Antenna device

Abstract

A vehicle-mounted antenna device (100) is provided with: an antenna case (101); an antenna base (102) forming an accommodating space, together with the antenna case (101); a first antenna element (108) accommodated in the accommodating space for at least circular polarization transmission or reception; a second antenna element (110) disposed proximate to the first antenna element (108) for at least linear polarization transmission or reception; and at least one parasitic element (111), (112a), (112b), or (112c) that constitutes a reflector or a waveguide for the second antenna element (110).

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, as an antenna device to be mounted on a vehicle or the like, a small, low-profile in-vehicle antenna device to be mounted on the roof of the vehicle has been known.

[0003] In recent years, there has been a demand for in-vehicle antenna devices to be equipped with multiple antennas that can receive and transmit signals in various frequency bands, such as signals for radio broadcasting, signals for terrestrial digital broadcasting, signals for acquiring location information, and signals for supporting advanced driver-assistance systems (ADAS).

[0004] For example, Patent Document 1 discloses an antenna device that includes a first antenna unit that receives AM / FM signals, a second antenna unit that is a cellular antenna, and a third antenna unit that receives GNSS signals in order to accommodate signals of various frequency bands. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 121748 Summary of the Invention [Problem to be solved by the invention]

[0006] Multi-band vehicle-mounted antenna devices, such as the antenna device of Patent Document 1, which are equipped with multiple types of antenna elements corresponding to different frequency bands, have become mainstream.

[0007] However, when multiple types of antenna elements corresponding to different frequency bands are installed in the housing space of a small, low-profile vehicle-mounted antenna device, the antenna elements must be placed close to each other, which makes it difficult to ensure isolation between them, and therefore can make it difficult to obtain good antenna characteristics.

[0008] An object of the present invention is to provide a small antenna device in which a plurality of antenna elements are arranged close to each other in a small space, while still achieving good antenna characteristics. [Means for solving the problem]

[0009] One aspect of the present invention is Case and a base that forms a storage space together with the case; a first antenna element accommodated in the accommodation space and configured to at least transmit or receive circularly polarized waves; a second antenna element disposed adjacent to the first antenna element and configured to transmit or receive linearly polarized waves; and at least one parasitic element that serves as a reflector or director for the second antenna element. [Effects of the Invention]

[0010] According to the above aspects of the present invention, in a small antenna device, it is possible to obtain good antenna characteristics even when a plurality of antenna elements are arranged close to each other in a small space. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of an in-vehicle antenna device according to an embodiment of the present invention; [Figure 2] 2 is an enlarged left side view showing a front portion of the vehicle-mounted antenna device according to the embodiment; FIG. [Figure 3] FIG. 10 is an enlarged perspective view of the vicinity of a second antenna unit with the resin holder removed according to one embodiment. [Figure 4] FIG. 1 is a perspective view showing the positional relationship between a circularly polarized antenna and a parasitic element in a model used in a simulation to verify the influence of a parasitic element on a circularly polarized antenna. [Figure 5] FIG. 5 is an enlarged view of the vicinity of the circularly polarized antenna shown in FIG. [Figure 6] FIG. 5 is a side view of the vicinity of the circularly polarized antenna shown in FIG. [Figure 7] This figure shows the results of a simulation for the circularly polarized antenna shown in Figure 4 when the length L of the ungrounded parasitic element EL is 80 [mm], and shows the angular distribution of the axial ratio around the angle φ at the angle θ = 80 [degrees]. [Figure 8] This figure shows the results of a simulation in which an ungrounded parasitic element EL is not provided for the circularly polarized antenna shown in Figure 4, and shows the angular distribution of the axial ratio around the angle φ at angle θ = 80 degrees. [Figure 9] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the non-grounded parasitic element EL and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ when the angle θ = 0 [degrees] for the circularly polarized antenna shown in FIG. [Figure 10] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the ungrounded parasitic element EL and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ = 60 [degrees] for the circularly polarized antenna shown in FIG. [Figure 11] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the ungrounded parasitic element EL and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ=80 [degrees] for the circularly polarized antenna shown in FIG. [Figure 12] FIG. 5 is a diagram showing the results of a simulation regarding the directivity of gain of a circularly polarized wave (right-handed polarized wave) around an angle φ at an angle θ=60 degrees when the operating frequency of the circularly polarized antenna AN shown in FIG. 4 is 1575 MHz. [Figure 13]FIG. 5 is a diagram showing the results of a simulation regarding the directivity of the gain of a circularly polarized wave (right-handed polarized wave) around an angle φ at an angle θ=80 degrees when the operating frequency of the circularly polarized antenna AN shown in FIG. 4 is 1575 MHz. [Figure 14] This figure shows the results of a simulation regarding the relationship between the length L [mm] of the non-grounded parasitic element EL and the gain directivity of a circularly polarized wave (right-hand polarized wave) around the angle φ at the angle θ = 60 [degrees] when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz. [Figure 15] FIG. 10 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the non-grounded parasitic element EL and the gain directivity of a circularly polarized wave (right-hand polarized wave) around the angle φ at the angle θ=80 [degrees] when the operating frequency of the circularly polarized antenna AN shown in FIG. 4 is 1575 MHz. [Figure 16] FIG. 10 is an enlarged perspective view of a second antenna unit with the resin holder removed, according to Modification 1. [Figure 17] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ = 0 [degrees] for the circularly polarized antenna shown in FIG. [Figure 18] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ = 60 [degrees] for the circularly polarized antenna shown in FIG. [Figure 19] FIG. 5 is a diagram showing the results of a simulation regarding the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ = 80 [degrees] for the circularly polarized antenna shown in FIG. [Figure 20] The following shows the results of a simulation of the directivity of the gain of a circularly polarized wave (right-handed polarized wave) around an angle φ at an angle θ=60 degrees when the operating frequency of the circularly polarized antenna AN shown in FIG. 4 is 1575 MHz. [Figure 21]The following shows the results of a simulation of the directivity of the gain of a circularly polarized wave (right-handed polarized wave) around an angle φ at an angle θ=80 degrees when the operating frequency of the circularly polarized antenna AN shown in FIG. 4 is 1575 MHz. [Figure 22] This figure shows the results of a simulation regarding the relationship between the length L [mm] of the parasitic element EL in the grounded state and the gain directivity of a circularly polarized wave (right-hand polarized wave) around the angle φ at the angle θ = 60 [degrees] when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz. [Figure 23] This figure shows the results of a simulation regarding the relationship between the length L [mm] of the grounded parasitic element EL and the gain directivity of a circularly polarized wave (right-hand polarized wave) around the angle φ at the angle θ = 80 [degrees] when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz. [Figure 24] FIG. 11 is a perspective view showing an example of a parasitic element according to Modification 3. [Figure 25] FIG. 13 is a side view showing an example of a configuration in which a parasitic element is connected to a substrate via a filter in Modification 4. [Figure 26] 10 is a diagram showing the electrical characteristics of the second antenna unit 104 when the models of Examples 1 and 2 and the comparative example are placed on an infinite ground plane. The operating frequency is 5.9 GHz, and the diagram shows the results of a simulation regarding the directivity of gain of vertically polarized waves around the angle φ when θ=90 degrees. [Figure 27] FIG. 10 is a diagram showing the electrical characteristics of the first antenna section 103 when the models of Examples 1 and 2 and the comparative example are placed on a circular ground plane, and is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ when the angle θ=0 [degrees]. [Figure 28] FIG. 10 is a diagram showing the electrical characteristics of the first antenna section 103 when the models of Examples 1 and 2 and the comparative example are placed on a circular ground plane, and is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ=60 [degrees]. [Figure 29]FIG. 10 is a diagram showing the electrical characteristics of the first antenna section 103 when the models of Examples 1 and 2 and the comparative example are placed on a circular ground plane, and is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio within the angular distribution of the axial ratio around the angle φ at the angle θ=80 [degrees]. [Figure 30] 10 is a diagram showing the configuration of a first antenna element, a third parasitic element, and a capacitively loaded element according to Modification 5. FIG. [Figure 31] 13 is a diagram showing the configuration of a first antenna element, a third parasitic element, and a capacitively loaded element according to Modification 6. FIG. [Figure 32] 13 is a diagram showing the configuration of a first antenna element, a third parasitic element, and a capacitively loaded element according to Modification 7. FIG. [Figure 33] 13 is a diagram showing the configuration of a first antenna element, a third parasitic element, and a capacitively loaded element according to Modification 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all the drawings, like components are designated by like reference numerals, and the description thereof will be omitted as appropriate.

