Vehicle-mounted antenna device

Abstract

The present invention provides a vehicle-mounted antenna device, which is installed on the roof of a vehicle. The vehicle-mounted antenna device is characterized in that it has: an antenna base; an antenna shell covering the antenna base from above; and an antenna vibrator arranged on the inner side of the antenna shell, the antenna base has: a metal base fixed to the roof; and a metal plate electrically connected to the metal base, the metal base has a protrusion for fixing to the roof, and the resonance frequency generated by the roof and the antenna base electrically connected via the protrusion becomes outside the communication frequency band of the antenna vibrator.

Description

[0001] This invention application is a divisional application of an invention application with an international application date of December 20, 2018, an international application number of PCT / JP2018 / 047080, a national application number of 201880081856.2 entering the Chinese national phase, and an invention name of “Vehicle-mounted antenna device”. Technical Field

[0002] The present invention relates to a vehicle-mounted antenna device mounted on a roof of a vehicle. Background Art

[0003] A vehicle-mounted antenna device installed on the roof of a vehicle such as a car is known, wherein an antenna element is housed in a streamlined housing that takes fluid resistance into consideration. The vehicle-mounted antenna device is usually installed in the center of the rear portion of the roof, and is sometimes referred to as a "shark fin antenna" or "dolphin antenna" depending on the posture of the vehicle when installed and the appearance of the vehicle-mounted antenna device.

[0004] For example, Patent Document 1 discloses in detail a vehicle-mounted antenna device, which divides a space for accommodating a metal base and an antenna vibrator by covering an antenna housing on a resin base, and the metal base also functions as a floor. In addition, the document discloses the following structure: by providing a conductor plate with a leaf spring portion between the metal base and the roof, a reduction in antenna gain caused by excess resonance is prevented. In other words, in the structure of Patent Document 1, by providing a conductor plate between the metal base and the roof, the capacitance is increased, and the resonance frequency is deviated in a direction lower than the communication frequency band of the antenna vibrator, thereby preventing the antenna gain from being reduced.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-32166 Summary of the invention

[0008] In Patent Document 1, the gap between the resin base and the roof is waterproofed by a cushion member or a sealing member, and rainwater and the like are prevented from reaching the vicinity of the conductor plate. However, the shape of the roof, which is the object to which the vehicle-mounted antenna device is installed, is not flat. Specifically, the roof is a gently curved surface, and the degree of curvature varies depending on the type of vehicle to which the vehicle-mounted antenna device is installed. Therefore, it is considered that there may be a case where complete waterproofing cannot be ensured even with a cushion member or a sealing member. In this case, corrosion of the conductor plate cannot be avoided.

[0009] The fundamental countermeasure against the corrosion of the conductor plate is to omit the conductor plate. In this case, another method is required to assume the function of adjusting the resonance frequency of the unnecessary resonance to outside the communication frequency, which is borne by the conductor plate.

[0010] For example, it is possible to prepare multiple types of metal bases with different resonance frequencies for redundant resonance and replace them according to the installation conditions. However, the metal base is a precision casting made of aluminum or the like. Therefore, compared with the case of fewer types, not to mention design changes, even maintaining multiple types will consume manufacturing costs and management costs.

[0011] In addition, it is also considered whether it is sufficient to prepare a single type of metal base if, for example, the resonant frequency of the extra resonance is sufficiently far away from the lower limit of the communication frequency band with a relatively large safety margin by increasing the long side dimension of the metal base. However, from the perspectives of the cost and miniaturization of the vehicle-mounted antenna device, and the appearance effect when installed in the vehicle, this cannot be said to be a preferred solution.

[0012] On this basis, in reality, as described above, the shape of the roof is not flat, and its curvature is also different, so the capacitance (capacitor grounding) generated between the metal base and the roof is uncertain. Therefore, no matter how well the metal base is designed, it may not be able to fully exert its design performance depending on the type of vehicle it is installed on.

[0013] An object of the present invention is to provide a technique for realizing a vehicle-mounted antenna device that prevents a reduction in antenna gain due to unnecessary resonance by a method other than providing a conductive plate between a metal base and a vehicle roof.

[0014] The first embodiment of the present invention is a vehicle-mounted antenna device, which is installed on the roof of a vehicle, and the vehicle-mounted antenna device has: an antenna base; an antenna shell covering the antenna base from above; and an antenna vibrator arranged on the inner side of the antenna shell, and the antenna base has: a metal base fixed to the roof; and a metal plate electrically connected to the metal base.

[0015] According to the first method, the metal plate forms an inductance and a capacitance between the roofs, and the resonant frequency of the superfluous resonance can be adjusted. Thus, the reduction in the gain of the antenna vibrator can be suppressed without providing a component equivalent to the conductor plate described in Patent Document 1. In addition, the adjustment of the resonant frequency of the superfluous resonance by a component such as a metal plate that can be made of sheet metal can be achieved, and a plurality of different specifications can be prepared cheaply and simply. Thus, even if the metal base is made universal, the superfluous resonance generated between the metal base and the roof can be simply and cheaply changed by adjusting the metal plate used or the installation position of the metal plate, and the reduction in antenna gain caused by the superfluous resonance can be simply and cheaply dealt with with respect to a plurality of types of vehicles.

[0016] As a vehicle-mounted antenna device, the antenna base may have a shape with the front-to-rear direction of the vehicle as the long side direction when installed on the roof, and the metal plate is arranged on the front end side and / or the rear end side of the metal base in the installation posture, and in the long side direction, the electrical length including the metal base and the metal plate is longer than the electrical length including only the metal base.

