions described above, elements 53, 54 and the feed point 55 are the same as elements 50, 51 and the feed point 52, so a detailed explanation is omitted here. In this example, the positions of elements 53 and 54 in a plan view are assumed to be the positions obtained by rotating elements 50 and 51 90° clockwise or counterclockwise around the power supply unit 52, but they may be positions that are shifted from the 90° rotated positions.

[0034] In the antenna device 10 shown in Figure 1, the dipole antennas 41 and 42 are arranged such that the linear polarization direction of the dipole antenna 41 intersects (in this case, orthogonal) with the linear polarization direction of the dipole antenna 42. As a result, the cross dipole antenna 30, including the dipole antennas 41 and 42, corresponds to a circular polarization element composed of orthogonal components with a phase difference of 90°.

[0035] In a plan view of the substrate 40, the feed point 52 on the front surface of the substrate 40 and the feed point 55 on the back surface of the substrate 40 are positioned to overlap each other. In other words, although the feed point 52 of the cross dipole antenna 41 and the feed point 55 of the cross dipole antenna 42 are spaced apart in the thickness direction of the substrate, they are positioned in approximately the same location in a plan view of the substrate. Note that "overlapping in a plan view of the substrate" is not limited to cases where the feed points are perfectly aligned, but also includes cases where at least a part of the feed points are positioned in the same location.

[0036] The dipole antennas 41 and 42 correspond to "radiating elements." Dipole antenna 41, that is, elements 50 and 51, correspond to the "first conductor part." Dipole antenna 42, that is, elements 53 and 54, correspond to the "second conductor part." Dipole antennas 41 and 42 are arranged on the front and back surfaces of the substrate 40. Therefore, dipole antennas 41 and 42 are "arranged on different surfaces of the substrate." The base plate 20 corresponds to "a metal part that is arranged opposite to the radiating elements (i.e., dipole antennas 41 and 42) and is located in the opposite direction to the main radiation direction of the radiating elements." The main radiation direction of the radiating elements is in the +Z direction (zenith direction) in this case.

[0037] (Support Member 31) The support member 31 in Figure 1 is a member that is placed on the circuit board 32, which will be described later, and supports the board 40. The support member 31 supports the board 40 such that the distance between the back surface of the board 40 and the front surface (+Z side surface) of the base plate 20 is distance h. Distance h corresponds to the height in the Z direction to the board 40 with respect to the base plate 20, but for convenience, the thickness of the board 40 can be ignored, and it is defined as the distance between the base plate 20 and the cross dipole antenna 30 formed on the board 40.

[0038] The support member 31 is, for example, a cylindrical member made of resin or the like, and two power supply lines (not shown) connected to the power supply units 52 and 55 are arranged inside the support member 31. The support member 31 is formed on the substrate 40 and supports the substrate 40 so that the cross dipole antenna 30 (i.e., dipole antennas 41 and 42) and the ground plate 20 face each other.

[0039] Here, "the antenna and the ground plate are facing each other" means that the antenna and the ground plate are facing each other, and they do not need to overlap in a plan view. However, even if the antenna and the ground plate do not overlap in a plan view, the ground plate must function as a reflector for the antenna.

[0040] In the antenna device 10 of FIG. 1, in a plan view, the support member 31 supports the substrate 40 such that the geometric center of the circular ground plane 20 and the geometric center of the square substrate 40 overlap. Hereinafter, the geometric center of a member having a predetermined shape may be simply referred to as the "center of the member".

[0041] Also, here, the distance h is made longer than λ / 4 of the corresponding frequency of the antenna device 10 so that the ground plane 20 of FIG. 1 functions sufficiently as a reflector of the cross dipole antenna 30. That is, in the antenna device 10, in order to make the ground plane 20 function as a reflector, the diameter φ of the ground plane 20 is set to 150 mm (>λ / 2), and the distance h is made longer than λ / 4.

[0042] (Circuit board 32) The circuit board 32 is a dielectric substrate to which two power supply lines from each of the power supply units 52 and 55 are connected. On the circuit board 32, for example, a low noise amplifier (LNA: Low Noise Amplifier), various electronic components for impedance adjustment, etc. are mounted. Here, for the sake of convenience, the illustration of the low noise amplifier and various electronic components is omitted.

[0043] ==Relationship between dipole antenna and ground plane== FIG. 2 is a schematic diagram for explaining the relationship between the dipole antenna and the ground plane. The upper part of FIG. 2 (hereinafter referred to as FIG. 2(a)) is a diagram for explaining the influence of the image current and parasitic capacitance on the dipole antenna, and the lower part of FIG. 2 (hereinafter referred to as FIG. 2(b)) is a diagram for explaining the role of the opening 70 (described later) formed in the ground plane.

[0044] In FIG. 2, among the above-described cross dipole antenna 30, the dipole antenna 41 and the ground plane 20 are schematically illustrated. As shown in FIG. 2(a), when the distance h becomes short, the dipole antenna 41 is strongly affected by the ground plane 20.

[0045] Specifically, for example, when the distance h is λ / 4 or less of the corresponding frequency of the antenna device 10, as shown on the lower left side of FIG. 2(a), a so-called image current Iimg flows in the ground plane 20 in a direction that cancels the current I flowing through the dipole antenna 41. As a result, the gain of the dipole antenna 41 may decrease.

[0046] Similarly, when the distance h is equal to or less than λ / 4 of the corresponding frequency of the antenna device 10, as shown in the lower right side of FIG. 2(a), the influence of the parasitic capacitance between the dipole antenna 41 and the ground plane 20 becomes stronger. As a result, the impedance between the dipole antenna 41 and a feeding line (not shown) deviates from a desired value (for example, 50 Ω), which may adversely affect, for example, the VSWR (Voltage Standing Wave Ratio) of the dipole antenna 41.

[0047] In FIG. 2, for the sake of convenience, only the dipole antenna 41 is described, but the same phenomenon occurs with the dipole antenna 42. Therefore, for example, when the antenna device 10 is made low-profile and the distance h is made equal to or less than λ / 4, it may adversely affect the electrical characteristics (for example, gain and VSWR) of the cross dipole antenna 30.

[0048] Therefore, as shown in FIG. 2(b), the antenna device (described later) of the present embodiment forms an opening 70 (details will be described later) in the ground plane 20 facing the dipole antenna 41, thereby reducing the influence of the image current Iimg and the parasitic capacitance. Hereinafter, the details of the antenna device of the present embodiment will be described.

