Antenna device

Abstract

Provided is an antenna device mounted on a vehicle, wherein: the antenna device comprises a first antenna element that extends in the lateral direction of the vehicle, and a second antenna element that is electrically connected to the first antenna element; and the second antenna element extends the electrical length of an antenna having the first antenna element and the second antenna element.

Description

Antenna device

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

[0002] In recent years, various antenna devices have been developed. As described in Patent Document 1, an antenna device may be mounted in a cavity inside a vehicle spoiler. The antenna device described in Patent Document 1 includes a circuit board and an element portion electrically connected to the circuit board. The element portion is formed of sheet metal.

[0003] JP 2016-12915 A

[0004] As described in Patent Document 1, when an antenna has only a metal plate as an antenna element, a current distribution is likely to be generated throughout the antenna. When a current distribution is generated throughout the antenna, the antenna is likely to be electrically coupled to surrounding conductors, and the antenna impedance is likely to become unstable. When the antenna impedance becomes unstable, it may be difficult to improve the antenna gain.

[0005] One object of the present invention is to improve the gain of an antenna. Other objects of the present invention will become apparent from the description herein.

[0006] One aspect of the present invention is an antenna device mounted on a vehicle, comprising a first antenna element extending in the left-right direction of the vehicle and a second antenna element electrically connected to the first antenna element, wherein the second antenna element extends the electrical length of an antenna having the first antenna element and the second antenna element.

[0007] According to the above aspect of the present invention, the gain of the antenna can be improved.

[0008] 5A is a side view of a vehicle equipped with an antenna device according to an embodiment, and FIG. 5B is an enlarged side view of the rear of a vehicle equipped with an antenna device according to an embodiment. FIG. 5B is an exploded perspective view of an antenna device according to an embodiment. FIG. 5C is a perspective view of an antenna device according to an embodiment with a base removed, viewed from the opposite side to FIG. 2. FIG. 5D is a perspective view of a case and a bobbin according to an embodiment. FIG. 5E is a bottom view of a case and a bobbin according to an embodiment. FIG. 5F is a cross-sectional view taken along the line A-A in FIG. 5. FIG. 5G is a perspective view of a portion of a case according to an embodiment. FIG. 5H is a perspective view of a portion of a case according to an embodiment, viewed from a different viewpoint than FIG. 7. FIG. 5I is a diagram for explaining an example of a method for attaching a case and a bobbin according to an embodiment. FIG. 5I is a schematic view showing a current distribution in an antenna according to an embodiment. FIG. 5I is a schematic view showing a current distribution in an antenna having an antenna element different from the helical element according to an embodiment. FIG. 5I is a graph showing the influence of a surrounding conductor on an antenna having a helical element according to an embodiment, and the influence of a surrounding conductor on an antenna not having a helical element according to an embodiment. FIG. 5I is a graph showing the frequency characteristics of the FM band gain of an antenna having a bent portion according to an embodiment and the FM band gain of an antenna not having a bent portion according to an embodiment. FIG. 5I is a model diagram for explaining the operating principle of an antenna according to an embodiment. 15 is a graph showing the frequency characteristics of the gain of the antenna when the ratio h1 / h (h: total length of the antenna from the ground to the tip of the antenna, h1: distance from the ground to the power feed point) in the model of FIG. 14 is varied. FIG. 16 is a graph showing the peak gain and average gain of the antenna when the ratio h1 / h (h: total length of the antenna from the ground to the tip of the antenna, h1: distance from the ground to the power feed point) in the model of FIG. 14 is varied. FIG. 17 is a diagram showing a principle model of an antenna according to an embodiment. (a) is a graph showing the frequency characteristics of the gain of an antenna that resonates at two frequencies and an antenna that resonates at one frequency in the range of 100 MHz to 300 MHz, and (b) is a graph showing the frequency characteristics of the gain of an antenna that resonates at two frequencies and an antenna that resonates at one frequency in the range of 174 MHz to 240 MHz.1 is a graph showing the frequency characteristics of the voltage standing wave ratio (VSWR) at 174 MHz to 240 MHz of an antenna that resonates at two frequencies and an antenna that resonates at one frequency. (a) to (d) are diagrams showing various examples of loading elements mounted on the antenna. (a) is a schematic diagram showing a first example of the arrangement of the antenna element and the helical element, and (b) is a schematic diagram showing a second example of the arrangement of the antenna element and the helical element. (a) is a graph showing the frequency characteristics of the gain of vertically polarized waves of an antenna in a state where the antenna element and the helical element are arranged parallel to the horizontal plane and in a state where the antenna element and the helical element are inclined obliquely with respect to the horizontal plane, and (b) is a graph showing the frequency characteristics of the gain of horizontally polarized waves of an antenna in a state where the antenna element and the helical element are arranged parallel to the horizontal plane and in a state where the antenna element and the helical element are inclined obliquely with respect to the horizontal plane. This is an exploded perspective view of an antenna device according to Modification 1, as seen from above. This is a perspective view of an antenna device according to Modification 1, as seen from below. 25A and 25B are bottom views of a case according to Modification 1 with the base removed; and a cross-sectional view taken along the line B-B of FIG. 25A with the base and case attached to each other. (a) is a perspective view of a grommet according to Modification 1, and (b) is a perspective view of a grommet according to Modification 1 with one extraction hole blocked by a resin pin; and (b) is an exploded perspective view of an antenna device according to Modification 2. (a) is a bottom view of a case of an antenna device according to Modification 3 with the base removed; and (b) is a graph showing frequency characteristics of gain of a harmonic antenna according to Modification 3 and a two-resonance antenna according to an embodiment; and (b) is a graph showing frequency characteristics of VSWR of a harmonic antenna according to Modification 3 and a two-resonance antenna according to an embodiment. (b) is a Smith chart of a harmonic antenna according to Modification 3 and a two-resonance antenna according to an embodiment.

[0009] Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings. In all the drawings, like components are designated by like reference numerals, and descriptions thereof will be omitted as appropriate.

[0010] Fig. 1A is a side view of a vehicle 1 equipped with an antenna device 10 according to an embodiment. Fig. 1B is an enlarged side view of the rear part of the vehicle 1 equipped with the antenna device 10 according to an embodiment.

[0011] To explain the directions, the X direction, Y direction, and Z direction are defined. The Z direction is the up-down direction of the antenna device 10. The X direction is one of the directions perpendicular to the Z direction. The X direction is the front-to-rear direction of the antenna device 10. The Y direction is a direction perpendicular to the Z direction and the X direction. The Y direction is the left-to-right direction of the antenna device 10. In each figure related to the embodiment, the directions indicated by the arrows of the X axis, Y axis, and Z axis are defined as the forward direction, left direction, and upward direction, respectively. In FIG. 1(b), the X direction and Z direction are inclined downward with respect to the forward direction of the vehicle 1. In FIG. 1(b), the Y direction is approximately parallel to the left-to-right direction of the vehicle 1.

[0012] In some of the drawings, the arrows of the X-axis, Y-axis, or Z-axis are shown as white circles with black dots. The white circles with black dots indicate that the tips of the arrows of the X-axis, Y-axis, or Z-axis are pointing towards the front of the paper. In some of the drawings, the arrows of the X-axis, Y-axis, or Z-axis are shown as white circles with Xs. The white circles with Xs indicate that the tips of the arrows of the X-axis, Y-axis, or Z-axis are pointing towards the back of the paper.

[0013] Hereinafter, as needed, the side indicated by the X-axis arrow will be referred to as the +X side, and the side opposite the side indicated by the X-axis arrow will be referred to as the -X side. Hereinafter, as needed, the side indicated by the Y-axis arrow will be referred to as the +Y side, and the side opposite the side indicated by the Y-axis arrow will be referred to as the -Y side. Hereinafter, as needed, the side indicated by the Z-axis arrow will be referred to as the +Z side, and the side opposite the side indicated by the Z-axis arrow will be referred to as the -Z side.

[0014] A vehicle 1 according to the embodiment will be described with reference to FIGS. 1(a) and 1(b).

[0015] In the examples shown in Figures 1(a) and 1(b), the vehicle 1 is an automobile. However, the vehicle 1 may be a motorcycle instead of an automobile. Unless otherwise specified, the following description will be given assuming that the vehicle 1 is an automobile. As shown in Figure 1(a), the vehicle 1 includes a body 2, a rear window 4, and a rear spoiler 6. The body 2 includes a conductor such as sheet metal. When viewed from the Y direction, the rear window 4 extends diagonally downward and rearward from the rear end of the roof 2a of the body 2. The rear spoiler 6 is made of, for example, resin, is hollow inside, and is attached to the rear end of the roof 2a.

[0016] 1(b), the antenna device 10 is mounted in a hollow portion inside the rear spoiler 6. When viewed from the X direction, the antenna device 10 may be located on the left or right side of the rear spoiler 6 in the Y direction, or may be located in approximately the center of the rear spoiler 6 in the Y direction.

[0017] As shown in FIG. 1B , a gap exists between the antenna device 10 and the inner wall of the rear spoiler 6, and the antenna device 10 and the body 2 are spaced apart from each other. The gap between the antenna device 10 and the body 2 and the gap between the antenna device 10 and the inner wall of the rear spoiler 6 provide space for water droplets and air to flow, thereby preventing puddles and condensation from forming around the antenna device 10. In recent years, in consideration of the reduction in the height and design of the body 2, the antenna device 10 is sometimes disposed above the body 2 so that the antenna device 10 and the body 2 overlap each other in the Z direction. When the antenna device 10 is disposed above the body 2, separating an antenna 12 (described later) of the antenna device 10 from the body 2 by, for example, 5 mm or more can suppress electrical coupling between the antenna 12 of the antenna device 10 and the body 2, thereby suppressing a decrease in gain of the antenna device 10 due to electrical coupling between the antenna 12 of the antenna device 10 and the body 2. The rear window 4 may also be part of the body 2. Even when the rear window 4 is part of the body 2, the gap between the antenna device 10 and the body 2 and the gap between the antenna device 10 and the inner wall of the rear spoiler 6 ensure space for water droplets and air to flow, thereby preventing puddles and condensation from forming around the antenna device 10.

[0018] In the example shown in FIGS. 1A and 1B , the antenna device 10 is installed at the rear of the vehicle 1. However, the installation location of the antenna device 10 is not limited to the rear of the vehicle 1. The antenna device 10 may be installed at at least one of the front, rear, left, right, bottom, and interior of the vehicle 1. The antenna device 10 may be mounted in these portions of the vehicle 1, for example, in a cavity of the vehicle 1. Mounting the antenna device 10 in a cavity of the vehicle 1 can make the antenna device 10 less noticeable. The antenna device 10 may be mounted in a cavity of the vehicle 1 covered with a resin material, for example, in a spoiler. When the antenna device 10 is installed at the bottom of the vehicle 1, the antenna device 10 may be mounted in a cavity inside the chassis of the vehicle 1, for example. When the antenna device 10 is installed inside the vehicle 1, the antenna device 10 may be mounted in a cavity inside the passenger compartment of the vehicle 1, for example. When the antenna device 10 is installed at least one of the front, rear, left, right, bottom, and interior of the vehicle 1, the antenna device 10 can be made less noticeable than when the antenna device 10 is installed on the upper part of the vehicle 1, such as on the upper side of the roof 2a. For example, the antenna device 10 may be installed on the front fender 2b, rear fender 2c, or pillar 2d of the body 2, or may be installed along a reinforcement extending in the left-right direction of the vehicle 1 at the front, rear, or center of the vehicle 1. The antenna device 10 may also be installed on the bumper or side mirror of the vehicle 1. When the vehicle 1 is a motorcycle (bike), the antenna device 10 may be mounted in a hollow space within a side box of the motorcycle.

[0019] A single antenna device 10 may be mounted on the vehicle 1, or multiple antenna devices 10 may be mounted on the vehicle 1, for example, as a diversity antenna. For example, multiple antenna devices 10 may be arranged in opposing positions in the left-right direction of the vehicle 1, multiple antenna devices 10 may be arranged in opposing positions in the front-rear direction of the vehicle 1, or multiple antenna devices 10 may be arranged in both directions. When multiple antenna devices 10 are mounted, the media supported by each antenna device 10 may be the same or different. For example, when multiple antenna devices 10 are used as an FM (Frequency Modulation) diversity antenna, one antenna device 10 may be used as an FM main antenna or FM1 antenna, and another antenna device 10 may be used as an FM sub-antenna or FM2 antenna.

[0020] Fig. 2 is an exploded perspective view of the antenna device 10 according to the embodiment. Fig. 3 is a perspective view of the antenna device 10 according to the embodiment with the base 100 removed, viewed from the opposite side to Fig. 2 .

[0021] The antenna device 10 will be described with reference to FIGS.

[0022] As shown in FIG. 2, the antenna device 10 according to the embodiment includes a base 100, a case 200, a pad 300, an antenna element 400, a bobbin 500, a helical element 600, a substrate 700, and two cables 800.

[0023] As shown in FIG. 2 , the base 100 has a generally plate-like shape that is generally perpendicular to the Z direction. The base 100 is formed of an insulating material such as resin. The base 100 has a base main body 110 and a pair of support protrusions 120. When viewed from the Z direction, the base main body 110 has a generally rectangular shape with a pair of short sides generally parallel to the X direction and a pair of long sides generally parallel to the Y direction, with the corners on the +X side and the -Y side missing. In other words, when viewed from the Z direction, the base main body 110 has a generally pentagonal shape. The pair of support protrusions 120 are provided at both ends of the base main body 110 in the Y direction. When viewed from the Z direction, a through-hole 122 that penetrates each support protrusion 120 in the Z direction is provided at the approximately center of each support protrusion 120. The antenna device 10 and the rear spoiler 6 shown in Fig. 1(b) are attached to each other by fastening each support protrusion 120 and the rear spoiler 6 shown in Fig. 1(b) to each other with a fastening member such as a screw that passes through the through-hole 122 of each support protrusion 120. However, the antenna device 10 and the rear spoiler 6 may be attached to each other via a structure other than the pair of support protrusions 120. The number of support protrusions 120 provided on the base 100 does not have to be two, and may be only one, or may be three or more.

[0024] For example, bolts and nuts may be used to attach the support protrusion 120. For example, with the head of the bolt positioned on one of the +Z and −Z sides of the support protrusion 120, the bolt shaft may pass through the through-hole 122 of the support protrusion 120 from one of the +Z and −Z sides of the support protrusion 120, and a nut may be provided on the other of the +Z and −Z sides of the support protrusion 120. In the example shown in FIG. 2 , both Z-direction surfaces of the support protrusion 120 are substantially flat surfaces that are substantially perpendicular to the Z direction. Therefore, surfaces for installing the bolt head and nut can be secured on both Z-direction surfaces of the support protrusion 120. Attachment of the support protrusion 120 is not limited to the example using bolts and nuts. The support protrusion 120 may also be fixed by, for example, a clip.

