Antenna device

Abstract

The present invention provides an antenna device that has good reception characteristics in a plurality of frequency bands and has a simple and small structure. The antenna (AT1) of the antenna device includes: a capacitive element (50); an antenna coil (35a) having one end connected to a power supply point (P) and the other end connected to the capacitive element (50); an antenna coil (35b) having one end connected to the capacitive element (50); and a capacitive section (311) having one end connected to the antenna coil (35b) and the other end connected to a ground point (G).

Description

Technical Field

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

[0002] Conventionally, as an in-vehicle antenna device provided on the ceiling of a vehicle such as an automobile, an antenna device that can receive radio waves of wireless communication methods (standards) such as AM (Amplitude Modulation) radio broadcast (frequency band is MW (Medium Wave: medium wave) (LW (Long Wave: long wave)) band) / FM (Frequency Modulation) radio broadcast (frequency band is VHF (Very High Frequency: ultra-short wave) band) is known. This antenna device inserts a fixing portion provided on the bottom surface of the antenna device into a fixing ceiling hole (fixing opening) formed on the installation surface of the vehicle ceiling and fixes it by an appropriate method.

[0003] In recent years, there has been an increasing demand for low-profile in-vehicle antenna devices represented by shark fin antenna devices in the shape of a shark fin. However, if a monopole antenna is made low-profile, since the part involved in radiation becomes physically shorter, there is a drawback of a decrease in antenna gain. Therefore, as a method for increasing the antenna gain reduced due to low-profile, a method of making the antenna into a folded-back structure is sometimes used.

[0004] Regarding this folded-back structure, in the case of a monopole antenna type, generally two or more coils are used, one is powered, and the other is grounded (short-circuited). For example, an antenna device is known that includes an outer plate for receiving AM radio broadcast (MW (LW) band) and a folded-back monopole antenna for receiving FM radio broadcast (VHF band). One end of the first coil of this monopole antenna is connected to a power supply point, the other end is connected to one end of a capacitor plate (capacitor element), one end of the second coil is connected to the other end of the capacitor plate, and the other end is grounded (see Patent Document 1).

[0005] In addition, as an antenna device for receiving signals in the MW (LW) band and VHF band, a monopole antenna is known that includes a coil and a capacitor plate. One end of the coil is connected to a power supply point, the other end is connected to one end of the capacitor plate, and the other end of the capacitor plate is an open end.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-170622 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, in the antenna device of the folded monopole antenna in Patent Document 1, when it is made into a combined antenna of the MW (LW) band and the VHF band required for a vehicle-mounted antenna device, due to grounding, it is difficult to receive the MW (LW) band, and an outer plate for the MW (LW) band is additionally provided to function as a combined antenna, making the structure heavy.

[0011] In addition, in the above-mentioned monopole antenna with an open end, a folded-back method cannot be formed, so in the VHF band, the resonance point of the antenna cannot be made to coincide with the desired frequency.

[0012] Furthermore, in the antenna device of the above-mentioned folded monopole antenna, it is necessary to enlarge the capacitor plate, which is not suitable for a shape that emphasizes design such as a shark fin antenna device.

[0013] The problem of the present invention is to achieve good reception characteristics in multiple frequency bands in an antenna device and to make the structure simple and small.

[0014] Solution for Solving the Problem

[0015] To solve the above problem, Solution 1 is an antenna device comprising: a capacitive element; a first coil having one end connected to a power supply point and the other end connected to the capacitive element; a second coil having one end connected to the capacitive element; and a capacitive portion having one end connected to the second coil and the other end connected to a ground point.

[0016] Solution 2 The antenna device according to Solution 1, wherein the second coil and the capacitive portion are each plural, the second coils are respectively electrically connected to one capacitive portion, and each capacitive portion is electrically connected to the ground point.

[0017] Solution 3 The antenna device according to Solution 1 or 2, wherein the first coil and the second coil are thin film components or lead components of a distributed constant coil or a lumped constant coil.

[0018] Solution 4 The antenna device according to Solution 1 or 2, wherein the capacitive portion is a thin film component or a lead component of a distributed constant capacitive portion or a capacitor.