[0017] This solves the problem without changing the lateral width of the vehicle-mounted antenna device. This makes it possible to provide a vehicle-mounted antenna device designed in consideration of air resistance when the vehicle is traveling.

[0018] Furthermore, since the electrical length including the metal base and the metal plate is longer than the electrical length including only the metal base, the antenna gain can be suppressed from decreasing by shifting the resonance frequency of the unnecessary resonance to the lower frequency side from the communication frequency band of the antenna element.

[0019] In the vehicle-mounted antenna device, the metal plate may have a meandering shape or a spiral shape.

[0020] Accordingly, the electrical length can be increased more effectively than using a simple rectangular metal plate. If measures are taken to increase the electrical length, the resonant frequency of the redundant resonance can be further away from the communication band. In addition, the same electrical length as that of a rectangular metal plate can be achieved by a small installation area, thereby enabling miniaturization of the vehicle-mounted antenna device. Being able to achieve a small vehicle-mounted antenna device means that the installation area of ​​the roof of the vehicle can be reduced, thereby reducing the difference in the antenna gain reduction effect caused by the difference in the roof shape, and even a single specification can achieve a stable antenna gain reduction suppression effect relative to multiple vehicles.

[0021] In the vehicle-mounted antenna device, the antenna base may include an electrical length adjustment circuit for adjusting an electrical length between the metal base and the metal plate, and the metal base and the metal plate may be electrically connected via the electrical length adjustment circuit.

[0022] According to this, the electrical length can be changed by the electrical length adjustment circuit, thereby achieving miniaturization of the vehicle-mounted antenna device.

[0023] The vehicle-mounted antenna device may be configured such that the metal base has a protrusion for fixing to the vehicle roof, and a resonance frequency generated by the vehicle roof and the antenna base being electrically connected via the protrusion is outside a communication frequency band of the antenna element.

[0024] Accordingly, the metal base has a protrusion for fixing to the roof, thereby realizing the following vehicle-mounted antenna device, which is easy to ensure the fixing strength to the roof and can also achieve electrical connection between the metal base and the roof with high precision. On the other hand, the same effect as the above method can be achieved through the metal plate.

[0025] In the vehicle-mounted antenna device, the antenna base may include a resin base, and the metal plate may be disposed on the resin base.

[0026] According to this, it is possible to realize a vehicle-mounted antenna device in which a metal plate is disposed on a resin base.

[0027] In the vehicle-mounted antenna device, the resin base may include a positioning shape portion for suppressing displacement of the metal plate from a predetermined position.

[0028] According to this, when manufacturing the vehicle-mounted antenna device, it is easy to arrange the metal plate at a predetermined position. In addition, it is possible to suppress the metal plate from being displaced from the predetermined position. Thus, the metal plate can be easily installed.

[0029] The vehicle-mounted antenna device may include a second antenna element different from the antenna element, and the second antenna element may be arranged so that a part or the whole of the second antenna element is located above the metal plate.

[0030] This makes it possible to realize a vehicle-mounted antenna device in which the second antenna element is arranged so that a part or the entirety of the second antenna element is located above the metal plate.

[0031] In the vehicle-mounted antenna device, the metal base and the metal plate may be made of different materials.

[0032] Alternatively, in the vehicle-mounted antenna device, the metal base and the metal plate may be made of the same material.

[0033] The second embodiment of the present invention is a vehicle-mounted antenna device installed on the roof of a vehicle, and the vehicle-mounted antenna device comprises: an antenna base, which has a metal plate fixed to the roof and a resin base; an antenna shell covering the antenna base from above; and an antenna vibrator arranged on the inner side of the antenna shell, and the metal plate is arranged on the resin base.

[0034] According to the second aspect, it is possible to configure a vehicle-mounted antenna device that achieves the same operational effects as the first aspect.

[0035] In the vehicle-mounted antenna device, a part or all of the antenna element may be located on the metal plate, and the metal plate may be formed such that a portion located under the antenna element is partially hollowed out.

[0036] This can suppress a decrease in antenna gain.

[0037] The vehicle-mounted antenna device may have a shape whose long side direction is the front-rear direction of the vehicle when the antenna base is mounted on the roof, and the metal plate may be provided on the front side and / or the rear side of the antenna base in the mounting position.

[0038] This solves the problem without changing the lateral width of the vehicle-mounted antenna device. This makes it possible to provide a vehicle-mounted antenna device designed in consideration of air resistance when the vehicle is traveling. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a side perspective view showing a configuration example of the antenna device according to the first embodiment.

[0040] Figure 2 It is an internal plan view of the antenna device according to the first embodiment.

[0041] Figure 3 yes Figure 2 III-III section view.

[0042] Figure 4 It is a diagram showing an example of the type of metal plate in the first embodiment.

[0043] Figure 5 This is a graph (part 1) showing the VSWR of the antenna device according to the first embodiment.

[0044] Figure 6 It is a top view of the inside of the antenna device according to the second embodiment.

[0045] Figure 7 This is a graph (part 1) showing the VSWR of the antenna device according to the second embodiment.

[0046] Figure 8 It is an internal plan view in a modification of the first embodiment.

[0047] Fig. 9 This is a graph (part 2) showing the VSWR of the antenna device according to the first embodiment.

[0048] Fig.10 It is an internal plan view in a modification of the second embodiment.

[0049] Fig.11 It is a side perspective view showing a configuration example of a modification of the antenna device according to the first embodiment.

