ANTENNA DEVICE

Abstract

An antenna device for mounting on a vehicle, the antenna device comprising: a first antenna element having a receiving area and configured to receive a radio wave in a first frequency band on the receiving area; a shielding element spaced apart from the first antenna element and arranged so that it overlaps at least part of the first antenna element when viewed from a direction perpendicular to the receiving surface; and a second antenna element, spaced apart from the first antenna element and the shielding element, and configured to receive a radio wave in a second frequency band that is higher than the first frequency band, wherein the first antenna element has a first edge and a second edge located at a position farther from the vehicle than the first edge, and The second antenna element, when viewed from the direction perpendicular to the receiving surface, extends along the second edge to a position that is further away from the vehicle than the first antenna element.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an antenna device. BACKGROUND

[0002] Conventionally, an antenna device for a vehicle is used with a plurality of antenna elements. For example, Japanese Patent Publication No. 2017-228860 (JP2017-228860) discloses an antenna device for mobile communications that includes a substrate provided on a roof panel of an automobile, two antennas uprightly disposed on the substrate, and a shield plate disposed between the two antennas. SUMMARY

[0003] In recent years, many electronic devices are mounted in automobiles, and noise is radiated from these electronic devices. In the antenna device described in JP2017-228860, the interference between the two antennas is reduced by shielding an electric field formed between the two antennas with the shielding plate, but it is difficult for the shielding plate to reduce the noise radiated from an interference source mounted in the vehicle. In JP2017-228860, the antenna device is placed on a roof panel, and the antenna device is shielded from an interference source by the roof panel. However, depending on the arrangement position of the antenna device, for example, the reception sensitivity of the antenna device may deteriorate due to the influence of noise from the interference source.JP 2008- 092 244 A and JP 2001- 102 826 A describe comparable vehicle antenna systems with multiple antenna elements to improve reception quality.

[0004] Therefore, it is necessary to provide an antenna device for a vehicle that can reduce the influence of noise.

[0005] In one aspect, an antenna device for mounting on a vehicle is provided. The antenna device includes a first antenna element having a receiving surface and configured to receive a radio wave in a first frequency band on the receiving surface; a shielding element spaced from the first antenna element and arranged to overlap at least a portion of the first antenna element when viewed from a direction perpendicular to the receiving surface; and a second antenna element spaced from the first antenna element and the shielding element and configured to receive a radio wave in a second frequency band higher than the first frequency band. The first antenna element includes a first edge and a second edge located at a position farther from the vehicle than the first edge.Viewed from the direction perpendicular to the receiving surface, the second antenna element extends along the second edge at a position further away from the vehicle than the first antenna element.

[0006] In this antenna device, since the shielding element is provided to overlap at least a part of the first antenna element, the first antenna element can be shielded from the noise source by the shielding element. Furthermore, since the second antenna is provided at a position farther from the vehicle than the first antenna element, the influence of noise on the second antenna element can be reduced. Therefore, with this antenna device, it is possible to reduce the influence of noise radiated from an electronic device or the like mounted on a vehicle, and as a result, it is possible to improve the reception performance of the first antenna element and the second antenna element.

[0007] In one embodiment, the first antenna element can receive an FM broadcast wave, and the second antenna element can receive a DAB broadcast wave. In another embodiment, the first antenna element can receive an AM broadcast wave and an FM broadcast wave.

[0008] In one embodiment, the receiving surface of the first antenna may include a first region and a second region located closer to the vehicle than the first region, and the shielding member may overlap only the first region of the receiving surface when viewed from the direction perpendicular to the receiving surface. When a conductor is disposed near the first antenna element, the capacitance of the first antenna element changes, and the receiving sensitivity may decrease. Since the overlap between the first antenna element and the shielding member is partial in this embodiment, it is possible to suppress a decrease in the receiving sensitivity of the first antenna element.

[0009] The shielding element may include a main portion facing the receiving surface and a bent portion inclined with respect to the main portion, and the bent portion may be at least partially disposed between the first antenna element and the second antenna element. In this embodiment, interference between the first antenna element and the second antenna element can be suppressed by disposing the bent portion between the first antenna element and the second antenna element.

[0010] In one embodiment, the shielding element may be electrically connected to the vehicle. Since the shielding element is electrically connected to the vehicle, the shielding element may be grounded via the vehicle, so that a decrease in the reception sensitivity of the first antenna element and the second antenna element can be suppressed.

[0011] In one embodiment, the first antenna element and the second antenna element may be made of sheet metal.

[0012] In one embodiment, the shielding member may include an effective shielding portion that overlaps the first antenna element and a shielding attachment portion that does not overlap the first antenna element when viewed from a direction perpendicular to the receiving surface, and a grounding member to be connected to a ground potential may be attached to the shielding member.

[0013] In one embodiment, when a direction parallel to the first edge is defined as a first direction and a direction perpendicular to a direction perpendicular to the receiving surface and the first direction is defined as a second direction, a width of the shield fixing portion in the second direction may be smaller than a width of the effective shielding portion in the second direction, and a larger one of a distance in the first direction between one end of the effective shielding portion in the first direction and a connection position of the grounding member with the shielding member and a distance in the first direction between another end of the effective shielding portion in the first direction and the connection position of the grounding member with the shielding member may be 1 / 8 or less of a wavelength of the radio wave received by the second antenna element.By setting the distance in the first direction between the end of the effective shielding portion and the connection position of the grounding element with respect to the shielding element to 1 / 8 or less of the wavelength of the radio wave received by the second antenna element, the resonance between the second antenna element and the shielding element can be suppressed. As a result, deterioration of the reception sensitivity of the second antenna element can be suppressed.

