Vehicle antenna device

Abstract

To provide a vehicle antenna device that suppresses reduction in reception sensitivity of an antenna on the basis of wiring of electronic equipment when the electronic equipment and the antenna are arranged close to each other.SOLUTION: A vehicle antenna device 100 includes electronic equipment 30, an antenna 40 arranged near the electronic equipment 30 and transmitting and receiving radio waves in a predetermined frequency band, a transmission line 50 that connects the electronic equipment 30 and an ECU 60 installed in a vehicle, a stub 70 which is a conductor connected to the electronic equipment 30 and having a predetermined length LS. The length LS of the stub 70 is set according to the length of the transmission line 50 so as to suppress a decrease in the antenna gain of radio waves included in the frequency band transmitted and received by the antenna 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vehicle antenna device.

Background Art

[0002] In recent years, various electronic devices such as visible light cameras, radars, and sensors have tended to be integrated and installed in brackets in vehicles, particularly in the windshield. Conventionally, an antenna pattern (antenna) made of a conductor for receiving broadcast waves may be disposed on a vehicle window glass such as a windshield. In such a case, in the windshield, the electronic device and the antenna are disposed close to each other so as not to block the view of the vehicle occupants more than necessary. On the other hand, when the electronic device and the antenna are disposed close to each other, the operation of the antenna may become unstable due to noise emitted from the electronic device or the like, and there is a possibility that a desired antenna gain cannot be obtained.

[0003] Therefore, a technique for reducing noise generated when an electronic device and an antenna are disposed close to each other in a vehicle window glass has been studied (for example, Patent Documents 1 and 2). Patent Document 1 discloses that by forming an opening with a conductive pattern larger than the sensor, noise superimposed on the antenna outside the sensor is reduced. Patent Document 2 discloses a configuration in which a noise removal line made of a conducting wire is disposed around a radar device in order to reduce noise generated along with the operation of the radar device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technologies disclosed in Patent Document 1 and Patent Document 2, noise generated from an electronic device is reduced, but coupling to an antenna due to resonance caused by wiring connecting the electronic device and an ECU or the like is not considered. Therefore, even if the technologies disclosed in Patent Document 1 and Patent Document 2 are used, the reception sensitivity of the antenna is reduced due to resonance caused by the wiring connecting the electronic device and the ECU or the like.

[0006] An object of the present invention is to provide a vehicular window antenna device that suppresses a reduction in reception sensitivity of an antenna based on wiring of an electronic device when the electronic device and the antenna are disposed close to each other.

Means for Solving the Problem

[0007] A vehicular antenna device according to an aspect of the present invention includes an electronic device, an antenna disposed in the vicinity of the electronic device and transmitting and receiving radio waves in a predetermined frequency band, a transmission line connecting the electronic device and an ECU installed in a vehicle, and at least one stub which is a conductor having a predetermined length L S and is connected to the electronic device, and the length L S of the at least one stub is set so as to suppress a decrease in antenna gain of radio waves included in the frequency band transmitted and received by the antenna according to the length of the transmission line.

[0008] In the vehicular antenna device described above, the electronic device may be attached to a vehicular window glass, and external information of the vehicle may be acquired through the vehicular window glass.

[0009] In the vehicular antenna device described above, the antenna may be attached in the vicinity of the vehicular window glass.

[0010] In the vehicular antenna device described above, the antenna may be attached to the surface of the vehicular window glass or enclosed in the vehicular window glass.

[0011] In the above-described vehicle antenna device, the vehicle window glass may include a windshield.

[0012] In the above-described vehicle antenna device, the vehicle window glass may include a rear glass.

[0013] In the above-described vehicle antenna device, the at least one stub may be electrically connected to the ground potential portion of the electronic device.

[0014] In the above-described vehicle antenna device, the at least one stub may extend from the electronic device by a single wire.

[0015] In the above-described vehicle antenna device, the at least one stub includes a short stub whose end on the side opposite to the electronic device is connected to the ground, the frequency band of the radio wave transmitted and received by the antenna is λ, the wavelength shortening rate of the dielectric around the short stub is k, and when N is an integer of N≧0, the length L of the short stub SS may satisfy (0.05×(λ / 2)+(λ / 2)×N)×k≦L SS ≦(1.0×(λ / 2)+(λ / 2)×N)×k.

[0016] In the above-described vehicle antenna device, the short stub may be air-wired.

[0017] In the above-described vehicle antenna device, the short stub may be common to the ground wire of the electronic device.

[0018] In the above-described vehicle antenna device, the at least one stub includes an open stub whose end on the side opposite to the electronic device is an open end, the frequency band of the radio wave transmitted and received by the antenna is λ, the wavelength shortening rate of the dielectric around the open stub is k, and when M is an integer of M≧0, the length L of the open stub OS may satisfy (0.1×(λ / 4)+(λ / 2)×M)×k≦L OS ≦(1.0×(λ / 4)+(λ / 2)×M)×k.

[0019] In the above vehicle antenna device, the open stub is disposed on a vehicle window glass to which the electronic device is attached, and k may be a wavelength shortening rate of the vehicle window glass.