[0019] Solution 5 The antenna device according to Solution 1 or 2, further comprising: a main substrate portion having the power supply point and the ground point; and an antenna substrate portion erected on the main substrate portion, electrically connected to the capacitive element, and having the first coil and the second coil.

[0020] Solution 6 The antenna device according to Solution 5, further comprising a support portion for supporting the capacitive element.

[0021] Embodiment 7: The antenna device according to Embodiment 6, further comprising: an antenna base portion provided with the main body substrate portion and the support portion; a vehicle mounting portion for mounting the antenna base portion on a vehicle; and a shark fin-shaped antenna cover portion.

[0022] Advantages of the Invention

[0023] According to the present invention, in the antenna device, it is possible to achieve good reception characteristics for multiple frequency bands, and the structure is simple and compact. Description of the Drawings

[0024] Figure 1 Fig. is an external perspective view of the antenna device according to an embodiment of the present invention.

[0025] Figure 2 Fig. is an exploded perspective view of the antenna device.

[0026] Figure 3 Fig. is a developed view of a capacitive element.

[0027] Figure 4 Fig. is an assembled perspective view of the antenna device inside the antenna cover portion.

[0028] Figure 5 Fig. is a circuit diagram of the antenna.

[0029] Figure 6 In Fig., (a) is a graph showing the capacitive reactance of the MW band antenna with respect to capacitance, and (b) is a graph showing the capacitive reactance of the VHF band antenna with respect to capacitance.

[0030] Figure 7 In Fig., (a) is a graph showing the AM gain of the antenna device with the capacitance of the capacitance portion changed with respect to frequency, and (b) is a graph showing the FM gain of the antenna device with the capacitance of the capacitance portion changed with respect to frequency.

[0031] Figure 8 In Fig., (a) is a perspective view showing the installation positions of various antenna devices in the front of the vehicle, and (b) is a perspective view showing the installation positions of various antenna devices in the rear of the vehicle.

[0032] In the figure:

[0033] 1 - Antenna device, AT1 - Antenna, 10 - Antenna cover part, 20 - Antenna base part, 21 - Flat part, 21h1, 21h2, 21h3 - Threaded holes, 21h4 - Hole part, 30 - Substrate part, 31 - Main substrate, 31h - Hole part, 311 - Capacitance part, 32 - Cable guiding part, 33a, 33b, 33c, 33d - Connection terminals, 34 - Antenna substrate, 35a, 35b - Antenna coils, 36a, 36b - Connection terminals, 40 - Inner cover part, 41 - Round top part, 41a, 41b - Threaded hole parts, 42 - Flat part, 42h - Hole part, 50 - Capacitor element, 51 - Capacitor plate part, 51a, 51b - Hole parts, 60 - Washer part, 61, 62 - Washers, 70 - Vehicle mounting part, S1, S2, S3, S4 - Screws. Detailed implementation mode

[0034] Hereinafter, with reference to the drawings, the implementation modes of the present invention will be described in detail. However, the scope of the invention is not limited to the illustrated examples.

[0035] Refer to Figures 1 to 7 , and the antenna device 1 of the implementation mode of the present invention will be described. Figure 1 is a perspective view showing the appearance of the antenna device 1 of the present implementation mode. Figure 2 is an exploded perspective view showing the antenna device 1. Figure 3 is an exploded view of the capacitor element 50. Figure 4 is an assembled perspective view showing the antenna device 1 inside the antenna cover part 10. Figure 5 is a circuit diagram of the antenna AT1.

[0036] The antenna device 1 of the present implementation mode is an in-vehicle antenna device of a so-called shark fin antenna that is installed in a fixing opening (not shown) on the installation surface of the ceiling of a vehicle such as an automobile, and is a composite antenna device that receives AM radio broadcasts (frequency band: MW (LW) band) / FM radio broadcasts (frequency band: VHF band).

[0037] As Figure 1 shown, the antenna device 1 includes an antenna cover part 10 and has a structure such as a main body part that houses an antenna inside the antenna cover part 10. The antenna cover part 10 is installed on the antenna base part 20 described later, and is formed to bulge in a streamline shape from the front to the back, and is formed in a low-profile shark fin shape so as not to damage the appearance of the vehicle or the like. The antenna cover part 10 is made of a synthetic resin such as ABS (Acrylonitrile Butadiene Styrene) resin that has radio wave permeability and insulation, and is made into a molded product with an open lower surface.

