Vehicle antenna system

Abstract

Provided is a vehicle antenna system capable of efficiently receiving a signal of circular polarization from the zenith direction. A vehicle antenna system (100) is provided with a window glass (30) for a vehicle (20), and an antenna element (40) capable of receiving a signal of a predetermined frequency band. The antenna element (40) is provided on a first major surface of a dielectric substrate (43), and includes a radiating conductor (41) capable of receiving a signal of circular polarization of a first frequency, and a ground conductor (44) disposed opposite the radiating conductor (41) with the dielectric substrate (43) therebetween. The direction of a normal to the first major surface is less than or equal to 45° with respect to the vertical direction. The radiating conductor (41) is spaced apart from the inner surface of the window glass (30) toward the interior of the vehicle, with a dielectric layer (60) therebetween.

Description

Technical Field

[0001] The present invention relates to a vehicle antenna system.

Background Art

[0002] In recent years, vehicles such as automobiles are equipped with an antenna for receiving signals transmitted from artificial satellites, and a satellite positioning system for receiving radio waves of a predetermined frequency in the GHz band has been introduced. For example, Patent Document 1 discloses a patch antenna capable of receiving GNSS (Global Navigation Satellite System) signals in a plurality of frequency bands. Further, Patent Document 1 discloses an example in which the patch antenna is mounted on a vehicle roof and housed in a radio wave transmissive antenna case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As disclosed in Patent Document 1, an antenna element capable of receiving signals from an artificial satellite is housed in an antenna case mounted on the roof of a car in order to enhance its directivity towards the zenith. On the other hand, in addition to the above-mentioned antenna element, multiple antenna elements may be clustered together and arranged in the antenna case mounted on the roof of a car. Therefore, if the above-mentioned antenna element is placed in an antenna case mounted on the roof of a car, the structure inside the antenna case becomes complex, and interference with antennas that transmit and receive radio waves in a different frequency band than the signals from the artificial satellite may occur. In that case, the above-mentioned antenna element may not be able to obtain the desired reception performance, and may not be able to efficiently receive circularly polarized signals from the zenith, such as GNSS signals. Furthermore, some cars do not have an antenna case with a protrusion on the roof (so-called shark fin), and the antenna is located inside the car or embedded in a resin case without a protrusion. Moreover, multiple above-mentioned antenna elements may be mounted on a car; for example, one may be placed in the antenna case on the roof and another in another location.

[0005] The present invention aims to provide a vehicle antenna system in which the antenna element is positioned at a location other than an antenna case with a protrusion on the roof of the vehicle, and which is capable of efficiently transmitting and receiving circularly polarized signals from the zenith direction. [Means for solving the problem]

[0006] A vehicle antenna system according to one aspect of the present invention comprises a vehicle window glass and an antenna element capable of receiving signals in a predetermined frequency band, wherein the antenna element includes a first radiating conductor provided on a first main surface of a first dielectric substrate and capable of receiving circularly polarized signals of a first frequency, and a grounding conductor disposed opposite the first radiating conductor via the first dielectric substrate, wherein the normal direction of the first main surface is 45° or less with respect to the vertical direction, and the first radiating conductor is disposed away from the inner surface of the window glass in the direction inward of the vehicle via a dielectric layer.

[0007] In the above-described vehicle antenna system, the first radiating conductor is arranged parallel to the inner surface of the window glass, and the relative permittivity of the dielectric layer is ε r When the thickness of the dielectric layer is t [mm] and the first frequency is f [MHz], in the range 0.5 mm ≤ t ≤ 16 mm, 1 ≤ ε r ≤(-0.097648×f+173.47)×t( 0.000125185×f×f-0.395272×f+311.375 ) may satisfy the following conditions.

[0008] In the above-described vehicle antenna system, the antenna element further includes a second radiating conductor disposed opposite to the first radiating conductor via the first dielectric substrate, and the ground conductor is disposed opposite to the first and second radiating conductors via the second dielectric substrate, and the second radiating conductor may be capable of receiving circularly polarized waves of a second frequency lower than the first frequency.

[0009] In the above-described vehicle antenna system, the first radiating conductor is arranged parallel to the inner surface of the window glass, and the relative permittivity of the dielectric layer is ε r When the thickness of the dielectric layer is t [mm] and the first frequency is f [MHz], in the range 0.5 mm ≤ t ≤ 16 mm, 1 ≤ ε r ≤(-0.00197869×f) 2 +6.18143×f+4817.72)×t (0.0001538×f×f-0.317206×f+247.206) It may satisfy the requirement.

[0010] In the vehicle antenna system described above, the first radiating conductor may be arranged non-parallel to the inner surface of the window glass.

[0011] In the above-described vehicle antenna system, the antenna element further includes a second radiating conductor disposed opposite to the first radiating conductor via the first dielectric substrate, and the ground conductor is disposed opposite to the first and second radiating conductors via the second dielectric substrate, and the second radiating conductor may be capable of receiving circularly polarized waves of a second frequency lower than the first frequency.

[0012] In the above vehicle antenna system, the first radiating conductor is arranged at an angle of 20° to 25° with respect to the inner surface of the window glass, and the relative permittivity of the dielectric layer is ε r , when the minimum value of the thickness of the dielectric layer is t min [mm], 0.5 mm ≤ t min ≤ 16 mm, 0.5 ≤ ε r ≤ 7.11882 × t min -0.385302 may be satisfied.

[0013] In the above vehicle antenna system, the dielectric layer may include an air layer.

[0014] In the above vehicle antenna system, the dielectric layer may include the air layer adjacent to the inner surface of the window glass and a non-air layer adjacent to the air layer and different from air.

[0015] In the above vehicle antenna system, the first radiating conductor may be attached at an angle of 0° to 30° with respect to the horizontal plane with the plane of the first radiating conductor.

[0016] In the above vehicle antenna system, the window glass may be attached at an angle of 0° to 30° with respect to the horizontal plane.

[0017] In the above vehicle antenna system, the window glass may include a windshield.

[0018] In the above vehicle antenna system, the window glass may include a roof glass, and the plane of the first radiating conductor may be substantially parallel to the horizontal plane. [Advantages of the Invention]

[0019] According to one aspect of the present invention, there is provided a vehicle antenna system in which an antenna element is arranged at other positions instead of in an antenna case having a protrusion on the outer roof of the vehicle, and can efficiently transmit and receive a circularly polarized wave signal from the zenith direction. [Brief explanation of the drawing]

[0020] [Figure 1] This is a perspective view illustrating a vehicle to which the vehicle antenna system described in Example 1 is installed. [Figure 2] This figure shows an example of the antenna element configuration for Example 1. [Figure 3] This figure illustrates an example of the arrangement of antenna elements in a vehicle antenna system according to Example 1. [Figure 4] This figure illustrates an example of the arrangement of antenna elements in a vehicle antenna system according to Example 2. [Figure 5] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 6] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 7] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 8] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 9] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 10] This figure shows an example configuration of a vehicle antenna system according to Example 3. [Figure 11] This is an enlarged cross-sectional view taken when the cutting line AA is used. [Figure 12] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 13] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 14] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 15] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 16] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 17] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 18]This figure shows an example configuration of a vehicle antenna system according to Example 5. [Figure 19] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 20] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 21] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 22] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 23] This diagram shows the relationship between the dielectric constant of the dielectric layer and the FB ratio. [Figure 24] This figure shows an example configuration of a vehicle antenna system according to Example 6. [Figure 25] This figure shows an example configuration of a vehicle antenna system according to Example 7. [Modes for carrying out the invention]

[0021] Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, in order to clarify the explanation, the following description and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted as necessary. In each embodiment, deviations in directions such as parallel, horizontal, and vertical are permitted to the extent that they do not impair the effects of the present invention. Also, in drawings used to explain embodiments, unless otherwise specified, directions refer to directions as shown in the drawings.