[0025] As shown in Figure 2, the case 200 is located on the +Z side of the +Z side surface of the base main body 110. The case 200 is formed, for example, from a resin that is radio wave transparent. The case 200 has a case plate 210 and a case side wall 220. The case plate 210 has a generally plate shape that is generally perpendicular to the Z direction. When viewed from the Z direction, the shape of the base main body 110 and the shape of the case plate 210 are generally identical. The case side wall 220 extends from the entire periphery of the case plate 210 in the Z direction toward the -Z side.

[0026] With the base body 110 and the case sidewall 220 attached to each other, the base 100 and the case 200 form a housing that forms a housing space that houses the antenna element 400, the bobbin 500, the helical element 600, the substrate 700, and parts of the two cables 800. The base 100 and the case 200 are attached to each other by engaging a plurality of locking pieces 130 provided on the base body 110 with a plurality of case grooves 222 provided on the case sidewall 220, and by fastening the base body 110 and the case sidewall 220 with a plurality of base mounting screws 112.

[0027] As shown in FIG. 2 , the multiple locking pieces 130 extend from the outer periphery of the base body 110 in the Z direction toward the +Z side. A locking hole 132 is provided at the end on the +Z side of each locking piece 130. As shown in FIGS. 2 and 3 , the outer periphery of the case side wall 220 in the Z direction defines multiple case grooves 222. The multiple locking ribs 230 are provided inside the multiple case grooves 222 on the outer periphery of the case side wall 220 in the Z direction. The base body 110 and the case side wall 220 are attached to each other with each of the multiple locking pieces 130 fitting into each of the multiple case grooves 222 and each of the multiple locking ribs 230 fitting into each of the multiple locking holes 132. By each of the multiple locking pieces 130 fitting into each of the multiple case grooves 222, the multiple locking pieces 130 and each of the multiple case grooves 222 are positioned relative to each other. Each of the plurality of locking ribs 230 fits into each of the plurality of locking holes 132, thereby locking the locking holes 132 and the locking ribs 230 to each other. The number and positions of the plurality of locking pieces 130 and the plurality of locking ribs 230 are not limited to the examples shown in FIGS. 2 and 3 .

[0028] Each of the multiple locking pieces 130 and each of the multiple locking ribs 230 are locked to one another by snap-fitting. Each locking piece 130 has a shape that is approximately parallel to the Z direction when no external force perpendicular to the Z direction is applied to the +Z side end of each locking piece 130. When an external force is applied to the +Z side end of each locking piece 130 away from the base body 110, each locking piece 130 can bend with its +Z side end tilted away from the base body 110. In the snap-fitting process, an external force is first applied to the +Z side end of each locking piece 130 away from the base body 110, bending each locking piece 130 so that its +Z side end tilts away from the base body 110. Next, with each locking piece 130 in its bent state, each locking piece 130 covers each case groove 222. Next, the external force on the +Z side end of each locking piece 130 is released, causing each locking piece 130 to return to its original shape substantially parallel to the Z direction. As each locking piece 130 returns to its original shape, each locking piece 130 fits into each case groove 222, and each locking rib 230 fits into each locking hole 132. Thus, each locking hole 132 and each locking rib 230 are locked to each other. However, the base body 110 and the case side wall 220 may be attached to each other by a locking mechanism other than a snap fit of the multiple locking pieces 130 and multiple locking ribs 230.

[0029] 2 and 3, the plurality of base mounting screws 112 penetrate the outer periphery of the base body 110 in the Z direction from the -Z side surface of the base body 110 and are screwed into the -Z side ends of the plurality of screw bosses 226 provided on the inner surface perpendicular to the Z direction of the case side wall 220. The base body 110 and the case side wall 220 are fastened together by the screwing of each base mounting screw 112. The number and positions of the base mounting screws 112 are not limited to the example shown in FIG.

[0030] As shown in FIG. 2 , the multiple locking pieces 130 and multiple base mounting screws 112 are alternately provided around the Z direction of the base body 110 on both sides of the base body 110 in the X direction and on the -Y side. Therefore, deformation and damage to the base 100 and case 200 caused by screwing in each base mounting screw 112 can be suppressed compared to when multiple locking pieces 130 are not provided and multiple base mounting screws 112 are provided around the Z direction periphery of the base body 110 at the intervals shown in FIG. 2 . Furthermore, the number of multiple base mounting screws 112 can be reduced compared to when multiple base mounting screws 112 are provided instead of multiple locking pieces 130 at the positions where multiple locking pieces 130 are provided in FIG. 2 . However, the base 100 and case 200 may be attached to each other only by screwing in multiple base mounting screws 112 without providing locking pieces 130.

[0031] The attachment of the base 100 and the case 200 is not limited to screwing with the multiple base attachment screws 112. For example, the base 100 and the case 200 may be attached to each other by a method other than screwing, such as welding using ultrasonic waves or a laser. By using welding, the screw bosses 226 can be eliminated, and the manufacturing process of the antenna device 10 can be simplified.

[0032] As shown in Fig. 3, the pad 300 is embedded in a recessed groove 224 provided on the end surface on the -Z side of the case side wall 220. The pad 300 is made of an elastic material such as elastomer or rubber. As shown in Fig. 2, a base rib 140 is provided on the +Z side surface of the base body 110 in a portion that overlaps with the pad 300 in the Z direction. When the base 100 and the case 200 are attached to each other, the pad 300 is compressed in the Z direction by the tip end of the base rib 140 on the +Z side and the end portion on the -Z side of the case side wall 220. By compressing the pad 300 in the Z direction, the area surrounded by the pad 300 is waterproofed when viewed from the Z direction.

[0033] As shown in FIG. 3 , the pad 300 is located closer to the inside of the case 200 than the screw bosses 226 around the multiple screw bosses 226. The multiple screw bosses 226 are provided so as not to protrude from the outer surface of the case side wall 220 perpendicular to the Z direction. Therefore, the antenna device 10 can be made smaller than when the multiple screw bosses 226 protrude from the outer surface of the case side wall 220 perpendicular to the Z direction. Furthermore, when viewed from the Z direction, the pad 300 is curved in a substantially arc shape toward the inside of the case 200 around the multiple screw bosses 226 so as to avoid the multiple screw bosses 226. Therefore, the waterproofness of the pad 300 can be maintained better than when the pad 300 is bent in a substantially polygonal shape, such as a substantially square shape, toward the inside of the case 200 around the multiple screw bosses 226 so as to avoid the multiple screw bosses 226 as viewed from the Z direction. Furthermore, a larger storage space can be secured between the base 100 and the case 200 than if the pad 300 were bent in a generally polygonal shape around the screw bosses 226. However, the screw bosses 226 may protrude from the outer surface of the case side wall 220 perpendicular to the Z direction, or the pad 300 may be bent in a generally polygonal shape, such as a generally rectangular shape, around the screw bosses 226 toward the inside of the case 200 so as to avoid the screw bosses 226, as viewed from the Z direction. As shown in FIG. 3 , the outer edge of the antenna element 400 is cut out in a generally arc-shaped shape around the screw bosses 226 so as to avoid the screw bosses 226, as viewed from the Z direction. By shaping the outer edge of the antenna element 400 to fit the arc-shaped screw bosses 226, the area of ​​the antenna element 400 can be maximized in a limited space.

[0034] The antenna element 400, the helical element 600, and the substrate 700 are electrically connected in series. The antenna element 400 and the helical element 600 constitute an antenna 12 compatible with the AM (Amplitude Modulation) frequency band and the FM (Frequency Modulation) frequency band. The electrical capacitance of the helical element 600 is less than the electrical capacitance of the antenna element 400. The helical element 600 is provided to compensate for the insufficient antenna length of the antenna element 400 in order to support the FM frequency band. The antenna element 400 also operates as a capacitance antenna to support the AM frequency band. The substrate 700 has an amplifier circuit that amplifies signals received by the antenna element 400 and the helical element 600.

[0035] Hereinafter, unless otherwise specified, the antenna 12 according to the embodiment will be described as being compatible with the AM frequency band and the FM frequency band. However, the matters described about the antenna 12 according to the embodiment can also be applied to an antenna compatible with only one of the AM frequency band and the FM frequency band, or an antenna compatible with a frequency band other than the AM frequency band and the FM frequency band. Examples of frequency bands other than the AM frequency band and the FM frequency band include the DAB (Digital Audio Broadcasting) frequency band and the DTV (Digital Television) frequency band.

[0036] As shown in FIG. 3 , the antenna element 400 is located on the −Z side of the −Z side surface of approximately half of the −X side of the case plate 210. The antenna element 400 has a main body 410, multiple bent portions 420, and an extended portion 430. The main body 410, multiple bent portions 420, and extended portion 430 are an integral metal plate. However, the antenna element 400 may be a conductor pattern provided on a substrate such as a printed circuit board (PCB). Alternatively, the antenna element 400 may be a film. The film is formed, for example, by a flexible substrate such as a flexible printed circuit board (FPC). The antenna element 400 may have a meander structure to ensure the electrical length of the antenna element 400.

[0037] The main body 410 has a generally plate-like shape that is generally perpendicular to the Z direction. When viewed from the Z direction, the main body 410 has a generally rectangular shape with a pair of short sides that are generally parallel to the X direction and a pair of long sides that are generally parallel to the Y direction. As shown in FIG. 3 , a plurality of first case ribs 242 are provided on the -Z side surface of approximately half of the -X side of the case plate 210. The plurality of first case ribs 242 penetrate the main body 410 in the Z direction. The main body 410 is positioned by the plurality of first case ribs 242 penetrating the main body 410 in the Z direction. The plurality of first case ribs 242 are aligned in the Y direction. However, the number and positions of the plurality of first case ribs 242 are not limited to the example shown in FIG. 3 .

[0038] As shown in FIG. 2 , multiple base pillars 150 are provided on the +Z side surface of the base main body 110. In the example shown in FIG. 2 , two base pillars 150 are aligned in the Y direction. However, the number and positions of the multiple base pillars 150 are not limited to the example shown in FIG. 2 . The +Z side surface of each base pillar 150 defines a communication hole that communicates with the storage space formed inside the base 100 and the case 200. When the base 100 and the case 200 are attached to each other, the +Z side surface of each base pillar 150 is covered with a vent filter 152. Each vent filter 152 is, for example, a porous film. Therefore, even if air in the storage space of the base 100 and the case 200 expands, for example, under high temperature conditions, the air can escape to the outside through the communication hole on the +Z side surface of each base pillar 150, thereby suppressing deformation of the base 100 and the case 200. Furthermore, the provision of the vent filter 152 can prevent foreign matter such as dust and water from outside the base 100 and the case 200 from entering the housing space of the base 100 and the case 200 .

[0039] Each bent portion 420 has a generally plate-like shape that is generally perpendicular to the X direction. The main body 410 and each bent portion 420 are bent at a generally right angle along the -Z side surface of the case plate 210 and the +X side inner peripheral surface of the portion of the case sidewall 220 provided on the -X side edge of the case plate 210. As will be described in detail later, providing each bent portion 420 on the main body 410 can improve the characteristics of the antenna 12. For example, in the AM frequency band, the gain of the antenna 12 can be improved. Furthermore, in the FM frequency band, the bandwidth available for the antenna 12 in the FM frequency band can be widened. Furthermore, the dimension of the antenna 12 in the X direction can be reduced compared to when each bent portion 420 is not bent in the Z direction relative to the main body 410.

[0040] As shown in FIG. 3 , a plurality of second case ribs 244 are provided on the −Z side surface of the case plate 210 at approximately the center in the X direction. The plurality of second case ribs 244 are aligned along the +X side edge of the main body 410. A plurality of third case ribs 246 are provided on the +X side inner peripheral surface of the portion of the case side wall 220 provided on the −X side edge of the case plate 210. The plurality of third case ribs 246 are aligned along the −Z side edges of the plurality of bent portions 420. When the case 200 and the antenna element 400 are attached to each other, the plurality of second case ribs 244 hold the +X side edge of the main body 410, and the plurality of third case ribs 246 hold the −Z side edges of each bent portion 420. Therefore, the case 200 can hold the antenna element 400 while rattle of the antenna element 400 is suppressed by the plurality of second case ribs 244 and the plurality of third case ribs 246. Therefore, it is possible to prevent the antenna element 400 from falling off due to vibration or impact of the vehicle 1, and also to suppress the generation of abnormal noise due to vibration or impact of the vehicle 1.

[0041] As shown in FIG. 3 , the lead-out portion 430 is formed by partially cutting and raising the end portion on the +Y side of the main body portion 410. When viewed from the Y direction, the lead-out portion 430 is generally L-shaped, including a portion extending in the Z direction and a portion extending in the X direction. The lead-out portion 430 may have a shape other than a generally L-shape. However, the lead-out portion 430 does not necessarily have to be provided. Alternatively, for example, a conductor welded to the end portion on the +Y side of the main body portion 410 may be provided instead of the lead-out portion 430.

[0042] As shown in FIG. 3 , the bobbin 500 and the helical element 600 are positioned on the −Z side of the −Z side surface of the +Y side end of the case plate 210, with the helical element 600 held by the bobbin 500. The bobbin 500 serves as a holder for the helical element 600. The helical element 600 includes a helical conductor 610, a first lead conductor 620, and a second lead conductor 630. The helical conductor 610, the first lead conductor 620, and the second lead conductor 630 are integral conductors such as metal wires. The helical element 600 is a tuning coil for the FM frequency band. However, the antenna device 10 may include an antenna element as a tuning element having the same function as a tuning coil for the FM frequency band instead of the helical element 600. For example, a conductor pattern provided on a substrate such as a PCB may be provided instead of the helical element 600.

[0043] As shown in FIGS. 2 and 3 , the helical conductor 610 is wound around the outer peripheral surface of the bobbin 500 in the X direction, except for both ends of the bobbin 500 in the X direction. The bobbin 500 is made of, for example, resin. The bobbin 500 extends in the X direction. The outer peripheral surface of the bobbin 500 in the X direction, except for both ends of the bobbin 500 in the X direction, defines a groove in which the helical conductor 610 is embedded. As shown in FIG. 2 , a plurality of first guide ribs 512 are provided on the +Z side surface of the bobbin 500. The plurality of first guide ribs 512 are arranged at approximately equal intervals in the X direction. As shown in FIG. 3 , a plurality of second guide ribs 514 are provided on the −Z side surface of the bobbin 500. The plurality of second guide ribs 514 are arranged at approximately equal intervals in the X direction. The helical conductor 610 is guided by a groove on the outer peripheral surface of the bobbin 500 in the X direction, a plurality of first guide ribs 512 and a plurality of second guide ribs 514 .

[0044] 2 and 3, the helical conductor 610 extends helically in a direction substantially perpendicular to the height direction in the Z direction of the case 200. In the example shown in Fig. 2 and 3, the helical conductor 610 extends helically in the X direction. Therefore, compared to a case in which the helical conductor 610 extends helically in the Z direction, the antenna device 10 can be made lower in height in the Z direction. However, the helical conductor 610 may extend helically in the Z direction.