[0013] In this specification, ordinal numbers such as "first," "second," and "third" are used merely to distinguish between similarly named configurations, unless otherwise specified, and do not imply any particular characteristics (e.g., order or importance) of the configurations.

[0014] [Embodiment] An in-vehicle antenna device (hereinafter also simply referred to as "antenna device") 100 according to one embodiment of the present invention is a device that is attached to the roof of a vehicle and that transmits or receives at least radio waves in a plurality of different frequency bands. Note that, although this embodiment will be described using an example of the antenna device 100 that transmits or receives at least three types of radio waves, the types of radio waves that the antenna device transmits or receives may be two or more.

[0015] As shown in the perspective view of Fig. 1 and the left side view of the front portion of Fig. 2, the in-vehicle antenna device 100 includes an antenna case 101, an antenna base 102, a first antenna unit 103, a second antenna unit 104, and a third antenna unit 105. Note that in Figs. 1 and 2, the antenna case 101 is depicted as being see-through.

[0016] 1, "front" or "forward" refers to the front side of the vehicle on which the antenna device 100 is mounted, and "rear" or "rearward" refers to the opposite rear side of the vehicle. "Right" or "right side" refers to the right side as seen by the driver of the vehicle, and "left" or "left side" refers to the opposite side. "Down" or "below" refers to the direction of gravity of the vehicle on which the antenna device 100 is mounted, and "up" or "upper" refers to the opposite direction.

[0017] These directional terms are used in the following description and in other drawings for the purpose of explanation only and are not intended to limit the present invention.

[0018] The antenna case 101 is a hollow member made of radio wave-transmitting synthetic resin (e.g., ABS resin). The antenna case 101 is a case that forms a storage space together with the antenna base 102 by covering the antenna base 102 from above. The antenna case 101 has a shark-fin shape, and the storage space becomes wider and higher from the front to the rear. Therefore, the rear portion of the storage space is wider than the front portion. Here, the width refers to the length in the left-right direction, and the height refers to the length in the up-down direction.

[0019] The external dimensions of the antenna case 101 are, for example, approximately 190 mm to 200 mm in the front-rear direction, approximately 60 mm to 65 mm in the up-down direction, and approximately 70 mm to 75 mm in the left-right direction.

[0020] The antenna base 102 includes a conductive base that becomes grounded by conducting to the roof when mounted on the roof of a vehicle via the pad P. The antenna base 102 may be composed of only the conductive base, or may be composed of an insulating base and a conductive base, an insulating base and a metal plate, or an insulating base, a conductive base and a metal plate. The conductive base may also be composed of a plurality of electrically connected or separated components and an insulating base that holds them.

[0021] A first antenna unit 103, a second antenna unit 104, and a third antenna unit 105 are fixed to an antenna base .

[0022] In this embodiment, the second antenna unit 104, the first antenna unit 103, and the third antenna unit 105 are attached to the antenna base 102 in this order from the front, and are thereby arranged in the accommodation space. In this embodiment, the second antenna unit 104 is arranged in the front of the accommodation space, but it may also be arranged in the center or rear of the accommodation space.

[0023] The first antenna unit 103 includes a first substrate 107 and a first antenna element 108 .

[0024] The first substrate 107 is a substrate fixed to the antenna base 102, and is, for example, a PCB (Printed Circuit Board).

[0025] The first antenna element 108 is provided on the first substrate 107. The first antenna element 108 is an antenna element that receives radio waves for the Global Navigation Satellite System (GNSS), and includes a patch antenna.

[0026] Note that GNSS radio waves are an example of circularly polarized waves. The first antenna element 108 is only required to transmit or receive circularly polarized waves, and the radio waves are not limited to GNSS radio waves and may be, for example, radio waves for SDARS (Satellite Digital Audio Radio Service). Furthermore, the first antenna element 108 may be replaced with multiple circularly polarized antennas, or may be a single antenna compatible with multiple frequency bands.

[0027] 2 and 3, second antenna section 104 has second substrate 109, second antenna element 110, first parasitic element 111, second parasitic elements 112a to 112c, and resin holder 113. Fig. 3 is an enlarged perspective view of the vicinity of second antenna section 104 without resin holder 113. Note that first parasitic element 111 is not shown in Figs. 1 and 2 because it is disposed inside resin holder 113.

[0028] Second substrate 109 is a substrate, such as a PCB, that is fixed to antenna base 102. Second antenna element 110, first parasitic element 111, second parasitic elements 112a to 112c, and resin holder 113 are provided on and fixed to second substrate 109.

[0029] The second antenna element 110 is an antenna element that at least transmits or receives radio waves for V2X (Vehicle-to-Everything), and is fed with power via a circuit on the second substrate 109.

[0030] The second antenna element 110 is accommodated in the accommodation space and is arranged close to the first antenna element .

[0031] Note that the V2X radio wave is an example of a vertically polarized wave, which is a linearly polarized wave. The second antenna element 110 is only required to transmit or receive at least a vertically polarized wave, and the radio wave is not limited to a V2X radio wave and may be, for example, a vertically polarized wave for DTV (Digital TV) or the like.

[0032] In this embodiment, the second antenna element 110 is a monopole antenna, and is configured with a linear conductor erected on the second substrate 109. Since radio waves for V2X are typically in the 5.9 GHz band, the length of the second antenna element 110 is approximately half the wavelength (approximately 25 mm) of the vertically polarized waves for V2X.

[0033] The length of the second antenna element 110 may be a quarter wavelength (approximately 12.5 mm). The second antenna element 110 is not limited to a monopole antenna, but may be a dipole antenna, a sleeve antenna, or the like. The second antenna element 110 is not limited to a linear conductor, but may be made of conductors of various shapes, such as sheet metal, or may be made of a linear circuit provided on a substrate. The term "linear" is not limited to a straight line, but may include a curved or bent shape.

[0034] The first parasitic element 111 and the second parasitic elements 112a to 112c are parasitic elements that function as reflectors or directors to give the second antenna element 110 forward directivity.

[0035] The directivity of the second antenna element 110 formed by the parasitic elements 111, 112a to 112c is not limited to the forward direction, but may be any direction away from the first antenna element 108, such as left and right, forward left, forward right, or forward upward.

[0036] First parasitic element 111 and second parasitic elements 112a to 112c are configured by ungrounded linear conductors provided on second substrate 109.

[0037] Each of the first parasitic element 111 and the second parasitic elements 112a to 112c is ungrounded, and the total length of each is 1 / 2 or less of the wavelength of the circularly polarized wave transmitted or received by the first antenna element 108 (approximately 190 mm in this embodiment), and preferably 3 / 10 or less of the wavelength of the circularly polarized wave.

[0038] Here, each of the parasitic elements 111, 112a to 112c acts as a wave source, which may deteriorate the antenna characteristics (axial ratio, etc.) of the first antenna element 108. A simulation was performed using the models shown in FIGS. 4 to 6 to examine the influence of the ungrounded parasitic elements 111, 112a to 112c on the first antenna element 108, which is a circularly polarized antenna.

[0039] Fig. 4 is a perspective view showing the arrangement of a circularly polarized antenna and a parasitic element in a model used in a simulation to verify the influence of a parasitic element on a circularly polarized antenna. Fig. 5 is an enlarged view of the vicinity of the circularly polarized antenna AN shown in Fig. 4. Fig. 6 is a side view of the vicinity of the circularly polarized antenna AN shown in Fig. 4, viewed from the positive direction of the Y axis.

[0040] 4 to 6, the XY plane, which includes the mutually perpendicular X-axis and Y-axis, is parallel to the circular ground plate PL. The direction from the center of the circularly polarized antenna AN toward the parasitic element EL is the positive X-axis direction, and the Y-axis direction is to the right as viewed from the positive X-axis direction. The axis that passes through the center of the circular ground plate PL and is perpendicular to the circular ground plate PL is the Z-axis, and the direction in which the circularly polarized antenna AN is located relative to the circular ground plate PL is the positive Z-axis direction. Furthermore, θ represents the angle with respect to the Z-axis, and φ represents the angle with respect to the X-axis.