[0049] <<Antenna Device 11>> FIG. 3 is a diagram for explaining the antenna device 11 of the present embodiment. The antenna device 11 includes a ground plane 21, a cross dipole antenna 30, a support member 31, and a circuit board 32. The cross dipole antenna 30 includes a substrate 40, dipole antennas 41 and 42, and a feeding portion (not shown). The antenna device 11 is disposed, for example, on a resin base member (not shown). Comparing the antenna device 10 and the antenna device 11, since the configurations other than the ground plane 21 are the same, the ground plane 21 will be mainly described here.

[0050] The ground plate 21, like the ground plate 20, is a conductive member that functions as a reflector to improve the directivity of the cross dipole antenna 30 toward the zenith. The ground plate 21 is a metal plate-like member that has a circular shape in plan view and has an opening 70. The ground plate 21 corresponds to the "ground section". Furthermore, the ground plate 21 corresponds to "a metal part that is positioned opposite to the radiating elements (i.e., the dipole antennas 41 and 42) and is located in the opposite direction to the main radiation direction of the radiating elements".

[0051] The opening 70 is, for example, a square-shaped portion with side length Lb. In this embodiment, the geometric centers of the substrate 40, the base plate 21, and the opening 70 are positioned such that they coincide in a plan view. Figure 3 illustrates an example where length Lb and length La are equal.

[0052] Here, the characteristics of the antenna device 11 when the length Lb of one side of the aperture 70 is changed will be explained with reference to Figure 4. In this case, the diameter φ of the ground plate 21 is set to 150 mm and the distance h is set to 44 mm so that the ground plate 21 functions as a reflector in the antenna device 11. Note that the distance h is shorter than λ / 4 (48 mm) of a typical frequency in the L1 band and λ / 4 (64 mm) of a typical frequency in the L5 band. Therefore, the distance between the ground plate 21 and the substrate 40 (i.e., the cross dipole antenna 30) is less than 1 / 4 of the wavelength λ of the frequency to which the antenna device 11 corresponds.

[0053] Furthermore, Figure 4 also shows the frequency characteristics of antenna device 10 for comparison with antenna device 11, with the diameter φ of the ground plate 20 of antenna device 10 being 150 mm and the distance h being 44 mm.

[0054] Figure 4 is a diagram illustrating the frequency characteristics of the antenna device 11. The upper part of Figure 4 (hereinafter referred to as Figure 4(a)) is a diagram illustrating the frequency characteristics of the gain of the antenna device 11 in the zenith direction. In Figure 4(a), the vertical axis represents the gain [dBic], and the horizontal axis represents the frequency [MHz].

[0055] Figure 4(a) shows the frequency characteristics of the gain of the antenna device 11 when the side length Lb of the aperture 70 is varied to 0, 40 mm, 50 mm, 60 mm, and 70 mm. Note that when length Lb = 0, there is no aperture 70, so this is essentially the gain of the antenna device 10. From Figure 4(a), as the side length Lb of the aperture 70 is gradually increased from 0 to 60 mm, the gain of the antenna device 11 in the corresponding frequency band increases.

[0056] Furthermore, if the length Lb of the side of the aperture 70 is increased from 60 mm (the length La of the side of the substrate 40) to 70 mm, the gain decreases compared to the case where the length is 60 mm. However, by providing an aperture 70 with a length Lb of 70 mm in the base plate 21, the gain is improved compared to the case where there is no aperture 70 (i.e., the antenna device 10).

[0057] The middle section of Figure 4 (hereinafter referred to as Figure 4(b)) is a diagram illustrating the frequency characteristics of the axial ratio of the antenna device 11. In Figure 4(b), the vertical axis represents the axial ratio [dB], and the horizontal axis represents the frequency [MHz]. In the GNSS frequency bands (L1 band and L5 band) to which the antenna device 11 corresponds, the axial ratio is improved when an aperture 70 with a side length Lb of 40 mm to 70 mm is provided, compared to when no aperture 70 is provided.

[0058] The lower part of Figure 4 (hereinafter referred to as Figure 4(c)) is a diagram illustrating the frequency characteristics when the diameter φ of the ground plate 21 of the antenna device 11 is changed. In Figure 4(c), the vertical axis shows the gain [dBic] in the zenith direction, and the horizontal axis shows the frequency [MHz].

[0059] In Figure 4(c), the gain when the diameter φ of the base plate 21 is 150 mm and the side length Lb of the opening 70 is 60 mm is shown by a dashed line, and the gain when the diameter φ of the base plate 21 is 120 mm and the side length Lb of the opening 70 is 60 mm is shown by a single dashed line. Furthermore, in Figure 4(c), the frequency characteristics of the gain of the antenna device 10 are shown by a dotted line for comparison.

[0060] As is clear from Figure 4(c), even if the diameter φ of the base plate 21 of the antenna device 11 is 120 mm, the gain is improved compared to the antenna device 10, which has a base plate 20 with a diameter φ of 150 mm, when there is an opening 70 with a length Lb = 60 mm. Thus, even if the diameter φ of the base plate 21, which functions as a reflector, is reduced, the antenna device 11 can obtain a higher gain in the zenith direction than the antenna device 10 due to the effect of the opening 70 with a length Lb = 60 mm. Therefore, in the antenna device 11, for example, in addition to reducing the height, the size of the base plate 21 can also be reduced.

[0061] Thus, the opening 70 provided in the ground plate 21 has a shape that adjusts the electrical characteristics (e.g., gain, axial ratio) of the cross dipole antenna 30 (dipole antennas 41, 42) in the antenna device 11. The opening 70 formed in the ground plate 21 is set to a size that does not function as a so-called slot that radiates radio waves into space by exciting electromagnetic waves. Specifically, the total length of the opening 70 is set so that it is not, for example, around λ / 2. The opening 70 corresponds to a "first opening that is a non-radiating structure and has a shape that adjusts the electrical characteristics of the radiating element."

[0062] Furthermore, in the antenna device 11, if the length Lb of the aperture 70 is shorter than the length La, a portion of the dipole antennas 41 and 42 and the aperture 70 will overlap in a plan view. Even in such a case, as shown in Figure 2, the cross dipole antenna 30 is less affected by the image current and parasitic capacitance of the ground plate 21, and therefore its gain is higher than that of the antenna device 10, for example, as shown by the gain (solid line) at length Lb = 40 mm in Figure 4(a).

[0063] Therefore, if the dipole antennas 41 and 42 and the aperture 70 are arranged so that at least a portion of them overlap in a plan view, the characteristics of the antenna device 11 can be improved.