[0045] 2 and 3, the main body 410 and the helical conductor 610 extend in different directions from each other when viewed from the Z direction. In the example shown in FIGS. 2 and 3, the Y direction, which is the extension direction of the main body 410, and the X direction, which is the extension direction of the helical conductor 610, are approximately perpendicular to each other. Therefore, compared to a case in which the main body 410 and the helical conductor 610 extend in the same direction when viewed from the Z direction, the dimension of the antenna 12 in the same direction can be reduced. However, the main body 410 and the helical conductor 610 may also extend in the same direction when viewed from the Z direction.

[0046] As shown in FIG. 3 , the first extraction conductor 620 is extracted from the +X-side end of the helical conductor 610 toward the substrate 700. Details of the substrate 700 will be described later. One end of the first extraction conductor 620 on the side where the substrate 700 is located and the +X-side and +Y-side corners of the -Z-side surface of the substrate 700 are electrically connected to each other by solder or other bonding. However, this end of the first extraction conductor 620 and the substrate 700 may also be electrically connected to each other via a conductor component. As shown in FIG. 3 and FIGS. 4 to 6 , which will be described later, a first retaining rib 522 is provided on the -Z-side surface of the +X-side end of the bobbin 500. When viewed from the X-direction, the first retaining rib 522 is generally T-shaped, including a portion extending in the Z-direction and a portion extending in the Y-direction. A portion of the first extraction conductor 620 is wrapped around the Z-direction-extending portion of the first retaining rib 522 in the Z-direction. The part of the first lead conductor 620 is prevented from slipping out of the first retaining rib 522 toward the −Z side by the part of the first retaining rib 522 extending in the Y direction.

[0047] As shown in FIG. 3 , the second lead conductor 630 is led out from the −X-side end of the helical conductor 610 toward the lead portion 430. One end of the second lead conductor 630 on the side where the lead portion 430 is located and a portion of the lead portion 430 extending in the X-direction are electrically connected to each other by solder or other bonding. As shown in FIG. 3 and FIGS. 4 to 6 described below, a second retaining rib 524 is provided on the −X-side surface of the −X-side end of the bobbin 500. When viewed from the Y-direction, the second retaining rib 524 has a substantially T-shape including a portion extending in the X-direction and a portion extending in the Z-direction. A portion of the second lead conductor 630 is wrapped around the portion of the second retaining rib 524 extending in the X-direction. The portion of the first lead conductor 620 is prevented from slipping out of the second retaining rib 524 toward the −X-direction by the portion of the second retaining rib 524 extending in the Z-direction.

[0048] As shown in FIG. 3 , the substrate 700 is located on the −Z side of the −Z-side surface of approximately one-quarter of the +X and +Y sides of the case plate 210. The substrate 700 is, for example, a printed circuit board (PCB). As shown in FIGS. 2 and 3 , the substrate 700 has a generally plate shape that is generally perpendicular to the Z direction. When viewed from the Z direction, the substrate 700 has a generally rectangular shape with a pair of short sides that are generally parallel to the X direction and a pair of long sides that are generally parallel to the Y direction. However, the shape of the substrate 700 is not limited to the example shown in FIGS. 2 and 3 . As described above, one end of the first extraction conductor 620 on the side where the substrate 700 is located and the +X and +Y corners of the −Z side surface of the substrate 700 are electrically connected to each other by joining with solder or the like. Therefore, the +X and +Y corners of the −Z side surface of the substrate 700 form the power supply section 710. However, the power supply section 710 may be located at a location other than the corner on the +X and +Y sides of the −Z side surface of the substrate 700 .

[0049] As shown in FIG. 3 , the case plate 210 and the board 700 are attached to each other by two board mounting screws 702. The two board mounting screws 702 are provided at diagonal corners of the board 700. In the example shown in FIG. 3 , the two board mounting screws 702 penetrate from the −Z side of the board 700 through the corners on the +X and −Y sides and the corners on the −X and +Y sides of the board 700, and are inserted into the case plate 210. Therefore, the board 700 can be held in the case 200 by the board mounting screws 702. Furthermore, the board mounting screws 702 can prevent the board 700 from falling toward the base body 110. However, the number and positions of the board mounting screws 702 are not limited to the examples shown in FIGS. 2 and 3 .

[0050] As shown in Fig. 3, the antenna element 400, the bobbin 500, the helical element 600, and the substrate 700 are located on approximately the same plane that is approximately perpendicular to the height direction of the case 200 in the Z direction. Therefore, the antenna device 10 can be made lower in height in the Z direction compared to when the antenna element 400, the bobbin 500, the helical element 600, and the substrate 700 overlap one another in the Z direction. The arrangement of the antenna element 400, the bobbin 500, the helical element 600, and the substrate 700 is not limited to the example shown in Fig. 3. For example, the antenna element 400 and any of the bobbin 500, the helical element 600, and the substrate 700 may be located on approximately the same plane that is approximately perpendicular to the Z direction, with the bobbin 500, the helical element 600, and the substrate 700 at least partially overlapping one another in the Z direction. Alternatively, the antenna element 400, the bobbin 500 and the helical element 600 may be at least partially overlapping in the Z direction, and the substrate 700 and any one of the antenna element 400, the bobbin 500 and the helical element 600 may be positioned on approximately the same plane that is approximately perpendicular to the Z direction.

[0051] As shown in FIG. 3 , two cables 800 are pulled out from the −Y side edge of the substrate 700 to the outside of the case 200 via the notched corners on the +X and −Y sides of the case sidewall 220. The ends of each cable 800 on the side where the substrate 700 is located and the substrate 700 are electrically connected to each other by soldering or other bonding. A hole for fitting a grommet 810 is provided in the notched corner on the +X and −Y sides of the case sidewall 220. Fitting the grommet 810 into the hole in the case sidewall 220 prevents water from entering the storage space inside the base 100 and the case 200 through a gap between the inner circumferential surface of the hole in the case sidewall 220 and the outer circumferential surface of the grommet 810. The two cables 800 pass through the grommet 810 and are pulled out to the outside of the case 200. By passing the two cables 800 through the grommet 810, the portion of the case side wall 220 through which the two cables 800 pass can be waterproofed by the grommet 810.

[0052] In the embodiment, one cable 800 is a coaxial cable and functions as a signal line. The other cable 800 is a cable having twisted wires such as copper wires and functions as a power line. In the embodiment, outside the base 100 and the case 200, a ground cable (not shown) branches off from the outer conductor of the cable 800 operating as a coaxial cable, and the ground cable and the body 2 are electrically connected to each other. For example, the ground cable may have a crimp terminal that can be bolted, and the ground cable and the body 2 may be electrically connected to each other via the crimp terminal. When multiple cables 800 operating as coaxial cables are used, the multiple outer conductors of the multiple cables 800 may be fastened together to the crimp terminal. Alternatively, multiple crimp terminals may be fastened together at the same position on the body 2 when the multiple outer conductors of the multiple cables 800 operating as coaxial cables are fastened to multiple crimp terminals.

[0053] FIG. 4 is a perspective view of the case 200 and the bobbin 500 according to the embodiment. FIG. 5 is a bottom view of the case 200 and the bobbin 500 according to the embodiment. FIG. 6 is a cross-sectional view taken along the line A-A in FIG. 5. FIG. 7 is a perspective view of a portion of the case 200 according to the embodiment. FIG. 8 is a perspective view of a portion of the case 200 according to the embodiment, from a different perspective than FIG. 7. For the sake of explanation, the base 100, the pad 300, the antenna element 400, the helical element 600, the substrate 700, and the two cables 800 have been removed from FIGS. 4 to 6. For the sake of explanation, the base 100, the pad 300, the antenna element 400, the bobbin 500, the helical element 600, the substrate 700, and the two cables 800 have been removed from FIGS. 7 and 8.

[0054] The case 200 and the bobbin 500 according to the embodiment will be described with reference to FIGS. 4 to 6, and if necessary, with reference to FIGS.

[0055] As shown in FIGS. 4 to 6 , the +X side end and the −X side end of the bobbin 500 are respectively locked to the case plate 210 by a first locking claw 251 and a second locking claw 252. The first locking claw 251 includes a first beam 251a and a first hook 251b. The first beam 251a extends from the −Z side surface of the case plate 210 toward the −Z side. The first hook 251b is provided on the −X side surface of the −Z side end of the first beam 251a. The second locking claw 252 includes a second beam 252a and a second hook 252b. The second beam 252a extends from the −Z side surface of the case plate 210 toward the −Z side. The second hook 252b is provided on the +X side surface of the −Z side end of the second beam 252a.

[0056] The first locking claw 251 serves as a locking portion that locks the +X side end of the bobbin 500 by snap-fitting. The first beam 251a is shaped approximately parallel to the Z direction when no external force perpendicular to the Z direction is applied to the first hook 251b. When an external force toward the +X side is applied to the first hook 251b, the first beam 251a can be deflected with the -Z side end of the first beam 251a tilted toward the +X side. Therefore, compared to when the first beam 251a is not deflected, the first locking claw 251 makes it easier to assemble the +X side end of the bobbin 500. As shown in FIGS. 4 to 6 , the -Z side surface of the +X side end of the bobbin 500 includes a first flat surface 501. The first flat surface 501 is a flat surface that is approximately perpendicular to the Z direction. As shown in Figure 6, when the first beam 251a is shaped approximately parallel to the Z direction and the first hook 251b covers the first flat surface 501, the first locking claw 251 locks the end of the bobbin 500 on the +X side.

[0057] 7, the corners between the +X side surface of the +Z side end of the first beam 251a and the -Z side surface of the case plate 210 are rounded. The corners between both Y-direction surfaces of the +Z side end of the first beam 251a and the -Z side surface of the case plate 210 are rounded. Therefore, compared to when these corners are simply right angles, stress concentration at the +Z side end of the first beam 251a when the first beam 251a is in a deflected state can be alleviated. However, the above-mentioned corners may also be simply right angles.

[0058] As shown in Fig. 5, the first locking claw 251 locks the approximate center in the Y direction of the +X side end of the bobbin 500. Therefore, compared to when the first locking claw 251 locks the +Y or -Y side portion of the +X side end of the bobbin 500, the +X side end of the bobbin 500 can be more stably locked. However, the portion of the bobbin 500 that is locked by the first locking claw 251 is not limited to the example shown in Fig. 5. For example, the first locking claw 251 may lock a portion of the bobbin 500 other than the +X side end.

[0059] The second beam 252a serves as a locking portion that locks the -X side end of the bobbin 500. Even if an external force is applied to the second hook 252b in the X direction, the second beam 252a does not bend and can maintain a shape that is approximately parallel to the Z direction. Therefore, the bobbin 500 can be stably held by the second beam 252a compared to when the second beam 252a bends. Furthermore, the second beam 252a can be manufactured more easily compared to when a flexible beam is manufactured. Furthermore, the second locking claw 252 can be designed more easily compared to when a design is required to allow the second beam 252a to bend by a snap fit. However, the second beam 252a may also lock the -X side end of the bobbin 500 by a snap fit. As shown in FIGS. 4 to 6 , the -Z side surface of the -X side end of the bobbin 500 includes a second flat surface 502. The second flat surface 502 is a flat surface that is approximately perpendicular to the Z direction. As shown in Figure 6, when the second beam 252a is shaped approximately parallel to the Z direction and the second hook 252b covers the second flat surface 502, the second locking claw 252 locks the end of the bobbin 500 on the -X side.

[0060] As shown in FIG. 5 , the second locking claw 252 locks the +Y side portion of the −X side end of the bobbin 500. The second locking rib 524 is provided on the −Y side portion of the −X side end of the bobbin 500. Therefore, the second locking claw 252 and the second locking rib 524 are offset from each other in the Y direction. This prevents the second locking claw 252 and the second locking rib 524 from interfering with each other. However, the portion of the bobbin 500 locked by the second locking claw 252 is not limited to the example shown in FIG. 5 . For example, the second locking claw 252 may lock a portion of the bobbin 500 other than the −X side end. If the second locking rib 524 is unnecessary and not provided, or if the second locking rib 524 is provided in a position other than that shown in FIG. 5 , the second locking claw 252 may be provided in approximately the center in the Y direction or on the −Y side of the −X side end of the bobbin 500.

[0061] In the embodiment, the case 200 and the bobbin 500 are attached to each other by the first locking claw 251 locking the +X side end of the bobbin 500 and the second locking claw 252 locking the −X side end of the bobbin 500. Therefore, the case 200 and the bobbin 500 can be attached to each other without the need for fastening members such as screws. Therefore, compared to when fastening members are used, the bobbin 500 can be easily assembled to the antenna device 10, and the bobbin 500 can be assembled to the antenna device 10 at low cost. Furthermore, compared to when fastening members are required, the absence of fastening members makes it easier to ensure space for positioning the antenna element 400, the bobbin 500, the helical element 600, and the substrate 700 on approximately the same plane that is approximately perpendicular to the height direction of the case 200 in the Z direction.

[0062] In the embodiment, multiple portions of the bobbin 500 are locked by the first locking claw 251 locking the +X-side end of the bobbin 500 and the second locking claw 252 locking the −X-side end of the bobbin 500. Therefore, the bobbin 500 can be locked more stably than when only a single portion of the bobbin 500 is locked. Furthermore, when both X-direction end portions of the bobbin 500 are locked, interference between the locking portion that locks the bobbin 500 and the helical conductor 610 can be reduced compared to when a portion between the X-direction end portions of the bobbin 500 is locked. However, the multiple portions of the bobbin 500 locked by the locking portion are not limited to the X-direction end portions of the bobbin 500. For example, the locking portion may lock the approximate center of the bobbin 500 in the X-direction instead of one of the X-direction end portions of the bobbin 500. Alternatively, the locking portions may lock both ends of the bobbin 500 in the X direction and the approximate center of the bobbin 500 in the X direction.

[0063] As shown in FIGS. 4, 5, 7, and 8, a first locking pillar 253 and a second locking pillar 254 are located on the +Y and -Y sides, respectively, of the +X-side end of the bobbin 500. The first locking pillar 253 and the second locking pillar 254 extend from the -Z-side surface of the case plate 210 toward the -Z side. The first locking pillar 253 and the second locking pillar 254 face each other in the Y direction. As shown in FIG. 7, a first pressing rib 253a is provided on the -Y-side surface of the first locking pillar 253. As shown in FIG. 8, a second pressing rib 254a is provided on the +Y-side surface of the second locking pillar 254. As shown in FIG. 5, the +Y-side surface of the +X-side end of the bobbin 500 includes a third flat surface 503. 4 and 5, the −Y side surface of the +X side end of the bobbin 500 includes a fourth flat surface 504. As shown in Fig. 5, the third flat surface 503 and the fourth flat surface 504 are flat surfaces that are approximately perpendicular to the Y direction.