[0022] (First embodiment) [Example 1] Using Figure 1, an example of the configuration of a vehicle antenna system 100 according to Example 1 of the first embodiment will be described. Figure 1 is a perspective view illustrating a vehicle to which the vehicle antenna system according to Example 1 is attached. The vehicle antenna system 100 is attached to a vehicle 20 and comprises a window glass 30 and an antenna element 40.

[0023] The window glass 30 may be a windshield, a roof glass, or a rear glass. The window glass 30 is mounted on the window frame (not shown) of the vehicle 20 at a predetermined mounting angle (angle θ1) with respect to the driving surface of the vehicle 20. In other words, the window glass 30 is mounted on the window frame of the vehicle 20 at an angle θ1 with respect to the horizontal plane. The angle θ1 may be, for example, 0° to 45°, 0° to 30°, or 20° to 25°. Details of the window glass 30 will be described later. In addition, when the angle θ1 is approximately 0°, a roof glass is provided in which the normal direction of the glass surface approximately coincides with the zenith direction. In this embodiment, unless otherwise specified, the window glass 30 will be described as a windshield.

[0024] In Figure 1, the vehicle antenna system 100 is shown as comprising one window glass 30 and one antenna element 40, but it may also comprise two or more window glass 30s and the same number of antenna elements 40 as the number of window glass 30s. In this case, the window glass 30 may include two or more of the windshield, roof glass, and rear glass, and multiple antenna elements 40 may be provided on the window glass 30s.

[0025] The antenna element 40 is an antenna element capable of receiving signals in a predetermined frequency band. Specifically, the antenna element 40 may be configured to receive GNSS signals in a predetermined frequency band transmitted from the zenith direction in circular polarization. The predetermined frequency band may be the 1.2 GHz band or the 1.6 GHz band. The 1.2 GHz band may be, for example, 1.226 GHz to 1.228 GHz, and the 1.6 GHz band may be, for example, 1.559 GHz to 1.606 GHz. Furthermore, the antenna element 40 may be configured to receive SDARS (Satellite Digital Audio Radio Service) signals in the 2.3 GHz S-band (2.320 GHz to 2.345 GHz). In this embodiment, the antenna element 40 will be described as an antenna element capable of receiving GNSS signals in the 1.6 GHz band, which is circularly polarized, among the frequency bands described above.

[0026] The antenna element 40 may be positioned in a location that does not obstruct the view of the occupants of the vehicle 20, for example, close to the upper edge of the window glass 30. Alternatively, if the antenna element 40 is positioned on the interior side of the vehicle 20, it may be fixed near the window glass 30 via a housing.

[0027] Next, an example of the configuration of the antenna element 40 according to Example 1 will be described using Figure 2. Figure 2 is a perspective view of the antenna element 40 according to Example 1, and the antenna element 40 comprises a radiating conductor 41, a dielectric substrate 43, and a grounding conductor 44.

[0028] The radiating conductor 41 is provided on the first main surface (xy plane) of the dielectric substrate 43, which is the main surface on the positive z-axis side. In other words, the radiating conductor 41 is a patch antenna provided on the first main surface of the dielectric substrate 43, which is located on the side of the main surface where the radiating conductor 41 radiates radio waves. The radiating conductor 41 is configured to receive circularly polarized signals included in the predetermined frequency band described above, such as GNSS signals. As shown in Figure 2, the radiating conductor 41 is basically rectangular in shape, but has notches 41a and 41b at opposing corners. Thus, the radiating conductor 41 is configured to receive circularly polarized signals by having notches 41a and 41b. The notches 41a and 41b correspond to known degenerate separation elements and perturbation elements, and the area of ​​the portion removed from the square when notches 41a and 41b are absent is the area determined by the degenerate separation method. The radiating conductor 41 is provided with a feed point 42. At the feed point 42, the radiating conductor 41 is connected to the signal line of a transmission line such as a coaxial cable or microstrip line (not shown) via a conductor (not shown) that extends in the thickness direction. Hereinafter, the transmission line that feeds power to the antenna element 40 will be described as a coaxial cable.

[0029] The dielectric substrate 43 is, for example, a ceramic substrate, but it may also be a resin substrate. As described above, a radiating conductor 41 is provided on the first main surface of the dielectric substrate 43. A grounding conductor 44 is provided on the second main surface of the dielectric substrate 43, opposite to the first main surface. In other words, the grounding conductor 44 is positioned opposite the radiating conductor 41 via the dielectric substrate 43. Inside the dielectric substrate 43, a conductor (not shown) is provided in the thickness direction corresponding to the power supply point 42 on the radiating conductor 41.

[0030] The grounding conductor 44 is a conductor that forms the ground plane. The grounding conductor 44 is connected via a grounding wire, which is the outer conductor of a coaxial cable (not shown), and forms the ground plane. The grounding conductor 44 is spaced apart from a conductor (not shown) formed in the thickness direction of the dielectric substrate 43.

[0031] Next, using Figure 3, we will explain the details of each component of the vehicle antenna system 100 according to Example 1, and an example of the arrangement of the antenna elements 40. Figure 3 is an enlarged cross-sectional view when Figure 1 is cut along the cutting line AA passing through the feed point 42 of the antenna elements 40, and this cross-section is a plane perpendicular to the horizontal plane.

[0032] As shown in Figure 3, the vehicle antenna system 100 includes a window glass 30, an antenna element 40, a coaxial cable 50, and a dielectric layer 60. Note that explanations of the window glass 30 and antenna element 40 that overlap with the above explanations will be omitted as appropriate.

[0033] The window glass 30 is a laminated glass having a first glass plate 31, a second glass plate 32, and an interlayer 33 sandwiched between the first glass plate 31 and the second glass plate 32. At least one of the first glass plate 31 and the second glass plate 32 can be an example of glass that satisfies the following relationship in terms of composition expressed as a molar percentage on an oxide basis. Examples include, but are not limited to, glass containing 50-80% SiO2, 0-10% B2O3, 0.1-25% Al2O3, a total of 3-30% of at least one alkali metal oxide selected from the group consisting of Li2O, Na2O, and K2O, 0-25% MgO, 0-25% CaO, 0-5% SrO, 0-5% BaO, 0-5% ZrO2, and 0-5% SnO2. In the case of single-pane glass, examples of glass with the above composition include, but are not limited to, glass with the above composition.

[0034] The interlayer 33 can be made from materials such as polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), cycloolefin polymer, urethane resin, or polyvinylidene fluoride resin (PVDF). Alternatively, a thermosetting resin that is liquid before heating may be used. In other words, the interlayer 33 only needs to be in a layered state when the window glass 30 is laminated glass, and the interlayer 33 may be liquid or otherwise in a state before the first glass plate 31 and the second glass plate 32 are joined.

[0035] The antenna element 40 comprises a radiating conductor 41, a dielectric substrate 43, a ground conductor 44, and a conductor 45. The radiating conductor 41 is powered by being connected to a signal line 51, which is an internal conductor of the coaxial cable 50, via the conductor 45. The radiating conductor 41 is positioned away from the inner surface of the window glass 30 in the direction toward the interior of the vehicle, via a dielectric layer 60.

[0036] The radiating conductor 41 may be positioned non-parallel to the inner surface of the window glass 30, or it may be positioned parallel to the inner surface of the window glass 30. Specifically, the antenna element 40 may be mounted such that the plane of the radiating conductor 41 is at an angle of 0° to 25° with respect to the horizontal plane. In other words, the antenna element 40 may be mounted on the window glass 30 such that the plane of the radiating conductor 41 faces towards the zenith, or it may be mounted so that the plane of the radiating conductor 41 is parallel to the window glass 30.