[0064] <<Antenna Device 12>> Figure 5 is a diagram illustrating the antenna device 12 of this embodiment. The antenna device 12 has a base plate 22, a cross dipole antenna 30, a support member 31, and a circuit board 32. The cross dipole antenna 30 has a substrate 40, dipole antennas 41 and 42, and a feed unit (not shown). The antenna device 12 is placed on, for example, a resin base member (not shown). Comparing the antenna device 12 with the antenna device 10, the configurations other than the base plate 22 are the same, so here we will mainly describe the base plate 22.

[0065] The ground plate 22, like the ground plate 20, is a conductive member that functions as a reflector to improve the directivity of the cross dipole antenna 30 toward the zenith. The ground plate 22 is a circular metal plate-like member with an opening 71. The ground plate 22 corresponds to the "ground section". Furthermore, the ground plate 22 corresponds to "a metal part that is positioned opposite to the radiating elements (i.e., the dipole antennas 41 and 42) and is located in the opposite direction to the main radiation direction of the radiating elements".

[0066] The opening 71, like the opening 70, is a square-shaped portion with, for example, a side length Lb of 60 mm. In the ground plate 21 of the antenna device 11 shown in Figure 3, the geometric center of the opening 71 coincides with the geometric center of the ground plate 21 in a plan view. However, in the ground plate 22, the geometric center O1 of the opening 71 is located at a distance dm in the -Y direction from the geometric center O2 of the ground plate 22. The geometric center O2 of the ground plate 22 coincides with, for example, the center of the cross dipole antenna 30.

[0067] Figure 6 shows the change in the zenith direction gain of antenna device 12 when the distance dm is varied to 0, 10 mm, 20 mm, and 30 mm. For reference, the zenith direction gain of antenna device 10 is also shown here. As is clear from the figure, even when the distance dm is gradually increased from 0 to 30 mm, the zenith direction gain increases compared to the case of antenna device 10.

[0068] As shown in Figure 5, when the distance dm is a positive value, the aperture 71 includes both an overlapping region with the cross dipole antenna 30 and a non-overlapping region in a plan view. Even in such a case, the antenna device 12 can improve the gain in the zenith direction.

[0069] Thus, the opening 71 provided in the ground plate 22 has a shape that adjusts the electrical characteristics (e.g., gain) of the cross dipole antenna 30 (dipole antennas 41, 42) in the antenna device 12. Note that, like the opening 70, the opening 71 is sized so that it does not function as a so-called slot that radiates radio waves into space by exciting electromagnetic waves. The opening 71 corresponds to the "first opening, which is a non-radiating structure and has a shape that adjusts the electrical characteristics of the radiating element."

[0070] Furthermore, in a plan view, the antenna device 12 has a configuration in which parts of the dipole antennas 41 and 42 and the aperture 71 overlap with each other. Even in such a case, as shown in Figure 2, the cross dipole antenna 30 is less affected by the image current and parasitic capacitance of the ground plate 21.

[0071] Therefore, if the dipole antennas 41 and 42 and the aperture 71 are arranged so that at least a portion of them overlap in a plan view, the characteristics of the antenna device 12 can be improved.

[0072] <<Antenna Device 13>> Figure 7 is a diagram illustrating the antenna device 13 of this embodiment. The antenna device 13 includes a base plate 23, a cross dipole antenna 30, a support member 31, and a circuit board 32. The cross dipole antenna 30 includes a substrate 40, dipole antennas 41 and 42, and a feed unit (not shown). The antenna device 13 is placed on, for example, a resin base member (not shown). Comparing the antenna device 13 with the antenna device 10, the configurations other than the base plate 23 are the same, so here we will mainly describe the base plate 23.

[0073] The ground plate 23, like the ground plate 20, is a conductive member that functions as a reflector to improve the directivity of the cross dipole antenna 30 toward the zenith. The ground plate 23 has an annular member 80 and plate-shaped members 81a to 81d. The ground plate 23 corresponds to the "ground section". The ground plate 23 also corresponds to the "metal part that is positioned opposite the radiating elements (i.e., the dipole antennas 41 and 42) and is located in the opposite direction to the main radiation direction of the radiating elements". In this embodiment, the outer edge shape of the annular member 80 is a perfect circle, but it is not limited to this and may be elliptical or have other surrounding shapes.

[0074] The annular member 80 is a metal member formed to surround the opening 72 in a plan view. In this embodiment, the diameter (outer diameter here) φ = 150 mm of the annular member 80, and the geometric center of the base plate 23 is the geometric center of the annular member 80. Each of the plate-shaped members 81a to 81d has a length equal to the inner diameter of the annular member 80 and a width W. The plate-shaped members 81a to 81d are arranged in a spoke-like manner in the opening 72 of the annular member 80.

[0075] The opening 72 is located at the geometric center of the annular member 80 and is divided into eight openings 72a to 72h by the plate-like members 81a to 81d. Each of the openings 72a to 72h has a sector shape with a central angle of a predetermined angle (in this case, an angle less than 45°) in a plan view. In this embodiment, each of the openings 72a to 72h has the same predetermined central angle in a plan view, but is not limited to this, and each of the openings 72a to 72h may have different predetermined angles, or some may have the same predetermined angle and some may have different predetermined angles.

[0076] Figure 8 shows the change in the average gain (hereinafter simply referred to as gain) of the antenna device 13 in the zenith direction when the width W of the plate-shaped members 81a to 81d is changed to 5 mm, 10 mm, 15 mm, and 20 mm. For reference, the gain of antenna device 10 is also shown here. As is clear from Figure 8, the average gain of antenna device 13 is higher than that of antenna device 10, which does not have an aperture, regardless of the length of the width W. However, in the range of width W from 5 mm to 20 mm, the effect of improving the gain decreases as the width W increases.

[0077] Thus, even when the cross dipole antenna 30 overlaps with multiple openings 72a to 72h of the ground plate 23 in a plan view, the antenna device 13 can improve the gain in the zenith direction.

[0078] Thus, the openings 72a to 72h provided in the ground plate 23 have a shape that adjusts the electrical characteristics (e.g., gain) of the cross dipole antenna 30 (dipole antennas 41, 42) in the antenna device 12. Note that, like the opening 70, the openings 72a to 72h are set to a size that does not function as so-called slots that radiate radio waves into space by exciting electromagnetic waves. The openings 72a to 72h correspond to "a first opening that is a non-radiating structure and has a shape that adjusts the electrical characteristics of the radiating element."