[0050] Fig.12 This is an example of the configuration of an electrical length adjustment circuit.

[0051] Fig.13 This is a graph (part 2) showing the VSWR of the antenna device according to the second embodiment.

[0052] Fig.14 It is an internal plan view of a modified example of the antenna device.

[0053] Fig.15 It is a three-dimensional perspective view of the antenna device according to the first application example.

[0054] Fig.16 It is a side perspective view of the antenna device of the first application example.

[0055] Fig.17 It is a three-dimensional perspective view of the antenna device of the second application example.

[0056] Fig.18 It is a three-dimensional perspective view of the antenna device of the third application example.

[0057] Fig.19 It is a side perspective view of the antenna device of the third application example.

[0058] Fig. 20 It is a top view of a metal plate used in the antenna device of the third application example.

[0059] Fig.21 It is a side view of a metal plate used in the antenna device of the third application example.

[0060] Fig. 22 It is a top view of the metal plate of the comparative example.

[0061] Fig.23 It is a side view of the metal plate of a comparative example.

[0062] Description of Reference Numerals

[0063] 3…Roof

[0064] 10…Antenna device

[0065] 11…Antenna base

[0066] 13…Antenna housing

[0067] 15…Antenna element

[0068] 17...Substrate

[0069] 20…Resin base

[0070] 30…Metal base

[0071] 32…Cable insertion part

[0072] 40…Metal sheet

[0073] 52…Antenna fixing bolt

[0074] 61…Electrical length adjustment circuit DETAILED DESCRIPTION

[0075] Hereinafter, an example of an embodiment to which the present invention is applied will be described, but the form to which the present invention can be applied is of course not limited to the following embodiment.

[0076] [First embodiment]

[0077] Figure 1 It is a side perspective view showing a configuration example of the antenna device 10 according to the present embodiment. Figure 2 It is a plan view of the antenna device 10 according to the present embodiment with the antenna case 13 removed, that is, an internal plan view. Figure 3 yes Figure 2 III-III section view.

[0078] like Figure 1 As shown, the antenna device 10 is designed to be installed on an exterior structure portion corresponding to the roof 3 of a vehicle 5 (e.g., a passenger car, a truck, an agricultural machine, etc.), and is an antenna device in which an antenna vibrator and the like are built into a housing. The "front and back" in the antenna device 10 is the same direction as the front and back of the vehicle 5 on which the antenna device 10 is installed on the roof 3, meaning Figure 1 That is, along the front-to-back direction of the streamlined appearance, the relatively low and thin front side ( Figure 1 The left side of the antenna is set as the front of the antenna device, and the opposite direction ( Figure 1 ) is set to the rear.

[0079] The antenna device 10 includes an antenna base 11 and a resin antenna case 13 covering the antenna base 11. The antenna case 13 is usually made of a non-light-transmitting resin so that the inside is not visible. Figure 1 In the figure, only the outline of the antenna housing 13 is drawn and shown in perspective.

[0080] The antenna device 10 is long in the front-to-back direction as a whole, and the mounting surface is flat, and has a so-called shark fin shape that looks like the back of a shark or dolphin when viewed from the side. In addition, it is mounted on the upper surface of the roof 3 in such a way that the long side direction is along the front-to-back direction of the vehicle 5. In other words, the antenna base 11 has a shape with the long side direction of the front-to-back direction of the above-mentioned vehicle as the mounting posture mounted on the roof 3 of the vehicle 5.

[0081] An accommodation space is defined between the antenna base 11 and the antenna case 13, and an antenna element 15 and a substrate 17 on which various circuits for the antenna are mounted are housed.

[0082] However, the components built into the storage space are not limited to these, and can be appropriately selected. For example, in the present embodiment, one antenna element 15 is provided, but a configuration may be adopted in which a plurality of types of other antenna elements having different uses are built in.

[0083] The antenna base 11 of the present embodiment includes a resin base 20 , a metal base 30 , and a metal plate 40 .

[0084] The resin base 20 is a plate-shaped body formed of a non-conductive resin that forms the main flat bottom surface of the antenna device 10. Figure 2 As shown, a plurality of protrusions 21 for screw-fastening the antenna housing 13 are provided on its outer circumference.

[0085] In addition, the resin base 20 has a rib 23 slightly higher than the outer edge, and a seat 22 is formed inside the rib. The upper surface of the seat 22 is a flat surface parallel or substantially parallel to the bottom surface. In addition, a through portion 24 is provided in the center of the seat 22 to penetrate the resin base 20 along the front and back when viewed from above (see FIG. Figure 2 The through portion 24 is used to be inserted into the protrusion of the metal base 30 and to lead out the cable 19 .

[0086] Furthermore, the base portion 22 is provided with a plurality of protrusions 26 (see Figure 3 ), the metal base 30 covers the base portion 22 from above and is screwed in place with the mounting screws 28 (see Figure 2 ).

[0087] The metal base 30 is a metal component that is long in the longitudinal direction of the antenna device 10 and is, for example, a cast product of an aluminum alloy. Figure 2 as well as Figure 3 As shown, the metal base 30 has a protrusion 31 protruding downward from the lower surface for fixing to the roof 3 (see Figure 3 ); a plurality of protrusions 33; and a plurality of substrate mounting screw protrusions 35.