[0020] In the above vehicle antenna device, the electronic device includes a heating wire for heating the vehicle window glass, and the open stub may extend from the heating wire.

[0021] In the above vehicle antenna device, the open stub may extend so as to move away from the antenna.

[0022] In the above vehicle antenna device, the open stub may be capacitively coupled to a metal body of the vehicle.

[0023] In the above vehicle antenna device, a distance between a connection point of the electronic device and the at least one stub and a feeding point of the antenna may be 500 mm or less.

[0024] In the above vehicle antenna device, the at least one stub includes a first stub and a second stub, and a length of the first stub may be different from a length of the second stub.

[0025] In the above vehicle antenna device, a length of the transmission line includes a length L from a position where the transmission line intersects an end of a metal body of the vehicle to the ECU and a length d from the position to the electronic device, and a range of the length L may be 1800 mm to 5000 mm.

[0026] In the above vehicle antenna device, the antenna may be capable of receiving radio waves having frequencies in a VHF band to a UHF band.

[0027] In the above vehicle antenna device, the antenna may be capable of receiving at least one of radio waves of DAB Band III and terrestrial digital broadcast waves. [Effect of the Invention]

[0028] According to one aspect of the present invention, when an electronic device and an antenna are arranged close to each other, a vehicle antenna device can be provided that suppresses a reduction in the reception sensitivity of the antenna based on the wiring of the electronic device. [Brief Description of the Drawings]

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0030] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. For clarity of explanation, the following description and drawings are appropriately omitted and simplified. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary. In each embodiment, a deviation within a range that does not impair the effects of the present invention is allowed in directions such as parallel, horizontal, and vertical. In addition, in the drawings for explaining the embodiments, unless otherwise specified, the directions on the drawings shall be referred to.

[0031] (First Embodiment) The vehicle antenna device 100 according to the first embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram of the vehicle antenna device according to the first embodiment. FIG. 1 is a view of the interior of the vehicle with the vehicle window glass 20 described later attached to the vehicle, and is an enlarged view of a portion of the vehicle window glass 20 where the electronic device 30 and the antenna 40 are arranged. In FIG. 1, the X-axis direction corresponds to the horizontal direction and the vehicle width direction, and the Y-axis direction corresponds to the vertical direction orthogonal to the horizontal direction. Note that although FIG. 1 is described as a view of the interior of the vehicle, it may also be referred to as a view of the exterior of the vehicle.

[0032] As shown in FIG. 1, a vehicle antenna device 100 according to a first embodiment includes a vehicle window glass 20, an electronic device 30, an antenna 40, a transmission line 50, an ECU (Electronic Control Unit) 60, and a stub 70.

[0033] The vehicle window glass 20 is a dielectric that forms part of the vehicle where the vehicle antenna device 100 is disposed, and the entire surface may be formed of a glass plate. Also, the dielectric near the electronic device 30 is not limited to the vehicle window glass 20, and part or all of it may contain resin. For example, it may be a shark fin on the roof covered by resin or an aerodynamic part. Hereinafter, the dielectric near the electronic device 30 will be described as the vehicle window glass 20. The vehicle window glass 20 is attached to the metal body 10 of the vehicle and fixed to a body flange formed in the vehicle body housing. The upper part of the vehicle window glass 20 is fixed by a urethane resin or the like near the end 10a of the metal body 10. The vehicle window glass 20 may be a windshield, a rear glass, a side glass, a rear quarter glass, or a roof glass. Note that although FIG. 1 is illustrated as a view showing the upper part of the vehicle window glass 20, when the positions where the electronic device 30 and the antenna 40 are disposed are, for example, the lower part, the left part, or the right part of the vehicle window glass 20, the end 10a may be read as the corresponding end.

[0034] The electronic device 30 includes, for example, a visible light camera, a radar (including millimeter waves), sensors such as an infrared sensor, a rain sensor, a temperature and humidity sensor, and a dew condensation sensor, and a heating wire that heats the vehicle window glass 20 in front of the camera to achieve an anti-fogging and anti-icing effect. The electronic device 30 may be disposed in a bracket (housing) disposed above the driver's seat of the vehicle, and may be attached, for example, to be embedded in the ceiling such as in an overhead console. The electronic device 30 may be attached to the vehicle window glass 20 via a housing, or may be directly attached to the vehicle window glass 20. The electronic device 30 acquires external information of the vehicle or information inside the vehicle compartment through the vehicle window glass 20.

[0035] Antenna 40 is an antenna that transmits and receives radio waves in a predetermined frequency band. Antenna 40 may be an antenna capable of receiving radio waves in the VHF (Very High Frequency) band to UHF (Ultra High Frequency) band. Specifically, Antenna 40 may be an antenna capable of receiving radio waves with a frequency of 30 MHz to 3 GHz. Also, Antenna 40 may be an antenna capable of receiving at least one of the radio waves of DAB (Digital Audio Broadband) Band III (174 MHz to 240 MHz) and terrestrial digital television broadcast waves (470 MHz to 710 MHz) included in the VHF band to UHF band. Note that Antenna 40 may be an antenna capable of receiving radio waves in the frequency band of FM broadcast waves (76 MHz to 108 MHz) and narrow-band ITS (Intelligent Transport Systems) radio waves including 760 MHz.