[0037] Furthermore, if the window glass 30 is roof glass, the antenna element 40 may be mounted on the window glass 30 such that the plane of the radiating conductor 41 is approximately parallel to the horizontal plane (for example, 0° to 10°). If the angle θ1 of the inner surface of the window glass 30 with respect to the horizontal plane is 0° to 30°, the antenna element 40 may be mounted such that the plane of the radiating conductor 41 is at an angle of 0° to 30° with respect to the horizontal plane.

[0038] Furthermore, the antenna element 40 may be attached to the window glass 30 such that the normal direction of the radiating conductor 41 is between 0° and 45° with respect to the vertical direction. In other words, the antenna element 40 may be arranged on the window glass 30 such that the normal direction of the first main surface of the dielectric substrate 43 is 45° or less with respect to the vertical direction. In Figure 3, the dashed arrows represent the vertical direction, and the solid arrows represent the normal direction of the first main surface.

[0039] The dielectric substrate 43 has conductors 45 arranged in the thickness direction corresponding to the position corresponding to the feed point 42 shown in Figure 2. The ground conductor 44 is connected to the ground wire 52, which is the outer conductor of the coaxial cable 50. The coaxial cable 50 is the transmission line of the antenna element 40, with one end connected to the antenna element 40 and the other end connected to communication equipment (not shown). The signal line 51, which is the inner conductor of the coaxial cable 50, is connected to the conductor 45 of the antenna element 40 and is connected to the radiating conductor 41 via the conductor 45. The ground wire 52, which is the outer conductor of the coaxial cable 50, is connected to the ground conductor 44 of the antenna element 40.

[0040] The dielectric layer 60 may include, for example, an air layer or a non-air layer. The non-air layer may be, for example, a resin or glass. Furthermore, the dielectric layer 60 may be composed of multiple layers of air and resin, in which case the relative permittivity of the dielectric layer 60 can be adjusted by appropriately selecting the thickness and material of the resin. In addition, if the dielectric layer 60 includes a non-air layer, it may contain two or more dielectrics with different relative permittivity.

[0041] As explained above, in the vehicle antenna system 100, the radiating conductor 41 is positioned away from the inner surface of the window glass 30 in the direction toward the interior of the vehicle via a dielectric layer 60. In other words, the vehicle antenna system 100 is mounted on the window glass 30 so that the radiating conductor 41 does not come into contact with the window glass 30. Therefore, the vehicle antenna system 100 can adjust the receiving surface of the (GNSS) signal of the radiating conductor 41 to an angle different from the angle θ1 of the window glass 30 with respect to the horizontal plane. Furthermore, in the vehicle antenna system 100, the antenna element 40 is mounted on the window glass 30 such that the normal direction of the first main surface on which the radiating conductor 41 is provided is 45° or less with respect to the vertical direction. In this way, by positioning the antenna element 40 on the vehicle 20, even if the antenna element 40 is positioned inside the vehicle rather than inside an antenna case on the roof outside the vehicle, it can efficiently receive circularly polarized signals from the zenith direction. Furthermore, as will be described in detail later, the vehicle antenna system 100 can receive circularly polarized signals from the zenith direction more efficiently by satisfying the following equation.

[0042] [Example 2] Next, we will explain Example 2. Example 2 is a specific example of Example 1, and will explain an example of the configuration of a vehicle antenna system 200 using Figure 4. Figure 4 is an enlarged cross-sectional view when Figure 1 is cut along the cutting line AA so as to include the feed point 42 of the antenna element 40, and this cross-section is a plane perpendicular to the horizontal plane.

[0043] In the vehicle antenna system 200 of Example 2, the plane of the radiating conductor 41 in the antenna element 40 is arranged parallel to the inner surface of the window glass 30. The configuration of the window glass 30, antenna element 40, coaxial cable 50, and dielectric layer 60 is the same as in Example 1, so the explanation will be omitted as appropriate.

[0044] In this embodiment, the window glass 30 is a windshield, and the angle θ1 is, for example, 20° to 25°. Therefore, the plane of the radiating conductor 41 is positioned at the same angle θ1 with respect to the horizontal plane. Also, as shown in Figure 4, the angle between the normal direction of the first main surface of the dielectric substrate 43 and the vertical direction is also the same angle θ1.

[0045] The dielectric layer 60 may include, for example, an air layer, a non-air layer, or be composed of multiple layers including both. In this case as well, the relative permittivity of the dielectric layer 60 can be adjusted by appropriately selecting the thickness and resin material of the resin. Furthermore, if the dielectric layer 60 includes a non-air layer, it may be constructed by laminating two or more dielectrics with different relative permittivity, each with the same thickness. As in Example 2, when the radiating conductor 41 is arranged parallel to the inner surface of the window glass 30, the thickness t [mm] of the dielectric layer 60 may be 0.5 mm to 16 mm. Also, when the thickness t of the dielectric layer 60 is 0.5 mm to 16 mm and the frequency of the signal received by the radiating conductor 41 is f [MHz], the relative permittivity of the dielectric layer 60 is ε r The following equation (1) may also be satisfied.

number

[0046] In other words, the vehicle antenna system 200 according to Example 2 may have its relative permittivity set such that the thickness t of the dielectric layer 60 is between 0.5 mm and 16 mm, and that equation (1) is satisfied. Furthermore, if the thickness t exceeds 16 mm, the distance from the window glass 30 increases, which reduces the space inside the vehicle. Moreover, if the thickness t is less than 0.5 mm, it becomes difficult to adjust the relative permittivity in the dielectric layer 60, and there is a risk that the desired reception performance cannot be obtained.

[0047] Next, the receiving performance of the antenna element 40 of the vehicle antenna system 200 in Example 2 will be explained using the FB (Front-Back) ratio of the antenna element 40. The FB ratio is an index value that indicates the ratio [dB] of radiated power between the direction of radio wave emission of the antenna element 40 (Front direction) and the direction opposite to the direction of radio wave emission of the antenna element 40 (Back direction). The FB ratio in the vehicle antenna system 200 in Example 2 was determined by simulation using the power [dB] in the direction of radio wave emission of the antenna element 40 (Front direction) and the power [dB] in the direction opposite to the direction of radio wave emission of the antenna element 40 (Back direction). From here on, the FB ratio of the antenna elements included in each vehicle antenna system will be explained, but it has been confirmed that the antenna gain of the antenna elements in question is not significantly worse than when the antenna elements are installed on the roof outside the vehicle. Also, in the following explanation, the FB ratio will be referred to as the FB ratio.

[0048] Here, the thickness t [mm] of the dielectric layer 60 and the relative permittivity ε of the dielectric layer 60 are given. r The reception performance of the vehicle antenna system 200 was evaluated by calculating the front-to-back ratio [dB] when the antenna element 40 was changed and comparing the calculated front-to-back ratio with the reference front-to-back ratio. The reference front-to-back ratio was the front-to-back ratio in the state where the antenna element 40 was not attached to the window glass 30 (reference state), and was set to 5 [dB] based on the results measured in advance. The evaluation was that if the calculated front-to-back ratio was higher than the reference front-to-back ratio, it meant that the reception performance of the vehicle antenna system 200 was higher than the reception performance in the reference state. In other words, if the front-to-back ratio was higher than the reference front-to-back ratio, it was evaluated that the reception performance of the vehicle antenna system 200 was high even when the antenna element 40 was attached to the window glass 30.

