Low profile antenna assembly

Abstract

Provided is a low-profile antenna device that has no problems with antenna reception characteristics, is easy to manufacture, saves costs, and has reduced manufacturing errors. The low-profile antenna device includes a substrate (10), a top load element (20), and an antenna cover (30). The top load element (20) has a ridgeline portion (21), a side surface portion (22), and a slit (23). The ridgeline portion (21) extends in the longitudinal direction of the top load element (20) and is inclined relative to the substrate (10). The slit (23) extends from one side surface portion (22a) through the ridgeline portion (21) to a certain point of the other side surface portion (22b), and divides the ridgeline portion (22) into a front portion and a rear portion. In order to make the ridgeline portion (21) close to the highest position inside the antenna cover (30), the top load element (20) is folded into a curved shape so that the height of the ridgeline portion (21) changes across the slit (23).

Description

Technical Field

[0001] The present invention relates to low profile antenna devices, and more particularly to low profile antenna devices for vehicles. Background Art

[0002] Various types of antenna devices are installed on vehicles recently. One example is an AM / FM radio antenna for receiving AM and FM broadcasts. The AM / FM radio antenna is generally a rod-shaped antenna. The rod-shaped antenna includes an element portion and a substrate for mounting the element portion, in which an element (helical element) composed of a spiral conductor is covered by a cover member.

[0003] When the rod antenna is mounted on the vehicle body, the component portion protrudes significantly from the vehicle body. This may damage the aesthetics and appearance of the vehicle and cause damage during storage in a garage or car wash. In addition, the rod antenna is exposed from the vehicle body, making the component portion likely to be stolen.

[0004] In order to cope with these problems, a low-profile antenna device is proposed, which is designed so that the height of the entire device is lower than that of a rod antenna, so that the elements are contained in an antenna housing to prevent them from being exposed to the outside, and the antenna housing is formed into a FUKAHIRE shape (shark fin shape) in consideration of the appearance characteristics of the entire vehicle on which the antenna device is mounted. In consideration of regulations, such a low-profile antenna device generally has a height of 70 mm or less and a longitudinal length of about 200 mm.

[0005] However, a low-profile antenna device with a height as low as 70 mm or less may reduce radiation efficiency due to antenna conductor loss (reduced element length), which may lead to reduced sensitivity. For example, in order to solve this problem, Patent Document 1 discloses the following low-profile antenna device in which a coil is inserted between a top load element and an amplifier loop.

[0006] In addition, as in Patent Document 2, a vehicle antenna device having an antenna and a camera is known, wherein, in order to increase the antenna gain, the length of the capacitor loading element in the height direction is smaller at a portion overlapping with the camera in a top view and / or a side view than at a portion not overlapping with the camera.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2012-204996

[0010] Patent Document 2: PCT International Publication No. 2019 / 156138 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In a low-profile antenna device, the antenna element is preferably arranged at a position as high as possible inside the antenna cover to prevent degradation of the antenna reception characteristics. The antenna cover defines the outer shape of the antenna device and has a streamlined shape with an arc-shaped top. Therefore, the top of the top load element is formed in an arc shape to follow the inner shape of the top of the arc-shaped antenna cover. For example, in Patent Document 1, the top load element is bent so that the angle of its top relative to the substrate changes on the way. In Patent Document 2, the top load element is formed in a zigzag shape and follows the topmost position inside the antenna cover.

[0013] Furthermore, another example is a top load member obtained by stretching, for example, a metal plate, which is configured to completely match the inner shape of the antenna cover.

[0014] However, the above top load element has a complex shape and high manufacturing cost. In addition, due to the complex shape, the manufacturing error in the top load element directly affects the antenna reception characteristics, so it is necessary to provide a correction loop to correct the error and adjust the error in the top load element of each low profile antenna device.

[0015] Therefore, it is desirable to develop a low-profile antenna device that has no problem in antenna reception characteristics, is easy to manufacture and suppresses costs, and has reduced manufacturing errors.

[0016] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-profile antenna device which has no problem in antenna reception characteristics, is easy to manufacture and suppresses costs, and has reduced manufacturing errors.