[0038] As Figure 2 shown in the exploded view of the antenna device 1 of Figure 2(The illustration is omitted), an antenna base portion 20, a substrate portion 30, an inner cover portion 40 as a support portion, a capacitor element 50, a washer portion 60, and a vehicle mounting member 70 as a vehicle mounting portion.

[0039] When the antenna cover portion 10 is installed with the antenna base portion 20 etc., a storage space for the substrate portion 30, the inner cover portion 40, the capacitor element 50 etc. is formed.

[0040] The antenna base portion 20 is the base portion of the antenna device 1, supports the substrate portion 30, and has a structure with fixing openings installed on the installation surface of the vehicle. The antenna base portion 20 has a flat plate portion 21. The flat plate portion 21 is a metal-made substantially flat plate-shaped base portion made of die-castings such as aluminum and zinc, and has threaded holes 21h1, 21h2, 21h3, hole portions 21h4, and convex portions (illustration omitted). In addition, the flat plate portion 21 may also be made of sheet metal such as a steel plate.

[0041] The threaded hole 21h1 is a through inner threaded hole for threadedly engaging with the external threaded portion of the vehicle mounting member 70 to install the vehicle mounting member 70. The threaded hole 21h2 is a non-through inner threaded hole for threadedly engaging with the screw S1 of the external threaded member (screw) to install the inner cover portion 40. The threaded hole 21h3 is a non-through inner threaded hole for threadedly engaging with the screw S2 as the external threaded member (screw) to install the substrate portion 30. The convex portions (illustration omitted) are provided on the lower side of the flat plate portion 21 to install the vehicle mounting member 70.

[0042] The substrate portion 30 has a main substrate 31 as a main substrate portion, a cable guiding portion 32, connection terminals 33a, 33b, 33c, 33d, an antenna substrate 34 as an antenna substrate portion, antenna coils 35a, 35b as first and second coils, and connection terminals 36a, 36b. The main substrate 31 is a PCB (Printed circuit board) with its plane arranged in the horizontal direction, on which electronic components such as a capacitor portion 311 described later are installed, a circuit pattern is formed, and connection terminals 33a, 33b, 33c, 33d are installed on the upper surface, and the cable guiding portion 32 is installed on the lower surface and a plurality of hole portions 31h are formed.

[0043] The hole portion 31h is a through hole for the screw S2 to pass through. The substrate portion 30 is fixedly installed on the antenna base portion 20 by threadedly engaging the screw S2 with the threaded hole 21h3 via the hole portion 31h. In addition, an antenna AT1 of a folded monopole antenna for receiving AM radio broadcasts / FM radio broadcasts is constituted by the capacitor portion 311, the antenna coils 35a, 35b, the capacitor element 50 etc.

[0044] The connection terminals 33a, 33b, 33c, and 33d are M-shaped metal connection terminals that sandwich the antenna substrate 34 and support the connection. The connection terminal 33a is electrically connected to the terminal of the circuit pattern on the main body substrate 31 that includes the power supply point P (described later) on the power supply side, and through the connection of the antenna substrate 34, it is electrically connected to the terminal of the circuit pattern on the antenna substrate 34 that is electrically connected to the antenna coil 35a. The connection terminal 33b is electrically connected to the terminal of the circuit pattern on the main body substrate 31 that includes the capacitor portion 311 on the ground side and the ground point G (described later), and through the connection of the antenna substrate 34, it is electrically connected to the terminal of the circuit pattern on the antenna substrate 34 that is electrically connected to the antenna coil 35b. In addition, it can also be configured such that the connection terminal 33a is electrically connected to the terminal of the circuit pattern on the ground side, and the connection terminal 33b is electrically connected to the terminal of the circuit pattern on the power supply side.

[0045] The antenna substrate 34 is erected on the main body substrate 31, is a PCB with its plane arranged in the vertical direction, supports the antenna coils 35a and 35b, forms circuit patterns electrically connected to the antenna coils 35a and 35b, and has terminals for the connection terminals 33a, 33b, 36a, and 36b.