[0049] To evaluate the front-to-back ratio in the vehicle antenna system 200 described in Example 2, the simulation conditions were set as follows. The dielectric substrate 43 is made of ceramic material. The frequency f [MHz] of the signal received by antenna element 40: 1574 [MHz] (= 1.574 [GHz]) Size of the radiating conductor 41 of the antenna element 40: 18 [mm] x 18 [mm] Dimensions of the ground conductor 44 of the antenna element 40: 70 [mm] x 70 [mm] Size of the dielectric substrate 43 of the antenna element 40: 70 [mm] x 70 [mm] Thickness of the dielectric substrate 43 of the antenna element 40: 60 [mm] Dimensions of the window glass 30 on which the antenna element 40 is placed: 200 mm x 200 mm

[0050] First, using Figure 5, the relative permittivity ε of the dielectric layer 60 at a thickness t=2 mm of the dielectric layer 60. r The relationship with the FB ratio is shown below. Figure 5 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio. In Figure 5, the horizontal axis shows the relative permittivity of the dielectric layer, and the vertical axis shows the FB ratio.

[0051] As shown in Figure 5, when the thickness of the dielectric layer 60 is t = 2 mm, the FB ratio of the vehicle antenna system 200 is given by the relative permittivity ε r In the range of 1 to 10, the FB ratio was higher than the reference FB ratio. When calculated using a thickness t = 2 mm and a frequency f = 1574 MHz for each relative permittivity that resulted in a high FB ratio, it was found that the above equation (1) was satisfied. That is, the vehicle antenna system 200 according to Example 2 has a dielectric layer thickness t [mm] and relative permittivity ε r When the relationship with frequency f [MHz] satisfies equation (1) above, the front-to-back ratio is improved, and GNSS signals, which are circularly polarized signals from the zenith direction, can be received efficiently.

[0052] Next, using Figure 6, the relative permittivity ε of the dielectric layer 60 at a thickness t = 4 mm of the dielectric layer 60 is shown. r The relationship with the FB ratio is shown. Figure 6 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio. Note that the horizontal and vertical axes of the diagrams showing the relationship between the relative permittivity of the dielectric layer and the FB ratio, including Figure 6, are the same as in Figure 5, so no explanation is given.

[0053] As shown in Figure 6, when the thickness of the dielectric layer 60 is t = 4 mm, the FB ratio of the vehicle antenna system 200 is given by the relative permittivity εr In the range of 1 to 8.9, the FB ratio was higher than the reference FB ratio. When calculated using a thickness t = 4 mm and a frequency f = 1574 [MHz] for each relative permittivity that resulted in a high FB ratio, it was found that the above equation (1) was satisfied.

[0054] Next, using Figure 7, the relative permittivity ε of the dielectric layer 60 at a thickness t = 7 mm of the dielectric layer 60. r This shows the relationship with the FB ratio. Figure 7 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0055] As shown in Figure 7, when the thickness of the dielectric layer 60 is t = 7 mm, the FB ratio of the vehicle antenna system 200 is given by the relative permittivity ε r In the range of 1 to 6.1, the FB ratio was higher than the reference FB ratio. When calculated using a thickness t = 7 mm and a frequency f = 1574 MHz for each relative permittivity that resulted in a high FB ratio, it was found that the above equation (1) was satisfied.

[0056] Next, using Figure 8, the relative permittivity ε of the dielectric layer 60 at a thickness t = 10 mm of the dielectric layer 60 is shown. r This shows the relationship with the FB ratio. Figure 8 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0057] As shown in Figure 8, when the thickness of the dielectric layer 60 is t = 10 mm, the FB ratio of the vehicle antenna system 200 is given by the relative permittivity ε r In the range of 1 to 5.1, the FB ratio was higher than the reference FB ratio. When calculated using a thickness t = 10 mm and a frequency f = 1574 MHz for each relative permittivity that resulted in a high FB ratio, it was found that the above equation (1) was satisfied.

[0058] Next, using Figure 9, the dielectric constant ε of the dielectric layer 60 at a thickness t = 14 mm of the dielectric layer 60. r This shows the relationship with the FB ratio. Figure 9 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0059] As shown in Figure 9, when the thickness of the dielectric layer 60 is t = 14 mm, the FB ratio of the vehicle antenna system 200 is given by the relative permittivity ε r In the range of 1 to 4.1, the FB ratio was higher than the reference FB ratio. When calculated using a thickness t = 14 mm and a frequency f = 1574 MHz for each relative permittivity that resulted in a high FB ratio, it was found that the above equation (1) was satisfied.

[0060] As described above, the vehicle antenna system 200 according to Example 2 can achieve a higher front-to-back ratio than the reference front-to-back ratio by satisfying equation (1) for the frequency of the signal received by the radiating conductor 41, the dielectric constant of the dielectric layer 60, and the thickness t of the dielectric layer 60 at 2 mm, 4 mm, 7 mm, 10 mm, and 14 mm. In other words, the vehicle antenna system 200 according to Example 2 can achieve high reception performance, and can efficiently receive circularly polarized signals from the zenith direction, such as GNSS. The thickness t of the dielectric layer 60 may be 2 mm or less, or 14 mm or more. As mentioned above, the thickness t of the dielectric layer 60 may be 0.5 mm or more, 1.0 mm or more, or 1.5 mm or more. Furthermore, the thickness t of the dielectric layer 60 may be 16 mm or less, or 15 mm or less.

[0061] [Example 3] Next, using Figure 10, we will explain an example configuration of the vehicle antenna system 300 according to Example 3. Figure 10 shows an example configuration of the vehicle antenna system 300 according to Example 3, in which the dielectric layer 60 of the vehicle antenna system 200 according to Example 2 is replaced with a dielectric layer 70. Specifically, in Example 2, the dielectric layer 60 was composed of one dielectric layer, but in Example 3, the dielectric layer 70 is composed of multiple dielectric layers. Note that the configuration of the window glass 30, antenna element 40, and coaxial cable 50 is the same as in Example 2, so we will omit the explanation as appropriate.

[0062] The dielectric layer 70 includes a first dielectric layer 71 and a second dielectric layer 72. The first dielectric layer 71 is, for example, an air layer adjacent to the inner surface of the window glass 30. The second dielectric layer 72 is a non-air layer adjacent to the first dielectric layer 71. Alternatively, the dielectric layer 70 may be a combination in which the first dielectric layer 71 is a non-air layer and the second dielectric layer is an air layer. Furthermore, the dielectric layer 70 may be a combination in which the first dielectric layer 71 is a first non-air layer and the second dielectric layer 72 is a second non-air layer. In this case, the relative permittivity of the first non-air layer is different from that of the second non-air layer. The vehicle antenna system 300 according to Example 3 may satisfy the thickness t [mm] of the dielectric layer 70 being between 0.5 mm and 16 mm, similar to Example 2. Furthermore, in the vehicle antenna system 200 according to Example 3, similar to Example 2, the thickness t [mm] of the dielectric layer 70 is 0.5 mm to 16 mm, and when the frequency of the signal received by the radiating conductor 41 is f [MHz], the relative permittivity ε of the dielectric layer 70 is... r The above equation (1) may also be satisfied.

[0063] Relative permittivity ε of dielectric layer 70 r This can be calculated using equation (2) with the relative permittivity ε1 and thickness t1 [mm] of the first dielectric layer 71 and the relative permittivity ε2 and thickness t2 [mm] of the second dielectric layer 72. In other words, the relative permittivity ε of the dielectric layer 70 r The relative permittivity ε of equation (2) is determined by the ratio of the thickness of the first dielectric layer 71 and the second dielectric layer 72 to the total thickness of the dielectric layer 70. r This can be calculated using the following formula. In other words, in the vehicle antenna system 300 according to Example 3, the thickness of the dielectric layer 70 and the relative permittivity may be set using formulas (1) and (2) such that the thickness t [mm] of the dielectric layer 70 satisfies 0.5 mm to 16 mm and also satisfies formula (1).