[0088] The protrusion 31 (see Figure 3 ) is inserted into the fixing part of the vehicle through the through hole and the through portion 24 provided in the roof 3. After the cap-shaped fastener 50 is installed on the inserted protrusion 31 and temporary positioning and anti-falling measures are implemented, the antenna fixing bolt 52 is locked into the screw portion cut out at the lower end of the protrusion 31 to fix it to the roof 3 (at Figure 3 , the cap-shaped fastener 50 and the antenna fixing bolt 52 are shown in a disassembled state. With this, it is easy to ensure the fixing strength to the roof 3. In addition, by tightening the antenna fixing bolt 52, the locking claw of the cap-shaped fastener 50 bites into the roof 3, so that the metal base 30 and the roof 3 are electrically connected. That is, grounding is achieved.

[0089] In addition, the metal base 30 is provided with a cable insertion hole 32 (see Figure 2 ), the cable 19 from the substrate 17 is introduced into the vehicle through the cable insertion hole 32 and the through portion 24. The cable 19 introduced into the vehicle is connected to a signal cable arranged inside the vehicle.

[0090] A plurality of protrusions 33 are provided on the front side and in the vicinity of the middle of the metal base 30, and are used to fix the metal base 30 to the resin base 20 by screws. They can also be used to fix when an antenna element for other purposes is additionally mounted.

[0091] In addition, a substrate mounting screw boss 35 (see FIG. 1 ) for mounting the substrate 17 on which the antenna element 15 is mounted is provided on the rear side of the metal base 30. Figure 3 ), and is fixed to the resin base 20 together with the substrate 17 by the substrate mounting screws 54. Furthermore, the substrate 17 and the metal base 30 are electrically connected by the substrate mounting screws 54.

[0092] The metal plate 40 is a metal component formed of a material different from the metal base 30. For example, the metal plate 40 is a plate made of sheet metal, and is the first electrical length adjustment element for adjusting the resonance frequency of the redundant resonance in this embodiment. Here, the thickness of the metal plate 40 can be thinner than the thickness of the metal base 30, and the strength of the metal plate 40 can be lower than the strength of the metal base 30. In other words, the metal plate 40 can be formed of a component that is cheaper than the metal base 30. In addition, the metal plate 40 can be formed of a conductive resin.

[0093] The metal plate 40 is attached to the rear end side of the base portion 22 of the resin base 20 in such a manner that the plate surface faces the roof 3 via the resin base 20. In other words, when the metal plate 40 is considered to be a part of the metal base 30, it can be said that the metal plate 40 is provided so that the top view overlapping area of ​​the metal base 30 alone, which appears to overlap with the roof 3 in a top view, is enlarged by including the metal plate 40. And a part of it is fastened and fixed to the resin base 20 together with the substrate 17 and the metal base 30 by the substrate mounting screws 54, and is electrically conductive with the substrate 17 and the metal base 30.

[0094] When the metal plate 40 is mounted so that a part of the metal plate 40 overlaps with the metal base 30, an unnecessary resonance may occur due to the overlapping area. Therefore, it is desirable that the overlapping area of ​​the metal plate 40 and the metal base 30 is small. For example, when the metal plate 40 and the metal base 30 are overlapped by co-fastening using the substrate mounting screws 54, the overlapping area is preferably limited to the portion overlapped by co-fastening.

[0095] Furthermore, by installing the metal plate 40, the strength of the resin base 20 can be increased to include the strength of the metal plate 40, compared to when the metal plate 40 is not installed. Specifically, deformation or damage caused by external force or temperature can be prevented. Figure 1 to Figure 3 In the example shown, the metal plate 40 and the seat portion 22 are fixed by screw fastening, but they may also be fixed by concave-convex fitting, elastic fixing, pressure fixing, etc.

[0096] In addition, a part of the metal plate 40 is fixed to the metal base 30 and electrically connected by the common fastening performed by the substrate mounting screws 54, but other methods may be used. For example, the metal plate 40 and the metal base 30 may be electrically connected by connecting the metal plate 40 and the metal base 30 with substrate wiring, connectors, wires, etc.

[0097] Figure 4 4 is a diagram showing an example of the types of the metal plate 40 in this embodiment. The metal plate 40 is prepared in a plurality of types with different electrical lengths. Figure 4 In any of the graphs (1) to (3), if Figure 1 to Figure 3 As shown, the electrical length including the metal base 30 and the metal plate 40 connected in the longitudinal direction is longer than the electrical length including only the metal base 30 in the longitudinal direction (front-rear direction).

[0098] For example, Figure 4 The metal plate 40a of (1) is designed to have a notch or a cut so as to have a meandering shape (curved shape) when viewed from above. Figure 4 In the case of the electrical length of the metal plate 40a of (1), it is possible to Figure 4 The metal plate 40b of (2) is designed to have a smaller number of bending repetitions than the metal plate 40a. In addition, if the electrical length does not need to be so long, it can be Figure 4 The metal plate 40c of (3) is formed into a rectangular flat plate shape without a cutout or a cutout. Of course, the deformation of the metal plate 40 is not limited to Figure 4 For example, other deformations such as polygonal or spiral shapes can be appropriately designed. For example, the metal plate can also be set to a shape in which the end opposite to the end connected to the metal base 30 of the two ends of the metal plate 40 is extended in a manner surrounding the metal base 30.

[0099] Furthermore, by providing the metal plate 40, even without providing the conductor plate described in Patent Document 1, the resonance frequency of the unwanted resonance can be adjusted so that it is outside the communication frequency band of the antenna element 15, thereby suppressing the reduction in antenna gain. Specifically, an electromagnetic action occurs between the metal plate 40 and the roof 3, and the electrical length of the antenna base 11 increases by the electrical length of the metal plate 40 compared to the electrical length of the metal base 30 alone, thereby reducing the resonance frequency of the unwanted resonance generated by the roof 3 and the antenna base 11. As a result, the resonance frequency of the unwanted resonance can be moved from the lower limit of the communication frequency band of the antenna element 15 to the lower range.