[0017] Solutions for solving problems

[0018] In order to achieve the above-mentioned object of the present invention, the low-profile antenna device according to the present invention includes: a substrate fixed to a vehicle; a top load element arranged to be spaced apart from the substrate in the height direction and configured to be used as an antenna for a first frequency band; and an antenna cover fitted to the substrate and accommodating the top load element inside, wherein the top load element includes: a ridge portion extending in a longitudinal direction of the top load element in a manner inclined relative to the substrate; side surface portions extending from both sides of the ridge portion; and a slit extending from the side surface portion on one side to the middle of the side surface portion on the other side in a manner passing through the ridge portion to divide the ridge portion into a front side portion and a rear side portion, the slit provided in the side surface portion facing a direction perpendicular to the ridge portion. The top load element is bent so that the height of the ridge portion changes before and after the slit so that the ridge portion is close to the topmost position inside the antenna cover.

[0019] The top load member may be in a flat plate state before bending, and in the flat plate state, the ridgeline portion is designed such that the ridgeline portion on the rear side of the slit is offset relative to the ridgeline portion on the front side of the slit in the slit depth direction.

[0020] The side surface portion of the top load member may extend beyond the ridge line portion in the longitudinal direction of the top load member.

[0021] The side surface portion of the top load member may have a constant distance from the base plate in a height direction.

[0022] The slit may include a plurality of slits, and the top load member may be bent such that a height of the ridge portion changes respectively in front of and behind each of the plurality of slits to bring the ridge portion closer to a topmost position inside the antenna cover.

[0023] The top load member may further include: a pair of wiring slits provided on the side surface portion so as to face in a direction perpendicular to the ridge line portion; and a plate-shaped wiring portion formed by being cut out from the top load member through the wiring slits.

[0024] The low-profile antenna device may further include: a loop board, which is arranged on the substrate and has a feeding terminal; and a coil, which is connected between the top load element and the feeding terminal and is adjusted to realize the function of a resonant antenna of a second frequency band by utilizing a series loop of the top load element and the coil.

[0025] The coil may be arranged such that its axial direction is parallel to the base plate and parallel to the longitudinal direction of the top load element.

[0026] The coil may be arranged below a portion of the ridge line portion located on a front side of the slit.

[0027] Effects of the Invention

[0028] A low-profile antenna device according to the present invention has the advantages of having no problem in antenna reception characteristics, being easy to manufacture and suppressing costs, and having reduced manufacturing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] [ Figure 1 ] Figure 1 is a schematic side view for illustrating a low profile antenna device according to the present invention.

[0030] [ Figure 2 ] Figure 2 is a development view showing an unbent state of a top load element constituting a low-profile antenna device according to the present invention.

[0031] [ Figure 3 ] Figure 31 is a schematic side view for explaining the opposite side surfaces of a top load element constituting the low-profile antenna device according to the present invention.

[0032] [ Figure 4 ] Figure 4 is a schematic side view for comparing a top load element of a low profile antenna assembly according to the present invention and a conventional top load element.

[0033] [ Figure 5 ] Figure 5 is a schematic perspective view for explaining a modified example of a top load element constituting a low-profile antenna element according to the present invention.

[0034] [ Figure 6 ] Figure 6 is a schematic side view for explaining another modified example of a top load element constituting a low-profile antenna element according to the present invention. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments for practicing the present invention will be described by way of illustrated examples. Figure 1 1 is a schematic side view for illustrating a low profile antenna device according to the present invention. A portion thereof is a cross-sectional view for illustrating the interior of the low profile antenna device. As shown in the figure, the low profile antenna device according to the present invention includes a substrate 10, a top load element 20, and an antenna cover 30.

[0036] The substrate 10 is fixed to the vehicle. Specifically, the substrate 10 may be a so-called resin base formed of an insulator such as a resin, or may be a so-called metal base formed of a conductor such as a metal. In addition, the substrate 10 may be a composite base of a resin and a metal. For example, a threaded boss 11 is provided on the substrate 10. The threaded boss 11 is inserted into a hole formed in a roof of a vehicle, etc., and a nut is tightened from the vehicle compartment side to fix the substrate 10 to the roof, etc., thereby sandwiching the roof, etc. between the nut and the substrate 10. A power supply cable or a signal cable for connecting the interior of the vehicle and the antenna device is inserted through the threaded boss 11. In addition, the substrate 10 is configured to be covered by an antenna cover 30, details of which will be described later.