[0041] The circular ground plate PL is a circular plate with a diameter of 1 m. The circularly polarized antenna AN is an antenna installed at the center of the circular ground plate PL, and its operating frequency is 1555 to 1610 MHz, receiving right-hand polarized waves. The parasitic element EL is installed near the circularly polarized antenna AN, and the distance between the parasitic element EL and the circularly polarized antenna AN is 20 mm. The parasitic element EL is a straight rod-shaped element with a length L mm in the Z-axis direction, and is not electrically connected to the circular ground plate PL, so it is not grounded.

[0042] Fig. 7 shows the results of a simulation in which the length L of the ungrounded parasitic element EL is 80 mm for the circular polarized antenna shown in Fig. 4, and shows the angular distribution of the axial ratio around the angle φ at the angle θ = 80 degrees. Fig. 8 shows the results of a simulation in which the ungrounded parasitic element EL is not provided for the circular polarized antenna shown in Fig. 4, and shows the angular distribution of the axial ratio around the angle φ at the angle θ = 80 degrees.

[0043] 7 and 8, the circumferential direction represents the angle φ [degrees], and the distance from the center represents the axial ratio [dB].

[0044] 7 and 8, when an ungrounded parasitic element EL with a length L of 80 mm is installed, the axial ratio increases sharply at a specific angle φ compared to when an ungrounded parasitic element EL is not installed. This suggests that the parasitic element EL affects the axial ratio.

[0045] In the simulation, the maximum value of the axial ratio was set to 40 dB, so when the axial ratio is 40 dB or more, the axial ratio is shown as 40 dB in Figures 7 and 8. Therefore, when the axial ratio is 40 dB, there is a possibility that the actual axial ratio is 40 dB or more, and this also applies to the results of the following simulations.

[0046] Fig. 9 shows the results of a simulation of the relationship between the length L [mm] of the ungrounded parasitic element EL and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 0 [degrees] for the circularly polarized antenna shown in Fig. 4. Fig. 10 shows the results of a simulation of the relationship between the length L [mm] of the ungrounded parasitic element EL and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 60 [degrees] for the circularly polarized antenna shown in Fig. 4. Fig. 11 shows the results of a simulation of the relationship between the length L [mm] of the ungrounded parasitic element EL and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 80 [degrees] for the circularly polarized antenna shown in Fig. 4.

[0047] 9 to 11, the horizontal axis represents the length L [mm] of the parasitic element EL, and the vertical axis represents the maximum value of the axial ratio [dB].

[0048] 9 to 11, the solid line indicates the simulation results when the operating frequency is 1560 MHz, the dotted line indicates the simulation results when the operating frequency is 1575 MHz, and the dashed-dotted line indicates the simulation results when the operating frequency is 1600 MHz.

[0049] 9 to 11, the maximum value of the axial ratio increases as the length L of the parasitic element EL increases from 0 mm, and reaches a maximum when the length L is approximately 80 mm. In other words, the axial ratio deteriorates as the length L of the parasitic element EL increases from 0 mm, and is at its worst when the length L is approximately 80 mm.

[0050] Here, the length L of the parasitic element EL, 80 mm, corresponds to approximately 1 / 2 wavelength of the operating frequencies of the circularly polarized antenna, 1560 MHz, 1575 MHz, and 1600 MHz. Therefore, when the parasitic element EL is ungrounded, the length L of the parasitic element EL should be approximately 1 / 2 wavelength or less, more preferably 3 / 10 wavelength or less, of the operating frequency of the circularly polarized antenna AN.

[0051] Figure 12 shows the results of a simulation of the directivity of gain of a circularly polarized wave (right-hand polarized wave) around an angle φ at an angle θ = 60 degrees when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz. Figure 13 shows the results of a simulation of the directivity of gain of a circularly polarized wave (right-hand polarized wave) around an angle φ at an angle θ = 80 degrees when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz.

[0052] 12 and 13, the circumferential direction represents the angle φ [degrees], and the distance from the center represents the gain [dBic].

[0053] 12 and 13, the solid line indicates the simulation results when the length L of the parasitic element EL is 0 mm, i.e., when the parasitic element EL is not provided. The dotted line indicates the simulation results when the length L of the parasitic element EL is 40 mm. The dashed-dotted line indicates the simulation results when the length L of the parasitic element EL is 80 mm. The two-dot chain line indicates the simulation results when the length L of the parasitic element EL is 100 mm.

[0054] 12 and 13, as the length L of the parasitic element EL increases from 0 mm, the directivity of the circularly polarized antenna AN changes, with the largest change occurring when the length L is approximately 80 mm. Even when the length L of the parasitic element EL is 100 mm, the directivity of the circularly polarized antenna AN changes. This suggests that the directivity of the circularly polarized antenna AN is biased toward a specific angle due to the influence of the parasitic element EL.

[0055] Fig. 14 is a diagram showing the results of a simulation of the relationship between the length L [mm] of the ungrounded parasitic element EL and the gain directivity of a circularly polarized wave (right-hand polarized wave) about the angle φ at the angle θ = 60 degrees when the operating frequency of the circularly polarized antenna AN shown in Fig. 4 is 1575 MHz. Fig. 15 is a diagram showing the results of a simulation of the relationship between the length L [mm] of the ungrounded parasitic element EL and the gain directivity of a circularly polarized wave (right-hand polarized wave) about the angle φ at the angle θ = 80 degrees when the operating frequency of the circularly polarized antenna AN shown in Fig. 4 is 1575 MHz.

[0056] 14 and 15, the horizontal axis represents the length L [mm] of the parasitic element EL, and the vertical axis represents the gain [dB].

[0057] 14 and 15, the solid line represents the ratio of the maximum value to the minimum value (MAX / MIN), the dotted line represents the maximum value (MAX) of the gain directivity, and the dash-dotted line represents the minimum value (MIN) of the gain directivity.

[0058] 14 and 15, as the length L [mm] of the parasitic element EL increases from 0 [mm], the ratio of the maximum value to the minimum value (MAX / MIN) increases, reaching a maximum when the length L is approximately 80 [mm]. The ratio of the maximum value to the minimum value (MAX / MIN) gradually decreases when the length L exceeds approximately 80 [mm], but the ratio (MAX / MIN) when the length L is 100 [mm] is greater than the ratio (MAX / MIN) when the length L is 0 [mm].

[0059] This suggests that the parasitic element EL affects the directivity of the circularly polarized antenna AN when its length L [mm] is long. Therefore, when the parasitic element EL is ungrounded, the length L of the parasitic element EL should be approximately 1 / 2 wavelength or less, more preferably 3 / 10 wavelength or less, of the operating frequency of the circularly polarized antenna AN.

[0060] As a result of such simulations, the inventors found that it is possible to suppress deterioration of the antenna characteristics of first antenna element 108 by adjusting the overall length of parasitic elements 111, 112a to 112c. Specifically, as described above, in the case of ungrounded parasitic elements 111, 112a to 112c, by setting the overall length to ½ or less of the wavelength of the circularly polarized wave transmitted or received by first antenna element 108, it is possible to suppress deterioration of the antenna characteristics of first antenna element 108. Furthermore, by setting the overall length to 3 / 10 or less of the wavelength of the circularly polarized wave, it is possible to further suppress deterioration of the antenna characteristics of first antenna element 108.

[0061] In detail, first parasitic element 111 is an element that functions as a director of second antenna element 110, and is arranged on the opposite side of first antenna element 108 in the front-to-rear direction with second antenna element 110 interposed therebetween. That is, first parasitic element 111 according to this embodiment is provided forward of second antenna element 110. With this arrangement, first parasitic element 111 can be arranged inside case 101 at a height according to the shape of case 101 that rises from the tip (the front end in this embodiment). Therefore, it is possible to control the directivity while making effective use of the space inside case 101, and to reduce the size of antenna device 100.

[0062] First parasitic element 111 according to this embodiment is disposed substantially perpendicular to second substrate 109 and has a linear shape extending in the vertical direction.