[0100] More specifically, when the antenna device 10 is mounted on the roof 3, an extra resonance having a frequency corresponding to the length of the metal base 30 in the long side direction is generated by the roof 3 and the metal base 30. The longer the metal base 30 is, the more the resonance frequency moves to the low-frequency side. Therefore, a method of increasing the metal base 30 to move the resonance frequency to the low-frequency side is considered. However, for this method, the cost increases due to the increase in the length of the metal base 30. Since the metal base 30 is a cast component that is more expensive than the metal plate 40, it is desirable to avoid increasing the metal base 30. Moreover, preparing different metal bases 30 for multiple types of vehicles 5 having different shapes of the roof 3 is also a major cause of the cost increase. On the other hand, in the present embodiment, since the metal plate 40 that is cheaper than the metal base 30 is configured to move the resonance frequency to the low-frequency side, the cost increase can be suppressed. In addition, the metal base 30 is set as a common component for multiple types of vehicles 5, and it is sufficient to prepare a metal plate 40 for each of the multiple types of vehicles 5, thereby suppressing the cost increase from this point.

[0101] Next, the results of simulations of the antenna device 10 according to the present embodiment will be described.

[0102] Figure 5 It is a graph of VSWR (voltage standing wave ratio) of the antenna device 10 of the present embodiment, and shows the difference due to the presence or absence of the metal plate 40 .

[0103] The antenna element 15 of the antenna device 10 of the present embodiment can send and receive signals in the carrier frequency band of the mobile phone (for example, the 699MHz to 960MHz band, the 1710MHz to 2690MHz band). In the case where the metal plate 40 is not provided, as shown by the dotted line, the superfluous resonance is generated near the lower limit of the communication frequency band. In this case, if the change in the installation condition caused by the shape of the roof 3 and the like is considered, it cannot be said that sufficient margin can be obtained. However, as shown by the thin solid line and the thick solid line, by providing the metal plate 40 to reduce the resonant frequency of the superfluous resonance, the resonant frequency can be greatly moved away from the lower limit of the communication frequency band. In the case where the metal plate 40 is provided in the same manner, the case where it is set to a meandering shape such as the metal plate 40a can obtain the same setting area when viewed from above, and the electrical length can be further increased, as compared to the case where it is set to a quadrilateral flat plate shape such as the metal plate 40c. Therefore, corresponding to this case, the resonant frequency of the superfluous resonance can be further reduced.

[0104] As described above, according to the present embodiment, it is possible to prevent a reduction in antenna gain due to unnecessary resonance by a method other than providing a conductive plate between the metal base and the roof.

[0105] Furthermore, the resonance frequency of the unwanted resonance can be adjusted by changing the specifications of the metal plate 40. Therefore, a cast component (in this case, the metal base 30) that is more expensive than the metal plate 40 can be made a common component, thereby enabling inexpensive and simple handling of multiple types of vehicles 5.

[0106] That is, when the antenna device 10 is configured as a product series suitable for different types of vehicles, it is sufficient to prepare the difference in deformation of the metal plate 40, so that not only the construction of the product series can be achieved, but also the cost of managing the stock of parts or manufacturing can be suppressed to a very low level. Alternatively, multiple types of metal plates 40 are packaged together from the beginning, and when the antenna device 10 is installed on a vehicle and sufficient antenna gain cannot be obtained, the metal plate 40 can be replaced, and a countermeasure can be taken directly on site at a low cost.

[0107] In addition, as a secondary effect, by providing the metal plate 40, the flat ground plane can be expanded toward the rear end side in the storage space of the antenna device 10. Therefore, when the antenna element 15 is installed above the metal plate 40, and when other antenna elements are additionally installed above the metal plate 40, the distance between these antenna elements and the ground plane as the metal plate 40 is the same as that assumed in the design, and thus the same antenna gain as designed can be obtained.

[0108] [Second embodiment]

[0109] Next, a second embodiment to which the present invention is applied will be described.

[0110] In the first embodiment, a method of reducing the resonant frequency of the unwanted resonance is adopted, but this embodiment adopts a method of increasing the resonant frequency of the unwanted resonance. The following mainly describes the differences from the first embodiment, and the same reference numerals are given to the same components as the first embodiment, and repeated descriptions are omitted.

[0111] Figure 6 This is a top view of the antenna device 10B of the present embodiment with the antenna case removed. The antenna base 11B of the antenna device 10B has a metal base 30B shorter than the antenna base 11 of the first embodiment in the longitudinal direction (front-back direction). Specifically, a metal plate 40B is provided at the front end side of the metal base 30B with a gap therebetween, and the two are not electrically connected.

[0112] The front-to-back length of the metal base 30B of this embodiment is shorter than that of the metal base 30 of the first embodiment. Figure 6 In the example, the metal base 30B corresponds to the center portion and the rear portion when the metal base 30 of the first embodiment is divided into three parts: the front portion, the center portion, and the rear portion.

[0113] On the other hand, the metal plate 40B of the present embodiment corresponds to the front portion when the metal base 30 of the first embodiment is divided into three parts, namely, the front portion, the center portion, and the rear portion, and is mounted on the resin base 20 by the mounting screws 28 .