[0014] In one embodiment, when a direction parallel to the first edge is defined as a first direction and a direction perpendicular to a direction perpendicular to the receiving surface and the first direction is defined as a second direction, a width of the shield fixing portion in the second direction may be larger than a width of the effective shield portion in the second direction, and a larger of a distance in the first direction between one end of the effective shield portion in the first direction and a connection position of the grounding member with the shielding member and a distance in the first direction between another end of the effective shield portion in the first direction and a connection position of the grounding member with the shielding member may be 1 / 5.6 or less of a wavelength of the radio wave received by the second antenna element.By setting the distance in the first direction between the end of the effective shielding portion and the connection position of the grounding element with respect to the shielding element to 1 / 5.6 or less of the wavelength of the radio wave received by the second antenna element, resonance between the second antenna element and the shielding element can be suppressed. As a result, deterioration of the reception sensitivity of the second antenna element can be suppressed.

[0015] In one embodiment, the effective shielding portion and the shielding attachment portion may be spaced apart from each other.

[0016] In one embodiment, the grounding element may be a bracket that connects the shielding element to the vehicle. In this embodiment, the shielding element may be attached to the vehicle using the bracket.

[0017] The shielding member may include an effective shielding portion that overlaps the first antenna element and a shielding attachment portion that does not overlap the first antenna element when viewed from the direction perpendicular to the receiving surface, wherein the effective shielding portion and the shielding attachment portion may be spaced apart from each other, and the antenna device may further include a line length adjusting unit that electrically connects the effective shielding portion and the shielding attachment portion and adjusts a line length of the shielding member.For example, by setting the resonance frequency of the shielding element to a frequency different from the frequencies of the radio waves received by the first antenna element and the second antenna element by the line length setting unit, the resonance between the first antenna element and the shielding element and the resonance between the second antenna element and the shielding element can be suppressed.

[0018] The line length adjustment unit can contain a coil or a meander pattern. If the line length adjustment unit contains a coil or a meander pattern, the line length of the shielding element can be adjusted.

[0019] According to one aspect and various embodiments of the present invention, the influence of noise can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view showing an antenna device according to an embodiment. Fig. 2 is a bottom view showing an antenna device according to an embodiment. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is a block diagram showing a functional configuration of the circuit substrate. Fig. 5 is a side view showing an antenna device mounted on a vehicle in a partially broken view. Fig. 6 is a plan view showing an antenna device mounted on a vehicle. Fig. 7 is a plan view showing an antenna device used in Comparative Example 1 and Comparative Example 2. Fig. is a graph showing the reception sensitivity of the DAB broadcast wave in Comparative Example 1 and Comparative Example 2. Fig. is a graph showing the receiving sensitivity of the FM broadcast wave in Comparative Example 1 and Comparative Example 2. Fig. is a diagram showing the reception sensitivity of the DAB radio wave in Example 1. Fig. is a diagram showing the reception sensitivity of the horizontally polarized wave of the FM broadcast wave in Example 1. Fig. is a diagram showing the reception sensitivity of the vertically polarized FM broadcast wave in Example 1. Fig. is a bottom view showing an antenna device according to another embodiment. Fig. is a bottom view showing an antenna device according to another embodiment. Fig. is a bottom view showing an antenna device according to another embodiment. Fig. is a bottom view showing an antenna device according to another embodiment. Fig. is a bottom view showing an antenna device according to another embodiment. Fig. is a bottom view showing an antenna device according to another embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same element or the element having the same function is denoted by the same reference numeral, and redundant description is omitted.

[0021] Fig. 1 and Fig. 2 are a plan view and a bottom view showing an antenna device 1 according to an embodiment. Fig. 3 is a cross-sectional view along the line III-III of the Fig. 1. The antenna device 1 of the embodiment is a monopole antenna or a dipole antenna mounted on a vehicle, such as an automobile, and has the function of receiving radio waves used for, for example, AM radio, FM radio, DAB (Digital Audio Broadcast), or the like. The antenna device 1 is mounted on a vehicle and connected to a vehicle-mounted electronic device. The antenna device 1 is housed, for example, in a rear spoiler of a vehicle.

[0022] As in the Fig. 1 to 3, the antenna device 1 includes a first antenna element 10, a second antenna element 20, a shielding element 30, an insulating element 40, and a circuit substrate 50.

[0023] The first antenna element 10 receives, for example, an AM radio wave and an FM radio wave as radio waves in the first frequency band. The first antenna element 10 is, for example, a plate-shaped antenna with a substantially rectangular, flat shape and is formed from an alloy sheet. The first antenna element 10 has a pair of main surfaces 11 and 12. The pair of main surfaces 11 and 12 form a receiving surface for receiving an AM radio wave and an FM radio wave. In the following description, a direction parallel to a pair of edges 13c and 13d, which will be described later, is referred to as an X direction (second direction), a direction parallel to a pair of edges 13a and 13b, which will be described later, is referred to as a Y direction (first direction), and a direction perpendicular to a receiving surface (main surfaces 11 and 12) of the first antenna element 10 is referred to as a Z direction.

[0024] As in Fig. 1, the first antenna element 10 has a substantially rectangular shape when viewed from the Z direction and includes a pair of edges 13a and 13b and a pair of edges 13c and 13d. The pair of edges 13a and 13b extend parallel to each other in the Y direction, and the pair of edges 13c and 13d extend parallel to each other in the X direction. The main surface 11 of the first antenna element 10 is divided into a first region R1 and a second region R2 in a direction parallel to the pair of edges 13c and 13d, that is, in the X direction. The first region R1 is a region on the main surface 11 that is located on the edge 13b side of the pair of edges 13a and 13b. The second region R2 is a region on the main surface 11 located on the side of the edge 13a of the edge pair 13a and 13b. This means that the second region R2 is located closer to the vehicle than the first region R1.As will be described later, the first region R1 is arranged to overlap the shielding member 30 when viewed from the Z direction.