[0063] Note that first parasitic element 111 does not have to be substantially perpendicular to second substrate 109, and may extend upward at an angle relative to second substrate 109. Furthermore, first parasitic element 111 may include a curved or bent portion connected to a straight portion fixed to second substrate 109, similar to second parasitic elements 112a to 112c, so that the tip end thereof may protrude in a direction different from the direction in which the straight portion extends.

[0064] Second parasitic elements 112a to 112c are elements that function as reflectors for second antenna element 110, and are arranged in the front-to-rear direction between first antenna element 108 and second antenna element 110. In this arrangement, second parasitic elements 112a to 112c that rise from the tip (the front end in this embodiment) can be arranged in case 101 at a height that corresponds to the shape of case 101. Therefore, it is possible to effectively use the space in case 101 while controlling the directivity, and it is possible to reduce the size of antenna device 100.

[0065] In this embodiment, the number of second parasitic elements 112a to 112c functioning as reflectors of second antenna element 110 is three, which is greater than the number of first parasitic elements 111 functioning as directors of second antenna element 110.

[0066] That is, the antenna device 100 according to this embodiment is provided with one parasitic element 111 that functions as a director and three parasitic elements 112a to 112c that function as reflectors. This makes it possible to provide the second antenna element 110 with desired directivity and achieve desired antenna characteristics for the second antenna element 110, while also achieving miniaturization of the antenna device 100 and reducing the manufacturing cost of the antenna device 100.

[0067] It is sufficient that at least one of parasitic elements 111 and 112a to 112c is provided. That is, either first parasitic element 111 functioning as a director or second parasitic elements 112a to 112c functioning as reflectors does not need to be provided, and there may be multiple first parasitic elements 111, or one or two, or four or more second parasitic elements 112a to 112c.

[0068] Second parasitic element 112a is a parasitic element provided directly behind second antenna element 110. Second parasitic element 112b is a parasitic element provided to the right rear of second antenna element 110. Second parasitic element 112c is a parasitic element provided to the left rear of second antenna element 110.

[0069] When viewed from the front, second parasitic element 112b and second parasitic element 112c are provided on different sides of second antenna element 110. In this embodiment, second parasitic element 112b and second parasitic element 112c are provided at positions that are roughly symmetrical with respect to an imaginary line that passes through the center of first antenna element 108 and the center of second antenna element 110 when viewed from above.

[0070] Second parasitic element 112a according to this embodiment has straight portion 112a_1 that is provided substantially perpendicular to second substrate 109 and extends in the up-down direction, curved or bent portion 112a_2, and tip portion 112a_3 that extends forward. Thus, tip portion 112a_3 is connected to the upper end of straight portion 112a_1 via bent portion 112a_2, and thereby protrudes forward.

[0071] Second parasitic element 112b has straight portion 112b_1 that is provided substantially perpendicular to second substrate 109 and extends in the up-down direction, curved or bent portion 112b_2, and tip portion 112b_3 that extends rearward. Thus, tip portion 112b_3 is connected to the upper end of straight portion 112b_1 via bent portion 112b_2, and thereby protrudes rearward.

[0072] Similar to second parasitic element 112b, second parasitic element 112c has straight portion 112c_1 extending vertically and substantially perpendicular to second substrate 109, curved or bent portion 112c_2, and tip portion 112c_3 extending rearward. Thus, tip portion 112c_3 is connected to the upper end of straight portion 112b_1 via bent portion 112c_2, and thereby protrudes rearward.

[0073] Here, in order to make first parasitic element 111 function as a director and second parasitic elements 112a to 112c function as reflectors, the total length of each of second parasitic elements 112a to 112c is longer than the total length of first parasitic element 111.

[0074] This is because whether the parasitic element primarily functions as a director or a reflector of the antenna element varies depending on the wavelength of the radio waves transmitted or received by the antenna element.

[0075] For example, first parasitic element 111 functions as a director by having a total length equal to or less than approximately half the wavelength (approximately 50 mm in this embodiment) of the linearly polarized wave (here, vertically polarized wave) transmitted or received by second antenna element 110. Each of second parasitic elements 112a to 112c functions as a reflector by having a total length longer than approximately half the wavelength of the vertically polarized wave.

[0076] Furthermore, second parasitic elements 112a-112c, which are long enough to function as reflectors, may not fit into the accommodation space if they are entirely straight. In this embodiment, by including bent portions 112a_2, 112b_2, and 112c_2 in second parasitic elements 112a-112c, the second parasitic elements can be accommodated in the accommodation space while still having a length sufficient to function as a reflector. This makes it possible to reduce the size of the antenna device 100 while improving the antenna characteristics of the second antenna element 110.

[0077] Furthermore, the protruding directions of tips 112a_3, 112b_3, and 112c_3 of second parasitic element 112a are different from those of second parasitic elements 112b and 112c. That is, tip 112a_3 of second parasitic element 112a, which is located in the front, protrudes backward, while tips 112b_3 and 112c_3 of second parasitic elements 112b and 112c, which are located in the rear, protrude forward.

[0078] This allows the three second parasitic elements 112a to 112c to be arranged compactly in the front-to-rear direction while still providing a sufficient length to function as a reflector, thereby improving the antenna characteristics of the second antenna element 110 and preventing the antenna device 100 from becoming too large.

[0079] Furthermore, each of the parasitic elements 111, 112a to 112c can also function as a wave source. Therefore, even if the parasitic elements have the above-mentioned length to function as a director or reflector, if the distance from the second antenna element 110 is large, the phase difference over that distance may have an effect and the parasitic elements may not be able to fully function as a director or reflector.

[0080] For example, first parasitic element 111 having the above-mentioned length and functioning as a director begins to function as a reflector as the distance from second antenna element 110 increases. Also, for example, each of second parasitic elements 112a to 112c having the above-mentioned length and functioning as a reflector begins to generate a deviation in gain in the horizontal plane as the distance from second antenna element 110 increases.

[0081] Therefore, it is desirable that each of the parasitic elements 111, 112a to 112c is arranged within a range of half the wavelength of the vertically polarized wave received by the second antenna element 110 from the installation position of the second antenna element 110.

[0082] This prevents the parasitic elements 111, 112a to 112c from becoming a wave source and suppresses deterioration of the antenna characteristics of the second antenna element 110, allowing the first parasitic element 111 to function as a director and the second parasitic elements 112a to 112c to function as reflectors with good characteristics, thereby providing the desired directivity and improving the antenna characteristics of the second antenna element 110.

[0083] Similarly, each of the parasitic elements 111, 112a to 112c acts as a wave source, thereby deteriorating the antenna characteristics (such as the axial ratio) of the first antenna element 108. For example, if the total length of the ungrounded parasitic elements 111, 112a to 112c is not equal to or less than half the wavelength of the circularly polarized wave transmitted or received by the first antenna element 108, it is desirable to arrange each of the parasitic elements 111, 112a to 112c at a distance of about 50 to 60 mm or more from the center of the first antenna element 108, for example, in the case of a circularly polarized antenna for 1555 to 1610 MHz.

[0084] This reduces the influence on first antenna element 108 caused by parasitic elements 111, 112a to 112c acting as a wave source, and suppresses deterioration of the axial ratio of first antenna element 108. Therefore, it becomes possible to suppress deterioration of the antenna characteristics of first antenna element 108.

[0085] Resin holder 113 is a solid resin member provided with through holes or grooves for holding second antenna element 110, first parasitic element 111, and second parasitic elements 112a to 112c.

[0086] The resin holder 113 according to this embodiment has a front holder portion 113a and a rear holder portion 113b. The resin holder 113 may be formed as a single unit, or may be configured by combining a plurality of separable parts, such as the front holder portion 113a and the rear holder portion 113b.

[0087] Front holder portion 113a is a rectangular parallelepiped having a height roughly the same as that of first parasitic element 111, and is longer in the front-to-rear direction than in the left-to-right direction.

[0088] The front holder portion 113a has through holes that penetrate in the vertical direction lined up front and back, with the first parasitic element 111 inserted into the front through hole and the second antenna element 110 inserted into the rear through hole.

[0089] The rear holder portion 113b has roughly the same height as the straight portions 112a_1, 112b_1, and 112c_1, and has a first holding portion 113b_1 consisting of a flat portion and a portion protruding rearward from its upper end, and a second holding portion 113b_2 protruding rearward from the center of the rear surface of the flat portion.