[0079] Furthermore, in a plan view, the antenna device 13 has a configuration in which the dipole antennas 41 and 42 and parts of the apertures 72a to 72h overlap with each other. Even in such a case, as shown in Figure 2, the cross dipole antenna 30 is less affected by the image current and parasitic capacitance of the ground plate 21.

[0080] Therefore, if the dipole antennas 41 and 42 and the apertures 72a to 72h are arranged so that at least a portion of them overlap in a plan view, the characteristics of the antenna device 13 can be improved.

[0081] <<Antenna Device 14>> Figure 9 is a diagram illustrating the antenna device 14 of this embodiment. The antenna device 14 has a base plate 21, a cross dipole antenna 30, a support member 31, a circuit board 32, and rib sections 85a to 85d. The cross dipole antenna 30 has a substrate 40, dipole antennas 41 and 42, and a feed section (not shown). The antenna device 14 is placed on, for example, a resin base member (not shown). Comparing the antenna device 14 with the antenna device 10, the configuration is the same except for the rib sections 85a to 85d, so here we will mainly describe the rib sections 85a to 85d.

[0082] The rib portion 85a is a metal part positioned on the front surface (+Z side) of the base plate 21 so as to increase the electrical length of the base plate 21. Specifically, the rib portion 85a has a plurality of protrusions 90 positioned on the +Y side of the square opening 76 on the base plate 21.

[0083] The protrusion 90 is a metal part having a rectangular parallelepiped shape with length Lx, width Wx, and height Hx. The length Lx of the protrusion 90 extends along the +Y side of the opening 76. In this embodiment, the length Lx is assumed to be the same as the length Lb, but it is not limited to this. The width Wx is sufficiently shorter than the length Lx, and the height Hx is sufficiently shorter than the distance h. The rib portion 85a includes, for example, 11 protrusions 90, but there may be other numbers.

[0084] Rib portion 85b has a plurality of protrusions 90 positioned on the +X side of the opening 70 on the base plate 21, and rib portion 85c has a plurality of protrusions 90 positioned on the -Y side of the opening 70 on the base plate 21. Rib portion 85d also has a plurality of protrusions 90 positioned on the -X side of the opening 70 on the base plate 21. Since rib portions 85b to 85d are the same as rib portion 85a except for their position on the base plate 21, a detailed explanation is omitted here.

[0085] Since the antenna device 14 of this embodiment has the same structure as the antenna device 11, it can improve the zenith-direction gain of the cross dipole antenna. Furthermore, in the antenna device 14, since rib portions 85a to 85d are arranged on the base plate 21, the electrical length of the base plate 21 can be increased. Therefore, compared to, for example, the case where only the base plate 21 is provided without the rib portions 85a to 85d, the diameter φ of the base plate 21 can be shortened in the antenna device 14. This makes it possible to reduce the size of the antenna device 14.

[0086] Furthermore, the rib sections 85a to 85d are positioned four times symmetrically with respect to the center of the base plate 21. Therefore, the influence of the antenna device 14 on the characteristics of the corresponding circular polarization can be reduced.

[0087] Furthermore, "n-fold symmetry with respect to the geometric center" or "n-fold symmetry with respect to the geometric center point" means that even when rotated at angles that divide 360° into n equal parts, the rotated figure matches the original shape. In other words, "n-fold symmetry with respect to the geometric center point" means that the figure is rotationally symmetric at predetermined rotation angles obtained by dividing 360° into n equal parts. For example, if n is 4, the predetermined rotation angle is 90°, and if n is 8, the predetermined rotation angle is 45°. Also, "n-fold symmetry" does not necessarily have to be strictly (mathematically) n-fold symmetry; it may be shifted from a predetermined position (the position of strict n-fold symmetry). In this embodiment, four rib sections 85a to 85d are arranged, resulting in four-fold symmetry with respect to the geometric center point, but this is not limited to this, and only one rib section may be arranged. However, it is preferable to arrange a number of rib sections that are n-fold symmetric with respect to the geometric center point.

[0088] <<Modifications of the floor plate>> Figure 10 is a diagram illustrating modifications of the floor plate. Figure 10(a) is an example in which a circular floor plate 25a has a circular opening 75a in a plan view. The shape of the opening 75a is circular but not limited to this, and may be polygonal, for example. Figure 10(b) is an example in which a floor plate 25b has a mesh-like opening 75b. Figure 10(c) is an example in which four openings 75c of a predetermined shape are provided so as to be four times symmetrical with respect to the geometric center of the circular floor plate 25c.

[0089] Figure 10(d) shows an example in which a circular base plate 25d includes the aforementioned opening 75a and four openings 75c. Figure 10(d) also shows an example in which a circular base plate 25e includes a spiral-shaped opening 75f. Note that the shape of the base plate does not have to be circular; for example, it may be a polygon or other shape, or even a three-dimensional shape.

[0090] For example, as shown in Figure 10(f), the ground plate 25f may be a three-dimensional shape including, for example, a quadrilateral flat plate portion 26 having an opening 75f and an outer edge portion 27 that is folded back and extends from the outer edge of the flat plate portion 26. In this way, the ground plate corresponding to the ground portion corresponds to a "conductive member in the shape of a plate or three dimensions".

[0091] Even when using the ground plate illustrated in Figure 10 for the antenna device, if, in a plan view, at least a portion of the dipole antenna and the opening in the ground plate overlap, the same effects as in this embodiment can be obtained.

[0092] <<Antenna Device 100>> Figure 11 is a diagram illustrating an example of an antenna device 100 in this embodiment. The antenna device 100 is a device that constitutes an air-gap type planar antenna. The direction of the antenna device 100 will be defined with reference to Figure 11.

[0093] ==Definition of Directions, etc.== As shown in Figure 11, the direction from the base plate 200 toward the element 300 is defined as the "+Z direction". The directions parallel to the +Z direction side of the base plate 200 and perpendicular to each other are defined as the "+X direction" and the "+Y direction". The +X direction is the direction from slot S2 toward slot S1 in the enlarged view of Figure 1, and the +Y direction is the direction from the closed end of slot S1 toward the open end E1.

[0094] The opposite directions of the +X, +Y, and +Z directions are defined as the -X, -Y, and -Z directions, respectively. Here, the +Z direction is defined as the upward or zenith direction, and the -Z direction is defined as the downward direction. Also, for example, both the +X and -X directions may simply be called the "X direction." Similarly, both the +Y and -Y directions may simply be called the "Y direction." Furthermore, both the +Z and -Z directions may simply be called the "Z direction."