[0037] The top load element 20 is used as an antenna for a first frequency band. For example, the top load element 20 may be a so-called capacitively loaded antenna element. Specifically, the first frequency band may be an AM band. In the AM band, the top load element 20 is used as a capacitive antenna. The top load element 20 may have an element length corresponding to the first frequency band. In this case, the first frequency band may be, for example, a DTV band. In the DTV band, the top load element 20 is used as a resonant antenna. The top load element 20 is arranged to be spaced apart from the substrate 10 in the height direction. Figure 1In the example shown, the left side is the vehicle travel direction, and the longitudinal direction of the top load element 20 faces the vehicle travel direction.

[0038] The antenna cover 30 is fitted to the substrate 10 in such a manner as to accommodate the top load element 20 therein. In the example shown, the antenna cover 30 defines the outer shape of the low-profile antenna device; however, the low-profile antenna device according to the present invention is not limited thereto. For example, the antenna cover 30 may have an inner cover and an outer cover. That is, this may be a double cover structure. In this case, the inner cover accommodates the top load element 20 therein, and the outer cover defines the outer shape.

[0039] As described with respect to the problems to be solved by the conventional low-profile antenna device, the antenna cover 30 that defines the outer shape of the low-profile antenna device has a streamlined shape with an arc-shaped top. Specifically, as shown in the figure, the height of the antenna cover 30 is lowest on the front end side in the vehicle's driving direction, gradually increases rearward, and then decreases from the topmost point toward the rear end. The top load element 20 is preferably arranged at the topmost position inside the antenna cover 30 so that the antenna characteristics are degraded as little as possible. At the same time, in order to reduce the variation in the antenna reception characteristics, the top load element 20 needs to have a reduced manufacturing error. To this end, in the low-profile antenna device according to the present invention, the top load element 20 is constructed as described below.

[0040] Figure 2 1 is a development view showing an unbent state of a top load element constituting a low profile antenna device according to the present invention. Figure 1 The same reference numerals in the figure denote the same parts. As shown in the figure, the top load element 20 has a ridge line portion 21, a side surface portion 22 and a slit 23. The top load element 20 is in a flat plate state before being bent. Then, a predetermined shape as shown in the figure is cut out from the flat plate, and then bent at a predetermined position, thereby forming the top load element 20.

[0041] The ridgeline portion 21 extends in the longitudinal direction of the top load element 20. After bending, the ridgeline portion 21 is inclined relative to the base plate 10, as shown in FIG. Figure 1 Specifically, Figure 1 As shown, the ridgeline portion 21 is inclined so as to rise rearward in the vehicle traveling direction. Figure 2 The ridgeline portion 21 shown does not have a linear shape but has a certain width that increases along the vehicle traveling direction. However, the present invention is not limited thereto, but the width of the ridgeline portion 21 may be appropriately determined according to the inner shape of the antenna cover 30.

[0042] The side surface portions 22 extend from both sides of the ridgeline portion 21. In the illustrated example, the right side in the vehicle traveling direction is referred to as the side surface portion 22a, and the left side is referred to as the side surface portion 22b. The ridgeline portion 21 and the side surface portions 22a and 22b extending obliquely from both sides of the ridgeline portion 21 form a mountain-like shape in the cross section of the top load member 20.

[0043] The slot 23, which is the most characteristic part of the low-profile antenna device according to the present invention, is formed as follows. Figure 2 As shown, the slit 23 extends from the side surface portion 22a through the ridgeline portion 21 to the middle of the side surface portion 22b. The slit 23 faces a direction perpendicular to the ridgeline portion 21. In other words, the slit 23 is arranged to intersect the fold line of the ridgeline portion 21 at a right angle. The slit 23 placed to pass through the ridgeline portion 21 divides the ridgeline portion 21 into a front part and a rear part. In the example shown, the front side is referred to as the ridgeline portion 21a, and the rear side is referred to as the ridgeline portion 21b.