[0090] The first holding portion 113b_1 has grooves extending vertically on its front surface and from front to rear on its top surface at symmetrical positions, and the second parasitic element 112b and the second parasitic element 112c are fitted into the right and left grooves, respectively.

[0091] The second holding portion 113b_2 has a groove extending in the vertical direction at the center of its rear surface and extending from rear to front on its upper surface, and the second parasitic element 112a is fitted in this groove.

[0092] Resin holder 113 according to this embodiment is fixed to second substrate 109 by screwing the portions extending to the left and right from the bottom of rear holder portion 113b. First parasitic element 111 and second parasitic elements 112a to 112c may be locked to resin holder 113 by fitting into grooves, or may be fixed with an appropriate adhesive or the like.

[0093] Dielectrics generally have the effect of shortening the wavelength of high-frequency electromagnetic waves (dielectric shortening). Therefore, by holding parasitic elements 111, 112a to 112c with resin holder 113, the dimensions of parasitic elements 111, 112a to 112c can be reduced. This makes it possible to miniaturize antenna device 100.

[0094] In particular, the shorter the wavelength, the greater the effect of dielectric shortening, even if the volume occupied by the dielectric is small. Therefore, the effect is particularly significant for the second antenna element 110 used for transmitting and receiving radio waves with relatively short wavelengths, such as radio waves for V2X.

[0095] The shape of resin holder 113 may be changed as appropriate, and resin holder 113 may be hollow in part or in whole. Furthermore, resin holder 113 does not have to be provided on second antenna unit 104.

[0096] The third antenna unit 105 includes a third substrate 114, a capacitive loading element 115a, and a helical element 115b.

[0097] The third substrate 114 is a substrate, such as a PCB, that is fixed to the antenna base 100. The capacitance loading element 115a and the helical element 115b are antenna elements that receive radio waves for DAB (Digital Audio Broadcast), for example. The capacitance loading element 115a is fixed to a holder that holds the helical element 115b, and the holder is fixed to the third substrate 114.

[0098] The radio waves received or transmitted by the third antenna unit 105 are not limited to DAB radio waves and may be changed as appropriate. For example, they may be AM / FM radio waves. The configuration of the antenna element of the third antenna unit 105 may also be changed as appropriate depending on the radio waves received by the third antenna unit 105.

[0099] In this embodiment, the upper end (top surface) of the first antenna unit 103 is positioned lower than the upper end of the second antenna element 110, but it may also be positioned higher than the upper end of the second antenna element 110.

[0100] When the upper end (top surface) of the first antenna unit 103 is positioned lower than the upper end of the second antenna element 110, the electrical characteristics of the second antenna element 110 can be improved. Also, when the upper end (top surface) of the first antenna unit 103 is positioned higher than the upper end of the second antenna element 110, the electrical characteristics of the first antenna unit 103 can be improved. By setting the height relationship between the first antenna unit 103 and the second antenna element 110 according to the design purpose, the antenna characteristics of the first antenna unit 103 and the second antenna element 110 can be ensured without compromising the design of the antenna device 100, and therefore the antenna device 100 can be made smaller.

[0101] In this embodiment, the upper end of the third antenna section 105 is positioned higher than the upper end of the second antenna element 110, but it may also be positioned lower than the upper end of the second antenna element 110.

[0102] When the upper end of the third antenna unit 105 is disposed at a position higher than the upper end of the second antenna element 110, the electrical characteristics of the third antenna unit 105 can be improved. When the upper end of the third antenna unit 105 is disposed at a position lower than the upper end of the second antenna element 110, the electrical characteristics of the second antenna element 110 can be improved. By setting the height relationship between the third antenna unit 105 and the second antenna element 110 according to the design purpose, the antenna characteristics of the third antenna unit 105 and the second antenna element 110 can be ensured without compromising the design of the antenna device 100, and therefore the antenna device 100 can be made smaller.

[0103] [Variation 1] In the embodiment, an example has been described in which the parasitic elements 111, 112a to 112c are not grounded, but the parasitic elements that give directivity to the second antenna element 110 may be grounded.

[0104] The second antenna section 204 according to the first modification has the same second substrate 109, second antenna element 110, and resin holder 113 as those of the embodiment, and a first parasitic element 211 and second parasitic elements 212a to 212c instead of the first parasitic element 111 and second parasitic elements 112a to 112c according to the embodiment. Except for these, the second antenna section 204 according to this modification may be configured similarly to the second antenna section 104 according to the embodiment.

[0105] FIG. 16 is an enlarged perspective view of second antenna section 204 according to Modification 1, and shows a state in which resin holder 113 is removed, similar to FIG.

[0106] Each of the first parasitic element 211 and the second parasitic elements 212a to 212c is grounded, and the total length of each is 1 / 4 or less of the wavelength of the circularly polarized wave transmitted or received by the first antenna element 108, and preferably 3 / 20 or less of the wavelength of the circularly polarized wave.

[0107] Here, each of the grounded parasitic elements 211, 212a to 212c, like each of the ungrounded parasitic elements 111, 112a to 112c described in the embodiment, can become a wave source and deteriorate the antenna characteristics (axial ratio, etc.) of the first antenna element 108. A simulation was performed to examine the influence of the ungrounded parasitic elements 211, 212a to 212c on the first antenna element 108, which is such a circularly polarized antenna.

[0108] The model used in the simulation of this modification is the model described with reference to FIGS. 4 to 6, but modified so that the parasitic element EL is grounded.

[0109] That is, in the simulation of this modification, the circular ground plate PL is a circular plate with a diameter of 1 m. The circularly polarized antenna AN is an antenna provided at the center of the circular ground plate PL, has an operating frequency of 1555 to 1610 MHz, and receives right-hand polarized waves. The parasitic element EL is provided near the circularly polarized antenna AN, and the distance between the parasitic element EL and the circularly polarized antenna AN is 20 mm. The parasitic element EL is a straight rod-shaped element with a length L mm in the Z-axis direction. However, in the simulation of this modification, the parasitic element EL is electrically connected to the circular ground plate PL, thereby being grounded.

[0110] Fig. 17 shows the results of a simulation of the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 0 [degrees] for the circularly polarized antenna shown in Fig. 4. Fig. 18 shows the results of a simulation of the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 60 [degrees] for the circularly polarized antenna. Fig. 19 shows the results of a simulation of the relationship between the length L [mm] of the parasitic element EL in the grounded state and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ at the angle θ = 80 [degrees].

[0111] 17 to 19, the horizontal axis represents the length L [mm] of the parasitic element EL, and the vertical axis represents the maximum value of the axial ratio [dB].

[0112] 17 to 19, the solid line indicates the simulation results when the operating frequency is 1560 MHz, the dotted line indicates the simulation results when the operating frequency is 1575 MHz, and the dashed-dotted line indicates the simulation results when the operating frequency is 1600 MHz.

[0113] 17 to 19, the maximum value of the axial ratio increases as the length L of the parasitic element EL increases from 0 mm, and reaches a maximum when the length L is approximately 40 mm. In other words, the axial ratio deteriorates as the length L of the parasitic element EL increases from 0 mm, and is at its worst when the length L is approximately 40 mm.

[0114] Here, the length L of the parasitic element EL, 40 mm, corresponds to approximately 1 / 4 wavelength of the operating frequencies of the circularly polarized antenna, 1560 MHz, 1575 MHz, and 1600 MHz. Therefore, when the parasitic element EL is grounded, the length L of the parasitic element EL should be approximately 1 / 4 wavelength or less, more preferably 3 / 20 wavelength or less, of the operating frequency of the circularly polarized antenna AN.

[0115] Figure 20 shows the results of a simulation of the directivity of gain of a circularly polarized wave (right-hand polarized wave) around an angle φ at an angle θ = 60 degrees when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz. Figure 21 shows the results of a simulation of the directivity of gain of a circularly polarized wave (right-hand polarized wave) around an angle φ at an angle θ = 80 degrees when the operating frequency of the circularly polarized antenna AN shown in Figure 4 is 1575 MHz.

[0116] 20 and 21, the circumferential direction represents the angle φ [degrees], and the distance from the center represents the gain [dBic].