[0025] For example, the first antenna element 10 has a width W1 of 20 mm or more and 60 mm or less in the X direction and a length L1 of 80 mm or more and 260 mm or less in the Y direction.

[0026] A power supply section 14 is formed on the edge 13d of the first antenna element 10. One end of a power supply line 15 is connected to the power supply section 14. The other end of the power supply line 15 is connected to the circuit substrate 50. The power supply line 15 transmits the signal received by the first antenna element 10 to the circuit substrate 50.

[0027] The second antenna element 20 receives, for example, a DAB broadcast wave as a radio wave in the second frequency band. The second frequency band is a higher frequency band than the first frequency band described above. The second antenna element 20 is, for example, a plate-shaped antenna with a substantially rectangular, flat shape and is formed from an alloy sheet. The second antenna element 20 is provided separately from the first antenna element 10 and the shielding element 30.

[0028] The second antenna element 20 has an elongated shape whose longitudinal direction is the Y direction. Specifically, the second antenna element 20 has, for example, a width W2 of 5 mm or more and 20 mm or less in the X direction and a length L2 of 70 mm or more and 300 mm or less in the Y direction.

[0029] As in Fig. As shown in Figure 1, the second antenna element 20 is arranged at a position that is shifted in the X direction relative to the first antenna element 10 and extends along the edge 13b of the first antenna element 10 when viewed from the Z direction. The second antenna element 20 extends substantially parallel to the first antenna element 10 and is located below the first antenna element 10 in the Z direction (see Fig. 3). As described later, when the antenna device 1 is mounted on the vehicle, the second antenna element 20 is arranged at a position farther from the vehicle than the first antenna element 10.

[0030] The second antenna element 20 includes a pair of edges 21a and 21b and a pair of edges 21c and 21d. The pair of edges 21a and 21b extend parallel to each other in the Y direction, and the pair of edges 21c and 21d extend parallel to each other in the X direction. The edge 21c of the second antenna element 20 is located outside the edge 13c of the first antenna element 10 in the Y direction, and the edge 21d of the second antenna element 20 is located outside the edge 13d of the first antenna element 10 in the Y direction. That is, the length L2 of the second antenna element 20 in the Y direction is longer than the length L1 of the first antenna element 10 in the Y direction. Viewed from the Z direction, the edge 21a of the second antenna element 20 and the edge 13b of the first antenna element 10 are arranged to be opposite to each other in the X direction.The distance D1 between the first antenna element 10 and the second antenna element 20 in the X direction is set to, for example, 10 mm or more and 150 mm or less (see . Fig. 1).

[0031] A power supply section 22 is formed on the edge 21d of the second antenna element 20. One end of a power supply line 23 is connected to the power supply section 22. The other end of the power supply line 23 is connected to the circuit substrate 50. The power supply line 23 transmits the signal received by the second antenna element 20 to the circuit substrate 50.

[0032] The shielding element 30 is spaced apart from the first antenna element 10 in the Z direction. The shielding element 30 is made of, for example, an alloy sheet and is arranged between the first antenna element 10 and a vehicle-mounted interference source to shield the first antenna element 10 from the interference source.

[0033] As in the Fig. 2 and Fig. 3, the shielding member 30 has a main portion 31 and a bent portion 32. The main portion 31 is in the shape of a plate and faces the first antenna element 10. The main portion 31 is arranged to overlap a part of the first antenna element 10 when viewed from the Z direction. More specifically, the main portion 31 is arranged to overlap the first region R1 of the first antenna element 10 and not to overlap the second region R2 when viewed from the Z direction. That is, only the first region R1 of the first region R1 and the second region R2 overlaps the shielding member 30 when viewed from the Z direction. Therefore, noise from the noise source toward the first region R1 of the first antenna element 10 is blocked by the shielding member 30.

[0034] The bent portion 32 is a plate member having a substantially rectangular, flat shape and is inclined with respect to the main portion 31. The bent portion 32 is connected to one end of the main portion 31 in the X-direction, and a connecting portion between the main portion 31 and the bent portion 32 extends in the Y-direction (see Fig. 2). The bent portion 32 is formed, for example, by bending a part of the shielding element 30. The bent portion 32 is at least partially disposed between the first antenna element 10 and the second antenna element 20. Therefore, the electric field formed between the first antenna element 10 and the second antenna element 20 is blocked by the bent portion 32. As a result, the interference between the first antenna element 10 and the second antenna element 20 is suppressed. The shortest distance D2 between the second antenna element 20 and the shielding element 30 is set, for example, to 10 mm or more (see Fig. 3).

[0035] A conductive support 33 is connected to the main portion 31 of the shielding element 30. As shown in Fig. As shown in Figure 2, the bracket 33 extends from the main portion 31 beyond the edge 13a in the X direction. A plurality of screw holes 33a are formed in the bracket 33, and the shielding member 30 is fixed to the vehicle by a plurality of screws. That is, the antenna device 1 is connected to the vehicle body via the bracket 33. Since the bracket 33 is conductive, the shielding member 30 is electrically connected and grounded to the vehicle via the bracket 33. The bracket 33 can be fixed to the vehicle via another conductive bracket.