[0044] exist Figure 2 In the flat state shown, the ridgeline portion 21 is designed so that the rear ridgeline portion 21b is offset relative to the front ridgeline portion 21a in the depth direction of the slit 23. That is, the ridgeline portions 21a and 21b divided by the slit 23 are not arranged in a straight line in the vehicle travel direction in the flat state before bending, and the ridgeline portion 21b is offset to the left side (lower side in the figure) in the vehicle travel direction.

[0045] like Figure 1 The top load element 20 shown is formed by bending such a flat plate. Figure 3 shown. Figure 3 1 is a schematic side view for illustrating the opposite side surface of the top load element constituting the low profile antenna device according to the present invention. Figure 1 The same reference numerals in FIG. 1 denote the same parts. In this example, only the top load element 20 is shown, and other components are omitted.

[0046] When the flat plate is folded as described above, the height of the ridge line portion 21 changes before and after the slit 23, as shown in FIG. Figure 1 and Figure 3 As shown. This allows the rear end portion of the ridgeline portion 21a to be close to the topmost position inside the antenna cover 30. As shown in the figure, the ridgeline portion 21 is made close to the topmost position of the inside of the antenna cover 30 at the following three parts: the front end portion of the top load element 20; the portion where the slit 23 is formed; and the rear end portion of the top load element 20. Therefore, the ridgeline portion 21 can be made closer to the topmost position inside the antenna cover 30. The folding mentioned here refers to "simply folding a flat plate linearly", which means that complicated processing such as stretching to form a curved surface or folding into a curved surface is not required.

[0047] Furthermore, in the flat plate state, the top load member 20 has a tapered shape in the vehicle travel direction, such as Figure 2 As shown. Specifically, the width of the side surface portion 22 decreases in the vehicle traveling direction. The reason for this is to make the side surface portion 22 have a constant distance from the substrate 10 in the height direction after being folded. That is, since the ridgeline portion 21 is inclined relative to the substrate 10, the side surface portion 22 is designed so that as the height of the ridgeline portion 21 increases going backward in the vehicle traveling direction, the height of the side surface portion 22 increases going backward in the vehicle traveling direction, thereby making the distance between the side surface portion 22 and the substrate 10 constant. This reduces the capacitive coupling between the top load element 20 and the substrate 10, while increasing the antenna capacitance of the top load element 20 as much as possible, thereby suppressing the deterioration of the antenna reception characteristics.

[0048] Next, we will use Figure 4 It will be described in more detail how close the ridgeline portion 21 of the top load element 20 constituting the low-profile antenna device according to the present invention is to the topmost position inside the antenna cover 30 . Figure 4 1 is a schematic side view for comparing a top load element of a low profile antenna assembly according to the present invention and a conventional top load element. Figure 1 1 and 2 , the same reference numerals denote the same parts. The top load element 20 of the low profile antenna device according to the present invention is indicated by a solid line, and a conventional top load element is indicated by a dotted line. The conventional top load element is formed by simply bending a flat plate without any modification. In this example, only the top load element 20 and the antenna cover 30 are shown, and other components are omitted.

[0049] As shown in the figure, the conventional top load member is formed so that the ridgeline portion is simply bent linearly without applying a modification to the top load member, and the resulting ridgeline portion extends straight from the front side to the rear side in the vehicle traveling direction. Therefore, only the front end and the rear end of the top load member are close to the topmost position inside the antenna cover 30, and the central portion is significantly separated from the topmost position.

[0050] On the other hand, in the top load element 20 of the low profile antenna device according to the present invention, the height of the ridgeline portion 21 is different at the front and rear sides of the slit 23. Specifically, the rear end of the ridgeline portion 21a is made close to the topmost position inside the antenna cover 30.

[0051] As described above, in the low-profile antenna device according to the present invention, the ridgeline portion can be brought close to the topmost position inside the antenna cover simply by linearly folding the top load member 20. Therefore, there is no problem with the antenna reception characteristics. In addition, neither a complicated design nor a complicated work such as stretching is required, thereby facilitating manufacturing, resulting in a reduction in manufacturing cost. In addition, due to the simple linear folding, manufacturing errors are reduced. As a result, the antenna reception characteristics have reduced variations.