[0117] 20-21, the solid line indicates the simulation results when the length L of the parasitic element EL is 0 mm, i.e., when no parasitic element EL is provided. The dotted line indicates the simulation results when the length L of the parasitic element EL is 40 mm. The dashed-dotted line indicates the simulation results when the length L of the parasitic element EL is 80 mm. The dashed-two-dotted line indicates the simulation results when the length L of the parasitic element EL is 100 mm.

[0118] 20-21, as the length L of the parasitic element EL increases from 0 mm, the directivity of the circularly polarized antenna AN changes, with the largest change occurring when the length L is approximately 40 mm. Even when the length L of the parasitic element EL is 100 mm, the directivity of the circularly polarized antenna AN changes. This suggests that the directivity of the circularly polarized antenna AN is biased toward a specific angle due to the influence of the parasitic element EL.

[0119] Fig. 22 is a diagram showing the results of a simulation of the relationship between the length L [mm] of the parasitic element EL in the grounded state and the directivity of the gain of a circularly polarized wave (right-handed polarized wave) about the angle φ at the angle θ = 60 [degrees] when the operating frequency of the circularly polarized antenna AN shown in Fig. 4 is 1575 MHz. Fig. 23 is a diagram showing the results of a simulation of the relationship between the length L [mm] of the parasitic element EL in the grounded state and the directivity of the gain of a circularly polarized wave (right-handed polarized wave) about the angle φ at the angle θ = 80 [degrees] when the operating frequency of the circularly polarized antenna AN shown in Fig. 4 is 1575 MHz.

[0120] 22 and 23, the horizontal axis represents the length L [mm] of the parasitic element EL, and the vertical axis represents the gain [dB].

[0121] 22 and 23, the solid line represents the ratio of the maximum value to the minimum value of the gain (MAX / MIN), the dotted line represents the maximum value (MAX) of the gain directivity, and the dash-dot line represents the minimum value (MIN) of the gain directivity.

[0122] 22 and 23, as the length L [mm] of the parasitic element EL increases from 0 [mm], the ratio of the maximum value to the minimum value (MAX / MIN) increases, reaching a maximum when the length L is approximately 40 [mm]. The ratio of the maximum value to the minimum value (MAX / MIN) gradually decreases when the length L exceeds approximately 40 [mm], but the ratio (MAX / MIN) when the length L is 100 [mm] is greater than the ratio (MAX / MIN) when the length L is 0 [mm].

[0123] This suggests that the parasitic element EL affects the directivity of the circularly polarized antenna AN when its length L [mm] is long. Therefore, when the parasitic element EL is grounded, the length L of the parasitic element EL should be approximately 1 / 4 wavelength or less of the operating frequency of the circularly polarized antenna AN, and more preferably 3 / 20 wavelength or less.

[0124] As a result of such simulations, the inventors found that by adjusting the overall length of each of the grounded parasitic elements 211, 212a to 212c, it is possible to suppress deterioration of the antenna characteristics of the first antenna element 108. Specifically, as described above, in the case of the grounded parasitic elements 211, 212a to 212c, by setting the overall length to ¼ or less of the wavelength of the circularly polarized wave transmitted or received by the first antenna element 108, it is possible to suppress deterioration of the antenna characteristics of the first antenna element 108. By setting the overall length to 3 / 20 or less of the wavelength of the circularly polarized wave, it is possible to further suppress deterioration of the antenna characteristics of the first antenna element 108.

[0125] Furthermore, the grounded first parasitic element 211 functions as a director by having a total length approximately equal to or less than ¼ of the wavelength of the vertically polarized wave transmitted or received by the second antenna element 110. Each of the grounded second parasitic elements 212a to 212c functions as a reflector by having a total length approximately longer than ¼ of the wavelength of the vertically polarized wave.

[0126] Here, the grounded first parasitic element 211 and second parasitic elements 211a to 211c function as a director or reflector with a length shorter than that of the ungrounded first parasitic element 111 and second parasitic elements 112a to 112c according to the embodiment.

[0127] In the case of a grounded parasitic element, it behaves as if there is another virtual parasitic element placed on the other side of the ground, and is therefore thought to function equivalently to a parasitic element that is approximately twice as long as the actual length of the parasitic element.

[0128] Therefore, by employing grounded parasitic elements 211, 212a to 212c, the lengths of these elements can be made shorter than when they are not grounded, and therefore, antenna device 100 can be made smaller.

[0129] 16, even if second parasitic elements 211a to 211c, which are provided behind first parasitic element 211, are linear, second parasitic elements 211a to 211c can be accommodated in the accommodation space. Therefore, second parasitic elements 211a to 211c do not need to be bent and can be easily manufactured. This reduces the effort required to manufacture antenna device 100 and enables production costs to be reduced.

[0130] [Variation 2] In the first modification, an example has been described in which each of the parasitic elements 211, 211a to 211c is provided substantially perpendicular to the second substrate 109, but the grounded parasitic elements 211, 211a to 211c may be provided at an angle to the second substrate 109. Furthermore, the grounded parasitic elements 211, 211a to 211c may include a curved or bent portion.

[0131] [Variation 3] In the embodiment, an example has been described in which the parasitic elements 111, 112a to 112c are configured from linear conductors, but the parasitic elements that give directionality to the second antenna element 110 may be configured from conductors embedded in resin or may be conductor patterns provided on a substrate.

[0132] 24 shows an example of a parasitic element 318 according to Modification 3. As shown in the figure, parasitic element 318 is a columnar member composed of a conductor 320 embedded in a resin part 319. Conductor 320 may be in the shape of a straight rod or column, or may include a curved or bent portion. Note that the parasitic element may be composed of a conductor pattern provided on a substrate by printing or the like.

[0133] The parasitic element 318 may be used in the antenna device 100 in place of, for example, some or all of the parasitic elements 111, 112a to 112c according to the embodiment. This provides the aforementioned effect of shortening induction, so that even if the parasitic element 318 is smaller than the parasitic elements 111, 112a to 112c it replaces, it is possible to provide the second antenna element 110 with equivalent directivity. This makes it possible to reduce the size of the antenna device 100.

[0134] [Variation 4] In the embodiment, an example has been described in which first parasitic element 111 is linear and second parasitic elements 112a to 112c are linear and include one curved or bent portion, but the shapes of parasitic elements 111 and 112a to 112c may be changed as appropriate.

[0135] For example, some or all of the parasitic elements 111 and 112a to 112c may be conductors formed in a zigzag or helical shape. Furthermore, some or all of the parasitic elements 111 and 112a to 112c may be plate-like conductors including flat or curved portions. This also provides the same effects as the embodiment.

[0136] Furthermore, a filter may be provided at any position of the parasitic elements 111, 112a to 112c to cut the frequency band used by the circularly polarized waves of the first antenna section 103 and to pass the frequency band used by the linearly polarized waves of the second antenna element 110.

[0137] For example, as shown in Fig. 25, the bottom ends of each of parasitic elements 111, 112a to 112c may be connected to the substrate via a filter F. However, Fig. 25 is a diagram showing a modified example in which a filter F is provided for the parasitic elements, and parasitic element 112b is not shown in the diagram because it is located to the right of 112c.

[0138] By providing a filter in this manner, each of the parasitic elements 111, 112a to 112c operates in an ungrounded state in the frequency band used by the first antenna section 103, and in a grounded state in the frequency band used by the second antenna element 110. Therefore, it is possible to reduce interference between the first antenna section 103 and the second antenna element 110.

[0139] [Examples 1 to 2 and Comparative Examples] The effects of the antenna devices according to the embodiment and Modification 1 were verified using simulation models of Examples 1 and 2 and Comparative Example. In Examples 1 and 2 and Comparative Example, directions are indicated using the same terms as in the embodiment and Modification Example 1: front-rear, left-right, and up-down. The angle relative to the upward direction is defined as θ [degrees], and the angle relative to the forward direction is defined as φ [degrees].

[0140] Example 1 is a simulation model in which the first antenna unit 103 and the second antenna unit 104 according to the embodiment are placed on a ground plane at ground potential. Example 2 is a simulation model in which the first antenna unit 103 and the second antenna unit 204 according to Modification 1 are placed on a ground plane at ground potential.