[0036] The insulating member 40 is made of an insulating material such as polypropylene (PP) and includes a base portion 41, a holding portion 42, and a substrate support portion 43. The base portion 41, the holding portion 42, and the substrate support portion 43 may be integrally formed.

[0037] As in Fig. 3, the base portion 41 has a substantially cuboid shape and is provided between the first antenna element 10 and the shielding member 30. The upper surface of the base portion 41 is connected to the first antenna element 10 by a mechanical connection method, such as a bolt or a rivet. The lower surface of the base portion 41 is connected to the main portion 31 of the shielding member 30 by a mechanical connection method, such as a bolt or a rivet. The base portion 41 of the insulating member 40 supports the first antenna element 10 and the shielding member 30 so that the distance between the first antenna element 10 and the shielding member 30 is maintained at a predetermined distance.

[0038] The holding portion 42 has an L-shape when viewed in the Y direction. One end of the holding portion 42 is connected to the base portion 41, and the other end of the holding portion is connected to the second antenna element 20. The holding portion 42 holds the second antenna element 20 in a suspended state. The substrate support portion 43 is arranged at a position shifted in the Y direction with respect to the base portion 41 and supports the circuit substrate 50 thereon.

[0039] The circuit substrate 50 is provided on the substrate support portion 43 of the insulating member 40. The circuit substrate 50 has a function of amplifying the signals received by the first antenna element 10 and the second antenna element 20. Fig. 4 is a block diagram showing an example of a functional configuration of the circuit substrate 50. As shown in Fig. 4, the circuit substrate 50 includes a coil 51, a distributor 52, an AM amplifier 53, an FM amplifier 54, a coil 56, and a DAB amplifier 57.

[0040] Coil 51 is, for example, an air-core coil. The AM and FM signals received by the first antenna element 10 are transmitted to coil 51 via power supply line 15. Coil 51 functions to adjust the antenna length of the first antenna element 10. The signal passed through coil 51 is output to distributor 52.

[0041] The distributor 52 splits the signal output by the coil 51 into an AM signal and an FM signal, and outputs the AM signal and FM signal to the AM amplifier 53 and the FM amplifier 54, respectively. The AM amplifier 53 and the FM amplifier 54 are lumped constant circuits, for example, and amplify the AM signal and FM signal split by the distributor 52. The amplified AM signal and FM signal are output to an electronic device in the vehicle, for example, via a coaxial cable.

[0042] Coil 56 is, for example, an air-core coil or a chip inductor. The DAB signal received by second antenna element 20 is transmitted to coil 56 via power supply line 23. Coil 56 functions to adjust the antenna length of second antenna element 20. The DAB signal passed through coil 56 is output to DAB amplifier 57. DAB amplifier 57 is, for example, a lumped-constant circuit and amplifies the DAB signal passed through coil 56. The amplified DAB signal is output to an electronic device in the vehicle, for example, via a coaxial cable.

[0043] The antenna device 1 described above is mounted, for example, on a vehicle body constituting a vehicle. Fig. Fig. 5 is a side view showing the antenna device 1 mounted on the vehicle, and Fig. 6 is a plan view showing the antenna device 1 mounted on the vehicle. In Fig. 5 shows a part of the vehicle body in a sketched view, and in Fig. 6 a rear spoiler 120 described later is omitted.

[0044] The Fig. The vehicle 100 shown in Figure 5 includes a rear spoiler 120. The rear spoiler 120 is essentially made of an insulating resin and is provided behind the roof panel 101b. The rear spoiler 120 is used as an exterior component that evens out the ambient air flow of the vehicle 100 while the vehicle 100 is traveling. As shown in Fig. 5, the antenna device 1 is arranged, for example, within the rear spoiler 120.

[0045] As in the Fig. 5 and Fig. As shown in Fig. 6, the antenna device 1 is fixed to the upper portion of the rear door 101a of the vehicle 100 by fastening the bracket 33 and the vehicle body 101 of the vehicle 100 using the screw 111. At this time, the antenna device 1 is fixed to the vehicle body 101 such that the edge 13b (second edge) of the first antenna element 10 is located at a position farther from the vehicle body 101 than the edge 13a (first edge). The distance D3 between the vehicle body 101 and the first antenna element 10 in the X direction can be set, for example, to 30 mm or more and 400 mm or less.

[0046] Since the antenna device 1 is fixed to the vehicle body 101 as described above, the second antenna element 20 is arranged at a position farther from the vehicle body 101 (rear of the vehicle 100) than the first antenna element 10. At this time, the distance between the vehicle body 101 and the second antenna element 20 can be set to, for example, 70 mm or more and 600 mm or less. Since the shielding member 30 of the antenna device 1 is fixed to the vehicle body 101 via the bracket 33, the shielding member 30 of the antenna device 1 is electrically connected to the vehicle body 101 and grounded.

[0047] Since the antenna device 1 is attached to the vehicle body 101 as described above, the first antenna element 10 is arranged above the second antenna element 20 and the shielding member 30 in the Z direction. Accordingly, the shielding member 30 is arranged between the rear glass 103 of the vehicle 100 and the first antenna element 10. Specifically, the first area R1 of the first antenna element 10 is arranged to overlap the shielding member 30 in the Z direction. Therefore, for example, noise generated from the tail lamp 102, which is a noise source, is blocked toward the first area R1 of the first antenna element 10 by the shielding member 30. In addition to the tail lamp 102, the rear door 101a may be provided with electrical components that serve as noise sources, such as a power amplifier. E.g. a high-mounted brake light, a defogger, a rear wiper and a rear-view camera.The shielding element 30 blocks at least part of the noise generated by these interference sources.