[0064] When the case 200 and the bobbin 500 are not attached to each other, the Y-direction dimension of the gap between the first pressing rib 253a and the second pressing rib 254a is less than the Y-direction dimension of the +X-side end of the bobbin 500. Therefore, when the case 200 and the bobbin 500 are attached to each other, the first pressing rib 253a presses the third flat surface 503, and the second pressing rib 254a presses the fourth flat surface 504. Therefore, when the case 200 and the bobbin 500 are attached to each other, the +X-side end of the bobbin 500 is press-fitted into the gap between the first pressing rib 253a and the second pressing rib 254a. Therefore, the first locking pillar 253 and the second locking pillar 254 serve as locking portions that lock the +X-side end of the bobbin 500 by press-fitting. By press-fitting the first locking pillar 253 and the second locking pillar 254, rattle of the bobbin 500 can be suppressed, and noise from the bobbin 500 due to vibration or impact of the vehicle 1 can be suppressed. The portion of the bobbin 500 that is locked by press-fitting is not limited to the end of the bobbin 500 on the +X side. Alternatively, no portion of the bobbin 500 may be locked by press-fitting.

[0065] The outer peripheral surface pressed by the first pressing rib 253a of the bobbin 500 is not a curved surface but a third flat surface 503. Therefore, compared to when the outer peripheral surface pressed by the first pressing rib 253a of the bobbin 500 is a curved surface, the first pressing rib 253a can more stably press the bobbin 500. The outer peripheral surface pressed by the second pressing rib 254a of the bobbin 500 is not a curved surface but a fourth flat surface 504. Therefore, compared to when the outer peripheral surface pressed by the second pressing rib 254a of the bobbin 500 is a curved surface, the second pressing rib 254a can more stably press the bobbin 500. However, at least one of the outer peripheral surface pressed by the first pressing rib 253a of the bobbin 500 and the outer peripheral surface pressed by the second pressing rib 254a of the bobbin 500 may be a curved surface. For example, both the outer peripheral surface pressed by the first pressing rib 253a of the bobbin 500 and the outer peripheral surface pressed by the second pressing rib 254a of the bobbin 500 may be curved surfaces.

[0066] 4 and 5, a plurality of guide frames 255 are positioned between the first locking claw 251 and the second locking claw 252. Each guide frame 255 is provided on the -Z side surface of the case plate 210. As shown in FIG. 4, each guide frame 255 has a substantially semicircular frame shape when viewed from the X direction. When the case 200 and the bobbin 500 are attached, the bobbin 500 is guided by the plurality of guide frames 255. The number and positions of the guide frames 255 are not limited to the examples shown in FIGS. 4 to 8.

[0067] As shown in Figure 6, a bobbin rib 532 is provided on the +Z side surface of the +X side end of the bobbin 500. The -Z side surface of the case plate 210 and the +Z side surface of the bobbin rib 532 face each other. The bobbin rib 532 serves as a stopper that restricts movement of the bobbin 500 to the +Z side. Therefore, the bobbin rib 532 can suppress variation in the position of the bobbin 500 in the Z direction. However, the bobbin rib 532 does not have to be provided.

[0068] FIG. 9 is a diagram for explaining an example of a method for attaching the case 200 and the bobbin 500 according to the embodiment.

[0069] An example of a method for manufacturing the antenna device 10 will be described with reference to FIGS.

[0070] First, the case 200 and the antenna element 400 are attached to each other. As shown in FIG. 3 , when attaching the case 200 and the antenna element 400, the antenna element 400 is mounted on the -Z side of approximately half of the -X side of the case plate 210. When the antenna element 400 is mounted on the case plate 210, the main body 410 is positioned by the multiple first case ribs 242 penetrating through the main body 410. When the case 200 and the antenna element 400 are attached to each other, the multiple second case ribs 244 hold the +X side edge of the main body 410, and the multiple third case ribs 246 hold the -Z side edges of the multiple bent portions 420.

[0071] Next, the case 200 and the board 700 are attached to each other. To attach the case 200 and the board 700, first, grommets 810 are attached to the two cables 800. Next, the two cables 800 are inserted from the outside to the inside through the notched corners on the +X and -Y sides of the case side wall 220, and the grommets 810 attached to the cables 800 are then attached to the notched corners on the +X and -Y sides of the case side wall 220. Next, one end of the board 700 and one end of each of the two cables 800 are electrically connected to each other by soldering or other means. Next, the board 700 is positioned on the -Z side of the -Z side surface of approximately one-quarter of the +X and +Y sides of the case plate 210. Next, the case plate 210 and the board 700 are fastened to each other using a plurality of board mounting screws 702.

[0072] Next, the bobbin 500 and the helical element 600 are attached to each other. As shown in Figure 3, when attaching the bobbin 500 and the helical element 600, first, a portion of the second lead conductor 630 is wound in the X direction around the portion of the second retaining rib 524 extending in the X direction. Next, the helical conductor 610 is wound around the outer peripheral surface of the bobbin 500 in the X direction. Next, a portion of the first lead conductor 620 is wound in the Z direction around the portion of the first retaining rib 522 extending in the Z direction. By winding the helical conductor 610 around the bobbin 500 with the portion of the second lead conductor 630 already wound around the portion of the second retaining rib 524, the wound shape of the helical conductor 610 can be made less likely to collapse. When attaching the bobbin 500 and the helical element 600, a portion of the first lead conductor 620 may be pre-wound around the above-mentioned portion of the first stop rib 522 in the Z direction, and then the helical conductor 610 may be wound around the outer peripheral surface of the bobbin 500 in the X direction, and then a portion of the second lead conductor 630 may be wound around the above-mentioned portion of the second stop rib 524.

[0073] The bobbin 500 is hollow due to a through hole that penetrates the bobbin 500 in the X direction. The through hole of the bobbin 500 is, for example, approximately circular with a portion of its circumference missing. In one example of winding the helical conductor 610 around the bobbin 500, a core having approximately the same shape as the through hole of the bobbin 500 is inserted into the through hole of the bobbin 500, and the bobbin 500 is rotated in the X direction. When the through hole of the bobbin 500 is approximately circular with a portion of its circumference missing, it is easier to rotate the bobbin 500 in the X direction with a core inserted through the through hole of the bobbin 500, compared to when the through hole of the bobbin 500 is circular. However, the shape of the through hole of the bobbin 500 is not limited to an approximately circular shape with a portion of its circumference missing.

[0074] Next, as shown in Fig. 9, the case 200 and the bobbin 500 are attached to each other. In Fig. 9, the helical element 600 has been removed for the sake of explanation. However, in reality, the helical element 600 is already held by the bobbin 500. The +X side surface of the +X side end of the bobbin 500 includes a bobbin inclined surface 505. When viewed from the Y direction, the bobbin inclined surface 505 is inclined inward from the -Z side to the +Z side.

[0075] 9 , when attaching the case 200 and the bobbin 500, first, with the −X side end of the bobbin 500 tilted obliquely toward the +Z side relative to the +X side end of the bobbin 500, the first hook 251b and the bobbin inclined surface 505 are brought into contact with each other, and the second hook 252b and the second flat surface 502 are brought into contact with each other. When attaching the case 200 and the bobbin 500, the bobbin 500 can be guided by a plurality of guide frames 255. Next, with the first hook 251b and the bobbin inclined surface 505 in contact with each other and the second hook 252b and the second flat surface 502 in contact with each other, the +X side end of the bobbin 500 is rotated around the −X side end of the bobbin 500, and the +X side end of the bobbin 500 is pushed toward the +Z side.

[0076] Even when the +X side end of the bobbin 500 is pushed toward the +Z side with the second hook 252b and the second flat surface 502 in contact with each other, the second hook 252b does not bend and maintains a shape that is approximately parallel to the Z direction. In contrast, the first beam 251a is flexible. Therefore, when the +X side end of the bobbin 500 is pushed toward the +Z side with the first hook 251b and the bobbin inclined surface 505 in contact with each other, the first hook 251b receives an external force from the +X side end of the bobbin 500, and the first beam 251a can bend with the -Z side end of the first beam 251a tilted toward the +X side, as shown by the first locking claw 251 in dashed lines in FIG. 9 .

[0077] 9 , when the +X side end of the bobbin 500 is pushed toward the +Z side, the bobbin inclined surface 505 comes into contact with the first hook 251b. Therefore, compared to when a surface perpendicular to the extension direction of the bobbin 500 contacts the first hook 251b instead of the bobbin inclined surface 505, the +X side end of the bobbin 500 can be more easily slid relative to the first hook 251b, and the +X side end of the bobbin 500 can be more easily pushed toward the +Z side.

[0078] Next, the +X side end of the bobbin 500 is further pushed toward the +Z side. The +X side end of the bobbin 500 is pushed toward the +Z side until the first flat surface 501 is positioned on the +Z side relative to the first hook 251b. When the first flat surface 501 is positioned on the +Z side relative to the first hook 251b, the first hook 251b is no longer subjected to external force from the +X side end of the bobbin 500, and the first beam 251a returns to its original shape substantially parallel to the Z direction. As the first beam 251a returns to its original shape, the first flat surface 501 is covered by the first hook 251b. Therefore, the +X side end of the bobbin 500 is locked by the first locking claw 251. Furthermore, when the +X side end of the bobbin 500 is locked by the first locking claw 251, the +X side end of the bobbin 500 and the -X side end of the bobbin 500 are aligned in the X direction. With the +X side end of the bobbin 500 and the −X side end of the bobbin 500 aligned in the X direction, the second flat surface 502 is covered by the second hook 252 b. Therefore, the −X side end of the bobbin 500 is locked by the second locking claw 252.

[0079] When the +X side end of the bobbin 500 is locked by the first locking claw 251, the third flat surface 503 and the fourth flat surface 504 are pressed by the first pressing rib 253a and the second pressing rib 254a, respectively. When the third flat surface 503 and the fourth flat surface 504 are pressed by the first pressing rib 253a and the second pressing rib 254a, respectively, the +X side end of the bobbin 500 is press-fit into the gap between the first pressing rib 253a and the second pressing rib 254a. Therefore, when attaching the case 200 and the bobbin 500, the +X side end of the bobbin 500 can be rotated around the -X side end of the bobbin 500 in a state where the -X side end of the bobbin 500 is not press-fitted, and the +X side end of the bobbin 500 can be pressed toward the +Z side. Therefore, compared to when the -X side end of the bobbin 500 is press-fitted, by rotating the +X side end of the bobbin 500 around the -X side end of the bobbin 500, the bobbin 500 can be assembled more stably.

[0080] Next, one end of the first extraction conductor 620 on the side where the substrate 700 is located and the corners on the +X and +Y sides of the -Z side surface of the substrate 700 are electrically connected to each other by joining with solder or the like. Also, one end of the second extraction conductor 630 on the side where the extraction section 430 is located and the portion of the extraction section 430 extending in the X direction are electrically connected to each other by joining with solder or the like.

[0081] Next, the base 100 and the case 200 are attached to each other. In this embodiment, the antenna element 400, bobbin 500, helical element 600, substrate 700, two cables 800, and grommet 810 are pre-attached to the case 200, and then the case 200, antenna element 400, bobbin 500, helical element 600, substrate 700, two cables 800, and grommet 810 can be assembled to the antenna device 10. When attaching the base 100 and the case 200, first, the pad 300 is inserted into the recessed groove 224 provided on the end surface of the -Z side of the case side wall 220. The +Z side surface of each base pillar 150 is then covered with a vent filter 152. Next, the base body 110 and the case 200 are stacked on top of each other in the Z direction, and the multiple locking pieces 130 and the multiple locking ribs 230 are locked to each other. Next, the base body 110 and the case side wall 220 are fastened together by a plurality of base mounting screws 112. With the base 100 and the case 200 attached to each other, the pad 300 is compressed in the Z direction by the tip end of the base rib 140 on the +Z side and the end of the case side wall 220 on the −Z side.

[0082] In this manner, the antenna device 10 is manufactured. The order of the steps in the manufacturing method of the antenna device 10 is not limited to the order described above. For example, the case 200 and the bobbin 500 may be attached to each other in a state where the bobbin 500 and the helical element 600 are attached to each other, and then the case 200 and the substrate 700 may be attached to each other.

[0083] In the embodiment, a gap is ensured between the coil wires constituting helical element 600 by winding helical element 600 around bobbin 500. However, helical element 600 does not have to be wound around bobbin 500. For example, helical element 600 may be wound in a state where the constituent coil wires are in close contact with each other (closely wound state). For example, helical element 600 may be fixed by a positioning component such as substrate 700 or a resin holder (not shown).

[0084] Fig. 10 is a schematic diagram showing the current distribution in the antenna 12 according to the embodiment. Fig. 11 is a schematic diagram showing the current distribution in an antenna 12Z having an antenna element 400Z different from the helical element 600 according to the embodiment.

[0085] 10 and 11 , the ground GND is, for example, a conductor such as the body located around the antenna of the vehicle 1. If the antenna is installed in a cavity inside the rear spoiler 6 shown in FIG. 1( b), the ground GND is, for example, a metal part of the rear gate of the vehicle 1.

[0086] FIG. 10 schematically illustrates a first current distribution CD1 extending from the +Y end of the antenna element 400 to the −Y end of the antenna element 400, and a second current distribution CD2 extending from the +X end of the helical element 600 to the −X end of the helical element 600. As shown in FIG. 10, the +Y end of the antenna element 400 and the −X end of the helical element 600 are electrically connected to each other. The +X end of the helical element 600 and the power feed 710 are electrically connected to each other. The width of the first current distribution CD1 in the X direction in FIG. 10 indicates the magnitude of the current density in the first current distribution CD1. The width of the second current distribution CD2 in the Y direction in FIG. 10 indicates the magnitude of the current density in the second current distribution CD2. The current densities in the first current distribution CD1 and the second current distribution CD2 decrease with increasing distance from the power feed 710 along the electrical path of the antenna 12 from the power feed 710 to the −Y end of the antenna element 400.

[0087] Helical element 600 extends the electrical length of antenna 12 compared to antenna element 400. Therefore, as shown schematically by first current distribution CD1 and second current distribution CD2 in Fig. 10 , the current density decreases over a shorter physical length from the +X side end of helical element 600 to the -X side end of helical element 600 than from the +Y side end of antenna element 400 to the -Y side end of antenna element 400. Therefore, the current distribution generated in antenna 12 can be concentrated in helical element 600 rather than in antenna element 400.

[0088] The antenna according to the example shown in FIG. 11 is similar to the antenna according to the embodiment shown in FIG. 10 , except for the following points. The antenna according to the example shown in FIG. 11 does not have an antenna element corresponding to the helical element 600 according to the embodiment, but has an antenna element 400Z. The antenna element 400Z is made of sheet metal. When viewed from the Z direction, the antenna element 400Z extends in a meandering shape. One end of the antenna element 400Z and the power feed portion 710 are electrically connected to each other. FIG. 10 schematically illustrates a current distribution CDZ from the +X side end of the antenna element 400Z to the −X side end of the antenna element 400Z. The width of the current distribution CDZ in the Y direction in FIG. 11 indicates the magnitude of the current density in the current distribution CDZ. The current density in the current distribution CDZ decreases from the +X side end of the antenna element 400Z toward the −X side of the antenna element 400Z.