[0046] The antenna coils 35a and 35b are coils with a distributed constant obtained by winding wires made of enameled copper wire, nickel-plated copper wire, etc. In addition, the antenna coils 35a and 35b can also be configured as thin-film components, lead components, etc. of lumped constant coils (inductors) mounted on the antenna substrate 34.

[0047] The connection terminals 36a and 36b are M-shaped metal connection terminals that sandwich the antenna substrate 34 and are fixedly connected. The connection terminal 36a has a hole for the screw S3 as an external threaded member (screw), and through the connection of the antenna substrate 34, it is electrically connected to the terminal of the circuit pattern on the antenna substrate 34 that is electrically connected to the antenna coil 35a. The connection terminal 36b has a hole for the screw S3, and through the connection of the antenna substrate 34, it is electrically connected to the terminal of the circuit pattern on the antenna substrate 34 that is point-connected to the antenna coil 35b.

[0048] The inner cover portion 40 is disposed inside the antenna cover portion 10, houses the substrate portion 30, and is a fixed holding portion that fixedly supports the capacitor element 50. Only through the connection of the antenna substrate 34 (connection terminals 36a and 36b) to the capacitor element 50, the fixing of the capacitor element 50 to the antenna base portion 20 is weak, so the capacitor element 50 is supported by the inner cover portion 40.

[0049] The inner cover portion 40 has a round top portion 41 and a flat plate portion 42, and has a structure in which metal components such as threaded hole portions 41a and 41b and resin are integrally formed. The round top portion 41 is made of a heat-resistant insulating resin, is a cover portion for accommodating the antenna substrate 34 etc. inside, and has threaded hole portions 41a and 41b. This heat-resistant insulating resin is, for example, a mixed material of PC (PolyCarbonate), PC / PET (Poly Ethylene Terephthalate), or a mixed material of PC / ABS.

[0050] The threaded hole portion 41a is a metal internal thread portion whose axis extends in the vertical direction, is threadedly engaged with the screw S3 via the hole portion of the connection terminal 36a, and is threadedly engaged with the screw S4 (a screw) as an external threaded member via the hole portion 51a of the capacitor element 50. The threaded hole portion 41b is a metal internal thread portion whose axis extends in the vertical direction, is threadedly engaged with the screw S3 via the hole portion of the connection terminal 36b, and is threadedly engaged with the screw S4 via the hole portion 51b of the capacitor element 50.

[0051] The screw S3 is threadedly engaged with the threaded hole portions 41a and 41b via the hole portions of the connection terminals 36a and 36b respectively, and the connection terminals 36a and 36b are connected to the antenna substrate 34, whereby the inner cover portion 40 is fixedly mounted on the substrate portion 30.

[0052] The flat plate portion 42 is made of the same resin as the round top portion 41, is a cover portion for accommodating the main body substrate 31 etc. inside, and has a plurality of hole portions 42h. The screw S1 is threadedly engaged with the threaded hole 21h2 via the hole portion 42h, whereby the inner cover portion 40 is fixedly mounted on the antenna base portion 20.

[0053] The capacitor element 50 has a capacitor plate portion 51. As Figure 3 shown, the capacitor plate portion 51 is a capacitor plate (metal plate) made of a metal such as tin, and has hole portions 51a and 51b. In addition, the capacitor plate portion 51 is not limited to a metal plate and may also be made of a substrate, a conductive resin, etc. The conductive resin is a high molecular compound as a resin that exhibits conductivity itself and is obtained by mixing fine particles of metal or carbon into the resin to impart conductivity.

[0054] The Figure 3 shown capacitor plate portion 51 is bent at multiple places, whereby it is formed into the Figure 2 shown three-dimensional shape and functions as a capacitor plate having a current path between the hole portion 51a and the hole portion 51b.

[0055] The gasket portion 60 is a component that prevents water, dust, etc. from the outside from entering the antenna device 1 and the interior of the vehicle when the antenna device 1 is installed on the ceiling of a vehicle or the like, and includes gaskets 61 and 62. The gasket 61 is a gasket made of an elastic material such as polyurethane foam, and is disposed between the antenna base portion 20 and the inner cover portion 40. By being clamped and compressed, it realizes the functions of waterproofing and dustproofing. The gasket 62 is a gasket made of an elastic material such as polyurethane foam, and is disposed between the antenna base portion 20 and the installation surface of the ceiling. By being clamped and compressed, it realizes the functions of waterproofing and dustproofing.