[0048] On the other hand, the second region R2 of the first antenna element 10 is arranged near the rear door 101a. Although the second region R2 is not arranged to overlap the shielding member 30 in the Z direction, the rear door 101a is located between the second region R2 and the noise source in the vehicle 100. The rear door 101a can block noise from noise sources such as an inverter, a motor, and a room lamp provided inside the vehicle body 101 toward the second region R2. Therefore, in the antenna device 1, the noise blocking performance for the first antenna element 10 can be further improved.

[0049] As in Fig. As shown in Figure 6, the second antenna element 20 is arranged at a position farther from the vehicle body 101 than the first antenna element 10 when viewed from the Z direction. Since the second antenna element 20 is arranged at a position away from the noise source mounted inside the vehicle body 101, the influence of noise on the second antenna element 20 can be reduced. In addition, since the shielding member 30 is partially disposed between the first antenna element 10 and the second antenna element 20, interference between the first antenna element 10 and the second antenna element 20 can be suppressed. Therefore, according to the antenna device, the influence of noise can be reduced, and as a result, the reception performance of the first antenna element 10 and the second antenna element 20 can be improved.

[0050] Furthermore, as in Fig. 6, the second antenna element 20 is arranged along the edge 13b of the first antenna element 10 when viewed from the Z direction. That is, since the first antenna element 10 and the second antenna element 20 are arranged to overlap in the Y direction, the width of the antenna device 1 in the Y direction can be reduced. Therefore, the antenna device 1 can be downsized.

[0051] In the following, the present invention will be described in more detail using examples, but the present invention is not limited to the following examples.

[0052] First, a comparative example 1 and a comparative example 2 are described. In the comparative example 1 and the comparative example 2, as in Fig. As shown in Figure 7, an antenna device 201 including an FM antenna element 210 and a DAB antenna element 220 and having no shielding element was manufactured, and the reception sensitivity of the antenna device 201 was measured. The FM antenna element 210 is an antenna element for receiving the FM broadcast wave with a width of 30 mm in the X direction and a length of 140 mm in the Y direction. The DAB antenna element 220 is an antenna element for receiving the DAB broadcast wave with a width of 10 mm in the X direction and a length of 200 mm in the Y direction.

[0053] In Comparative Example 1, the reception sensitivity of the FM antenna element 210 and the DAB antenna element 220 was measured in a state where the antenna device 201 was mounted on the vehicle such that the DAB antenna element 220 was arranged at a position farther from the vehicle than the FM antenna element 210. In Comparative Example 2, the reception sensitivity of the FM antenna element 210 and the DAB antenna element 220 was measured in a state where the antenna device 201 was mounted on the vehicle such that the DAB antenna element 220 was arranged at a position closer to the vehicle than the FM antenna element 210.

[0054] Fig. Fig. 8 is a diagram showing the reception sensitivity of the DAB broadcast wave received by the DAB antenna element 220, and Fig. Fig. 9 is a diagram showing the reception sensitivity of the FM broadcast wave received by the FM antenna element 210. As shown in Fig. 8, the reception sensitivity of the DAB antenna element 220 in Comparative Example 2 was lower than the reception sensitivity of the DAB antenna element 220 in Comparative Example 1. On the other hand, as shown in Fig. 9, the reception sensitivity of the FM antenna element 210 in Comparative Example 1 is lower than the reception sensitivity of the FM antenna element 210 in Comparative Example 2.

[0055] Through the Fig. 8 and Fig. From the results shown in Figure 9, it was confirmed that the reception performance of the DAB broadcast wave was deteriorated when the DAB antenna element 220 was arranged at a position closer to the vehicle than the FM antenna element 210, and conversely, the reception performance of the FM broadcast wave was deteriorated when the DAB antenna element 220 was arranged at a position farther from the vehicle than the FM antenna element 210. Specifically, in Comparative Example 1, it was confirmed that the antenna performance of the first antenna element 10 in a wide frequency band was 30 [dBµV] or less, and the reception performance of the FM broadcast wave with a wide width was deteriorated. From these results, it was confirmed that for the Fig. 7, it is difficult to achieve both the reception power of the FM broadcast wave and the reception power of the DAB broadcast wave.

[0056] Next, an example 1 is described. In example 1, as in Fig. 1, the antenna device 1 including the first antenna element 10, the second antenna element 20 and the shielding element 30 was manufactured. Then, as shown in Fig. 6, the antenna device 1 was mounted on the vehicle so that the second antenna element 20 was disposed at a position farther from the vehicle body 101 than the first antenna element 10, and the antenna performance of the first antenna element 10 and the second antenna element 20 was measured. In Example 1, an antenna element for receiving the FM broadcast wave with a width W1 of 35 mm in the X direction and a length L1 of 180 mm in the Y direction was used as the first antenna element 10, and an antenna element for receiving the DAB broadcast wave with a width W2 of 10 mm in the X direction and a length L2 of 280 mm in the Y direction was used as the second antenna element 20. The distance D4 between the vehicle body 101 and the second antenna element 20 was set to 100 mm.

[0057] Fig. 10 is a graph showing the reception sensitivity of the DAB broadcast wave received by the second antenna element 20 in Example 1. Fig. 11 is a diagram showing the reception sensitivity of the horizontal polarization of the FM broadcast wave received by the first antenna element 10 in Example 1. Fig. Fig. 12 is a diagram showing the reception sensitivity of the vertical polarization of the FM broadcast wave received by the first antenna element 10 in Example 1. As in Fig. 10, in Example 1, the reception sensitivity of the second antenna element 20 was higher than -10 [dBd] in substantially the entire frequency band of the DAB broadcast wave, and it was confirmed that the reception sensitivity of the DAB broadcast wave was improved compared to Comparative Example 2.