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[0064] Equation (2) is an equation for calculating the thickness and relative permittivity of dielectric layer 70 in an example where the vehicle antenna system 300 has two dielectric layers (first dielectric layer 71 and second dielectric layer). In general terms, it can be expressed as follows. When the vehicle antenna system has M dielectric layers (M: an integer of 1 or more), the thickness and relative permittivity of dielectric layer 70 may be set such that the thickness t [mm] of dielectric layer 70 satisfies 0.5 mm to 16 mm and satisfies equation (3). Note that in equation (3), the relative permittivity of the j-th layer is ε j Let t be the thickness of the j-th dielectric layer. j Let t be the total thickness of the dielectric layers.

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[0065] As described above, in the vehicle antenna system 300 according to Example 3, the dielectric layer 60 in Example 2 is replaced with a dielectric layer 70, but by using equations (1) and (2), the same configuration as the vehicle antenna system 200 according to Example 2 can be achieved. Furthermore, in the vehicle antenna system 300 according to Example 3, if the dielectric layer 70 comprises three or more dielectric layers, the same configuration as the vehicle antenna system 200 according to Example 2 can be achieved by using equations (1) and (3). Therefore, the vehicle antenna system 300 according to Example 3 can achieve a high FB ratio and reception performance, similar to the vehicle antenna system 200 according to Example 2, and can efficiently receive circularly polarized signals from the zenith direction, such as GNSS. Note that although the vehicle antenna system 300 according to Example 3 was explained using the vehicle antenna system 200 according to Example 2, the dielectric layer 60 of the vehicle antenna system 100 according to Example 1 may be replaced with a dielectric layer 70.

[0066] (Second embodiment) Next, a second embodiment will be described. In the first embodiment, the antenna element 40 was configured to have one radiating conductor 41, but in the second embodiment, the antenna element is configured to have two radiating conductors.

[0067] [Example 4] Using Figure 11, an example of the configuration of the vehicle antenna system 400 according to Example 4 will be explained. Figure 11 corresponds to Figure 3 and is an enlarged cross-sectional view when cut along the cutting line AA in Figure 1, and this cross-section is a plane perpendicular to the horizontal plane.

[0068] As shown in Figure 11, the vehicle antenna system 400 according to Example 4 comprises a window glass 30, an antenna element 80, a coaxial cable 50, and a dielectric layer 60. The vehicle antenna system 400 according to the second embodiment (Example 4) is configured such that the antenna element 40 in the vehicle antenna system 100 according to the first embodiment (Example 1) is replaced with an antenna element 80. In this embodiment as well, the window glass 30 will be described as a windshield. Furthermore, since the window glass 30, coaxial cable 50, and dielectric layer 60 have basically the same configuration as in the first embodiment, their descriptions will be omitted as appropriate. Also, descriptions of the antenna element 80 that are common to the antenna element 40 will be omitted as appropriate.

[0069] The antenna element 80 comprises a radiating conductor 41 and a radiating conductor 81, a dielectric substrate 43 and a dielectric substrate 82, a ground conductor 44, and a conductor 45. In other words, the antenna element 80 has a configuration comprising two radiating conductors and two dielectric substrates. Radiating conductor 41 is also referred to as the first radiating conductor, and radiating conductor 81 is also referred to as the second radiating conductor. Dielectric substrate 43 is also referred to as the first dielectric substrate, and dielectric substrate 82 is also referred to as the second dielectric substrate.

[0070] The radiating conductor 41 is a radiating conductor capable of receiving GNSS signals in the 1.6 GHz band, similar to the first embodiment. The radiating conductor 41 is arranged non-parallel to the inner surface of the window glass 30. The window glass 30 is positioned at an angle θ1 with respect to the horizontal plane, and the angle θ1 may be, for example, 20° to 25°. The antenna element 80 may be positioned such that the radiating conductor 41 is at an angle of 20° to 25° with respect to the inner surface of the window glass 30. In other words, the antenna element 80 may be positioned such that the normal direction of the radiating conductor 41 is substantially the same as the zenith direction.

[0071] A radiating conductor 41 is provided on the first main surface of the dielectric substrate 43. A radiating conductor 81 is provided on the second main surface of the dielectric substrate 43. In other words, the radiating conductor 81 is positioned opposite the radiating conductor 41 via the dielectric substrate 43.

[0072] The radiating conductor 81 is a radiating conductor capable of receiving circularly polarized signals at a frequency lower than that received by the radiating conductor 41, and is capable of receiving GNSS signals in the 1.2 GHz band. In the antenna element 80, the radiating conductor 81 is arranged parallel to the radiating conductor 41, so in this case, the radiating conductor 81 is positioned at an angle of 20° to 25° with respect to the inner surface of the window glass 30. The radiating conductor 81 is connected to the conductor 45 at a position corresponding to the feed point 42 of the radiating conductor 41. The radiating conductor 81 is connected to the signal line 51 of the coaxial cable 50 via the conductor 45 and is fed.

[0073] The dielectric substrate 82 is, for example, a substrate made of ceramics. A radiating conductor 81 is provided on the third main surface of the dielectric substrate 82, which is the main surface facing the window glass 30. A grounding conductor 44 is provided on the fourth main surface of the dielectric substrate 82, which is the main surface opposite to the third main surface. Conductors 45 are provided on the dielectric substrate 82 in the thickness direction corresponding to the power supply point 42 on the dielectric substrate 43.

[0074] The grounding conductor 44 is a conductor that forms a ground plane on the fourth main surface of the dielectric substrate 82. In other words, the grounding conductor 44 is arranged opposite the radiating conductor 41 and the radiating conductor 81 via the dielectric substrate 82.

[0075] The dielectric layer 60 may include an air layer or a non-air layer, as in the first embodiment. When the antenna element 80 is positioned such that the radiating conductor 41 is at an angle of 20° to 25° with respect to the window glass 30, as in Example 4, the minimum thickness t of the dielectric layer 60 is min [mm] may satisfy 0.5mm to 16mm. In this case, the minimum value t of the thickness of the dielectric layer 60 is... min[mm] may be between 0.7mm and 16mm, or between 1mm and 16mm. As shown in Figure 4, the minimum thickness t of the dielectric layer 60 is min [mm] is the distance between the edge of the dielectric substrate 43 closest to the window glass 30 and the window glass 30. The minimum thickness t of the dielectric layer 60. min When [mm] is between 0.5mm and 16mm, the relative permittivity ε of the dielectric layer 60 r The following equation (4) may also be satisfied.

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[0076] In other words, the vehicle antenna system 400 in Example 4 has a minimum thickness t of the dielectric layer 60. min The minimum thickness and relative permittivity of the dielectric layer 60 may be set such that [mm] satisfies 0.5 mm to 16 mm and also satisfies equation (4).

[0077] Next, the receiving performance of the vehicle antenna system 400 according to Example 4 will be described. In Example 4, as in Example 2, the FB ratio of the antenna element 80 was evaluated by simulation. In Example 4, the minimum value t of the thickness of the dielectric layer 60 min [mm] and relative permittivity ε of dielectric layer 60 r The front-to-back ratio [dB] was calculated when the FB ratio was changed. If the FB ratio was higher than the reference FB ratio, the receiving performance of the vehicle antenna system 400 was evaluated as being higher than the receiving performance in the reference state. In the reference state, when the antenna element 80 was not attached to the window glass 30, the FB ratio was 5 [dB] for the radiating conductor 41 and 3 [dB] for the radiating conductor 81. Therefore, the reference FB ratios for the radiating conductor 41 and radiating conductor 81 were set to 5 [dB] and 3 [dB], respectively. The evaluation indicates that if the FB ratio is higher than both reference FB ratios, the receiving performance of the vehicle antenna system 400 is higher than the receiving performance in the reference state.