[0095] The antenna device 100 in Figure 11, like the antenna device 10 in Figure 1, is a multiband device that can handle radio waves in the frequency bands of, for example, the L1 band and L5 band of GNSS. The antenna device 100 has a ground plate 200 and elements 300.

[0096] The ground plate 200 is a conductive plate-shaped member that functions as the ground for the antenna device 100 and corresponds to the "ground section". Here, the ground plate 200 has the shape of a square with side length Li, for example, but is not limited to this and may be a metal plate of other shapes such as a roughly quadrilateral, circle, or ellipse. Furthermore, the ground plate 200 corresponds to "a metal part that is positioned opposite the radiating element (i.e., element 300) and is located in the opposite direction to the main radiation direction of the radiating element".

[0097] Element 300 is a conductive plate-shaped member that, together with the ground plate 200, constitutes a planar antenna and corresponds to a "radiating element". Element 300 has, for example, a square shape with side length Lj, but is not limited to this and may be a metal plate of other shapes such as a roughly quadrilateral, circle, or ellipse.

[0098] Element 300 is positioned on the +Z side of the ground plate 200 so as to face the ground plate 200. Specifically, element 300 is supported by support members and a conductive substrate (not shown) such that the -Z side of element 300 and the +Z side of the ground plate 200 are approximately parallel. For convenience, support members and the like are omitted here. The distance between element 300 and the ground plate 200 is denoted as distance d.

[0099] The support member is a member that supports the element 300 in order to secure a predetermined distance between the element 300 and the ground plate 200, and is composed of, for example, double-sided tape, adhesive members, or a combination thereof. The support member is made of an insulating material and is preferably positioned in a location that does not overlap with the slit S1, slit S2, and power supply section in a plan view. For example, in a plan view, it may be arranged to have a shape that is symmetrical in all directions, such as a circle, annular, quadrilateral, frame, or cross shape, or a combination thereof. Alternatively, the support member may be configured by arranging multiple columnar members. In this case, the multiple support members may be arranged in predetermined positions. For example, in a plan view, four support members may be arranged on the diagonals of the element 300, and these four support members may be arranged symmetrically to each other.

[0100] As another example, one support member may be placed in the center of the element 300, and four more support members may be placed diagonally, such that the central support member and the four diagonal support members are symmetrical to each other. Here, the cross-sectional shape of the columnar member is not limited to a specific shape such as a rectangular prism or a cylindrical shape.

[0101] Furthermore, in another configuration, the element 300 may be housed in a housing and fixed to the wall inside the housing by double-sided tape or welding, thereby ensuring a predetermined distance between the element 300 and the base plate 200. Alternatively, the element 300 may be supported by a frame-shaped resin holder surrounding the outer shape or outer edge of the element 300, and the resin holder may be fixed to the base plate 210 with double-sided tape or adhesive material, thereby ensuring a predetermined distance between the element 300 and the base plate 210.

[0102] Element 300 has a feed point 301 located in the +X direction from the geometric center OA of element 300, and a feed point 302 located in the +Y direction. A feed line (not shown) for supplying power to element 300 is connected to each of the feed points 301 and 302.

[0103] Furthermore, on the +Y side of element 300, two slits S1 are formed in a plan view, sandwiching three slits S2. Each slit S1 has an open end E1 at the outer edge of element 300 and extends from the open end E1 toward the geometric center OA. The shape of each slit S1 is, for example, a quadrilateral with width W1 and length L1 in a plan view of element 300 from the +Z direction.

[0104] Like slit S1, slit S2 has an open end E2 at the outer edge of element 300 and extends from the open end E2 toward the geometric center OA. Furthermore, the shape of slit S2, in plan view, is, for example, a quadrilateral with width W2 and length L2. For example, widths W1 and W2 are equal, and length L2 is longer than length L1.

[0105] Element 300 has the two slits S1 and three slits S2 described above on each side in the X direction and on each side in the Y direction. Note that "both sides in the X direction in the part (e.g., element)" corresponds to the region in the +X direction from the geometric center and the region in the -X direction from the geometric center in the part (element). Similarly, "both sides in the Y direction in the part (e.g., element)" corresponds to the region in the +Y direction from the geometric center and the region in the -Y direction from the geometric center in the part (element).

[0106] In element 300, the two slots S1 and the three slots S2 are formed to be four times symmetric with respect to the geometric center OA, so that the surface current in the X direction and the surface current in the Y direction are balanced. In element 300, the surface current in the X direction and the surface current in the Y direction flow around the multiple slits S1 and S2, so the electrical length of element 300 is longer compared to when there are no multiple slits S1 and S2. As a result, the size of element 300 can be reduced by forming multiple slits S1 and S2 on element 300. In this embodiment, the shape of the slits S1 and S2 is quadrilateral, but is not limited to this, and the shape of the slits S1 and S2 may be a curved shape, a meandering shape, a bent shape, or a folded shape in which at least a part is.

[0107] (Gain of Antenna Device 100) Figure 12 shows the relationship between the size of the base plate 200 of the antenna device 100 and the gain of the antenna device 100 in the zenith direction (+Z direction). In Figure 12, the relationship between the size of the base plate 200 and the gain is illustrated for each case where the distance d is 2 mm, 4 mm, 6 mm, and 8 mm. Note that here, the notation for the case where the wavelength λ of the GNSS L5 band (f = 1176 MHz) is 255 mm is also included for each of the distance d and length Li.

[0108] As is clear from Figure 12, regardless of distance d, as the size of the ground plate 200 decreases, that is, as the length of one side of the ground plate 200, Li, decreases, the gain of the antenna device 100 gradually decreases. The upper part of Figure 13 (hereinafter, Figure 13(a)) shows the radiation characteristics of the antenna device 100 when the length of one side of the ground plate 200, Li, is 120 mm (0.47 λ). The lower part of Figure 13 (hereinafter, Figure 13(b)) shows the radiation characteristics of the antenna device 100 when the length of one side of the ground plate 200, Li, is 100 mm (0.39 λ). In Figures 13(a) and 13(b), an angle of 0° corresponds to the zenith direction of the antenna device 100 (the main radiation direction on the +Z side), and an angle of 180° corresponds to the nadir direction of the antenna device 100 (the opposite direction on the -Z side).

[0109] Here, the front-to-back ratio (FB ratio) of the antenna device 100 is negative at -4.33 dB when Li = 100 mm, but positive at 6.73 dB when Li = 120 mm. In other words, as the size of the base plate 200 (length of one side Li) decreases, the gain of the antenna device 100 in the rear (-Z direction) increases, while the gain in the front (+Z direction) decreases. Therefore, if the size of the base plate 200 is reduced when miniaturizing the antenna device 100, the gain of the antenna device 100 in the +Z direction will decrease.