[0058] In addition, as in the Fig. 11 and Fig. As shown in FIG. 12, in Example 1, the reception sensitivity of the first antenna element 10 for the horizontally polarized wave and the vertically polarized wave in substantially the entire frequency band of the FM broadcast wave was higher than 30 [dBµV], and it was confirmed that the reception sensitivity of the FM broadcast wave was improved compared to Comparative Example 1. From these results, it was confirmed that the antenna device 1 according to the embodiment can maintain the reception performance of both the FM broadcast wave and the DAB broadcast wave at a high level. It is presumed that such an effect is caused by the reduction of the interference between the first antenna element 10 and the second antenna element 20.

[0059] An antenna device according to another embodiment will be described below. Fig. 13 is a bottom view showing an antenna device according to another embodiment. The following mainly describes the differences from the antenna device 1 described above, and redundant descriptions are omitted.

[0060] The Fig. The antenna device 1A shown in FIG. 13 differs from the antenna device 1 in that it further includes a grounding member 35. In the following description, a portion of the shield member 30 that overlaps the first antenna element 10 is referred to as an effective shielding portion 36, and a portion of the shield member 30 that does not overlap the first antenna element 10 is referred to as a shield fixing portion 37. In the antenna device 1A, the width W4 of the shield fixing portion 37 in the X direction is smaller than the width W3 of the effective shielding portion 36 in the X direction.

[0061] The grounding member 35 is fixed to the effective shielding portion 36 or the shielding fixing portion 37 of the shielding member 30. The grounding member 35 is connected to a ground potential. That is, the shielding member 30 is electrically grounded via the grounding member 35. The grounding member 35 is connected to the vehicle body 101 by any connection method. For example, the grounding member 35 may be physically connected to the vehicle body 101 using a cable or the like, or it may be capacitively coupled to the vehicle body 101 via a resin or the like. A bracket that connects the shielding member 30 to the vehicle body 101 may be used as the grounding member 35.

[0062] As in Fig. As shown in FIG. 13, the larger distance D5 in the Y direction of the distance between the connection position of the grounding member 35 with the shielding member 30 and one end 30a of the shielding member 30 in the Y direction and the distance between the connection position of the grounding member 35 with the shielding member 30 and the other end 30b of the shielding member 30 in the Y direction is set to 1 / 8 (one-eighth) or less of the wavelength of the radio wave received by the second antenna element 20. For example, when the radio wave received by the second antenna element 20 is a DAB broadcast wave with an upper limit frequency of 240 MHz, the distance D5 is set to 156 mm or less. If the distance D5 can be set to 156 mm or less, the grounding member 35 can be connected to either the effective shielding portion 36 or the shielding fixing portion 37.

[0063] Since the second antenna element 20 and the shielding element 30 are provided substantially parallel to each other and have lengths close to each other in the Y direction, electromagnetic field coupling may occur between the second antenna element 20 and the shielding element 30, causing resonance. Such resonance causes deterioration of the reception sensitivity of the second antenna element 20. In contrast, the resonance between the second antenna element 20 and the shielding element 30 can be suppressed by setting the distance D5 in the Y direction between the connection position of the grounding element 35 with the shielding element 30 and one end 30a or the other end 30b of the shielding element 30 to be equal to or less than 1 / 8 of the wavelength of the radio wave received by the second antenna element 20.

[0064] Due to the current flow, resonance is likely to occur between the second antenna element 20 and the shielding element 30 at the open end side of the second antenna element 20. In the antenna device 1A, since one end 30a of the shielding element 30 is located closer to the open end of the second antenna element 20 than the other end 30b, setting the distance in the Y direction between the connection position of the grounding element 35 and one end 30a to 156 mm or less can suppress the resonance between the second antenna element 20 and the shielding element 30 more effectively than setting the distance in the Y direction between the connection position of the grounding element 35 and the other end 30b to 156 mm or less.

[0065] It will now Fig. 14. Fig. 14 is a bottom view showing an antenna device 1B according to another embodiment. The antenna device 1B differs from the antenna device 1A in that the width W4 of the shield attachment portion 37 in the X direction is equal to or greater than the width W3 of the effective shield portion 36 in the X direction.

[0066] In the antenna device 1B, the larger distance D5 in the Y direction of the distance between the connection position of the grounding element 35 with the shielding element 30 and one end 30a of the shielding element 30 in the Y direction and the distance between the connection position of the grounding element 35 with the shielding element 30 and the other end 30b of the shielding element 30 in the Y direction is set to 1 / 5.6 or less of the wavelength of the radio wave received by the second antenna element 20. For example, when the radio wave received by the second antenna element 20 is a DAB broadcast wave with an upper limit frequency of 240 MHz, the distance D5 is set to 220 mm or less.

[0067] In the antenna device 1B of the present embodiment, since the shielding member 30 has a line length different from that of the shielding member 30 of the antenna device 1A, even if the distance D5 is 1 / 8 or more of the wavelength of the radio wave received by the second antenna element 20, resonance of the shielding member 30 and the second antenna element 20 can be suppressed when the distance D5 is 1 / 5.6 or less of the wavelength of the radio wave received by the second antenna element 20.

[0068] Due to the current flow, resonance is likely to occur between the second antenna element 20 and the shielding element 30 at the open end side of the second antenna element 20. In the antenna device 1B, since one end 30a of the shielding element 30 is located closer to the open end of the second antenna element 20 than the other end 30b, setting the distance in the Y direction between the connection position of the grounding element 35 and one end 30a to 220 mm or less can suppress resonance between the second antenna element 20 and the shielding element 30 more effectively than setting the distance in the Y direction between the connection position of the grounding element 35 and the other end 30b to 220 mm or less.