[0089] The antenna 12 according to the embodiment shown in FIG. 10 will be compared with the antenna 12Z according to the example shown in FIG.

[0090] As shown in FIG. 11 , when the antenna 12Z does not include the helical element 600 but includes only the antenna element 400Z, a current distribution is likely to be generated throughout the antenna 12Z. When a current distribution is generated throughout the antenna 12Z, the antenna 12Z is ​​more likely to be electrically coupled to surrounding conductors, making the impedance of the antenna 12Z more likely to become unstable. When the impedance of the antenna 12Z becomes unstable, it may be difficult to improve the gain of the antenna 12Z. In contrast, as shown in FIG. 10 , in the embodiment, the current distribution generated in the antenna 12 can be concentrated toward the helical element 600 rather than the antenna element 400. Therefore, compared to when the antenna 12 does not include the helical element 600, the antenna 12 is less likely to be electrically coupled to surrounding conductors, improving the gain of the antenna device 10.

[0091] 11 , the physical length of the antenna element 400Z required to obtain the desired electrical length of the antenna 12Z may be relatively long, resulting in a relatively large antenna 12Z. In contrast, in the embodiment, the physical length of the antenna element 400 required to obtain the desired electrical length of the antenna 12 can be shortened by the amount of the physical length shortened by the helical element 600. Therefore, in the embodiment, the antenna 12 can be made smaller in size compared to the example shown in FIG.

[0092] An example of the conductor located around the antenna 12 is a conductor provided in the vehicle 1. Examples of the conductor provided in the vehicle 1 include a rear window defogger, a glass antenna, or another antenna housed in the case 200. In the embodiment, compared to the example shown in Fig. 11 , the antenna 12 can be made less likely to be electrically coupled to the conductor, and the degree of freedom in arranging the antenna 12 and the conductor can be improved.

[0093] 10 and 11 , conductor 8 extends in the Y direction as an example of a conductor provided in vehicle 1. As shown in Fig. 10 , by arranging helical element 600 in a direction perpendicular to conductor 8, the range of the portions where conductor 8 and helical element 600 are close to each other can be made smaller than when helical element 600 is arranged in a direction parallel to conductor 8, making it more difficult for conductor 8 and helical element 600 to be electrically coupled. However, even when helical element 600 is arranged in a direction parallel to conductor 8, the gain of antenna 12 according to the embodiment can be made higher than the gain of antenna 12Z according to the example shown in Fig. 11 .

[0094] FIG. 12 is a graph showing the influence of the surrounding conductors on an antenna having the helical element 600 according to the embodiment, and the influence of the surrounding conductors on an antenna not having the helical element 600 according to the embodiment.

[0095] In the graph shown in Fig. 12, the antenna plotted as "with helical element" has antenna element 400 and helical element 600, similar to the embodiment shown in Fig. 10. A substrate 700 is electrically connected to helical element 600. In the graph shown in Fig. 12, the antenna plotted as "without helical element" has antenna element 400Z without helical element 600 according to the embodiment, similar to the example shown in Fig. 11. A substrate is electrically connected to antenna element 400Z.

[0096] In the graph shown in Figure 12, for the antenna plotted as "with helical element," the antenna element 400, helical element 600, and substrate 700 are entirely covered by a metal plate substantially perpendicular to the Z direction. For the antenna plotted as "without helical element," the antenna element 400Z and the substrate are entirely covered by a metal plate substantially perpendicular to the Z direction. The horizontal axis represents the distance (unit: mm) in the Z direction between the antenna and the metal plate. The vertical axis represents the change Δf0 (unit: MHz) in the resonant frequency of the antenna. The change Δf0 represents the change from the resonant frequency of the antenna when no metal plate is provided.

[0097] 12, at any distance between the antenna and the metal plate, the change Δf0 of the antenna with helical element 600 is less than the change Δf0 of the antenna without helical element 600. Therefore, it can be said that helical element 600 can suppress the influence of the conductors surrounding the antenna.

[0098] FIG. 13 is a graph showing the frequency characteristics of the FM band gain of an antenna having the bent portion 420 according to the embodiment and the FM band gain of an antenna not having the bent portion 420 according to the embodiment.

[0099] In the graph shown in Figure 13, the antenna plotted as "with bent portion" has an antenna element 400 and a helical element 600, similar to the antenna shown in Figure 3. In the antenna plotted as "with bent portion," the antenna element 400 includes a main body 410 and a bent portion 420, similar to the antenna element 400 shown in Figure 3. In the graph shown in Figure 13, the antenna plotted as "without bent portion" is similar to the antenna plotted as "with bent portion," except that the antenna element 400 does not include the bent portion 420. The horizontal axis represents frequency (unit: MHz). The vertical axis represents FM band gain (unit: dBi).

[0100] 13, the FM band gain of the antenna with the bent portion 420 is higher in the FM frequency band of 76 MHz to 108 MHz than the FM band gain of the antenna without the bent portion 420. Therefore, it can be said that the bent portion 420 increases the capacity of the antenna and widens the bandwidth that can be used in the FM frequency band of the antenna.

[0101] FIG. 14 is a model diagram for explaining the operating principle of the antenna 12 according to the embodiment.

[0102] In the model shown in FIG. 14 , the body 2 is ground GND. As described with reference to FIG. 3 , the power supply unit 710 is provided on the substrate 700. Therefore, the body 2 and the power supply unit 710 are spaced apart from each other. In the model shown in FIG. 14 , the tip of the antenna 12 is spaced apart from the body 2 by the entire length h of the antenna 12. The power supply unit 710 is spaced apart from the body 2 by a distance h1. When the body 2 and the power supply unit 710 are spaced apart from each other, the ratio h1 / h of the distance h1 from the ground GND to the power supply unit 710 to the entire length h of the antenna 12 from the ground GND to the tip of the antenna 12 is, for example, 0.3 or greater. The dotted line on the right side of the antenna 12 schematically shows the current distribution in the antenna 12.

[0103] FIG. 15 is a graph showing the frequency characteristics of the gain of the antenna 12 when the ratio h1 / h (h: total length of the antenna 12 from ground GND to the tip of the antenna 12, h1: distance from ground GND to the power supply 710) in the model of FIG. 14 is varied. The horizontal axis of the graph in FIG. 15 represents frequency (unit: MHz), and the vertical axis represents gain (unit: dBi). The solid line plot represents the gain when h1 / h = 0, the dashed line plot represents the gain when h1 / h = 0.3, the dotted line plot represents the gain when h1 / h = 0.6, and the dash-dotted line plot represents the gain when h1 / h = 0.9. In FIG. 15 , the total length h is fixed at a constant value, and the distance h1 is varied to vary the ratio h1 / h. h1 / h = 0 means that the power supply 710 is located above ground GND.

[0104] 15, the larger the ratio h1 / h, the narrower the bandwidth of the antenna 12. The reason why the bandwidth of the antenna 12 narrows is that as the ratio h1 / h increases and the feeding part 710 becomes farther away from the body 2, the apparent inductance of the antenna 12 increases, as shown in FIG.

[0105] Fig. 16 is a graph showing the peak gain and average gain of the antenna 12 when the ratio h1 / h (h: total length of the antenna 12 from ground GND to the tip of the antenna 12, h1: distance from ground GND to the power supply 710) in the model of Fig. 14 is varied. The horizontal axis of the graph in Fig. 16 represents the ratio h1 / h, and the vertical axis represents the gain (unit: dBi). The peak gain and average gain of the antenna 12 in Fig. 16 are the peak gain and average gain of the antenna 12 from 100 MHz to 300 MHz.

[0106] As shown in FIG. 16 , when h1 / h = 0.9, the peak gain and average gain of the antenna 12 are lower than when h1 / h = 0, 0.3, and 0.6. The reason for the decrease in the peak gain and average gain of the antenna 12 is as follows. In the model shown in FIG. 14 , the total length h of the antenna 12 is constant, so the resonant frequency of the antenna 12 is constant regardless of the ratio h1 / h. However, as shown in FIG. 14 , the current distribution of the antenna 12 becomes smaller toward the tip of the antenna 12. As the ratio h1 / h increases and the feed portion 710 approaches the tip of the antenna 12, the feed portion 710 is located at a position where the current distribution is smaller. Therefore, as the ratio h1 / h increases, the peak gain and average gain of the antenna 12 may decrease.

[0107] 17 is a diagram showing a principle model of the antenna 12 according to the embodiment. Hereinafter, unless otherwise specified, for the sake of explanation, the antenna 12 will be described as operating as a DAB band antenna. The matters described for the antenna 12 operating as a DAB band antenna are also applicable to the antenna 12 operating as an FM band antenna.

[0108] In the model shown in FIG. 17 , similar to the model shown in FIG. 14 , the body 2 and the power feed portion 710 are positioned apart from each other. The body 2 and the antenna element 400 are also positioned apart from each other. In the electrical path, the helical element 600 is positioned between the power feed portion 710 and the antenna element 400 and is electrically connected to the power feed portion 710 and the antenna element 400. As described with reference to FIGS. 14 , 15 , and 16 , if the body 2 and the power feed portion 710 are positioned apart from each other, the bandwidth of the antenna 12 may be narrowed. However, in this embodiment, by using the helical element 600, the bandwidth of the antenna 12 can be widened and the difference between the maximum and minimum values ​​of the voltage standing wave ratio (VSWR) in the desired frequency band of the antenna 12 can be reduced. The reason for this will be explained using the model shown in FIG. 17 .

[0109] In the model shown in Figure 17, the dashed line marked "1 / 4λ" on the left side of the antenna 12 indicates the current distribution occurring at resonance at a first frequency where the electrical length between the body 2 and the tip of the antenna element 400 is 1 / 4λ. Hereinafter, unless otherwise specified, the "1 / 4λ current distribution" refers to the current distribution occurring at resonance at a first frequency where the electrical length between the body 2 and the tip of the antenna element 400 is 1 / 4λ. In the model shown in Figure 17, the dashed line marked "1 / 4λ'" on the right side of the antenna 12 indicates the current distribution occurring at resonance at a second frequency where the electrical length between the body 2 and the end of the helical element 600 electrically connected to the feed 710 is 1 / 4λ'. Hereinafter, unless otherwise specified, the "1 / 4λ' current distribution" refers to the current distribution occurring at resonance at a second frequency where the electrical length between the body 2 and the end of the helical element 600 electrically connected to the feed 710 is 1 / 4λ'. The first frequency is, for example, 145 MHz, and the second frequency is, for example, 220 MHz. Hereinafter, unless otherwise specified, λ and λ' indicate the wavelength of the frequency, and the numbers before λ and λ' indicate coefficients. Specifically, 1 / 4λ means a quarter wavelength of the first frequency.

[0110] 17, current flows not only through antenna element 400 and helical element 600, but also through the outer conductor of cable 800 between body 2 and power feed portion 710 and the ground of substrate 700. Therefore, a portion of the 1 / 4λ current distribution and a portion of the 1 / 4λ' current distribution exist between body 2 and power feed portion 710.

[0111] 17 , helical element 600 functions as a parallel resonant circuit of a coil and a capacitor. Therefore, antenna 12 is configured to resonate at two frequencies: a first frequency at which the electrical length between body 2 and the tip of antenna element 400 is ¼λ, and a second frequency at which the electrical length between body 2 and the end of helical element 600 electrically connected to feeder 710 is ¼λ'. In other words, antenna 12 can function as both a first monopole antenna at which the electrical length between body 2 and the tip of antenna element 400 is ¼λ, and a second monopole antenna at which the electrical length between body 2 and the end of helical element 600 electrically connected to feeder 710 is ¼λ'. Therefore, by resonating antenna 12 at multiple frequencies, the bandwidth of antenna 12 can be widened and the difference (deviation) between the maximum and minimum VSWR values ​​in the desired frequency band of antenna 12 can be reduced. Furthermore, for example, the antenna device 10 may include an LNA (Low Noise Amplifier) ​​described below. Impedance matching between the antenna 12 and the LNA can be easily performed even for an antenna 12 with a small VSWR deviation, and wideband frequency characteristics can be achieved.

[0112] As can be seen from the model shown in FIG. 17 , in the embodiment, a loading element such as the helical element 600 enables the antenna 12 to resonate at multiple frequencies. Therefore, even if the body 2 and the power supply 710 are spaced apart, the bandwidth of the antenna 12 can be widened, and the difference between the maximum and minimum VSWR values ​​in the desired frequency band of the antenna 12 can be reduced. If the antenna 12 were made of only a metal plate or rod, like a conventional antenna, without the helical element 600, the antenna 12 would resonate only at a single frequency corresponding to ¼λ and would not be able to resonate at multiple frequencies. However, in the embodiment, a loading element such as the helical element 600 enables the antenna 12 to resonate at multiple frequencies, widening the bandwidth of the antenna 12 and reducing the difference between the maximum and minimum VSWR values ​​in the desired frequency band of the antenna 12.

[0113] 17 , it can be said that by using a loading element such as helical element 600, the bandwidth of antenna 12 can be widened and the difference between the maximum and minimum VSWR values ​​in the desired frequency band of antenna 12 can be reduced even if the ratio of the length of cable 800 to the total length of antenna 12 is increased. Therefore, it can be said that by using a loading element such as helical element 600, the bandwidth of antenna 12 can be widened and the difference between the maximum and minimum VSWR values ​​in the desired frequency band of antenna 12 can be reduced while the effective length of antenna element 400 and helical element 600 of antenna 12 is shortened.

[0114] FIG. 18(a) is a graph showing the frequency characteristics of gain from 100 MHz to 300 MHz for an antenna that resonates at two frequencies and an antenna that resonates at one frequency. FIG. 18(b) is a graph showing the frequency characteristics of gain from 174 MHz to 240 MHz for an antenna that resonates at two frequencies and an antenna that resonates at one frequency. FIG. 19 is a graph showing the frequency characteristics of voltage standing wave ratio (VSWR) from 174 MHz to 240 MHz for an antenna that resonates at two frequencies and an antenna that resonates at one frequency. The horizontal axis of the graphs in FIGS. 18(a), 18(b), and 19 represents frequency (unit: MHz). The vertical axis of the graphs in FIGS. 18(a) and 18(b) represents gain (unit: dBi). The vertical axis of the graph in FIG. 19 represents VSWR. In the graphs shown in Figures 18(a) and 18(b), the solid line plots show the gain of an antenna that resonates at two frequencies, the dashed line plots show the gain of an antenna that resonates at one frequency, and the dotted line plots show the performance required of the antenna in the DAB band of 174 MHz to 240 MHz. In the graph shown in Figure 19, the solid line plots show the VSWR of an antenna that resonates at two frequencies, and the dashed line plots show the VSWR of an antenna that resonates at one frequency.

[0115] Hereinafter, unless otherwise specified, a dual-resonance antenna refers to an antenna that resonates at two frequencies, and a single-resonance antenna refers to an antenna that resonates at one frequency. Hereinafter, unless otherwise specified, the DAB band refers to the band from 174 MHz to 240 MHz.