[0110] The following describes an antenna device that can prevent a decrease in gain in the zenith direction (+Z direction) even when the size of the ground plate 200 is reduced.

[0111] <<Antenna Device 110>> Figure 14 is a diagram illustrating the antenna device 110 of this embodiment. The antenna device 110 has a base plate 210 and an element 300. Comparing the antenna device 110 with the antenna device 100, they are the same except for the base plate 210, so here we will describe the base plate 210.

[0112] The ground plate 210 is a conductive plate-shaped member that functions as the ground for the antenna device 110 and corresponds to the "ground section". Like the ground plate 200, the ground plate 210 is, for example, a square metal plate with side length Li, but is not limited to this and may be a metal plate of other shapes such as a roughly quadrilateral, circle, or ellipse. Furthermore, the ground plate 210 corresponds to "a metal part that is positioned opposite the radiating element (i.e., the element 300) and is located in the opposite direction to the main radiation direction of the radiating element".

[0113] The base plate 210 has five slits S10 on each side in the X direction and on each side in the Y direction. The slits S10 have an open end E10 at the outer edge of the base plate 210 and extend from the open end E10 toward the geometric center OB of the base plate. The shape of the slits S10 is, for example, a quadrilateral with a width W10 and a length L10 in plan view.

[0114] Furthermore, in the base plate 210, the five slots S10 on each side are formed to be four times symmetric with respect to the geometric center OB. Therefore, the five slits S10 on the +Y side and the five slits S10 on the -Y side of the base plate 210 are symmetric with respect to axis A10, and the five slits S10 on the +X side and the five slits S10 on the -X side are symmetric with respect to axis A11.

[0115] The slit S10 corresponds to the "first opening." The open end E10 of the slit S10 corresponds to the "open end at the outer edge of the floor plate 210 in a plan view," and the slit S10 extends from the outer edge of the floor plate 210 toward the interior of the floor plate 210 (i.e., toward the geometric center).

[0116] Furthermore, the slits S1 and S2 in the element 300 are arranged symmetrically four times at 90° rotation angles with respect to the center of the element 300. The slits S1 and S2 correspond to the "second opening". Note that the multiple slits formed in the element 300 are not limited to slits S1 and S2, but may be of other shapes, and the number of slits may also differ from that of the illustrated embodiment.

[0117] (Gain of Antenna Device 110) Figure 15 is a diagram showing the relationship between the gain of the antenna device 110 and the slits in the ground plate 210. The upper part of Figure 15 (hereinafter, Figure 15(a)) is a diagram showing the gain and FB ratio of the antenna device 110 when the number of slits per side of the ground plate 210 is changed. The lower part of Figure 15 (hereinafter, Figure 15(b)) is a diagram showing the gain of the antenna device 110 when the length L10 of the slit S10 is changed.

[0118] In Figure 15(a), the length L10 of the slit S10 in the base plate 210 is 16 mm, the width W10 is 2 mm, and the spacing between slits S10 when multiple slits S10 are provided is 5 mm. In Figure 15(b), the length L10 of the slit S10 in the base plate 210 is varied, but the width W10 remains 2 mm. Also in Figure 15(b), five slits S10 are provided on one side of the base plate 210, and the spacing between slits S10 is 5 mm. In addition, the antenna device 110 is fed to feed points 301 and 302 so that the antenna device 110 operates in modes corresponding to linear polarization and right-hand circular polarization, respectively.

[0119] As shown in Figure 15(a), increasing the number of slits S10 per side of the antenna device 110 increases the electrical length of the ground plate 210, which increases the gain corresponding to linear polarization and right-hand circular polarization, and also increases the FB ratio.

[0120] As shown in Figure 15(b), when the length L10 of the slit S10 of the antenna device 110 is increased from 16 mm to 24 mm, the electrical length of the ground plate 210 increases, and the gain corresponding to linear polarization and right-hand circular polarization increases. In particular, the gain increases up to a length L10 = 22 mm.

[0121] Thus, in the antenna device 110, by providing at least one slit S10 on each side of the base plate 210, the electrical length of the base plate 210 can be increased, thereby improving the characteristics of the antenna device 110. When the antenna device 110 is compatible with circular polarization, it is preferable that the slits formed in the base plate 210 be, for example, four-fold symmetrical.

[0122] <<Modifications of the Slit>> Figure 16 is a diagram illustrating a slit formed in the base plate. Note that in Figures 16(a) to 16(f), only a portion of the base plate is shown for convenience. As shown in Figure 16(a), the angle between the direction in which the slit S20 extends from its open end and the direction of the edge of the base plate 230a in which the slit S20 is formed does not have to be 90°. Also, as shown in Figure 16(b), the slit S21 may be formed at the corner of the base plate 230b.

[0123] As shown in Figure 16(c), the slit S22 formed in the base plate 230c may have a shape other than a quadrilateral. As shown in Figure 16(d), the slit S23 formed in the base plate 230d may have a branched shape. As shown in Figure 16(e), the slit S24 formed in the base plate 230e may be bent, and as shown in Figure 16(f), the slit S25 formed in the base plate 230f may be curved.

[0124] As shown in Figures 16(a) to 16(f), the shape of the slits can be anything as long as the electrical length of the ground plate can be increased. Even if slits S20 to S25 are used instead of slit S10 in the ground plate 210, the same effects as in this embodiment can be obtained.

[0125] <<Symmetry of the Slits>> Figure 17 is a diagram illustrating the positions of multiple slits formed in the base plate. In the base plate 210 shown in Figure 14, five slits S10 are formed symmetrically with respect to axes A10 and A11, but this is not limited to this. For example, as shown in Figure 17(a), four slits S10 may be arranged on each side so as to be four times symmetric with respect to the center of the square base plate 240a. In Figures 17(a) to 17(c), the intersection of the vertical dashed line and the horizontal dashed line corresponds to the geometric center of the base plate. In this embodiment, the geometric center of the base plate corresponds to the "center point of the base plate".

[0126] Furthermore, as shown in Figure 17(b), three slits S10 may be arranged at 90° intervals, i.e., at 90° rotation angles, on the outer circumference of the circular ground plate 240b, and as shown in Figure 17(c), one slit S32 may be arranged at 45° rotation angles, on the outer circumference of the circular ground plate 240c. As shown in Figures 17(a) to 17(c), when multiple slits are arranged rotationally symmetrically around the center of the ground plate, it is possible to increase the electrical length of the ground plate while preventing deterioration of the corresponding axial ratio of the circular polarization.