[0069] It will now Fig. 15. Fig. 15 shows an antenna device 1C according to another embodiment. The antenna device 1C differs from the antenna device 1A in that the shielding element 30 comprises a plurality of grounding elements 35. As shown in Fig. As shown in FIG. 15, in the antenna device 1C, the distance D5 in the Y direction between the connection position of the grounding member 35, which is arranged on the side of the end 30a of the shielding member 30 among the plurality of grounding members 35, and the end 30a of the shielding member 30 is set to be equal to or less than 1 / 8 of the wavelength of the radio wave received by the second antenna element 20. In the antenna device 1C, it is possible to suppress the resonance between the second antenna element 20 and the shielding member 30 and suppress the deterioration of the reception sensitivity of the second antenna element 20.

[0070] In the above-described embodiment, the effective shielding portion 36 and the shielding fixing portion 37 are formed by a plate member, but as shown in Fig. 16, the effective shielding portion 36 and the shielding fixing portion 37 may be separated from each other. In the embodiment shown in Fig. In the antenna device 1D shown in FIG. 16, a gap 38 is formed between the effective shielding portion 36 and the shielding fixing portion 37, and the effective shielding portion 36 and the shielding fixing portion 37 are arranged separately from each other. In this embodiment, the effective shielding portion 36 is connected to the ground potential via the grounding member 35, and the shielding fixing portion 37 is connected to the ground potential via the bracket 33. The shielding member 30 may be composed of a plurality of elements. When the shielding member 30 is composed of a plurality of elements, these elements may or may not be connected to each other.

[0071] Fig. 17 shows an antenna device 1E according to another embodiment. The antenna device 1E differs from the antenna device 1D in that it does not include the grounding element 35 and further includes a line length adjusting unit 39 for adjusting a line length of the shielding element 30. As shown in Fig. 17, the line length adjusting unit 39 is arranged in the gap 38 and electrically connects the effective shielding portion 36 and the shielding fixing portion 37. The line length adjusting unit 39 adjusts the line length of the shielding member 30 so that, for example, the resonance frequency of the shielding member 30 becomes a frequency between the frequency of the radio wave received by the first antenna element 10 and the frequency of the radio wave received by the second antenna element 20. For example, when the first antenna element 10 receives an AM broadcast wave from 422 kHz to 1710 kHz and an FM broadcast wave from 76 MHz to 108 MHz, and the second antenna element 20 receives a DAB broadcast wave from 174 MHz to 240 MHz, the line length adjusting unit 39 adjusts the line length of the shielding element 30 so that the resonance frequency of the shielding element 30 falls within the range of plus or minus 10 MHz with respect to 141 MHz.The line length adjusting unit 39 may include, for example, a coil or a wire having a meander shape (meander pattern) as an element for adjusting the line length.

[0072] In the antenna device 1E, the line length adjustment unit 39 adjusts the line length of the shielding element 30 so that the resonance frequency of the shielding element 30 differs from the frequency of the radio wave received by the first antenna element 10 and the frequency of the radio wave received by the second antenna element 20, thereby suppressing the resonance between the first antenna element 10 and the shielding element 30 and the resonance between the second antenna element 20 and the shielding element 30. Therefore, it is possible to suppress deterioration of the reception sensitivity of the first antenna element 10 and the second antenna element 20.

[0073] The antenna devices 1A to 1D described above include both the bracket 33 and the grounding element 35, but may also include only one of the bracket 33 and the grounding element 35. For example, as shown in Fig. 18, the bracket 33 may not be fixed to the shielding member 30, and only the grounding member 35 may be fixed to the shielding member 30.

[0074] Although the antenna device according to various embodiments has been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

[0075] For example, at least one of the first antenna element 10, the second antenna element 20, and the shielding element 30 of the antenna device 1 may be flexible. In this case, the antenna device 1 can be housed in the rear spoiler 120 in a state where the antenna device 1 can be easily deformed into a shape along the inner surface of the rear spoiler 120.

[0076] In the Fig. In the embodiment shown in FIG. 5, the antenna device 1 is provided in the rear spoiler 120, but the installation position of the antenna device 1 is not limited to the inside of the rear spoiler 120. The antenna device 1 may be provided, for example, in a side door or in the front roof area of ​​the vehicle 100. The antenna device 1 may be provided in an exterior component other than the rear spoiler 120. Even if the antenna device 1 is provided in these positions, the influence of noise on the first antenna element 10 and the second antenna element 20 can be reduced, and the reception performance of these antennas can be improved.

[0077] Furthermore, the planar shapes of the first antenna element 10 and the second antenna element 20 are not limited to rectangles. For example, the first antenna element 10 and the second antenna element 20 can have a circular or polygonal planar shape. The first antenna element 10 and the second antenna element 20 do not necessarily have to be formed from sheet metal, but can also be configured as a net-, grid-, or foil-shaped conductor. The first antenna element 10 and the second antenna element 20 can have a meandering structure.

[0078] In Fig. 1, the circuit substrate 50 is arranged at a position shifted in the Y direction relative to the first antenna element 10. However, the circuit substrate 50 may be provided, for example, between the first antenna element 10 and the shielding element 30. The circuit substrate 50 may be arranged inside the vehicle.

[0079] In the above-described embodiment, the first antenna element 10 receives the AM broadcast wave and the FM broadcast wave, and the second antenna element 20 receives the DAB broadcast wave. However, the types of the first antenna element 10 and the second antenna element 20 are not limited, as long as the first antenna element 10 receives the radio wave in the first frequency band and the second antenna element 20 receives the radio wave in the second frequency band higher than the first frequency band. For example, the first antenna element 10 can only receive the FM broadcast wave.