[0116] As can be seen from the graph shown in Figure 18(a), the single-resonance antenna has a resonant frequency near 200 MHz, while the dual-resonance antenna has two resonant frequencies near 175 MHz and 250 MHz. Therefore, the dual-resonance antenna can increase the minimum gain value in the DAB band compared to the single-resonance antenna. Furthermore, the dual-resonance antenna can reduce the gain deviation in the DAB band compared to the single-resonance antenna. For example, when combining an antenna and an LNA (Low Noise Amplifier), the smaller the gain deviation in the DAB band, the easier it is to design the LNA. In the graphs shown in Figures 18(a) and 18(b), the minimum gain value in the DAB band is -29.2 dBi for the single-resonance antenna and -23.8 dBi for the dual-resonance antenna. The gain deviation in the DAB band is 20.2 dB for the single-resonance antenna and 9.2 dB for the dual-resonance antenna.

[0117] As can be seen from the graph shown in Figure 19, the two-resonance antenna can reduce the maximum VSWR value in the DAB band compared to the one-resonance antenna. Therefore, the two-resonance antenna can suppress the reduction in antenna gain due to mismatch loss compared to the one-resonance antenna. In the graph shown in Figure 19, the maximum VSWR value in the DAB band is 1204 for the one-resonance antenna and 138 for the two-resonance antenna.

[0118] An example of setting two resonant frequencies of a dual-resonant antenna will be described. ｃ In this case, the electrical length of the first resonance frequency, which is one of the two resonance frequencies, is set to 3 / 8λ. ｃ More than 2 / 8λ ｃ or less, and the electrical length of the other of the two resonant frequencies, the second resonant frequency, is set to 2 / 8λ ｃ More than 1 / 8λ ｃBy providing a loading element such as helical element 600 so that the electrical lengths of the first resonant frequency and the second resonant frequency are set within the above-mentioned ranges, it is possible to increase the minimum value of the gain in the usable band, reduce the deviation of the gain in the usable band, and reduce the maximum value of the VSWR in the usable band, as described with reference to Figures 18(a), 18(b), and 19.

[0119] When the antenna 12 according to the embodiment is used as a single-resonance antenna, the electrical length from the body 2 to the tip of the antenna 12 may be shorter than the electrical length from the body 2 to the tip of the antenna 12 when the antenna 12 is used as a two-resonance antenna. By shortening the length from the body 2 to the substrate 700, i.e., the length of the cable 800, the body 2 and the power supply unit 710 are brought closer to each other, thereby reducing the apparent inductance of the antenna 12. This allows the antenna 12 to have a broadband. For example, the length of the cable 800 may be equal to or shorter than ¼ of the wavelength of the operating frequency of the antenna 12.

[0120] 20(a) to 20(d) are diagrams showing various examples of the loading element 13 mounted on the antenna 12. FIG.

[0121] In the embodiment, a helical element 600 is used as a tuning element that varies the electrical length of the antenna 12. However, the tuning element may be any loading element as long as it can vary the electrical length of the antenna 12. Examples of loading elements include positive or negative reactance elements. Inserting a positive or negative reactance element can make the electrical length variable.

[0122] For example, the loading element 13 may be an inductor 13a as shown in FIG. 20(a), a capacitor 13b as shown in FIG. 20(b), or a diode 13c as shown in FIG. 20(c). One or more loading elements 13 shown in FIGS. 20(a) to 20(c) may be electrically connected to the antenna element 400. Alternatively, as shown in FIG. 20(d), the antenna element 400 may be divided into a first segment 402 and a second segment 404, and the first inductor 131d, the first segment 402, the second inductor 132d, and the second segment 404 may be connected in series in this order. The first inductor 131d and the second inductor 132d may be capacitors or diodes as shown in FIG. 20(b) or 20(c). The loading element 13 is not limited to the examples shown in Figures 20(a) to 20(d), and may be composed of, for example, copper wire, sheet metal, or a substrate pattern, or may be composed of electronic components such as passive elements and semiconductors.

[0123] The number of loading elements electrically connected to the antenna element 400 may be one or more. By using two or more loading elements, the antenna 12 can resonate at two or more frequencies. For example, it is possible to receive radio waves in the FM band and one of the DAB band and DTV band with one antenna 12.

[0124] Figure 21(a) is a schematic diagram showing a first example of the arrangement of the antenna element 400 and the helical element 600, and Figure 21(b) is a schematic diagram showing a second example of the arrangement of the antenna element 400 and the helical element 600.

[0125] In a first example shown in Figure 21(a), similar to the embodiment, the antenna element 400 and the helical element 600 are arranged substantially parallel to a horizontal plane perpendicular to the Z direction. Hereinafter, unless otherwise specified, the horizontal plane refers to a plane perpendicular to the Z direction. In a second example shown in Figure 21(b), the antenna element 400 and the helical element 600 are inclined obliquely with respect to the horizontal plane. As shown in Figure 21(b), by inclining the antenna element 400 and the helical element 600 obliquely with respect to the horizontal plane, the gain of the antenna 12 can be improved without changing the external shape of the antenna device 10.

[0126] 22(a) is a graph showing the frequency characteristics of the gain of vertically polarized waves of the antenna 12 when the antenna element 400 and the helical element 600 are arranged parallel to the horizontal plane and when the antenna element 400 and the helical element 600 are inclined obliquely with respect to the horizontal plane. FIG. 22(b) is a graph showing the frequency characteristics of the gain of horizontally polarized waves of the antenna 12 when the antenna element 400 and the helical element 600 are arranged parallel to the horizontal plane and when the antenna element 400 and the helical element 600 are inclined obliquely with respect to the horizontal plane. The horizontal axis of the graphs shown in FIGS. 22(a) and 22(b) represents frequency (unit: MHz), and the vertical axis represents gain (unit: dBi). The dashed line plot shows the gain of the antenna 12 when the antenna element 400 and the helical element 600 are arranged parallel to the horizontal plane, and the solid line plot shows the gain of the antenna 12 when the antenna element 400 and the helical element 600 are inclined obliquely with respect to the horizontal plane. Vertically polarized waves are waves polarized in the Z direction shown in FIG. 21, and horizontally polarized waves are waves polarized in a direction perpendicular to the Z direction shown in FIG.

[0127] Hereinafter, unless otherwise specified, horizontal arrangement means that the antenna element 400 and the helical element 600 are arranged parallel to the horizontal plane, and inclined arrangement means that the antenna element 400 and the helical element 600 are inclined with respect to the horizontal plane.

[0128] As shown in Figure 22(a), the gain of vertically polarized waves from approximately 200 MHz to approximately 260 MHz is higher in the tilted arrangement than in the horizontal arrangement. From 200 MHz to 300 MHz, the peak gain of vertically polarized waves in the horizontal arrangement is -22.4 dBi, and the average gain of vertically polarized waves in the horizontal arrangement is -25.5 dBi. From 200 MHz to 300 MHz, the peak gain of vertically polarized waves in the tilted arrangement is -21.7 dBi, and the average gain of vertically polarized waves in the tilted arrangement is -25.0 dBi. From the results shown in Figure 22(a), it can be said that the gain of vertically polarized waves of antenna 12 can be improved by tilting antenna element 400 and helical element 600 obliquely with respect to the horizontal plane.

[0129] As shown in Figure 22(b), the gain of horizontally polarized waves from approximately 200 MHz to approximately 260 MHz is higher in the tilted arrangement than in the horizontal arrangement. From 200 MHz to 300 MHz, the peak gain of horizontally polarized waves in the horizontal arrangement is -17.7 dBi, and the average gain of horizontally polarized waves in the horizontal arrangement is -21.0 dBi. From 200 MHz to 300 MHz, the peak gain of horizontally polarized waves in the tilted arrangement is -16.9 dBi, and the average gain of horizontally polarized waves in the tilted arrangement is -20.3 dBi. From the results shown in Figure 22(b), it can be said that the gain of horizontally polarized waves of antenna 12 can be improved by tilting antenna element 400 and helical element 600 obliquely with respect to the horizontal plane.

[0130] Fig. 23 is an exploded perspective view of the antenna device 10A according to Modification 1 as seen from above. Fig. 24 is a perspective view of the antenna device 10 according to Modification 1 as seen from below. Fig. 25 is a bottom view of the case 200A according to Modification 1 with the base 100A removed. Fig. 26 is a cross-sectional view taken along line B-B of Fig. 25 with the base 100A and the case 200A attached to each other. The antenna device 10A according to Modification 1 is similar to the antenna device 10 according to the embodiment, except for the following points.

[0131] As shown in FIG. 23 , the antenna device 10A according to the first modification includes a base 100A, a case 200A, a pad 300A, an antenna element 400A, a bobbin 500A, a helical element 600A, a substrate 700A, two cables 800A, and a grommet 810A, similar to the antenna device 10 according to the embodiment. The base 100A according to the first modification includes a base main body 110A, a pair of support protrusions 120A, multiple locking pieces 130A, and a base rib 140A, similar to the base 100 according to the embodiment. Similar to the locking pieces 130 according to the embodiment, each locking piece 130A according to the first modification includes a locking hole 132A. Similar to the case 200 according to the embodiment, the case 200A according to the first modification includes a case plate 210A and a case sidewall 220A. Similar to the case side wall 220 according to the embodiment, the case side wall 220A according to the first modification defines a plurality of case grooves 222A, and each case groove 222A is provided with a locking rib 230A. Similar to the base 100 and case 200 according to the embodiment, the base 100A and case 200A according to the first modification are fastened to each other by a plurality of base mounting screws 112A. Similar to the case plate 210 and board 700 according to the embodiment, the case plate 210A and board 700A according to the first modification are attached to each other by two board mounting screws 702A. Similar to the antenna element 400 and helical element 600 according to the embodiment, the antenna element 400A and helical element 600A according to the first modification constitute the antenna 12A.

[0132] As shown in FIGS. 23 and 24 , the base main body 110A is provided with a first vent hole 150A. As can be seen from FIG. 23 , the opening on the +Z side of the first vent hole 150A is covered by a first vent filter 152A. The case plate 210A is provided with a second vent hole 260A. The opening on the -Z side of the second vent hole 260A is covered by a second vent filter 262A. The first vent filter 152A and the second vent filter 262A are, for example, porous films. Therefore, even if the air in the storage space of the base 100A and the case 200A expands due to high temperatures, for example, the air can escape to the outside through the first vent hole 150A or the second vent hole 260A, thereby preventing deformation or damage to the base 100A and the case 200A. Furthermore, by providing the first vent filter 152A and the second vent filter 262A, foreign matter such as dust and water from outside the base 100A and the case 200A can be prevented from entering the storage space of the base 100A and the case 200A.

[0133] As can be seen from FIGS. 23 and 24 , the first vent hole 150A and the second vent hole 260A ensure that a vent hole is always present on either the +Z or −Z side of the antenna device 10A according to Variation 1. Therefore, even if the antenna device 10A is mounted upside down, one of the first vent hole 150A and the second vent hole 260A always faces downward. This allows the antenna device 10A to be positioned without considering the top, bottom, left, or right, thereby improving the layout of the antenna device 10A. The surfaces on which the multiple vent holes corresponding to the first vent hole 150A and the second vent hole 260A are provided are not limited to both Z-direction surfaces of the housing formed by the base 100A and the case 200A. The multiple vent holes may be provided on multiple different surfaces of the housing, including both Z-direction surfaces of the housing, such as the +Z and +X sides, or the −Z and +Y sides. By providing a plurality of vent holes on a plurality of different surfaces, even if a vent hole on one surface of the container is blocked, the air inside the container can be released to the outside through the vent holes on the other surfaces of the container.

[0134] As shown in FIG. 24 , the Z-direction periphery of the base body 110A defines a first recess 114A recessed toward the +Z side relative to the center of the base body 110A. As shown in FIG. 23 , the Z-direction periphery of the case plate 210A defines a second recess 212A recessed toward the -Z side relative to the center of the case plate 210A. The position where the first recess 114A of the base body 110A is provided and the position where the second recess 212A of the case plate 210A is provided overlap with the pad 300A in the Z direction. However, the pad 300A is not present at the corresponding positions on the base body 110A and the case plate 210A. Therefore, the first recess 114A can partially recess the base body 110A, and the second recess 212A can partially recess the case plate 210A. Therefore, the base 100A and the case 200A can be made smaller by the amount of the first recess 114A and the second recess 212A.

[0135] As shown in FIG. 23 , a concave surface 214A is provided on the +Z side surface of the case plate 210A, extending from approximately the center in the Y direction to the +Y end, in a region that does not overlap with the bobbin 500A, helical element 600A, and substrate 700A in the Z direction. On the −Z side of the concave surface 214A, there are no components that interfere with the concave surface 214A, such as the bobbin 500A, helical element 600A, and substrate 700A. Therefore, the concave surface 214A can be recessed toward the −Z side more than the region other than the concave surface 214A on the +Z side surface of the case plate 210A. Therefore, the size of the case 200A can be reduced by the amount of the concave surface 214A. In the example shown in FIG. 23 , the region of the +Z side surface of the case plate 210A that overlaps with the −Y side portion of the antenna element 400A in the Z direction also defines the concave surface 214A. The portion of case plate 210A that overlaps with this region in the Z direction does not have to define concave surface 214A. If this portion of case plate 210A does not define concave surface 214A, an element such as a bobbin, a helical element, or a substrate that constitutes an antenna different from antenna 12A may be disposed in place of the -Y side portion of antenna element 400A.

[0136] 23 , concave surface 214A and helical element 600A at least partially overlap each other in the Z direction. Therefore, helical element 600A can be positioned closer to the center of antenna device 10A in the Z direction by the amount of concave surface 214A. By positioning helical element 600A closer to the center of antenna device 10A in the Z direction, even if antenna device 10A is turned upside down, the difference in distance between body 2 and helical element 600A can be reduced, and a decrease in gain of antenna 12A can be suppressed.

[0137] As shown in FIG. 23 , the antenna element 400A according to the modified example does not have a bent portion corresponding to the bent portion 420 of the antenna element 400 according to the embodiment, and has a generally plate-like shape that is generally perpendicular to the Z direction. The absence of a bent portion allows the dimension of the antenna element 400A in the X direction to be reduced. If it is necessary to increase the capacity of the antenna element 400A, the antenna element 400A may be extended, for example, in the X direction or Y direction. When the antenna element 400A is extended, the antenna element 400A may extend in a meandering shape. The antenna element 400A may have a partial recess. By providing a partial recess, the strength of the antenna element 400A against external forces such as vibration and bending can be improved.