[0078] To evaluate the front-to-back ratio in the vehicle antenna system 400 according to Example 4, the simulation conditions were set as follows. Note that the dielectric substrates 43 and 82 are made of ceramic material. The frequency f1 [MHz] of the signal received by the radiating conductor 41: 1575 [MHz] (= 1.575 [GHz]) The frequency f2 [MHz] of the signal received by the radiating conductor 81: 1228 [MHz] (= 1.228 [GHz]) Size of the radiating conductor 41 of antenna element 80: 20 [mm] x 20 [mm] Size of the radiating conductor 83 of antenna element 80: 26 [mm] x 26 [mm] Dimensions of grounding conductor 44: 70 mm x 70 mm Thickness of the dielectric substrate 43 of the antenna element 80: 3 [mm] Thickness of the dielectric substrate 82 of the antenna element 80: 3 [mm] Dimensions of the window glass 30 on which the antenna element 80 is placed: 200 mm x 200 mm Angle (θ1) between the window glass 30 and the radiating conductors 41 and 81: 23°

[0079] First, using Figure 12, the minimum value t of the thickness of the dielectric layer 60 is determined. min Relative permittivity ε of dielectric layer 60 at 1 mm = r The relationship with the FB ratio is shown. In Figure 12, the dotted line represents the FB ratio of the radiating conductor 41, and the solid line represents the FB ratio of the radiating conductor 81. Note that the relative permittivity ε of the dielectric layer 60 is shown below. r Similarly, in the diagram showing the relationship with the FB ratio [dB], the FB ratio of the radiating conductor 41 is shown, and the solid line represents the FB ratio of the radiating conductor 81, just as in Figure 12.

[0080] As shown in Figure 12, the minimum value t of the thickness of the dielectric layer 60 min When = 1 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is the relative permittivity ε r The FB ratio became higher than the reference FB ratio in the range of 1 to 10. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. minUsing =1mm in the calculation, it was found that the above equation (4) is satisfied.

[0081] Next, using Figure 13, the minimum value t of the thickness of the dielectric layer 60 is shown. min Relative permittivity ε of dielectric layer 60 at 2 mm = r This shows the relationship with the FB ratio [dB]. Figure 13 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0082] As shown in Figure 13, the minimum value t of the thickness of the dielectric layer 60 min When =2mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is the relative permittivity ε r The FB ratio was higher than the reference FB ratio in the range of 1 to 5.4. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. min Using =2mm in the calculation, it was found that the above equation (4) is satisfied.

[0083] Next, using Figure 14, the minimum value t of the thickness of the dielectric layer 60 is determined. min Relative permittivity ε of dielectric layer 60 at 4 mm = r This shows the relationship with the FB ratio [dB]. Figure 14 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0084] As shown in Figure 14, the minimum value t of the thickness of the dielectric layer 60 min When =4mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is the relative permittivity ε r The FB ratio was higher than the reference FB ratio in the range of 1 to 4.1. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. min Using =4mm in the calculation, it was found that the above equation (4) is satisfied.

[0085] Next, using Figure 15, the minimum value t of the thickness of the dielectric layer 60 is determined. min Relative permittivity ε of dielectric layer 60 at =7mm r This shows the relationship with the FB ratio [dB]. Figure 15 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0086] As shown in Figure 15, the minimum value t of the thickness of the dielectric layer 60 min At 7mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is given by the relative permittivity ε r The FB ratio was higher than the reference FB ratio in the range of 1 to 3.3. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. min Using =7mm in the calculation, it was found that the above equation (4) is satisfied.

[0087] Next, using Figure 16, the minimum value t of the thickness of the dielectric layer 60 is determined. min Relative permittivity ε of dielectric layer 60 at 10 mm = r This shows the relationship with the FB ratio [dB]. Figure 16 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0088] As shown in Figure 16, the minimum value t of the thickness of the dielectric layer 60 min When =10mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is the relative permittivity ε r The FB ratio was higher than the reference FB ratio in the range of 1 to 2.9. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. min Using =10mm in the calculation, it was found that the above equation (4) is satisfied.

[0089] Next, using Figure 17, the minimum value t of the thickness of the dielectric layer 60 is shown. min Relative permittivity ε of dielectric layer 60 at =14mm r This shows the relationship with the FB ratio [dB]. Figure 17 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0090] As shown in Figure 17, the minimum value t of the thickness of the dielectric layer 60 min When =14mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 400 is the relative permittivity ε r The FB ratio was higher than the reference FB ratio in the range of 1 to 2.5. For each relative permittivity that increases the FB ratio, the minimum value of the thickness of the dielectric layer 60 is t. minUsing =14mm, it was found that the above equation (4) is satisfied.

[0091] As described above, the vehicle antenna system 400 according to Example 4 has a minimum thickness t of the dielectric layer 60. min However, at thicknesses of 1 mm, 2 mm, 4 mm, 7 mm, 10 mm, and 14 mm, the relative permittivity satisfies equation (4), allowing the front-to-back ratio to be higher than the reference front-to-back ratio. In other words, the vehicle antenna system 400 according to Example 4 can achieve high reception performance, enabling efficient reception of circularly polarized signals from the zenith direction, such as GNSS. Note that the minimum thickness of the dielectric layer 60 is t. min This can be 0.5 mm or more, 0.7 mm or more, 16 mm or less, or 15 mm or less. Also, although θ1 was given as 23° as an example, it can be made higher than the reference FB ratio as long as it is in the range of at least 20° to 25°, by satisfying the above equation (4).

[0092] [Example 5] Next, we will explain Example 5. Example 5 is an example of a vehicle antenna system 500 in which radiating conductors 41 and 81 are arranged parallel to the inner surface of the window glass 30. Using Figure 18, we will explain an example of the configuration of the vehicle antenna system 500 according to Example 5. Figure 18 corresponds to Figure 11 and is an enlarged cross-sectional view when cut along the cutting line AA in Figure 1, and this cross-section is a plane perpendicular to the horizontal plane. Note that the configuration of the window glass 30, antenna element 80, coaxial cable 50, and dielectric layer 60 is the same as in Example 4, so we will omit the explanation as appropriate.

[0093] The radiating conductor 41 is arranged parallel to the inner surface of the window glass 30. The antenna elements 80 are positioned on the radiating conductor 41 at an angle θ1 (20° to 25°) with respect to the horizontal plane. Also, as shown in Figure 18, the angle between the normal direction of the first main surface of the dielectric substrate 43 and the vertical direction is the same as the angle θ1.

[0094] When the radiating conductor 41 is arranged parallel to the inner surface of the window glass 30, the thickness t [mm] of the dielectric layer 60 may be 0.5 mm to 16 mm. When the thickness t [mm] of the dielectric layer 60 is 0.5 mm to 16 mm and the frequency of the signal received by the radiating conductor 41 is f1 [MHz], the relative permittivity ε of the dielectric layer 60 is r You may set it so that it satisfies the following equation (5).

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[0095] In other words, the vehicle antenna system 500 according to Example 5 may have its dielectric layer thickness t [mm] set to 0.5 mm to 16 mm and its relative permittivity set to satisfy equation (5). Note that equation (5) does not use the frequency f2 of the signal received by the radiating conductor 81. This is because the frequency bandwidth of the 1.2 GHz band, which includes frequency f2, is narrower than the 1.6 GHz band, which includes frequency f1, and even if the frequency f2 is changed, the relative permittivity ε r This is because the impact is small.