[0056] The vehicle mounting member 70 is made of metal, for example, and has an external thread portion formed with an external thread and a leg portion that contacts the installation surface of the vehicle and the convex portion of the antenna base portion 20 during installation. By inserting the external thread portion of the vehicle mounting member 70 into the fixing opening of the ceiling and fastening it to the threaded hole 21h1 while clamping the gasket 62, the antenna device 1 is fixedly installed on the installation surface of the vehicle ceiling.

[0057] By assembling Figure 3 the components shown except for the vehicle mounting member 70, as Figure 4 shown, the assembled antenna device 1 is constituted. However, in Figure 4 the illustration of the antenna cover portion 10 and the inner cover portion 40 is omitted.

[0058] As Figure 5 shown, in the antenna AT1, one end of the antenna coil 35a is connected to the power supply point P of the main body substrate 31, and the other end is connected to the hole portion 51a at one end of the capacitor plate portion 51 of the capacitor element 50. One end of the antenna coil 35b is connected to the hole portion 51b at the other end of the capacitor plate portion 51, and the other end is connected to one end of the capacitor portion 311. The other end of the capacitor portion 311 is connected to the ground point G (grounding, short - circuit) of the main body substrate 31. The capacitor portion 311 is composed of a thin - film component and a lead component of a lumped - constant capacitor. In addition, the capacitor portion 311 is not limited to a lumped - constant capacitor, and may be configured as a distributed - constant capacitor portion (such as a slit in the main body substrate 31).

[0059] In this way, in the antenna AT1, a combined antenna for the MW (LW) band and the VHF band is realized by using the capacitor portion 311.

[0060] Next, with reference to Figure 6 (a), Figure 6 (b), the operation of the antenna AT1 will be described. Figure 6 (a) is a diagram showing the capacitive reactance of the antenna AT1 in the MW band with respect to capacitance. Figure 6 (b) is a diagram showing the capacitive reactance of the antenna AT1 in the VHF band with respect to capacitance.

[0061] Regarding the antenna AT1, when the antenna coil 35b is grounded (short-circuited), by connecting via the capacitor section 311, the capacitor element 50 is not enlarged, and signals in the MW (LW) band can be received efficiently. For example, the relationship between the capacitance of the capacitor section 311 and the capacitive reactance of the capacitor element 50 is an inverse proportional relationship. The larger the capacitance of the capacitor section 311, the smaller the capacitive reactance of the capacitor element 50.

[0062] In addition, the relationship between the capacitance of the capacitor section 311 and the capacitive reactance of the capacitor element 50 also depends on the frequency. As shown in the following formula (1), the higher the frequency, the smaller the capacitive reactance of the capacitor element 50 with a smaller capacitance of the capacitor section 311.

[0063]

Equation 1

[0064]

[0065] Among them, XC: capacitive reactance [Ω], f: frequency [Hz], C: capacitance [F].

[0066] Figure 6 (a) shows the capacitive reactance [Ω] of the capacitor element 50 with respect to the capacitance [pF] of the capacitor section 311 in the MW (LW) band (1 [MHz]) of the antenna AT1. Figure 6 (b) shows the capacitive reactance [Ω] of the capacitor element 50 with respect to the capacitance [pF] of the capacitor section 311 in the VHF band (98 [MHz]) of the antenna AT1. As Figure 6 (a), Figure 6 (b) shows, in the antenna AT1 which is a combined antenna of the MW (LW) band and the VHF band, by using the capacitor section 311 with a capacitance such that the capacitive reactance of the capacitor element 50 becomes larger in the MW (LW) band and smaller in the VHF band, the antenna AT1 can operate as an open-ended monopole antenna in the MW (LW) band and as a folded monopole antenna in the VHF band.