[0141] The comparative example is a simulation model in which first antenna unit 103 and grounded second antenna unit 104 according to the embodiment are placed on a ground plane at ground potential. That is, the comparative example is a simulation model in which parasitic elements having the same length and shape as first parasitic element 111 and second parasitic elements 112a to 112c according to the embodiment are set at ground potential.

[0142] Fig. 26 is a diagram showing the electrical characteristics of the second antenna unit 104 when the models of Examples 1 and 2 and the Comparative Example are placed on an infinite ground plane. The operating frequency is 5.9 GHz, and the diagram shows the results of a simulation regarding the directivity of gain of vertically polarized waves around angle φ when θ=90 degrees. In Fig. 26, the circumferential direction represents angle φ. Furthermore, the distance from the center represents gain [dBi].

[0143] As can be seen from FIG. 26, in all of Examples 1 and 2 and the comparative example, the second antenna element 110 can be provided with roughly the same excellent forward directivity by the parasitic element.

[0144] 27 to 29 are diagrams showing the electrical characteristics of the first antenna unit 103 when the models of Examples 1 and 2 and the comparative example are placed on a circular ground plane. Fig. 27 is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ when the angle θ = 0 [degrees]. Fig. 28 is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ when the angle θ = 60 [degrees]. Fig. 29 is a diagram showing the results of a simulation regarding the relationship between the operating frequency [MHz] and the maximum value of the axial ratio in the angular distribution of the axial ratio around the angle φ when the angle θ = 80 [degrees].

[0145] 27 to 29, the horizontal axis represents the operating frequency [MHz], and the vertical axis represents the maximum value of the axial ratio [dB].

[0146] 27 to 29, the solid line indicates the simulation result for Example 1. The dotted line indicates the simulation result for Example 2. The dashed-dotted line indicates the simulation result for the comparative example.

[0147] 27 to 29, Examples 1 and 2 all exhibit good axial ratio characteristics, but the axial ratio characteristics of the comparative example are worse than those of Examples 1 and 2. This is thought to be because, as described above, the influence on the electrical characteristics of the circularly polarized antenna (first antenna element 108) varies depending on the length L of the parasitic element, which depends on the grounding state (grounded / ungrounded).

[0148] In Example 1, the parasitic elements 111, 112a to 112c are ungrounded and have a size equal to or smaller than half the wavelength of the operating frequency of the circularly polarized antenna as described in the embodiment. In Example 2, the parasitic elements 211, 212a to 212c are grounded and have a size equal to or smaller than a quarter wavelength of the operating frequency of the circularly polarized antenna as described in Modification 1.

[0149] In contrast, in the comparative example, the parasitic elements are grounded as described above, but their lengths are equal to or greater than 1 / 4 wavelength and equal to or less than 1 / 2 wavelength of the operating frequency of the circularly polarized antenna, similar to the parasitic elements 111, 112a to 112c in the first embodiment.

[0150] These simulation results suggest that for ungrounded parasitic elements, good antenna characteristics can be obtained even when multiple antenna elements are placed close to each other by making the length of the parasitic element less than half the wavelength of the circularly polarized wave. Also, for grounded parasitic elements, good antenna characteristics can be obtained even when multiple antenna elements are placed close to each other by making the length of the parasitic element less than one-quarter the wavelength of the circularly polarized wave.

[0151] Furthermore, if the parasitic element is ungrounded, a circuit can be provided in an area of ​​the substrate located below the parasitic element, which allows for downsizing of the antenna device 100 in the left-right and front-back directions. Furthermore, if the parasitic element is grounded, the height of the parasitic element can be reduced, which allows for downsizing of the antenna device 100 in the up-down direction. In this way, by selecting whether the parasitic element is grounded or ungrounded depending on the design application, it is possible to downsize the antenna device 100 in the appropriate direction.

[0152] [Variations 5-8] In the embodiment, an example has been described in which the first antenna element 108 including a patch antenna is provided in one stage. However, the patch antenna may be provided in multiple stages, for example, multiple stages of first antenna elements 108 each including a patch antenna may be provided. Furthermore, a parasitic element may be provided corresponding to the first antenna element 108.

[0153] In the embodiment, an example has been described in which the capacitance loading element 115a including the meandering shape is divided into two parts, left and right. However, the capacitance loading element is not limited to a shape divided into two parts, left and right, and may be, for example, an integrated element, or each of the divided capacitance loading elements may be further divided into a plurality of parts.

[0154] Fig. 30 to 33 show modifications of these. Fig. 30 shows the configuration of first antenna element 108, third parasitic element 421, and capacitance loading element 415a according to Modification 5. Fig. 31 shows the configuration of first antenna element 108, third parasitic element 421, and capacitance loading element 515a according to Modification 6. Fig. 32 shows the configuration of first antenna element 408, third parasitic element 421, and capacitance loading element 415a according to Modification 7. Fig. 33 shows the configuration of first antenna element 408, third parasitic element 421, and capacitance loading element 515a according to Modification 8.

[0155] The following describes the first antenna element 408, the third parasitic element 421, and the capacitive loading elements 415a and 515a. Other than these components 408, 421, 415a, and 515a, each of the modified examples may be similar to the antenna device 100 according to the embodiment.

[0156] The first antenna element 408 is an antenna element in which two first antenna elements 108 similar to those in the embodiment are stacked one on top of the other in the vertical direction. Each of the first antenna elements 108 includes a patch antenna.

[0157] Third parasitic element 421 is a parasitic element provided above first antenna element 108 or first antenna element 408, and has a generally square or rectangular flat plate shape. In detail, third parasitic element 421 is provided above first antenna element 108 in Figures 30 and 31 (Modifications 5 and 6), and may be provided above first antenna element 408 in Figures 32 and 33 (Modifications 7 and 8).

[0158] That is, in the first antenna sections according to Modifications 5 and 6, a third parasitic element 421 is added to the first antenna section 108 according to the embodiment. In the first antenna sections according to Modifications 7 and 8, the first antenna section 108 according to the embodiment is replaced with a first antenna section 408, and a third parasitic element 421 is further added.

[0159] In each modified example, the third parasitic element 421 may be provided in any suitable manner, for example, it may be held in the case 101, or it may be fixed to the first substrate 107, the antenna base 102, etc. via a support body not shown.

[0160] Third parasitic element 421 is not limited to a flat plate shape, and may have any appropriate shape, such as a circular flat plate, a curved plate, etc. Third parasitic element 421 may be provided as needed, and in each of the modified examples, third parasitic element 421 need not be provided as long as design requirements are met.

[0161] The capacitive loading element 415a is an umbrella-shaped capacitive loading element formed integrally by connecting the tops, and includes a meandering shape.

[0162] The capacitance loading element 515a is composed of six divided partial elements and is bilaterally symmetrical. The six partial elements constituting the capacitance loading element 515a are arranged in a front-to-rear direction, with three partial elements on each side. The partial elements arranged on the left and right sides are gradually larger toward the rear. The six partial elements are electrically connected at the bottom, and are connected in the front-to-rear direction by a filter or other structure that electrically blocks the frequency bands used by the first and second antenna units. Each partial element constituting the capacitance loading element 515a is flat or curved, but may have any other suitable shape, including a meandering shape. The partial elements may also be connected at the top or bottom, or between them.

[0163] These modifications also provide the same effects as the embodiment.

[0164] [Variation 9] "On-board" means that it can be mounted on a vehicle, and therefore the antenna device 100 according to the embodiment is not limited to one that is attached to a vehicle, but also includes one that is brought into a vehicle and used inside the vehicle. In addition, in the embodiment, the antenna device has been described as being mounted on a "vehicle," which is a wheeled vehicle, but the present invention is not limited to this. For example, the antenna device may be mounted on a mobile object such as a drone, a probe, a construction machine without wheels, an agricultural machine, or a ship, and may be applied to an antenna device held on various mobile objects. The antenna device 100 according to the embodiment achieves the same effects as the embodiment even when applied to a mobile object other than a vehicle.

[0165] Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to these. The present invention includes modifications of the embodiments, further modifications of the modifications, combinations of the embodiments and the modifications, and further modifications of the combinations.