[0052] Reference again Figure 1 , the low-profile antenna device according to the present invention has a loop board 40 and a coil 50. Therefore, the low-profile antenna device according to the present invention can be designed as a composite antenna. The loop board 40 is arranged on the substrate 10 and has a feeding terminal 41. The loop board 40 has an amplifier loop and / or a filter loop as needed, and is configured to receive a signal. The coil 50 is connected between the top load element 20 and the feeding terminal 41. Through the series loop of the top load element 20 and the coil 50, the function of a resonant antenna for a second frequency band is achieved. The second frequency band can be an FM band. For example, the inductor of the coil 50 is appropriately selected to allow the series loop of the top load element 20 and the coil 50 to be used as a resonant antenna for the FM band.

[0053] As shown in the figure, the coil 50 is arranged so that its axial direction is parallel to the base plate 10 and parallel to the longitudinal direction of the top load element 20. Therefore, the coil 50 is arranged transversely, so that even when the length (number of turns) of the coil 50 is different depending on the vehicle type, only the transverse length changes, but the distance from the loop board 40 does not change. Therefore, adjusting the length of the coil 50 has little effect on the antenna reception characteristics.

[0054] The coil 50 is preferably arranged below the ridgeline portion 21a at the front side of the slit 23, rather than below the ridgeline portion 21b at the rear side of the slit 23. The coil 50 is not necessarily arranged directly below the ridgeline portion 21, but may be displaced to the left and right in the vehicle travel direction. In addition, the coil 50 may be arranged so that its axial direction is perpendicular to the longitudinal direction of the top load member 20.

[0055] In addition, a wiring portion for connecting the top load element 20 and the coil 50 can be formed by cutting the top load element 20. Specifically, the top load element 20 has a pair of wiring slits 24 and a plate-shaped wiring portion 25. Figure 2As shown, a pair of wiring slits 24 are formed in the side surface portion 22. The pair of wiring slits 24 face in a direction perpendicular to the ridge line portion 21. The plate-like wiring portion 25 is formed by cutting out the top load element 20 by the wiring slits 24. The plate-like wiring portion 25 is connected to the coil 50. As described above, the wiring portion connected to the coil 50 can be set by cutting the top load element 20, so that it is not necessary to newly prepare wiring, etc., thereby reducing manufacturing errors. In the example shown, the plate-like wiring portion 25 is provided for the case of using a coil; however, the present invention is not limited thereto, but the plate-like wiring portion 25 can be used even when the top load element 20 is directly connected to the feed terminal 41 without the coil 50.

[0056] Next, we will use Figure 5 Variations of the top loading element constituting the low profile antenna element according to the present invention are described. Figure 5 1 is a schematic perspective view for explaining a modified example of a top load element constituting a low profile antenna element according to the present invention. Figure 1 , the same reference numerals in the figure denote the same parts. In this example, only the top load element 20 is shown, and other components are omitted. As in this example, the side surface portion 22 of the top load element 20 extends beyond the ridgeline portion 21 in the longitudinal direction of the top load element 20. Specifically, the front end portion 22c of the side surface portion 22 extends beyond the front end portion of the ridgeline portion 21 toward the front side of the vehicle traveling direction. With this configuration, the front end portion 22c of the side surface portion 22 can be set at which the ridgeline portion 21 cannot be accommodated in the low height portion of the front side end of the antenna cover 30. That is, the space of the front end side of the antenna cover 30 having a low height can be effectively used, thereby allowing the antenna capacitance of the top load element 20 to be further increased. In the example shown, the side surface portion 22 extends beyond the ridgeline portion 21 toward the front side of the vehicle traveling direction; however, the present invention is not limited thereto, and the side surface portion 22 may extend beyond the ridgeline portion 21 toward the rear side of the vehicle traveling direction.