[0114] Figure 7 This is a VSWR graph of the antenna device 10B according to the present embodiment. Figure 7 The dotted line in represents the VSWR graph when the metal base 30 is used alone without the metal plate 40 in the first embodiment. In contrast, the thin solid line represents the VSWR graph obtained by combining the metal base 30B and the metal plate 40B in this embodiment, which clearly shows that the resonance frequency of the unnecessary resonance can be increased.

[0115] According to the antenna device 10B of the present embodiment, the resonance frequency of the unnecessary resonance can be greatly shifted to a frequency higher than the upper limit of the communication frequency band, thereby achieving the same effects as those of the antenna device 10 of the first embodiment.

[0116] [Variation]

[0117] An example of an embodiment to which the present invention is applied has been described above, but the embodiment to which the present invention can be applied is not limited to the above-described embodiment, and addition, omission, and modification of constituent elements can be appropriately implemented.

[0118] [Variation 1]

[0119] For example, the metal plate 40 of the first embodiment is formed into a two-dimensional planar shape, but may also be formed into a three-dimensional shape such as a meandering shape with turns also in the up-down direction.

[0120] [Variation 2]

[0121] In addition, it is also possible to Figure 8 The antenna device 10C shown in FIG. 1 is configured such that the metal base 30 and the metal plate 40 are electrically connected via an electrical length adjustment circuit 61. The electrical length adjustment circuit 61 is a second electrical length adjustment element for adjusting the resonance frequency of the unwanted resonance, and can be implemented as a so-called "transmission line length adjustment circuit" or "delay circuit". For example, Fig.12 As shown in (a), it is only composed of coils, such as Fig.12 As shown in (b) of FIG. 1 , the capacitor is used alone. Fig.12 As shown in (c), the circuit is composed of a capacitor and a coil connected in parallel, as shown in FIG. Fig.12 As shown in (d) of FIG. 1 , a circuit is formed by connecting a capacitor and a coil in series. Preferably, the circuit is formed as follows: Fig.12 As shown in (e), a switch is provided to switch the circuit constant. For example, the electrical length can be switched by providing a switch to switch on or off a capacitor or coil or the like.

[0122] Fig. 9 VSWR diagram of the antenna device 10 of the first embodiment, showing the difference due to the presence or absence of the electrical length adjustment circuit 61. Specifically, the thin solid line shows the case where there is no electrical length adjustment circuit 61 and the metal base 30 and the metal plate 40 are short-circuited ( Figure 5 The thick solid line represents the VSWR graph. Figure 8 VSWR diagram when the metal base 30 and the metal plate 40 are connected via the electrical length adjustment circuit 61. The electrical length adjustment circuit 61 in this modification is, for example, Fig.12 The circuit structure is as shown in (a). Fig. 9 As can be seen from the graph, when the metal base 30 and the metal plate 40 are electrically connected via the electrical length adjustment circuit 61, the electrical length becomes longer than when the metal base 30 and the metal plate 40 are short-circuited, thereby lowering the resonance frequency of the unnecessary resonance.

[0123] Similarly, the antenna device 10B according to the second embodiment can also be Fig.10 The antenna device 10D shown in FIG. 1 is configured such that the metal base 30B and the metal plate 40B are connected by an electrical length adjustment circuit 61. Specifically, Fig.13The solid line in the graph of VSWR shows the case where the metal base 30B and the metal base 40B of the second embodiment are connected by the electrical length adjustment circuit 61, and it can be seen that the resonance frequency of the unnecessary resonance can be increased. The electrical length adjustment circuit 61 in this modification example is, for example, Fig.12 The circuit configuration is as shown in (b).

[0124] According to the design of the circuit constants of the electrical length adjustment circuit 61, the resonant frequency of the redundant resonance can be reduced or increased. Fig.12 In addition to the switch for connecting or disconnecting elements such as capacitors and coils, as in (e), a switch for connecting or disconnecting the metal base 30 and the metal plate 40 may be provided.

[0125] [Variation 3]

[0126] In the above embodiment, a configuration with one metal plate is described, but a configuration with a plurality of metal plates may be used. For example, a configuration may be made such that a plurality of metal plates are provided at the front end and the rear end of the metal base 30 in the mounting posture.

[0127] [Variation 4]

[0128] In addition, when the antenna device of the above embodiment is configured to have a composite antenna built in, it is preferable that the second antenna element and the second substrate are provided above the metal plate. Fig.11 As shown, if a composite antenna is formed based on the first embodiment, the second antenna element 15B (for example, an AM wave or FM wave antenna) and the second substrate 17B serving as the substrate thereof are provided above the metal plate 40. The second antenna element 15B is located above the metal plate 40 in the range from the front to the rear.

[0129] exist Fig.11 In the example of the embodiment, the metal plate 40 of the first embodiment is arranged at the rear of the antenna device, thereby providing the second antenna element 15B and the second substrate 17B in the space behind the antenna element 15 in the antenna case 13. However, in the case where the metal plate 40B is provided on the front side of the metal base 30 as in the case of the second embodiment being a composite antenna, the second antenna element 15B and the second substrate 17B may be provided in the space in front of the antenna element 15 in the antenna case 13.

[0130] In any case, when the second antenna element 15B is arranged above the metal plate, the distance between the second antenna element 15B and the metal plate becomes fixed regardless of the type of vehicle 5 on which the antenna device is mounted, thereby achieving a stable antenna gain that meets the design regardless of the shape of the roof 3.