[0080] In the above embodiment, the shielding member 30 is arranged to overlap only the first region R1 as viewed from the Z direction, but the shielding member 30 may be arranged to overlap the entire surface of the first antenna element 10. Furthermore, the shielding member 30 may be formed of, for example, a mesh-like or lattice-like conductive member. The shielding member 30 may be a plate member in which a surface made of an insulating material is coated with a conductive material. The shielding member 30 is formed, for example, by applying a conductive material to a resin plate-shaped member, by depositing the conductive material, or by plating the conductive material.

[0081] In the Fig.In the embodiment shown in Figure 1, the length L2 of the second antenna element 20 in the Y direction is longer than the length L1 of the first antenna element 10 in the Y direction. However, depending on the vehicle in which the antenna device 1 is mounted, the length L2 of the second antenna element 20 in the Y direction may be equal to the length L1 of the first antenna element 10 in the Y direction or shorter than the length L1. The various embodiments described above can be combined without inconsistency. (List of reference symbols)

[0082] 1, 1A, 1B, 1C, 1D, 1E: Antenna device, 10: First antenna element, 20: Second antenna element, 13a: Edge (first edge), 13b: Edge (second edge), 30: Shielding member, 30a, 30b: End, 31: Main portion, 32: Bent portion, 33: Bracket, 35: Grounding member, 36: Effective shielding portion, 37: Shield fixing portion, 39: Line length adjusting unit, 40: Insulating member, 101: Vehicle body

Claims

[1] An antenna device for mounting on a vehicle, the antenna device comprising: a first antenna element having a receiving surface and configured to receive a radio wave in a first frequency band on the receiving surface; a shielding element spaced from the first antenna element and arranged to overlap at least a portion of the first antenna element when viewed from a direction perpendicular to the receiving surface; and a second antenna element spaced from the first antenna element and the shielding element and configured to receive a radio wave in a second frequency band higher than the first frequency band, wherein the first antenna element has a first edge and a second edge located at a position farther from the vehicle than the first edge, and the second antenna element extends along the second edge at a position further away from the vehicle than the first antenna element when viewed from the direction perpendicular to the receiving surface. [2] The antenna device according to claim 1, wherein the first antenna element receives an FM broadcast wave, and the second antenna element receives a DAB broadcast wave. [3] The antenna device according to claim 1 or 2, wherein the first antenna element receives an AM broadcast wave and an FM broadcast wave. [4] The antenna device according to any one of claims 1 to 3, wherein the receiving surface of the first antenna includes a first region and a second region closer to the vehicle than the first region, and the shielding member overlaps only the first region of the receiving surface when viewed from the direction perpendicular to the receiving surface. [5] The antenna device according to any one of claims 1 to 4, wherein the shielding member has a main portion facing the receiving surface and a bent portion inclined with respect to the main portion, and the bent portion is at least partially disposed between the first antenna element and the second antenna element. [6] The antenna device according to any one of claims 1 to 5, wherein the shielding member is electrically connected to the vehicle. [7] Antenna device according to one of claims 1 to 6, wherein the first antenna element and the second antenna element are made of sheet metal. [8] The antenna device according to any one of claims 1 to 7, wherein the shielding member has an effective shielding portion overlapping the first antenna element and a shielding fixing portion not overlapping the first antenna element when viewed from the direction perpendicular to the receiving surface, and a grounding member to be connected to a ground potential is attached to the shielding member. [9] The antenna device according to claim 8, wherein when a direction parallel to the first edge is defined as a first direction and a direction perpendicular to a direction perpendicular to the receiving surface and the first direction is defined as a second direction, a width of the shield fixing portion in the second direction is smaller than a width of the effective shield portion in the second direction, and wherein a larger of a distance in the first direction between one end of the effective shield portion in the first direction and a connection position of the grounding member with the shielding member and a distance in the first direction between another end of the effective shield portion in the first direction and the connection position of the grounding member with the shielding member is 1 / 8 or less of a wavelength of the radio wave received by the second antenna element. [10] The antenna device according to claim 8, wherein when a direction parallel to the first edge is defined as a first direction and a direction perpendicular to a direction perpendicular to the receiving surface and the first direction is defined as a second direction, a width of the shield fixing portion in the second direction is larger than a width of the effective shield portion in the second direction, and wherein a larger of a distance in the first direction between one end of the effective shield portion in the first direction and a connection position of the grounding member with the shielding member and a distance in the first direction between another end of the effective shield portion in the first direction and a connection position of the grounding member with the shielding member is 1 / 5.6 or less of a wavelength of the radio wave received by the second antenna element. [11] The antenna device according to any one of claims 8 to 10, wherein the effective shielding portion and the shielding fixing portion are separated from each other. [12] The antenna device according to any one of claims 8 to 11, wherein the grounding member is a bracket connecting the shielding member to the vehicle. [13] The antenna device according to any one of claims 1 to 7, wherein the shielding member has an effective shielding portion overlapping the first antenna element and a shielding fixing portion not overlapping the first antenna element when viewed from the direction perpendicular to the receiving surface, the effective shielding portion and the shielding fixing portion being spaced apart from each other, and the antenna device further comprises a line length adjusting unit that electrically connects the effective shielding portion and the shielding fixing portion and adjusts a line length of the shielding member. [14] The antenna device according to claim 13, wherein the line length adjusting unit comprises a coil. [15] The antenna device according to claim 13, wherein the line length adjusting unit comprises a meander pattern.

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