[0138] As can be seen from FIG. 23 , the −Z side surface of the case plate 210A and the +Z side surface of the antenna element 400A are adhered to each other via four pieces of double-sided tape 440A. The four pieces of double-sided tape 440A are pre-attached to the +Z side surface of the double-sided tape 440A. For example, the area where the double-sided tape 440A is attached on the +Z side surface of the antenna element 400A may be indicated by a groove marking. By attaching the double-sided tape 440A within the area indicated by the groove marking, the double-sided tape 440A can be attached to the desired position on the antenna element 400A. In the example shown in FIG. 23 , the double-sided tape 440A is provided on both ends of the antenna element 400A in the Y direction. This prevents both ends of the antenna element 400A in the Y direction from coming loose from the case plate 210A. Therefore, compared to when both ends of the antenna element 400A in the Y direction are free from the case plate 210A, it is possible to more easily suppress the generation of abnormal noise due to contact between the case plate 210A and the antenna element 400A. The area of ​​the +Z side surface of the antenna element 400A to which the double-sided tape 440A is attached is determined taking into consideration factors such as the weight of the antenna element 400A itself and vibrations and impacts applied to the antenna element 400A.

[0139] An example of mounting the case 200A and the antenna element 400A will be described. As shown in FIG. 25 , the -Y side end of the antenna element 400A has an end 401A, and the -Y side end of the case side wall 220A has a reference position 221A. When assembling the case 200A and the antenna element 400, first, the reference position 221A of the case side wall 220A and the end 401A of the antenna element 400A are assembled together. When viewed from the X direction, with the reference position 221A of the case side wall 220A and the end 401A of the antenna element 400A assembled together, the +Y side portion of the antenna element 400A is tilted away from the case plate 210A toward the -Z side. Next, as viewed from the X direction, the antenna element 400A is rotated around the reference position 221A of the case side wall 220A and the end 401A of the antenna element 400A so as to move the +Y side portion of the antenna element 400A toward the case plate 210A. Next, the case rib 242A provided on the +Y side portion of the case plate 210A is inserted into the assembly hole 403A provided on the +Y side portion of the antenna element 400A, and the case rib 242A and the assembly hole 403A are assembled to each other.

[0140] As shown in FIG. 25 , each cable 800A is inserted into a plurality of positioning grooves 270A provided on the -Z side of the case plate 210A. As shown in FIG. 26 , press-fit ribs 272A are provided on both inner surfaces of each positioning groove 270A in the X direction. Therefore, when each cable 800A is inserted into the positioning groove 270A, the cable 800A is press-fit into the area between the press-fit ribs 272A facing each other in the X direction. Therefore, the positioning grooves 270A can position the cable 800A, and the press-fit ribs 272A can hold the cable 800A. This can suppress noise and electrical performance changes due to rattle of the cable 800A. By suppressing rattle of the cable 800A, it is possible to restrict, for example, the distance between the antenna element 400A and the outer conductor of the cable 800A, and the distance between the outer conductor of the cable 800A and the outer conductor of another cable 800A.

[0141] As shown in Figures 23 and 26, the base main body 110A is provided with stopper ribs 116A that protrude toward the two cables 800A. In the example shown in Figure 23, three stopper ribs 116A are aligned in the Y direction. The distance between the +Z side end of the stopper rib 116A and the -Z side opening of each positioning groove 270A is less than the diameter of the cable 800A. This prevents the cable 800A from falling out of the positioning groove 270A. The base main body 110A and the stopper ribs 116A are molded as a single unit. This allows for a reduction in the number of parts required for the base 100A compared to when the base main body 110A and the stopper ribs 116A are separate components.

[0142] As can be seen from Figures 23 and 25, with grommet 810A positioned on the +Z side of pad 300A, pad 300A and grommet 810A are embedded in groove 224A provided on the -Z side end face of case sidewall 220. When base 100A and case 200A are attached to each other, pad 300A and grommet 810A are compressed in the Z direction by the +Z side tip of base rib 140A and the -Z side end of case sidewall 220A. As can be seen from Figure 23, two cables 800A are pulled out from two notches 228A provided in case sidewall 220A. When base 100A and case 200A are attached to each other, two cover ribs 142A provided on base main body 110A fit into the -Z side openings of the two notches 228A. By disposing grommet 810A inside base 100A and case 200A and covering grommet 810A with two cover ribs 142A, it is possible to prevent external forces from being directly applied to grommet 810A, thereby reducing deterioration of the waterproof function of grommet 810A. Furthermore, because grommet 810A is not exposed to the outside, this has an advantageous effect on the aging of grommet 810A and can improve dustproofness and waterproofness.

[0143] FIG. 27(a) is a perspective view of a grommet 810A according to the first modification, and FIG. 27(b) is a perspective view of the grommet 810A according to the first modification in a state in which one extraction hole 812A is blocked by a resin pin 820A.

[0144] In the example shown in FIG. 27( a), the grommet 810A defines three outlet holes 812A. In the example shown in FIG. 27( b), the central outlet hole 812A of the three outlet holes 812A is blocked by a resin pin 820A. Therefore, it is possible to accommodate the extraction of one to three cables by selecting which of the three outlet holes 812A to block with the resin pin 820A or by not using the resin pin 820A to extract any of the three outlet holes 812A. For example, in the example shown in FIG. 27( a), three cables can be extracted using the three outlet holes 812A. In the example shown in FIG. 27( b), two cables can be extracted using the two outlet holes 812A that are not blocked by the resin pin 820A.

[0145] 28 is an exploded perspective view of an antenna device 10B according to Modification 2. The antenna device 10B according to Modification 2 is similar to the antenna device 10 according to the embodiment, except for the following points.

[0146] The antenna device 10B according to the second modification includes a case 200B, a pad 300B, an AM / FM antenna element 400B1, a DAB antenna element 400B2, an AM / FM bobbin 500B1, a DAB bobbin 500B2, an AM / FM helical element 600B1, a DAB helical element 600B2, an AM / FM board 700B1, a DAB board 700B2, two AM / FM cables 800B1, and one DAB cable 800B2. The AM / FM antenna element 400B1 and the AM / FM helical element 600B1 constitute an AM / FM antenna 12B1 corresponding to the AM and FM frequency bands. The DAB antenna element 400B2 and the DAB helical element 600B2 constitute a DAB antenna 12B2 corresponding to the DAB frequency band. However, the matters described for the AM / FM antenna 12B1 according to the second modification are also applicable to antennas that support frequency bands other than the AM and FM frequency bands, and the matters described for the DAB antenna 12B2 according to the second modification are also applicable to antennas that support frequency bands other than the DAB frequency band.

[0147] Similar to the case 200 according to the embodiment, the case 200B according to the second modification has a case plate 210B and a case sidewall 220B. A pad 300B is embedded in a recessed groove 224B provided at the end of the case sidewall 220B on the -Z side. A grommet 810B is provided at the notched corners on the +X side and -Y side of the case sidewall 220B. Two AM / FM cables 800B1 and one DAB cable 800B2 pass through the grommet 810B and are pulled out toward the outside of the case 200B.

[0148] The AM / FM antenna 12B1 according to the second modification is similar to the antenna 12 according to the first embodiment, except that the total length in the Y direction of the AM / FM antenna element 400B1 according to the second modification is less than the total length in the Y direction of the antenna element 400 according to the first embodiment. The same matters as those described for the antenna 12 according to the first embodiment are applicable to the AM / FM antenna 12B1 according to the second modification.

[0149] The DAB antenna 12B2 according to the second modification is located on the -Y side relative to the AM / FM antenna 12B1 according to the second modification. In the second modification shown in FIG. 28, in order to secure space for arranging the DAB antenna element 400B2, the total length in the Y direction of the AM / FM antenna element 400B1 is less than the total length in the Y direction of the antenna element 400 according to the embodiment. The DAB antenna element 400B2 is provided in this space on the -Y side relative to the AM / FM antenna element 400B1. Two AM / FM cables 800B1 pass through the space on the +Z side of the DAB board 700B2. The same matters described for the antenna 12 according to the embodiment are applicable to the DAB antenna 12B2 according to the second modification.

[0150] In the antenna device 10B according to the second modification, an AM / FM antenna 12B1 and a DAB antenna 12B2, each corresponding to a different frequency band, are arranged in the Y direction. The antenna device may include three or more antennas corresponding to different frequency bands. The same matters described for the antenna 12 according to the embodiment are applicable to each antenna.

[0151] In the antenna device 10B according to the second modification, an AM / FM board 700B1 and two AM / FM cables 800B1 are provided for the AM / FM antenna 12B1, and a DAB board 700B2 and one DAB cable 800B2 are provided for the DAB antenna 12B2. In the second modification, one of the AM / FM cables 800B1 is a coaxial cable and functions as a signal line. The other AM / FM cable 800B1 is a cable having twisted wires such as copper wires and functions as a power line. In the second modification, the DAB cable 800B2 is a coaxial cable and functions as a signal line. The AM / FM board 700B1 and the DAB board 700B2 may be common to the AM / FM antenna 12B1 and the DAB antenna 12B2, and the AM / FM cable 800B1 operating as a coaxial cable and the DAB cable 800B2 operating as a coaxial cable may be common to the AM / FM antenna 12B1 and the DAB antenna 12B2.

[0152] 29 is a bottom view of the case 200C of the antenna device 10C according to Modification 3 with the base removed. The antenna device 10C according to Modification 3 is similar to the antenna device 10 according to the embodiment, except for the following points.

[0153] The antenna 12C of the antenna device 10C according to the third modification does not include a helical element equivalent to the helical element 600 according to the first embodiment. The antenna device 10C according to the third modification includes an antenna element 400C, a substrate 700C, and two cables 800C. The antenna element 400C and the two cables 800C are electrically connected to each other via the substrate 700C. The antenna 12C according to the third modification is a harmonic antenna using the antenna element 400C and the two cables 800C, thereby achieving a wideband antenna gain. A harmonic refers to a frequency component that is an integer multiple of the fundamental wave (first resonant frequency). For example, a frequency component three times the fundamental wave is called a "third harmonic," and a frequency component five times the fundamental wave is called a "fifth harmonic." An antenna that radiates at a frequency that resonates with a harmonic is called a harmonic antenna. The antenna 12C resonates over the entire length of the antenna element 400C and the cable 800C. By removing the helical element 600, the antenna 12C resonates at an nth harmonic (n is an integer greater than or equal to 2) without being limited to a desired frequency band. This generates multiple resonant frequencies within the band, thereby achieving a wideband antenna gain. Unlike the two-resonance antenna according to the embodiment, the harmonic antenna according to the third modification has a first resonant frequency lower than the used band. That is, the antenna device 10C according to the third modification intentionally resonates at a frequency lower than the desired frequency band. The antenna element 400C may be disposed outside the case 200C rather than inside the case 200C. Even when the antenna element 400C is disposed outside the case 200C, the antenna 12C can function as a harmonic antenna and achieve a wideband antenna gain, as long as the antenna element 400C is not electrically connected to the metal body 2 of the vehicle 1 or the GND of the substrate 700C.

[0154] As described above, the antenna 12C according to Modification 3 utilizes harmonics. Therefore, in Modification 3, there are no particular restrictions on the physical length of the antenna element 400C. However, the physical length of the antenna element 400C may be determined as follows. In the following description, λ is the wavelength of the desired frequency band. The antenna 12C according to Modification 3 will be described with reference to FIG. 14 . When the antenna 12C according to Modification 3 is applied to FIG. 14 , the physical length of the antenna element 400C is the physical length of the antenna 12 shown in FIG. 14 , and the length of the cable 800C is the distance h1 from the ground GND to the power supply 710 shown in FIG. 14 . If the distance h1 from the ground GND to the power supply 710 is less than ¼λ, the physical length of the antenna element 400C may be greater than or equal to ¼λ and less than or equal to ⅓λ. When the distance h1 from the ground GND to the power supply unit 710 is less than ¼λ and the physical length of the antenna element 400C is between ¼λ and ⅓λ, good characteristics can be obtained in the desired frequency band regardless of the distance h1 from the ground GND to the power supply unit 710. In other words, when the distance h1 from the ground GND to the power supply unit 710 is less than ¼λ, the resonant length of the antenna 12C is the physical length of the antenna element 400C, and the first resonant frequency can be used near the desired frequency band. On the other hand, when the distance h1 from the ground GND to the power supply unit 710 is ¼λ or more, the resonant length of the antenna 12C is the same as the resonant length of the antenna element 400C and the cable 800C, and the antenna 12C can be used as a harmonic antenna. Therefore, the antenna device 10C can be freely installed in the vehicle 1 without changing the design of the antenna element 400C.

[0155] In the third modification, the antenna element 400 and the substrate 700 are electrically connected to each other by solder. However, the antenna element 400 and the substrate 700 may be electrically connected to each other by means other than solder, such as a connector or a cable. The antenna element 400 and the substrate 700 may also be connected to each other via a mechanical connection, such as a metal screw or crimping. This mechanical connection can serve both the functions of electrically connecting the antenna element 400 and the substrate 700 and fixing the antenna element 400 and the substrate 700.

[0156] FIG. 30( a) is a graph showing the frequency characteristics of the gain of the harmonic antenna according to Modification 3 and the two-resonance antenna according to the embodiment, and FIG. 30( b) is a graph showing the frequency characteristics of the VSWR of the harmonic antenna according to Modification 3 and the two-resonance antenna according to the embodiment. The horizontal axis of the graphs in FIGS. 30( a) and 30(b) represents frequency (unit: MHz). The vertical axis of the graph in FIG. 30( a) represents gain (unit: dBd). The vertical axis of the graph in FIG. 30(b) represents VSWR. In the graph shown in FIG. 30( a), the solid line plot represents the gain of the harmonic antenna according to Modification 3, and the dashed line plot represents the gain of the two-resonance antenna according to the embodiment. In the graph shown in FIG. 30( b), the solid line plot represents the VSWR of the harmonic antenna according to Modification 3, and the dashed line plot represents the VSWR of the two-resonance antenna according to the embodiment.

[0157] As can be seen from the graph shown in Figure 30(a), the harmonic antenna according to Modification 3 has a maximum gain of -13.8 dBd, a minimum gain of -22.5 dBd, and a deviation of 8.70 dB. The two-resonance antenna according to the embodiment has a maximum gain of -10.6 dBd, a minimum gain of -32.4 dBd, and a deviation of 21.8 dB. As can be seen from the graph shown in Figure 30(b), the harmonic antenna according to Modification 3 has a maximum VSWR of 30.5, and the two-resonance antenna according to the embodiment has a maximum VSWR of 39.0.

[0158] 30(a) and 30(b), the harmonic antenna according to the third modification has a higher gain and a lower VSWR in the range of 120 MHz to 192 MHz compared to the two-resonance antenna according to the embodiment. As can be seen from the graph shown in FIG. 30(a), the harmonic antenna according to the third modification has a smaller gain deviation in the range of 72 MHz to 212 MHz compared to the two-resonance antenna according to the embodiment.

[0159] FIG. 31 is a Smith chart of the harmonic antenna according to Modification 3 and the two-resonance antenna according to the embodiment. The impedance in the Smith chart in FIG. 31 is normalized by 50Ω. The numerical values ​​attached to the horizontal line passing through the center of the Smith chart in FIG. 31 indicate resistance. The numerical values ​​attached to the outer periphery of the Smith chart in FIG. 31 indicate reactance. When the impedance in the Smith chart shown in FIG. 31 is plotted in the upper half from the horizontal line passing through the center, it indicates inductivity, and when the impedance is plotted in the lower half from the horizontal line passing through the center, it indicates capacitive. In the Smith chart shown in FIG. 31 , the solid line plot indicates the harmonic antenna according to Modification 3, and the dotted line plot indicates the two-resonance antenna according to the embodiment.