[0131] When the antenna device is viewed from above, as long as there is a space between the plurality of antenna elements, the metal plate may be disposed at a position sandwiched between the plurality of antenna elements.

[0132] In this embodiment, a metal plate is used, but the same effect can be obtained by arranging it in a pattern on a rigid substrate or a flexible substrate. By using a substrate, an electrical length adjustment circuit can be added without increasing the number of structural components.

[0133] [Variant 5]

[0134] In the above embodiment, the width direction ( Figure 2 The dimension in the vertical direction (in the vertical direction) is the same as or substantially the same as the dimension in the width direction of the metal base 30, but it is not limited thereto. For example, the dimension in the width direction of the metal plate 40 may be wider or narrower than the dimension in the width direction of the metal base 30. Compared with the dimension in the width direction of the wide metal plate 40, increasing the length in the front-to-back direction can more effectively shift the frequency of the unnecessary resonance.

[0135] [Variation 6]

[0136] In the above embodiment, the metal plate 40 is arranged on the base portion 22 of the resin base 20. Here, a structure for facilitating positioning and suppressing displacement from a predetermined position when the metal plate 40 is arranged may be provided on the base portion 22. For example, Fig.14 Yes means Figure 2 FIG. 10F is a diagram of an antenna device 10F which is a modified example of the antenna device 10. The antenna device 10F is different from Figure 2 The antenna device 10 is characterized in that a positioning shape portion 29 for preventing the metal plate 40 from being displaced from a predetermined position is provided on the base portion 22 of the resin base 20. The positioning shape portion 29 includes a convex portion 29b and a concave portion 29d, but only one of the convex portion 29b and the concave portion 29d may be provided. Fig.14In the embodiment, the central portion surrounded by the plurality of protrusions 29b becomes a concave portion 29d that is recessed in a dish shape, and the central portion becomes a predetermined position where the metal plate 40 should be arranged. When manufacturing the antenna device 10F, the metal plate 40 can be easily arranged at the predetermined position by the positioning shape portion 29. Specifically, the protrusion 29b or the concave portion 29d can be used as a guide when the metal plate 40 is arranged at the predetermined position. Moreover, when the metal plate 40 arranged at the predetermined position is installed by the substrate mounting screws 54, the protrusion 29b or the concave portion 29d can be used to suppress the metal plate 40 from being displaced from the predetermined position. Thus, the installation operation of the metal plate 40 can be simplified.

[0137] [Variation 7]

[0138] In the first embodiment, the metal base and the metal plate are used together, but it can be composed of only the metal plate. In this case, the metal plate has a mounting mechanism on the roof. Compared with the first embodiment, the expensive metal casting parts are reduced, and the parts connecting the metal base and the metal plate are also reduced, thereby reducing the cost.

[0139] [Application example]

[0140] Based on the above-mentioned embodiment and modification examples, several more specific application examples will be described.

[0141] 〔Application Example 1〕

[0142] Fig.15 , Fig.16 It is a diagram showing an antenna device 100A according to a first application example. Fig.15 It is a three-dimensional perspective view. Fig.16 1 is a side perspective view. The antenna device 100A has an antenna base 110A, an antenna case 130 covering the antenna base 110A from above, and antenna elements 151, 152, and 153 provided inside the antenna case 130, similarly to the above-mentioned embodiment. In addition, the antenna base 110A has a resin base 200, a metal base 300 fixed to the roof 3, and a metal plate 400A and a metal plate 400B electrically connected to the metal base 300. The metal base 300, the metal plate 400A, and the metal plate 400B are arranged on the resin base 200.

[0143] Antenna element 151 is a patch antenna. Antenna element 152 is a broadcast antenna. Antenna element 153 is a keyless antenna for a keyless entry system. The keyless entry system is also called a smart entry system, and the operating frequency of the keyless antenna is, for example, 925 MHz.

[0144] The antenna device 100A has an antenna element 153 of a keyless antenna at the rear of the metal base 300. The antenna element 153 is disposed on the metal plate 400B. Figure 6 Similarly, the antenna device 10B shown in the figure has a metal plate 400A in front of the metal base 300. The unnecessary resonance frequency generated by the metal base 300, the metal plate 400A, the metal plate 400B and the roof 3 becomes a frequency outside the band of the operating frequency of the keyless antenna. As a result, the gain of the keyless antenna can be improved.

[0145] 〔Application Example 2〕

[0146] Fig.17 1 is a diagram showing an antenna device 100B of the second application example, which is a perspective view. The antenna device 100B has an antenna base 110B, an antenna case 130 covering the antenna base 110B from above, and antenna elements 151 and 152 provided inside the antenna case 130, similarly to the above-mentioned embodiment. In addition, the antenna base 110B has a resin base 200, a metal base 300 fixed to the roof 3, and a metal plate 400B electrically connected to the metal base 300. The metal base 300 and the metal plate 400B are arranged on the resin base 200. The antenna element 151 is a patch antenna. The antenna element 152 is a broadcast antenna.

[0147] The antenna device 100B of the second application example is obtained by removing the antenna element 153 and the metal plate 400A from the antenna device 100A of the first application example. The positional relationship between the metal base 300 and the metal plate 400B is similar to Figure 2 , 3 The antenna device 10, and Fig.11 The antenna device 100E is the same as that of FIG. 4. And the antenna element 152 is configured so that a part of it is located above the metal plate 400B. In other words, the antenna element 152 is configured so that the rear end side is located above the metal plate 400B.