[0067] Next, referring to Figure 7 (a), Figure 7 (b), the antenna characteristics of the antenna device 1 will be described. Figure 7 (a) is a diagram showing the AM gain with respect to frequency of the antenna device 1 with the capacitance of the capacitor section 311 changed. Figure 7 (b) is a diagram showing the FM gain with respect to frequency of the antenna device 1 with the capacitance of the capacitor section 311 changed.

[0068] According to the structure of the antenna AT1, it has been found that the reception efficiency of signals in the MW (LW) band of the antenna device 1 is improved. Figure 7(a) is a graph showing the AM gain, which represents the reception level in the MW (LW) band with respect to the frequency [kHz], according to the presence or absence and the difference in the constant (capacitive reactance) of the capacitance section 311 between the grounded antenna coil 35b and the ground point G. The case without the capacitance section 311 is set as the open end (N.M.: No Mount).

[0069] According to Figure 7 (a), in the MW (LW) band, the reception level is the highest when it is completely set as the open end (N.M.), and as the constant of the capacitance section 311 increases, the reception level decreases. In addition, it can be seen that the reception level is the lowest in the case of grounding without passing through the capacitance section 311 (0 [Ω]).

[0070] In contrast, Figure 7 (b) is a graph showing the FM gain, which represents the reception level in the VHF band with respect to the frequency [MHz], according to the presence or absence and the difference in the constant (capacitive reactance) of the capacitance section 311 between the grounded antenna coil 35b and the ground point G.

[0071] According to Figure 7 (b), in the VHF band, when it is set as the open end (N.M.), a folded-back type structure cannot be formed, so the resonance point of the antenna device 1 cannot be made to coincide with the desired frequency. It can be seen that only when grounding is through the capacitance section 311 or without passing through the capacitance section 311 (0 [Ω]), the folded-back type structure is established, and the resonance point of the antenna device 1 is changed by the capacitance section 311 using the inductance of the antenna coil 35b, but the reception levels are approximately the same.

[0072] As described above, according to the present embodiment, the antenna AT1 of the antenna device 1 includes: a capacitive element 50; an antenna coil 35a having one end connected to the power supply point P and the other end connected to the capacitive element 50; an antenna coil 35b having one end connected to the capacitive element 50; and a capacitance section 311 having one end connected to the antenna coil 35b and the other end connected to the ground point G.

[0073] Therefore, in the antenna device 1, the reception characteristics in the MW (LW) band can be made good, and by adjusting the capacitive reactance of the capacitance section 311, the resonance point in the VHF band can be made to coincide with the desired frequency, making the reception characteristics good. Further, in the antenna device 1, a folded-back type structure can be adopted without adding additional antenna components, and the large size of the capacitive element 50 can be avoided by the capacitance section 311, so the structure can be simple and small.

[0074] In addition, the antenna coil 35a and the antenna coil 35b are thin film components or lead components of a distributed constant coil or a lumped constant coil. Therefore, the antenna coils 35a and 35b can be appropriately arranged.

[0075] In addition, the capacitor section 311 is a distributed constant capacitor section, a thin film component of a lumped constant capacitor, or a lead component. Therefore, the capacitor section 311 can be appropriately set.

[0076] In addition, the antenna device 1 includes: a main body substrate 31 having a power supply point P and a ground point G; and an antenna substrate 34 provided on the main body substrate 31, electrically connected to the capacitor element 50, and having antenna coils 35a and 35b. Therefore, the capacitor element 50 can be arranged at a desired position.

[0077] In addition, the antenna device 1 includes an inner cover portion 40 that supports the capacitor element 50. Therefore, the capacitor element 50 can be arranged at a desired position and reliably fixed and supported.

[0078] In addition, the antenna device 1 includes: an antenna base portion 20 provided with the main body substrate 31 and the inner cover portion 40; a vehicle mounting member 70 that mounts the antenna base portion 20 on a vehicle; and a shark fin-shaped antenna cover portion 10. Therefore, the antenna device 1 can be configured as a shark fin antenna device.

[0079] In addition, the description of the above embodiment is an example of the antenna device of the present invention, but is not limited thereto. For example, the antenna device 1 is provided with an antenna AT1 for receiving AM radio broadcasts / FM radio broadcasts, but is not limited thereto, and may be configured such that, in addition to the antenna AT1, the antenna device 1 is further provided with at least one other antenna such as a patch antenna for receiving GNSS signals from GNSS (Global Navigation Satellite System) satellites.