[0096] Next, the receiving performance of the vehicle antenna system 500 according to Example 5 will be described. In Example 5, as in Example 4, the FB ratio of the antenna element 80 was evaluated by simulation. In Example 5, the thickness t [mm] of the dielectric layer 60 and the relative permittivity ε of the dielectric layer 60 were used. r The front-to-back ratio [dB] was calculated when the value was changed, and a value higher than the reference front-to-back ratio was evaluated as indicating high receiving performance. The reference front-to-back ratio was set to 5 [dB] for the radiating conductor 41 and 3 [dB] for the radiating conductor 81, as in Example 4.

[0097] To evaluate the front-to-back ratio in the vehicle antenna system 500 described in Example 5, the simulation conditions were set as follows. The frequency f1 [MHz] of the signal received by the radiating conductor 41: 1575 [MHz] (= 1.575 [GHz]) The frequency f2 [MHz] of the signal received by the radiating conductor 81: 1228 [MHz] (= 1.228 [GHz]) Size of the radiating conductor 41 of antenna element 80: 20 [mm] x 20 [mm] Size of the radiating conductor 83 of antenna element 80: 26 [mm] x 26 [mm] Dimensions of grounding conductor 44: 70 mm x 70 mm Thickness of the dielectric substrate 43 of the antenna element 80: 3 [mm] Thickness of the dielectric substrate 82 of the antenna element 80: 3 [mm] Dimensions of the window glass 30 on which the antenna element 80 is placed: 200 mm x 200 mm

[0098] First, using Figure 19, the relative permittivity ε of the dielectric layer 60 at a thickness t=2 mm of the dielectric layer 60. r This shows the relationship with the FB ratio [dB]. Figure 19 is a diagram showing the relationship between the dielectric constant of the dielectric layer and the FB ratio.

[0099] As shown in Figure 19, when the thickness of the dielectric layer 60 is t = 2 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 500 is the relative permittivity ε r In the range of 1 to 7.1, the FB ratio was higher than the reference FB ratio. When calculated for each relative permittivity that resulted in a high FB ratio, using the thickness t=2mm of the dielectric layer 60 and the frequency f1=1575MHz, it was found that the above equation (5) was satisfied.

[0100] Next, using Figure 20, the relative permittivity ε of the dielectric layer 60 at a thickness t = 4 mm of the dielectric layer 60. r This shows the relationship with the FB ratio [dB]. Figure 20 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0101] As shown in Figure 20, when the thickness of the dielectric layer 60 is t = 4 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 500 is the relative permittivity ε rIn the range of 1 to 4.8, the FB ratio was higher than the reference FB ratio. When calculated for each relative permittivity that resulted in a high FB ratio, using the thickness t=4 mm of the dielectric layer 60 and the frequency f1=1575 MHz, it was found that the above equation (5) was satisfied.

[0102] Next, using Figure 21, the relative permittivity ε of the dielectric layer 60 at a thickness t = 7 mm of the dielectric layer 60 is shown. r This shows the relationship with the FB ratio [dB]. Figure 21 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0103] As shown in Figure 21, when the thickness of the dielectric layer 60 is t = 7 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 500 is the relative permittivity ε r In the range of 1 to 3.8, the FB ratio was higher than the reference FB ratio. When calculated for each relative permittivity that resulted in a high FB ratio, using the thickness t=7mm of the dielectric layer 60 and the frequency f1=1575MHz, it was found that the above equation (5) was satisfied.

[0104] Next, using Figure 22, the relative permittivity ε of the dielectric layer 60 when the thickness of the dielectric layer 60 is t = 10 mm. r This shows the relationship with the FB ratio [dB]. Figure 22 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0105] As shown in Figure 22, when the thickness of the dielectric layer 60 is t = 10 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 500 is given by the relative permittivity ε r In the range of 1 to 3.2, the FB ratio was higher than the reference FB ratio. When calculated for each relative permittivity that resulted in a high FB ratio, using the thickness t=10 mm of the dielectric layer 60 and the frequency f1=1575 MHz, it was found that the above equation (5) was satisfied.

[0106] Next, using Figure 23, the relative permittivity ε of the dielectric layer 60 when the thickness of the dielectric layer 60 is t = 14 mm. r This shows the relationship with the FB ratio [dB]. Figure 23 is a diagram showing the relationship between the relative permittivity of the dielectric layer and the FB ratio.

[0107] As shown in Figure 23, when the thickness of the dielectric layer 60 is t = 14 mm, the FB ratio of the radiating conductors 41 and 81 of the vehicle antenna system 500 is the relative permittivity ε r In the range of 1 to 2.7, the FB ratio was higher than the reference FB ratio. When calculated for each dielectric constant that resulted in a high FB ratio, using the thickness t = 14 mm of the dielectric layer 60 and the frequency f1 = 1575 MHz, it was found that the above equation (5) was satisfied.

[0108] As described above, the vehicle antenna system 500 according to Example 5 can achieve a higher front-to-back ratio than the reference front-to-back ratio by satisfying equation (5) at the frequency of the signal received by the radiating conductor 41, the relative permittivity of the dielectric layer 60, and the thickness t of the dielectric layer 60 at 2 mm, 4 mm, 7 mm, 10 mm, and 14 mm. In other words, the vehicle antenna system 500 according to Example 5 can achieve high reception performance, and can efficiently receive circularly polarized signals from the zenith direction, such as GNSS. The thickness t of the dielectric layer 60 may be 2 mm or less, or 14 mm or more. As mentioned above, the thickness t of the dielectric layer 60 may be 0.5 mm or more, 1.0 mm or more, or 1.5 mm or more. Furthermore, the thickness t of the dielectric layer 60 may be 16 mm or less, or 15 mm or less.

[0109] [Example 6] Next, using Figure 24, an example of the configuration of the vehicle antenna system 600 according to Example 6 will be described. The vehicle antenna system 600 according to Example 6 has a configuration in which the dielectric layer 60 of the vehicle antenna system 500 according to Example 5 is replaced with a dielectric layer 70. Specifically, in Example 5, the dielectric layer 60 was composed of one dielectric layer, but in Example 6, the dielectric layer 70 has a configuration that includes a first dielectric layer 71 and a second dielectric layer 72. Note that the configuration of the window glass 30, antenna element 80, and coaxial cable 50 is the same as in Example 5, so the explanation will be omitted as appropriate. Also, the dielectric layer 70 is the same as in Example 3, so the explanation will be omitted as appropriate.

[0110] The vehicle antenna system 600 according to Example 6 may, similarly to Example 5, have a dielectric layer thickness t [mm] of 0.5 mm to 16 mm. Furthermore, in the vehicle antenna system 600 according to Example 6, similarly to Example 5, the dielectric layer thickness t [mm] of 70 is 0.5 mm to 16 mm, and when the frequency of the signal received by the radiating conductor 41 is f1 [MHz], the relative permittivity ε of the dielectric layer 70 is... r The above equation (5) may also be satisfied.

[0111] Relative permittivity ε of dielectric layer 70 r This can be calculated using equations (2) and (5) based on the relative permittivity ε1 and thickness t1 [mm] of the first dielectric layer 71, and the relative permittivity ε2 and thickness t2 [mm] of the second dielectric layer 72. In other words, the relative permittivity ε of the dielectric layer 70 r This can be calculated using the relative permittivity corresponding to the ratio of the thickness of the first dielectric layer 71 and the second dielectric layer 72 to the total thickness of the dielectric layer 70.