[0148] The metal bases 30 and 300 are described as cast products of aluminum alloy, for example, but they may also be made of sheet metal. In addition, the metal plates 40, 400, 400A, and 400B are metal members made of a material different from that of the metal bases 30 and 300, but may also be formed of the same material.

[0149] 〔Application Example 3〕

[0150] Fig.18 , Fig.19 It is a diagram showing an antenna device 100C according to a third application example. Fig.18 It is a three-dimensional perspective view. Fig.19It is a side perspective view. The antenna device 100C has an antenna base 110C, an antenna housing 133 covering the antenna base 110C from above, antenna elements 154 and 155 arranged on the inner side of the antenna housing 133, a circuit substrate 174 for the antenna element 154, and a circuit substrate 175 for the antenna element 155. In addition, the antenna base 110C has a resin base 200C and a dual-purpose metal plate 400C fixed to the roof 3. The dual-purpose metal plate 400C is arranged on the resin base 200C. The dual-purpose metal plate 400C is a dual-purpose plate that integrates a metal base and a metal plate. Therefore, it can also be said that the dual-purpose metal plate 40 is a metal base having the function of the metal plate of the above-mentioned embodiment. The antenna element 155 is an antenna for television broadcasting (terrestrial digital television broadcasting), and the circuit substrate 175 is a circuit substrate for DTTB reception. The antenna element 154 is a broadcast antenna, and the circuit board 174 is a circuit board for broadcast reception.

[0151] exist Fig. 20 , Fig.21 The middle represents the combined use metal plate 400C. Fig. 20 It is a top view. Fig.21 is a side view. In addition, as a comparative example, Fig. 22 , Fig.23 The middle represents the combined use metal plate 400D. Fig. 22 is a top view of a dual-purpose metal plate 400D of a comparative example. Fig.23 It is a side view of a dual-purpose metal plate 400D of a comparative example.

[0152] The antenna device 100C of the third application example can also use the dual-purpose metal plate 400D of the comparative example, but is configured to use the dual-purpose metal plate 400C instead of the dual-purpose metal plate 400D. The dual-purpose metal plate 400C is hollowed out in the center of the rear side in the installation posture. To explain the relationship between it and the antenna vibrator 154, a part or all of the antenna vibrator 154 is located on the dual-purpose metal plate 400C. The part of the dual-purpose metal plate 400C located below the antenna vibrator 154 is partially hollowed out.

[0153] In addition, the dual-purpose metal plate 400C is formed so that the height position L2 of the lower surface on the rear side is higher than the height position L1 of the lower surface on the front side by a height Δh. Therefore, when the antenna device 100C is mounted on the roof 3, the distance between the rear side of the dual-purpose metal plate 400C and the roof 3 can be increased. As a result, the capacitance generated between the roof 3 and the dual-purpose metal plate 400C can be reduced, and the resonance frequency of the unnecessary resonance is moved away from the communication frequency band of the antenna vibrator to the high-frequency wave side, thereby suppressing the reduction of the antenna gain.

Claims

1. A vehicle-mounted antenna device, which is mounted on a roof of a vehicle, wherein the vehicle-mounted antenna device has: Antenna base; An antenna housing covering the antenna base from above; and an antenna vibrator disposed inside the antenna housing, A receiving space is defined between the antenna housing and the antenna base. The antenna base has: a metal base fixed to the roof; and a metal plate located in the receiving space and electrically connected to the metal base, The metal base has a protrusion for fixing to the roof. The resonance frequency generated by the roof and the antenna base electrically connected via the protrusion is outside the communication frequency band of the antenna element.

2. The vehicle-mounted antenna device according to claim 1, wherein: The metal plate is formed of a less expensive component than the metal base.

3. The vehicle-mounted antenna device according to claim 1, wherein: A gap is provided between the metal plate and the metal base.

4. The vehicle-mounted antenna device according to claim 1, wherein: An electrical length adjustment circuit is provided to electrically connect the metal base and the metal plate.

5. A vehicle-mounted antenna device, which is mounted on a roof of a vehicle, the vehicle-mounted antenna device being characterized by comprising: An antenna base having a metal plate fixed to the vehicle roof and a resin base; An antenna housing covering the antenna base from above; and an antenna vibrator disposed inside the antenna housing, A receiving space is defined between the antenna housing and the antenna base. The metal plate is disposed on the resin base and is located in the receiving space. A distance between the roof and a lower surface on a rear side of the metal plate is greater than a distance between the roof and a lower surface on a front side of the metal plate.

6. The vehicle-mounted antenna device according to claim 5, characterized in that: The strength of the resin base is improved by the metal plate.

7. The vehicle-mounted antenna device according to claim 5, characterized in that: The resin base has a positioning shape portion that suppresses positional displacement of the metal plate.

8. The vehicle-mounted antenna device according to any one of claims 1 to 7, characterized in that: The electrical length is adjusted by the metal plate.

9. The vehicle-mounted antenna device according to any one of claims 1 to 7, characterized in that: The flat ground contact surface is expanded by the metal plate.

10. The vehicle-mounted antenna device according to any one of claims 1 to 7, characterized in that: having another antenna element which is arranged above the metal plate and is different from the antenna element, The distance between the metal plate and the other antenna elements is fixed.

11. The vehicle-mounted antenna device according to claim 10, wherein: The metal plate is located between the antenna element and the other antenna elements.

12. The vehicle-mounted antenna device according to any one of claims 1 to 7, characterized in that: The metal plate is made of sheet metal or a conductor pattern is formed on a substrate.

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