[0127] <<Patch Antenna>> Figure 18 is a diagram illustrating a patch antenna. The antenna device 150 shown in Figure 18(a) is, for example, a device that corresponds to the L1 and L5 bands of GNSS radio waves, and has a ground plate 250 and a patch antenna 310.

[0128] The ground plate 250 is a metal plate-shaped member that functions as the ground for the patch antenna 310, and for example, has a square shape with sides of 70 mm. The patch antenna 310 has a dielectric 400 made of ceramic or the like, a radiating element 401, and feed terminals 420 and 421. The dielectric 400 is located on the lower surface (-X side) of the radiating element 401.

[0129] The radiating element 401 is a conductive element formed on the upper surface of the dielectric 400, and has slots and the like formed therein to accommodate circular polarization in the L1 and L5 bands (f = 1176 MHz) of GNSS. The radiating element 401 also has feed points 410 and 411.

[0130] Power supply terminals 420 and 421, which supply power to the radiating element 401, are connected to the power supply points 410 and 411. Power supply terminal 420 is connected to power supply point 410 by passing through the dielectric 400, and power supply terminal 421 is connected to power supply point 411 by passing through the dielectric 400. The -Z ends of each power supply terminal 420 and 421 are connected to, for example, a circuit board (not shown) located below the ground plate 250. Note that power supply terminals 420 and 421 correspond to "multiple power supply terminals".

[0131] The antenna device 151 shown in Figure 18(b) is also a device that corresponds to the L1 and L5 bands of GNSS, similar to the antenna device 150, and has a ground plate 251 and a patch antenna 310. The ground plate 251 is the same as the ground plate 250 except that three slits S10 are formed on each side. The three slits S10 on each side are formed in positions that are four times symmetrical with respect to the center of the ground plate 251.

[0132] The antenna device 152 shown in Figure 18(c) is also a device that corresponds to the L1 and L5 bands of GNSS, similar to the antenna device 150, and has a ground plate 252 and a patch antenna 310. The ground plate 252 is the same as the ground plate 250 except that five slits S10 are formed on each side. The five slits S10 on each side are formed in positions that are four times symmetrical with respect to the center of the ground plate 252.

[0133] Figure 19 shows the frequency characteristics of the gain of each antenna device 150 to 152 in the zenith direction (+Z direction). As shown in Figure 19, the gain of antenna device 151 is higher than that of antenna device 150, and furthermore, the gain of antenna device 152 is higher than that of antenna device 151. Therefore, in an antenna device including a patch antenna, the gain of the antenna device can be increased without increasing the size of the ground plate.

[0134] Furthermore, for example, by forming multiple slits similar to those on ground plate 252 on a ground plate smaller in size than ground plate 250 (not shown), it is possible to obtain the same gain as the antenna device 150. Therefore, for example, in an antenna device including a patch antenna, by using ground plates similar to ground plates 251 and 252, it is possible to miniaturize the antenna device while maintaining its characteristics. Ground plates 250 to 252 correspond to the "ground section," and feed terminals 420 and 421 correspond to the "feed terminals." Also, ground plates 250 to 252 correspond to "metal parts that are arranged opposite to the radiating element 401 and are located in the opposite direction to the main radiation direction of the radiating element."

[0135] <<Modification of the Ground Plate for a Patch Antenna>> Figure 20 is a diagram illustrating the ground plate on which a patch antenna is placed. The antenna device 160 shown in Figure 20(a) has a ground plate 260 and a patch antenna 310. The ground plate 260 functions as the ground for the patch antenna 310 and is a conductive plate surface member having a rectangular shape in which the length Lp in the Y direction is longer than the length Lq in the X direction.

[0136] When the patch antenna 310 is compatible with circular polarization, it is preferable to form the slit S10 on the shorter side of the ground plate 260 in the X direction, of the two sides in the X and Y directions. In this case, by forming the slit S10 on the side in the X direction, the electrical length of the ground plate 260 in the X direction can be increased, thereby reducing the difference between the electrical length of the ground plate 260 in the X direction and the electrical length in the Y direction.

[0137] Therefore, by forming the slit S10 in such a position, the characteristics of the antenna device 160 (e.g., gain and axial ratio) can be improved. Note that the shape and number of slits formed in the ground plate 260 are not limited to the illustrated example. The ground plate 260 corresponds to the "ground section," the two sides of the ground plate 260 with length Lp correspond to a "pair of long sides," the two sides of the ground plate 260 with length Lq correspond to a "pair of short sides," and the shape of the ground plate 260 is a "quadrilateral." Furthermore, the ground plate 260 corresponds to a "metal part that is positioned opposite the radiating element and in the opposite direction to the main radiation direction of the radiating element."

[0138] The antenna device 170 shown in Figure 20(b) has a ground plate 270 and a patch antenna 310. Here, the patch antenna 310 of the antenna device 170 corresponds to linear polarization in the X direction, for example, because the direction of the electric field induced by feeding (i.e., the excitation direction) is in the X direction.

[0139] In such cases, it is preferable to form the slit S10 on the X-direction side of the quadrilateral-shaped ground plate 270 that is parallel to the linear polarization direction (excitation direction) among the X-direction side and the Y-direction side. As a result, the electrical length of the ground plate 270 in the X direction can be increased, thereby improving the characteristics of the antenna device 170 (for example, gain and axial ratio). Note that the shape and number of slits formed in the ground plate 270 are not limited to the illustrated example.

[0140] <<Rib Section>> Figure 21 is a diagram illustrating a ground plate equipped with a rib section. Figure 21(a) is an example of an embodiment in which the ground plate 210 of Figure 14 described above is equipped with rib sections 82a to 82d. The rib sections 82a to 82d are arranged to be four times symmetric with respect to the geometric center of the ground plate 210. In this case, the electrical length of the ground plate 210 can be made longer, and therefore the antenna device using the ground plate 210 can be made smaller.

[0141] Figure 21(b) shows, for example, an example of an embodiment in which the ground plate 252 of the antenna device 151 in Figure 18(b) described above is equipped with rib portions 82a to 82d. The rib portions 82a to 82d are arranged to be four times symmetric with respect to the geometric center of the ground plate 252. In such a case, the electrical length of the ground plate 252 can be made longer, and therefore the antenna device using the ground plate 252 can be made smaller.