[0080] In addition, in the above embodiment, the antenna device 1 as a shark fin antenna device that emphasizes appearance is described, but is not limited thereto. Figure 8 (a) is a diagram showing the mounting positions of various antenna devices in the forward oblique direction of the vehicle V1. Figure 8 (b) is a diagram showing the mounting positions of various antenna devices in the rearward oblique direction of the vehicle V1.

[0081] As Figure 8 (a) shows, as an antenna device having the antenna AT1 with the circuit structure shown, in addition to the antenna device 1 mounted at the position p0 on the roof of the vehicle V1, for example, it may also be an antenna device having a dashboard antenna mounted at the position p1 inside the dashboard (instrument panel) of the vehicle V1, or an antenna device having a rearview mirror antenna mounted at the position p2 of the rearview mirror of the vehicle V1. In addition, as Figure 5 shown, in addition to the antenna device 1 mounted at the position p0 on the roof of the vehicle V1, for example, it may also be an antenna device having a dashboard antenna mounted at the position p1 inside the dashboard (instrument panel) of the vehicle V1, or an antenna device having a rearview mirror antenna mounted at the position p2 of the rearview mirror of the vehicle V1. In addition, as Figure 8As shown in (b), as the antenna device having the antenna AT1, it may also be an antenna device having a spoiler antenna installed at the position p3 of the rear spoiler of the vehicle V1, or an antenna device having a glass antenna installed at the position p4 of the rear windshield of the vehicle V1.

[0082] In addition, in the above-described embodiment, the antenna device 1 having the antenna AT1 with the composite antenna of the two bands of MW (LW) band and VHF band has been described, but it is not limited thereto. It may also be configured such that at least one of the two bands is set to another band (such as UHF (Ultra High Frequency) band, etc.).

[0083] In addition, in the above-described embodiment, the antenna device 1 having the antenna AT1 with the composite antenna that forms two bands using the antenna coils 35a and 35b and the capacitance unit 311 has been described, but it is not limited thereto. In the antenna AT1, it may also be configured to provide a circuit unit in which a plurality of antenna coils 35b and capacitance units 311 are connected in series, electrically connect one end of the antenna coil 35b of each circuit unit to the capacitance element 50, electrically connect one end of the capacitance unit 311 of each circuit unit to the ground point G, and connect the other end of each circuit unit to the ground point. With this structure, the antenna AT1 of the antenna device adds the grounded (short-circuited) antenna coils 35b and capacitance units 311, thereby enabling the formation of a composite antenna of three or more bands (for example, three bands of MW (LW) band, VHF band, and UHF band).

[0084] In addition to this, regarding the detailed part structure and detailed operation of the antenna device 1 in the above-described embodiment, appropriate changes may also be made without departing from the gist of the present invention.

Claims

1. An antenna device, characterized in that, Comprising: A capacitive element; A first coil having one end connected to a power supply point and the other end connected to the above capacitive element; A second coil having one end connected to the above capacitive element; And A capacitive portion having one end connected to the above second coil and the other end connected to a ground point, The above capacitive portion has a capacitor whose capacitive reactance increases in a first frequency band and decreases in a second frequency band.

2. The antenna device according to claim 1, characterized in that The above first coil and the above second coil are thin film components or lead components of a distributed constant coil or a lumped constant coil.

3. The antenna device according to claim 1 or 2, characterized in that The above capacitive portion is a thin film component or a lead component of a distributed constant capacitive portion or a capacitor.

4. The antenna device according to claim 1 or 2, characterized in that, Comprising: A main substrate portion having the above power supply point and the above ground point; and An antenna substrate portion erected on the above main substrate portion, electrically connected to the above capacitive element, and having the above first coil and the above second coil.

5. The antenna device according to claim 4, characterized in that It comprises a support portion for supporting the above capacitive element.

6. The antenna device according to claim 5, characterized in that, Comprising: An antenna base portion provided with the above main substrate portion and the above support portion; A vehicle mounting portion for mounting the above antenna base portion on a vehicle; and An antenna cover portion in the shape of a shark fin.

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