[0160] As shown by the five markers of numbers "1" to "5" surrounded by inverted triangles in Fig. 31 , in the harmonic antenna according to Modification Example 3, there are multiple harmonic resonance frequencies, i.e., nth-order harmonics, all of which are located at impedances higher than 50 Ω. As shown by the marker of number "6" surrounded by inverted triangles in Fig. 31 , in the two-resonance antenna according to the embodiment, there is a first resonance frequency of 112 MHz located at impedances lower than 50 Ω, and as shown by the marker of number "7" surrounded by inverted triangles, there is a second resonance frequency of 190 MHz located at impedances higher than 50 Ω.

[0161] Although the embodiments and modifications of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0162] According to the present specification, there are provided antenna devices of the following aspects: (Aspect 1.1) In aspect 1.1, the antenna device includes a holder, an antenna element held by the holder, and a locking portion that locks the holder.

[0163] The "holder" corresponds to the "bobbin," "AM / FM bobbin," and "DAB bobbin" in the above-described embodiments and modified examples. The "antenna element" corresponds to the "helical element," "AM / FM helical element," and "DAB helical element" in the above-described embodiments and modified examples. The "locking portion" corresponds to the "first locking claw," "second locking claw," "first locking pillar," and "second locking pillar" in the above-described embodiments.

[0164] According to the above-described aspect, the holder can be attached to the antenna device without using a fastening member such as a screw, which makes it easier to attach the holder to the antenna device than when a fastening member is used.

[0165] (Aspect 1.2) In aspect 1.2, the locking portion is at least partially flexible.

[0166] According to the above-described aspect, when the locking portion locks the holder, at least a portion of the locking portion can be deflected. Therefore, compared to when the locking portion does not deflect, the holder can be easily assembled by the locking portion.

[0167] (Aspect 1.3) In aspect 1.3, the locking portion locks the holder by press-fitting.

[0168] According to the above-described aspect, rattle of the holder can be suppressed by press-fitting the locking portion, and noise from the holder due to vibration or impact can be suppressed.

[0169] (Aspect 1.4) In aspect 1.4, the locking portion locks a plurality of portions of the holder.

[0170] According to the above-described aspect, the holder can be locked more stably than when only a single portion of the holder is locked.

[0171] (Aspect 1.5) In aspect 1.5, the antenna device further includes a substrate electrically connected to the antenna element, and the antenna element and the substrate are located on approximately the same plane.

[0172] According to the above-described aspect, the antenna device can be made lower in height compared to a case in which the antenna element and the substrate overlap each other.

[0173] (Aspect 1.6) In aspect 1.6, the antenna device further includes another antenna element electrically connected to the antenna element, and the antenna element and the other antenna element are positioned on approximately the same plane.

[0174] The "other antenna elements" correspond to the "antenna elements," "AM / FM antenna elements," and "DAB antenna elements" in the above-described embodiments and modifications.

[0175] According to the above-described aspect, the antenna device can be made lower in height compared to a case in which the antenna element and the other antenna overlap each other.

[0176] (Aspect 1.7) In aspect 1.7, the antenna device further includes a case that houses the holder and the antenna element, and the locking portion locks the holder and the case together.

[0177] According to the above-described aspect, the holder, the antenna element, and the case can be assembled to the antenna device in a state in which the holder and the case are locked together.

[0178] (Aspect 2.1) In aspect 2.1, an antenna device mounted on a vehicle includes a first antenna element extending in the left-right direction of the vehicle and a second antenna element electrically connected to the first antenna element, and the second antenna element extends the electrical length of an antenna having the first antenna element and the second antenna element.

[0179] The "first antenna element" corresponds to the "antenna element," "AM / FM antenna element," and "DAB antenna element" in the above-described embodiments and modifications. The "second antenna element" corresponds to the "helical element," "AM / FM helical element," and "DAB helical element" in the above-described embodiments and modifications.

[0180] According to the above-described aspect, the current distribution generated in the antenna can be concentrated in the second antenna element rather than in the first antenna element, which makes it difficult for the antenna to be electrically coupled to the surrounding conductors compared to an antenna not having the second antenna element, thereby improving the gain of the antenna device.

[0181] (Aspect 2.2) In aspect 2.2, the first antenna element and the second antenna element are arranged around a conductor provided on the vehicle.

[0182] According to the above-described aspect, the antenna is less likely to be electrically coupled to the conductor compared to when the antenna does not have a second antenna element, thereby improving the degree of freedom in arranging the antenna and the conductor.

[0183] (Aspect 2.3) In aspect 2.3, the first antenna element and the second antenna element are positioned on approximately the same plane.

[0184] According to the above-described aspect, the antenna device can be made lower in height compared to a case in which the first antenna element and the second antenna element overlap each other.

[0185] (Aspect 2.4) In aspect 2.4, the antenna device further includes a substrate electrically connected to the second antenna element, and the second antenna element and the substrate are located on approximately the same plane.

[0186] According to the above-described aspect, the antenna device can be made lower in height compared to when the second antenna element and the substrate overlap each other.

[0187] (Aspect 2.5) In aspect 2.5, the antenna device further includes a case that houses the first antenna element and the second antenna element, and the first antenna element and the second antenna element are attached to the case.

[0188] According to the above aspect, the first antenna element, the second antenna element, and the case can be assembled into the antenna device in a state in which the first antenna element and the second antenna element are attached to the case.

[0189] (Aspect 2.6) In aspect 2.6, at least a portion of the first antenna element is bent along the case.

[0190] According to the above-described aspect, by providing the bent portion of the first antenna element, the antenna characteristics can be improved. Furthermore, according to the above-described aspect, the antenna dimensions can be reduced compared to when the first antenna element is not bent.

[0191] (Aspect 2.7) In aspect 2.7, the antenna device is mounted in a hollow portion of the vehicle.

[0192] According to the above-described aspect, the antenna device is mounted in a hollow portion of the vehicle, so that the antenna device can be made inconspicuous.

[0193] (Aspect 2.8) In aspect 2.8, the electrical capacitance of the second antenna element is less than the electrical capacitance of the first antenna element.

[0194] According to the above aspect, it is possible to improve the gain of the antenna device in a state where the electrical capacitance of the second antenna element is less than the electrical capacitance of the first antenna element.

[0195] (Aspect 2.9) In aspect 2.9, the first antenna element and the second antenna element extend in different directions.

[0196] According to the above aspect, the dimension of the antenna in the same direction can be reduced compared to when the first antenna element and the second antenna element extend consecutively in the same direction.

[0197] (Aspect 2.10) In aspect 2.10, the first antenna element and the second antenna element constitute an antenna compatible with at least one of the AM frequency band, the FM frequency band, the DAB frequency band, and the DTV frequency band.

[0198] According to the above-described aspect, the gain of the antenna device can be improved when the first antenna element and the second antenna element form an antenna corresponding to at least one of the AM frequency band, the FM frequency band, the DAB frequency band, and the DTV frequency band.

[0199] (Aspect 3.1) In aspect 3.1, an antenna device mounted on a vehicle includes a first antenna element and a second antenna element electrically connected to the first antenna element, and the antenna device is installed in at least one of the front, rear, left, right, bottom, and interior of the vehicle, and extends the electrical length of an antenna having the first antenna element and the second antenna element.

[0200] (Aspect 3.2) In aspect 3.2, the first antenna element and the second antenna element are arranged around a conductor provided on the vehicle.

[0201] According to the above-described aspect, the antenna is less likely to be electrically coupled to the conductor compared to when the antenna does not have a second antenna element, thereby improving the degree of freedom in arranging the antenna and the conductor.

[0202] (Aspect 3.3) In aspect 3.3, the first antenna element and the second antenna element are positioned on approximately the same plane.

[0203] According to the above-described aspect, the antenna device can be made lower in height compared to a case in which the first antenna element and the second antenna element overlap each other.

[0204] (Aspect 3.4) In aspect 3.4, the antenna device further includes a substrate electrically connected to the second antenna element, and the second antenna element and the substrate are located on approximately the same plane.

[0205] According to the above-described aspect, the antenna device can be made lower in height compared to when the second antenna element and the substrate overlap each other.

[0206] (Aspect 3.5) In aspect 3.5, the antenna device further includes a case that houses the first antenna element and the second antenna element, and the first antenna element and the second antenna element are attached to the case.

[0207] According to the above aspect, the first antenna element, the second antenna element, and the case can be assembled into the antenna device in a state in which the first antenna element and the second antenna element are attached to the case.

[0208] (Aspect 3.6) In aspect 3.6, at least a portion of the first antenna element is bent along the case.

[0209] According to the above-described aspect, by providing the bent portion of the first antenna element, the antenna characteristics can be improved. Furthermore, according to the above-described aspect, the antenna dimensions can be reduced compared to when the first antenna element is not bent.

[0210] (Aspect 3.7) In aspect 3.7, the antenna device is mounted in a hollow portion of the vehicle.

[0211] According to the above-described aspect, the antenna device is mounted in a hollow portion of the vehicle, so that the antenna device can be made inconspicuous.

[0212] (Aspect 3.8) In aspect 3.8, the electrical capacitance of the second antenna element is less than the electrical capacitance of the first antenna element.

[0213] According to the above aspect, it is possible to improve the gain of the antenna device in a state where the electrical capacitance of the second antenna element is less than the electrical capacitance of the first antenna element.

[0214] (Aspect 3.9) In aspect 3.9, the first antenna element and the second antenna element extend in different directions.

[0215] According to the above aspect, the dimension of the antenna in the same direction can be reduced compared to when the first antenna element and the second antenna element extend consecutively in the same direction.

[0216] (Aspect 3.10) In aspect 3.10, the first antenna element and the second antenna element constitute an antenna compatible with at least one of the AM frequency band, the FM frequency band, the DAB frequency band, and the DTV frequency band.

[0217] According to the above-described aspect, the gain of the antenna device can be improved when the first antenna element and the second antenna element form an antenna corresponding to at least one of the AM frequency band, the FM frequency band, the DAB frequency band, and the DTV frequency band.

[0218] (Aspect 4) In aspect 4, the antenna device includes a power feeder located away from the ground, an antenna element located away from the ground, and a loading element electrically connected to the power feeder and the antenna element.

[0219] According to the above-described aspect, even if the ground and the power supply part are located apart, the bandwidth of the antenna device can be widened by using a loading element, and the difference between the maximum and minimum VSWR values ​​in the desired frequency band of the antenna device can be reduced.

[0220] (Aspect 5) In aspect 5, the antenna device includes an antenna element and a housing that houses the antenna element, and a plurality of vent holes are provided on a plurality of different surfaces of the housing.

[0221] According to the above-described aspect, even if the vent hole on one surface of the housing body is blocked, the air inside the housing body can be released to the outside through the vent hole on the other surface of the housing body.

[0222] This application claims priority based on Japanese Patent Application No. 2023-218153, filed December 25, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0223] 1 Vehicle, 2 Body, 2a Roof, 2b Front fender, 2c Rear fender, 2d Pillar, 4 Rear window, 6 Rear spoiler, 8 Conductor, 10, 10A, 10B, 10C Antenna device, 12, 12C Antenna, 12A1 AM / FM antenna, 12A2 DAB antenna, 12Z Antenna, 13 Loading element, 13a Inductor, 13b Capacitor, 13c Diode, 131d First inductor, 132d Second inductor, 100, 100A Base, 110, 110A Base body, 112, 112A Base mounting screw, 114A First recess, 116A Stopper rib, 120, 120A Support protrusion, 130, 130A Locking piece, 132, 132A Locking hole, 140 Base rib, 150 Base pillar, 150A First vent hole, 152 Vent filter, 152A First vent filter, 200, 200A, 200B, 200C Case, 210, 210A, 210B Case plate, 212A Second recess, 214A Recessed surface, 220, 220A, 220B Case side wall, 221A Reference position, 222, 222A Case groove, 224, 224A, 224B Recessed groove, 226 Screw boss, 230 Locking rib, 242 First case rib, 242A Case rib, 244 Second case rib, 246 Third case rib, 251 First locking claw, 251a First beam, 251b First hook, 252 Second locking claw, 252a Second beam, 252b Second hook, 253 First locking pillar, 253a First pressing rib, 254 Second locking pillar, 254a Second pressing rib, 255 Guide frame, 260A Second vent hole, 262A Second vent filter, 270A Positioning groove, 272A Press-fit rib, 300, 300A, 300B Pad, 400, 400A, 400C, 400Z Antenna element, 400B1 AM / FM antenna element, 400B2 DAB antenna element, 401A End, 402 First segment, 403A Assembly hole, 404 Second segment, 410 Main body, 420 Bending portion, 430 Pull-out portion, 440A Double-sided tape, 500,500A Bobbin, 500B1 AM / FM bobbin, 500B2 DAB bobbin, 501 First flat surface, 502 Second flat surface, 503 Third flat surface, 504 Fourth flat surface, 505 Bobbin inclined surface, 512 First guide rib, 514 Second guide rib, 522 First stop rib, 524 Second stop rib, 532 Bobbin rib, 600, 600A Helical element, 600B1 AM / FM helical element, 600B2 DAB helical element, 610 Helical conductor, 620 First lead conductor, 630 Second lead conductor, 700, 700A, 700C Board, 700B1 AM / FM board, 700B2 DAB board, 702 Board mounting screw, 710 Power supply unit, 800, 800A, 800C cable, 800B1 AM / FM cable, 800A2 DAB cable, 810, 810A, 810B grommet, 812A outlet hole, 820A resin pin, CD1 first current distribution, CD2 second current distribution, CDZ current distribution, GND ground,

Claims

1. An antenna device mounted on a vehicle, comprising: a first antenna element extending in the left-right direction of the vehicle; and a second antenna element electrically connected to the first antenna element, wherein the second antenna element extends the electrical length of an antenna having the first antenna element and the second antenna element.

2. The antenna device according to claim 1, wherein the first antenna element and the second antenna element are arranged around a conductor provided on the vehicle.

3. The antenna device according to claim 1 or 2, wherein the first antenna element and the second antenna element are located on substantially the same plane.

4. The antenna device according to claim 1 or 2, further comprising a substrate electrically connected to the second antenna element, wherein the second antenna element and the substrate are located on substantially the same plane.

5. The antenna device according to claim 1 or 2, further comprising a case for housing the first antenna element and the second antenna element, wherein the first antenna element and the second antenna element are attached to the case.

6. The antenna device according to claim 5, wherein at least a part of the first antenna element is bent along the case.

7. The antenna device according to claim 1 or 2, which is mounted in a cavity of the vehicle.

8. The antenna device according to claim 1 or 2, wherein the electrical capacitance of the second antenna element is less than the electrical capacitance of the first antenna element.

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