[0112] As described above, in the vehicle antenna system 600 according to Example 6, the dielectric layer 60 in Example 5 is replaced with a dielectric layer 70. However, if the dielectric layer 60 comprises M dielectric layers, the same configuration as the vehicle antenna system 500 according to Example 5 can be realized by using equations (5) and (3). Therefore, the vehicle antenna system 600 according to Example 6 can achieve high reception performance, similar to the vehicle antenna system 500 according to Example 5, and can efficiently receive circularly polarized signals from the zenith direction, such as GNSS.

[0113] [Example 7] Next, with reference to FIG. 25, a configuration example of the vehicle antenna system 700 according to Example 7 will be described. FIG. 25 is a diagram corresponding to FIG. 11. The vehicle antenna system 700 according to Example 7 has a configuration in which the dielectric layer 60 of the vehicle antenna system 400 according to Example 4 is replaced with a dielectric layer 70. Specifically, in Example 4, the dielectric layer 60 was composed of one dielectric layer, but in Example 7, the dielectric layer 70 includes a first dielectric layer 71 and a second dielectric layer 72. Since the configurations of the window glass 30, the antenna element 80, and the coaxial cable 50 are the same as those in Example 5, the description thereof will be omitted as appropriate.

[0114] The dielectric layer 70 includes a first dielectric layer 71 and a second dielectric layer 72. The first dielectric layer 71 is an air layer adjacent to the inner surface of the window glass 30. The first dielectric layer 71 is a dielectric layer having a constant thickness. The second dielectric layer 72 is a non-air layer adjacent to the first dielectric layer 71. Also, the dielectric layer 70 may be a combination in which the first dielectric layer 71 is a non-air layer and the second dielectric layer is an air layer. Furthermore, the dielectric layer 70 may be a combination in which the first dielectric layer 71 is a first non-air layer and the second dielectric layer 72 is a second non-air layer. In this case, the relative permittivity of the first non-air layer is different from the relative permittivity of the second non-air layer. The second dielectric layer 72 is formed between the first main surface of the dielectric substrate 43 and the first dielectric layer 71. The thickness of the second dielectric layer 72 varies according to the y coordinate. The thickness of the second dielectric layer 72 is formed to increase as it goes in the negative y-axis direction. In other words, the second dielectric layer 72 is formed such that the distance between the first main surface of the dielectric substrate 43 and the interface between the second dielectric layer 72 increases as it goes in the negative y-axis direction.

[0115] Similar to Example 4, for the vehicle antenna system 700 according to Example 7, the minimum value t min [mm] of the thickness of the dielectric layer 70 may satisfy 0.5 mm to 16 mm. Also, similar to Example 4, for the vehicle antenna system 700 according to Example 7, when the minimum value t min [mm] of the thickness of the dielectric layer 70 is 0.5 mm to 16 mm, the relative permittivity ε r of the dielectric layer 70 may satisfy Equation (4).

[0116] Relative permittivity ε of dielectric layer 70 r The relative permittivity of the first dielectric layer 71, the thickness of the radiating conductor 41 of the first dielectric layer 71 at the centroid, the relative permittivity of the second dielectric layer 72, and the thickness of the radiating conductor 41 of the second dielectric layer 72 at the centroid, can be calculated using equations (2) and (4). Specifically, if the thickness of the radiating conductor 41 of the first dielectric layer 71 at the centroid is t1 [mm], and the thickness of the radiating conductor 41 of the second dielectric layer 72 at the centroid is t2 [mm], then the relative permittivity of the dielectric layer 70 is ε r This may be calculated using equations (2) and (4). Furthermore, if the dielectric layer 70 comprises M dielectric layers, the relative permittivity ε of the dielectric layer 70 can be calculated using equations (3) and (4). r This is calculated.

[0117] As described above, in the vehicle antenna system 700 according to Example 7, the dielectric layer 60 in Example 4 is replaced with a dielectric layer 70, but by using equations (4) and (2), the same configuration as the vehicle antenna system 400 according to Example 4 can be realized. Furthermore, if the dielectric layer 70 of the vehicle antenna system 700 according to Example 7 comprises three or more dielectric layers, by using equations (4) and (3), the same configuration as the vehicle antenna system 400 according to Example 4 can be realized. Therefore, the vehicle antenna system 700 according to Example 7 can achieve high reception performance, similar to the vehicle antenna system 500 according to Example 4, and can efficiently receive circularly polarized signals from the zenith direction, such as GNSS.

[0118] In Figure 25, the first dielectric layer 71 is assumed to be a dielectric layer with a constant thickness regardless of the y-coordinate, but the thickness of the first dielectric layer 71 may be formed to increase as the y-axis moves in the negative direction. Furthermore, the first dielectric layer 71 and the second dielectric layer 72 may be formed such that the ratio of the thickness of the first dielectric layer 71 to the thickness of the second dielectric layer 72 is constant regardless of the y-coordinate. Even in this way, high reception performance can be achieved, similar to the vehicle antenna system 700 in Example 7, so that circularly polarized signals from the zenith direction, such as GNSS, can be efficiently received.

[0119] Although the present invention has been described above in reference to the embodiments described above, the present invention is not limited to the configuration of the embodiments described above, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application.

[0120] This application claims priority based on Japanese Patent Application No. 2021-82333, filed on 14 May 2021, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0121] 20 vehicles 30 Window glass 31. First glass plate 32. Second glass plate 33 Interlayer 40, 80 antenna elements 41 Radiating conductor 41a, 41b Notches 42 Power supply point 43 Dielectric substrate 44 Grounding conductor 45 Conductor 50 Coaxial Cables 51 Signal Line 52 Ground wire 60, 70 dielectric layers 71 First Dielectric Layer 72 Second Dielectric Layer 81 Radiating Conductors 82 Dielectric Substrate 100, 200, 300, 400, 500, 600, 700 Vehicle Antenna System

Claims

1. Vehicle window glass, It comprises an antenna element capable of receiving signals in a predetermined frequency band, The antenna element includes a first radiating conductor provided on the first main surface of a first dielectric substrate and capable of receiving a circularly polarized signal of a first frequency, and a ground conductor arranged opposite the first radiating conductor via the first dielectric substrate. The normal direction of the first main surface is 45° or less with respect to the vertical direction. The first radiating conductor is positioned away from the inner surface of the window glass in the direction inward of the vehicle, with a dielectric layer in between. The first radiating conductor is arranged non-parallel to the inner surface of the window glass, The antenna element further includes a second radiating conductor disposed opposite the first radiating conductor via the first dielectric substrate, The grounding conductor is positioned opposite the first radiating conductor and the second radiating conductor via a second dielectric substrate. The second radiating conductor is capable of receiving circularly polarized waves of a second frequency lower than the first frequency. The first radiating conductor is positioned at an angle of 20° to 25° with respect to the inner surface of the window glass. The aforementioned window glass includes the roof glass, The plane of the first radiating conductor is approximately parallel to the horizontal plane. Vehicle antenna system.

2. The vehicle antenna system according to claim 1, wherein the dielectric layer includes an air layer.

3. The vehicle antenna system according to claim 2, wherein the dielectric layer includes an air layer adjacent to the inner surface of the window glass and a non-air layer adjacent to the air layer that is different from air.

4. The vehicle antenna system according to any one of claims 1 to 3, wherein the first radiating conductor is mounted such that the plane of the first radiating conductor is at an angle of 0° to 10° with respect to the horizontal plane.

5. The vehicle antenna system according to any one of claims 1 to 3, wherein the window glass is mounted at an angle of 0° to 30° with respect to the horizontal plane.

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