[0057] In the above example, the number of the slits 23 is one, and the number of the portions where the height of the ridge line portion 21 changes is one; however, the present invention is not limited thereto. Figure 6 An example in which the height is changed at a plurality of portions is described. Figure 6 1 is a schematic side view for illustrating another variant of a top load element constituting a low profile antenna element according to the present invention. Figure 1 The same reference numerals in the figure denote the same parts. In this example, only the top load element 20 is shown, and other components are omitted. As shown in the figure, the top load element 20 has a plurality of slits 23a and 23b. Although two slits are formed in this example, the present invention is not limited thereto, but a greater number of slits may be formed.

[0058] As shown in the figure, the top load member 20 is bent so that the heights of the ridge line portions 21a, 21b, and 21c are changed in front and behind each of the plurality of slits 23a and 23b, respectively, so that the ridge line portion 21 approaches the topmost position inside the antenna cover 30. That is, when viewed from the side, the top load member 20 of this example has a sawtooth top shape. Therefore, by slightly changing the height of the ridge line portion 21, the ridge line portion 21 can be made to approach the topmost position at shorter intervals according to the internal shape of the antenna cover 30.

[0059] The low-profile antenna element according to the present invention is not limited to the above-illustrated examples, but various modifications may be made without departing from the scope of the present invention.

[0060] Description of Reference Numerals

[0061] 10: Substrate

[0062] 11: convex part

[0063] 20: Top load element

[0064] 21: Ridgeline

[0065] 22: Side surface

[0066] 23: Slit

[0067] 24: Wiring slit

[0068] 25: Plate wiring part

[0069] 30: Antenna cover

[0070] 40: Loop board

[0071] 41: Feeding terminal

[0072] 50: Coil

Claims

1. A low profile antenna device for a vehicle, the low profile antenna device comprising: a base plate fixed to the vehicle; a top load element arranged to be spaced apart from the substrate in a height direction and configured to function as an antenna for a first frequency band; and an antenna cover which is fitted to the base plate and houses a top load element therein, wherein The top load element comprises: a ridge portion extending in the longitudinal direction of the top load element in an inclined manner relative to the base plate; a side surface portion having a first side surface and a second side surface extending from both sides of the ridge line portion, respectively; and a slit extending from the first side surface to the middle of the second side surface in a manner of passing through the ridgeline portion to divide the ridgeline portion into a front side portion and a rear side portion, the slit provided in the side surface portion facing a direction perpendicular to the ridgeline portion; and The top load member is bent so that the height of the ridgeline portion changes before and after the slit so that the ridgeline portion approaches the topmost position inside the antenna cover.

2. The low profile antenna device of claim 1, wherein The top load-bearing member is in a flat plate state before flexing, and In the flat plate state, the ridgeline portion is designed such that the ridgeline portion on the rear side of the slit is offset relative to the ridgeline portion on the front side of the slit in the slit depth direction. 3 . The low-profile antenna device according to claim 1 , wherein the side surface portion of the top load element extends beyond the ridge line portion in a longitudinal direction of the top load element. 4 . The low-profile antenna device according to claim 1 , wherein the side surface portion of the top load element has a constant distance from the substrate in a height direction.

5. A low-profile antenna device according to any one of claims 1 to 4, wherein the slit includes a plurality of slits, and the top load element is bent so that the height of the ridge line portion changes in front of and behind each of the plurality of slits, respectively, so that the ridge line portion is close to the topmost position inside the antenna cover.

6. The low profile antenna device according to any one of claims 1 to 5, wherein The top load element further comprises: a pair of wiring slits provided on the side surface portion so as to face in a direction perpendicular to the ridge line portion; and The plate-shaped wiring portion is formed by cutting out the top load element through the wiring slit.

7. The low profile antenna device according to any one of claims 1 to 6, further comprising: A circuit board, which is arranged on the substrate and has a feeding terminal; and The coil is connected between the top load element and the feeding terminal and is adjusted to realize the function of a resonant antenna of the second frequency band by utilizing a series loop of the top load element and the coil.

8. The low profile antenna device of claim 7, wherein the coil is arranged such that its axial direction is parallel to the substrate and parallel to the longitudinal direction of the top load element. 9 . The low-profile antenna device according to claim 7 , wherein the coil is arranged below a portion of the ridge line portion located on a front side of the slit.

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