[0142] (Other) As the ground plate for the antenna devices 151 and 152, for example, a three-dimensional ground plate 25f as shown in Figure 10 may be used, and the slit S10 may be formed from the outer edge of the ground plate 25f. Even in such a case, the same effects as in this embodiment can be obtained.

[0143] In the antenna device 110, a configuration in which a support member is provided to secure a predetermined distance between the element 300 and the base plate 210 has been described, but the device is not limited to this. For example, a protrusion may be provided on the base plate 210, and the element 300 and the base plate 210 may be fixed to the protrusion using double-sided tape, adhesive material, etc. In this case, the height of the protrusion ensures a predetermined distance between the element 300 and the base plate 210. Alternatively, the base plate 210 itself may be given a predetermined thickness to ensure a predetermined distance between the element 300 and the base plate 210. Even in such a case, the same effects as in this embodiment can be obtained.

[0144] ==Summary== According to this specification, antenna devices in the following embodiments are provided.

[0145] (Aspect 1) Aspect 1 is an antenna device comprising a radiating element and a ground portion disposed opposite to the radiating element, wherein at least one first opening is formed in the ground portion, and the first opening is a non-radiating structure and has a shape that adjusts the electrical characteristics of the radiating element.

[0146] According to the above-described embodiment, it is possible to provide an antenna device that can suppress the influence on the characteristics of the antenna.

[0147] (Aspect 2) In aspect 2, the ground portion is a conductive member in the shape of a plate or three dimensions.

[0148] According to the above embodiment, the influence of conductive members on the radiating element can be suppressed.

[0149] (Aspect 3) In aspect 3, in a plan view of the radiating element, the radiating element and the first aperture are arranged so that at least a portion of them overlap each other.

[0150] According to the above embodiment, since a portion of the radiating element and the opening overlap, the influence of the ground portion on the radiating element can be suppressed.

[0151] (Aspect 4) In aspect 4, the ground portion further comprises a rib portion, and the rib portion has a shape that adjusts the electrical characteristics of the radiating element.

[0152] According to the above-described embodiment, the rib portion can, for example, increase the electrical length of the ground portion, thereby improving the characteristics of the antenna.

[0153] (Aspect 5) In aspect 5, the radiating element is formed on a substrate and further comprises a first conductor portion and a second conductor portion, wherein the first conductor portion is arranged on one side of the substrate and the second conductor portion is arranged on the other side of the substrate.

[0154] According to the above-described embodiment, the characteristics of a cross dipole antenna can be improved.

[0155] (Aspect 6) In aspect 6, the first opening has an open end at the outer edge of the ground portion in a plan view of the ground portion and extends from the outer edge toward the inside of the ground portion.

[0156] According to the above embodiment, the electrical length of the ground section can be increased, and the characteristics of the antenna can be improved.

[0157] (Aspect 7) In aspect 7, the first opening is positioned in a position that is rotationally symmetrical with respect to the center point of the ground portion at predetermined rotational angles in a plan view of the ground portion.

[0158] According to the above embodiment, when the radiating element corresponds to circular polarization, the influence on the characteristics of the radiating element can be suppressed.

[0159] (Aspect 8) In aspect 8, the device further comprises a dielectric located on the lower surface of the radiating element and a plurality of power supply terminals that penetrate the dielectric and supply power to the radiating element.

[0160] According to the above-described embodiment, for example, the size of the ground portion used in a patch antenna can be reduced, and the antenna device can be miniaturized.

[0161] (Aspect 9) In aspect 9, a second opening is formed in the radiating element, and the second opening is positioned in a position that is rotationally symmetric with respect to the center point of the radiating element at predetermined rotational angles in a plan view of the radiating element.

[0162] According to the above-described embodiment, the size of the radiating element in the planar antenna can be reduced, and the antenna device can be miniaturized.

[0163] (Aspect 10) In aspect 10, the ground portion is a quadrilateral having a pair of long sides and a pair of short sides, and the first opening is formed on each of the short sides.

[0164] According to the above embodiment, in a quadrilateral ground section having a pair of long sides and a pair of short sides, the difference in electrical length between the short sides and the long sides can be reduced, and the characteristics of the radiating element corresponding to circular polarization can be improved.

[0165] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof.

[0166] 10-14, 100, 110, 150-152 Antenna equipment 20-23, 25a-25d, 200, 210, 230a-230f, 240a-240c, 250-252, 260, 270 Ground plate 30 Cross dipole antenna 31 Support member 32 Circuit board 40 Board 41, 42 Dipole antenna 50, 51, 53, 54, 300 Elements 70, 71, 72, 72a-72h Opening 85a-85d Rib section S1, S2, S10, S20-S21, S10 Slit

Claims

1. An antenna device comprising a radiating element and a ground portion disposed opposite to the radiating element, wherein at least one first opening is formed in the ground portion, and the first opening is a non-radiating structure and has a shape that adjusts the electrical characteristics of the radiating element.

2. The antenna device according to claim 1, wherein the ground portion is a plate-shaped or three-dimensional conductive member.

3. The antenna device according to claim 1, wherein, in a plan view of the radiating element, the radiating element and the first aperture are arranged so that at least a portion of them overlap each other.

4. The antenna device according to claim 1, wherein the ground portion further comprises a rib portion, and the rib portion has a shape that adjusts the electrical characteristics of the radiating element.

5. The antenna device according to claim 3 or 4, further comprising a substrate on which the radiating element is formed, wherein the radiating element has a first conductor portion and a second conductor portion, the first conductor portion being arranged on one surface of the substrate and the second conductor portion being arranged on the other surface of the substrate.

6. The antenna device according to claim 1, wherein the first opening has an open end at the outer edge of the ground portion in a plan view of the ground portion and extends inward from the outer edge towards the inside of the ground portion.

7. The antenna device according to claim 6, wherein the first opening is positioned in a plan view of the ground portion at positions that are rotationally symmetrical at predetermined rotational angles with respect to the center point of the ground portion.

8. The antenna device according to claim 6 or 7, further comprising a dielectric located on the lower surface of the radiating element, and a plurality of power supply terminals that penetrate the dielectric and supply power to the radiating element.

9. The antenna device according to claim 7, wherein a second aperture is formed in the radiating element, and the second aperture is positioned in a position that is rotationally symmetric with respect to a predetermined rotation angle with respect to the center point of the radiating element in a plan view of the radiating element.

10. The antenna device according to claim 6, wherein the ground portion is a quadrilateral having a pair of long sides and a pair of short sides, and the first opening is formed on each of the short sides.

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