[0166] According to the present specification, the following aspects are provided. (Aspect 1) Aspect 1 is Case and a base that forms a storage space together with the case; a first antenna element accommodated in the accommodation space and configured to at least transmit or receive circularly polarized waves; a second antenna element disposed adjacent to the first antenna element and configured to transmit or receive linearly polarized waves; and at least one parasitic element that serves as a reflector or director for the second antenna element. According to the first aspect, in an antenna device including a first antenna element and a second antenna element disposed adjacent to the first antenna element, the second antenna element can be made to have directivity, thereby achieving good antenna characteristics. (Aspect 2) Aspect 2 is The parasitic element is disposed between the first antenna element and the second antenna element. 1 is an antenna device according to embodiment 1. Generally, a reflector has a greater effect on the directivity of the second antenna element than a director. Therefore, according to aspect 2, by using a parasitic element disposed between the first and second antenna elements as a reflector, it is possible to impart directivity to the second antenna element while suppressing the effect on the antenna characteristics of the first antenna element. Therefore, it is possible to obtain good antenna characteristics even when multiple antenna elements are disposed close to each other. (Aspect 3) Aspect 3 is The parasitic element is arranged within a range of 1 / 2 the wavelength of the linearly polarized wave from the installation position of the second antenna element. The antenna device according to aspect 1 or 2. According to the third aspect, the parasitic element functions as a wave source, and can function as a director or a reflector, thereby imparting a desired directivity and improving the antenna characteristics of the second antenna element. (Aspect 4) Aspect 4 is the parasitic elements include a first parasitic element and a second parasitic element, the first parasitic element is disposed on the opposite side of the second antenna element from the first antenna element and functions as a director of the second antenna element; the second parasitic element is disposed between the first antenna element and the second antenna element and functions as a reflector for the second antenna element. The antenna device according to any one of the first to third aspects. According to the fourth aspect, the first parasitic element functioning as a director and the second parasitic element functioning as a reflector can impart directionality to the second antenna element, thereby achieving good antenna characteristics. (Aspect 5) Aspect 5 is the number of the parasitic elements functioning as the reflectors is greater than the number of the parasitic elements functioning as the directors; 10 is an antenna device according to embodiment 4. As described above, reflectors generally have a greater effect on the directivity of the second antenna element than directors. According to aspect 5, since more parasitic elements functioning as reflectors are provided than parasitic elements functioning as directors, the directivity of the second antenna element can be controlled more precisely. Therefore, it is possible to obtain good antenna characteristics. (Aspect 6) Aspect 6 is The length of the parasitic element is 1 / 2 or less of the wavelength of the circularly polarized wave when it is not grounded, and is 1 / 4 or less of the wavelength of the circularly polarized wave when it is grounded. The antenna device according to any one of the first to fifth aspects. According to the sixth aspect, by setting the length of the ungrounded parasitic element to ½ or less of the wavelength of the circularly polarized wave transmitted or received by the first antenna element, it is possible to suppress deterioration of the antenna characteristics of the first antenna element. Also, by setting the length of the grounded parasitic element to ¼ or less of the wavelength of the circularly polarized wave, it is possible to suppress deterioration of the antenna characteristics of the first antenna element. Therefore, it is possible to obtain good antenna characteristics even when multiple antenna elements are arranged close to each other. (Aspect 7) Aspect 7 is The length of the parasitic element is 3 / 10 or less of the wavelength of the circularly polarized wave when it is not grounded, and is 3 / 20 or less of the wavelength of the circularly polarized wave when it is grounded. 10 is an antenna device according to embodiment 6. According to aspect 7, by setting the length of the ungrounded parasitic element to 3 / 10 or less of the wavelength of the circularly polarized wave transmitted or received by the first antenna element, deterioration of the antenna characteristics of the first antenna element can be further suppressed. Also, by setting the length of the grounded parasitic element to 3 / 20 or less of the wavelength of the circularly polarized wave, deterioration of the antenna characteristics of the first antenna element can be further suppressed. Therefore, even if multiple antenna elements are arranged close to each other, better antenna characteristics can be obtained. (Aspect 8) Aspect 8 is the parasitic element has a bent or curved portion; The antenna device according to any one of the first to eighth aspects. According to the eighth aspect, the parasitic element can be accommodated in the accommodation space while being long enough for the parasitic element to perform its function, thereby improving the antenna characteristics of the second antenna element and reducing the size of the antenna device. (Aspect 9) Aspect 9 is The parasitic element is a linear conductor. The antenna device according to any one of the first to eighth aspects. Generally, a linear parasitic element can reduce the effect on the antenna characteristics of the first antenna element compared to a plate-shaped parasitic element. Therefore, according to aspect 9, the second antenna element can be made directive while reducing the effect on the antenna characteristics of the first antenna element. Therefore, it is possible to obtain good antenna characteristics even when multiple antenna elements are arranged close to each other. (Aspect 10) Aspect 10 is Further provided with a resin holder, the resin holder holds at least one of the parasitic elements. The antenna device according to any one of the first to ninth aspects. According to the tenth aspect, the dimensions of the parasitic element can be reduced by dielectric shortening, thereby enabling the antenna device to be miniaturized.

[0167] This application claims priority based on Japanese Patent Application No. 2020-213149, filed December 23, 2020, the disclosure of which is incorporated herein in its entirety. This application claims priority based on U.S. Provisional Application No. 63170043, filed April 2, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0168] 100 Vehicle-mounted antenna device (antenna device) 101 Antenna Case 102 Antenna Base 103 First antenna section 104,204 Second antenna section 105 Third Antenna 107 First board 108,408 First antenna element 109 Second board 110 Second antenna element 111,211 First parasitic element 112a, 112b, 112c, 212a, 212b, 212c Second parasitic element 112a_1,112b_1,112c_1 Straight section 112a_2, 112b_2, 112c_2 Bent section 112a_3,112b_3,112c_3 Tip 113 Resin holder 113a Front holder part 113b rear holder part 113b_1 1st holding part 113b_2 Second holding part 114 Third board 115a, 415a, 515a Capacitive loading element 115b Helical element 318 Parasitic element 319 Resin part 320 Conductor 421 Third parasitic element P Pad PL round base plate AN circularly polarized antenna EL parasitic element F Filter

Claims

1. Case and a base that forms a storage space together with the case; a first antenna element accommodated in the accommodation space and configured to at least transmit or receive circularly polarized waves; a second antenna element disposed adjacent to the first antenna element and configured to transmit or receive linearly polarized waves; at least two parasitic elements serving as reflectors or directors of the second antenna element; the at least two parasitic elements include a first parasitic element and a second parasitic element, the first parasitic element is disposed on the opposite side of the second antenna element from the first antenna element and functions as a director of the second antenna element; The antenna device, wherein the second parasitic element is disposed between the first antenna element and the second antenna element and functions as a reflector for the second antenna element.

2. At least one of the at least two parasitic elements is arranged within a range of ½ of the wavelength of the linearly polarized wave from an installation position of the second antenna element. The antenna device according to claim 1 .

3. the number of the second parasitic elements is greater than the number of the first parasitic elements; 3. The antenna device according to claim 1 or 2.

4. at least one of the at least two parasitic elements has a bent or curved portion; The antenna device according to any one of claims 1 to 3.

5. At least one of the at least two parasitic elements is a linear conductor.

5. The antenna device according to claim 1.

6. Further provided with a resin holder, the resin holder holds at least one of the parasitic elements; The antenna device according to any one of claims 1 to 5.

7. Case and a base that forms a storage space together with the case; a first antenna element accommodated in the accommodation space and configured to at least transmit or receive circularly polarized waves; a second antenna element disposed adjacent to the first antenna element and configured to transmit or receive linearly polarized waves; and at least one parasitic element serving as a reflector or director of the second antenna element, The antenna device, wherein the length of the parasitic element is equal to or less than 1 / 2 of the wavelength of the circularly polarized wave when ungrounded, and equal to or less than 1 / 4 of the wavelength of the circularly polarized wave when grounded.

8. The length of the parasitic element is 3 / 10 or less of the wavelength of the circularly polarized wave when the parasitic element is not grounded, and is 3 / 20 or less of the wavelength of the circularly polarized wave when the parasitic element is grounded.

8. The antenna device according to claim 7.

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