[0036] Furthermore, Antenna 40 may be an antenna capable of transmitting and receiving radio waves in the LTE (Long Term Evolution) frequency band, an antenna capable of receiving radio waves in satellite communication frequency bands such as GNSS (Global Navigation Satellite System) and SDARS (Satellite Digital Audio Radio Service), or an antenna capable of transmitting and receiving radio waves in the frequency band of 5G (5th generation mobile communication system). Examples of antennas for 5G include antennas capable of transmitting and receiving radio waves in a narrow communication frequency band (for example, 5.8 GHz band) called DSRC (Dedicated Short Range Communication) used for V2X (Vehicle to Everything) such as vehicle-to-vehicle communication and road-to-vehicle communication. Also, Antenna 40 is not limited to one of the antennas exemplified above, and may be integrated and arranged at one location including a plurality of antennas, or a plurality of antennas may be individually dispersed and arranged near the vehicle window glass 20. Note that "transmitting and receiving" is used in the sense that Antenna 40 enables "transmitting" or "receiving" or both "transmitting" and "receiving" of radio waves.

[0037] The antenna 40 may be arranged such that the distance from the electronic device 30 is, for example, 500 mm or less. If the distance exceeds 500 mm, since the antenna 40 is arranged sufficiently far from the electronic device 30, isolation can be achieved between the two, and the antenna sensitivity of the antenna 40 is less likely to decrease. On the other hand, even if the antenna 40 and the electronic device 30 are separated, due to layout restrictions, it is preferable that the distance is 500 mm or less and the decrease in the antenna sensitivity of the antenna 40 can be suppressed, as this improves the degree of freedom in arrangement. Further, the distance may be 350 mm or less, may be 200 mm or less, or may be 100 mm or less. Furthermore, the distance may not particularly have a lower limit, but for example, it may be 0 mm or more, may be 5 mm or more, may be 10 mm or more, may be 30 mm or more, or may be 50 mm or more. The distance between the antenna 40 and the electronic device 30 is the distance between the center of the power supply unit 41 described later and the center of the electronic device 30. The antenna 40 is attached near the vehicle window glass 20.

[0038] The antenna 40 may be attached to the surface of the vehicle window glass 20. Alternatively, the antenna 40 may be encapsulated inside the vehicle window glass 20. Alternatively, if the antenna 40 is on a dielectric, it may be arranged inside an aerodynamic part made of resin such as a rear spoiler, and if the dielectric is air, the antenna 40 may be aerial-wired. Alternatively, the antenna 40 may be arranged on a metal. As an example of the antenna 40 being arranged on a metal, it may be an antenna (so-called shark fin antenna) inside a protruding resin radome installed on the metal roof of a vehicle. Since the shark fin antenna is often arranged at the rear of the vehicle roof, examples of the electronic device include, for example, a high-mounted stop lamp and a visible light camera (rear camera) attached near the rear glass.

[0039] The antenna 40 is arranged at a position that does not impair the field of view of the vehicle occupants in the vehicle where the vehicle antenna device 100 is arranged. In the present embodiment, the antenna 40 is described as being arranged above the vehicle window glass 20, but it is not limited to this.

[0040] In FIG. 1, the antenna 40 includes a power feeding unit 41 and a strip element 42. The antenna 40 shown in FIG. 1 is a so-called monopole antenna. Note that the antenna 40 may be a so-called dipole antenna further including a ground portion (not shown) and a strip element connected to the ground portion. The power feeding unit 41 is disposed close to the metal body 10. The power feeding unit 41 (and the ground portion) is connected to a communication device (not shown) via a transmission line such as a coaxial cable (not shown).

[0041] The strip element 42 is an antenna element made of a conductor. One end of the strip element 42 is connected to the power feeding unit 41, and the other end is an open end. The strip element 42 has, for example, an L shape. The strip element 42 is connected to the power feeding unit 41 at a point 42a with the point 42a as a connection point and extends from the point 42a to a point 42b in the negative Y-axis direction. The strip element 42 extends from the point 42b to a point 42c in the positive X-axis direction. In FIG. 1, the shape of the strip element 42 is an L shape, but it may be arbitrarily set according to the vehicle in which the vehicle antenna device 100 is disposed, such as forming a closed loop with the strip element.

[0042] The transmission line 50 connects the electronic device 30 and the ECU 60 installed in the vehicle where the vehicle antenna device 100 is disposed. The transmission line 50 is, for example, an AV cable, and a twisted pair cable may be used as a communication line conforming to the CAN (Controller Area Network) standard. The length of the transmission line 50 includes the length L from the point 50a to the ECU 60 and the length d from the point 50a to the electronic device 30. The point 50a is a position where the transmission line 50 intersects with the end portion (end portion 10a) of the metal body of the vehicle. As an example of the range of the length L, 1800 mm to 5000 mm can be cited. The upper and lower limits of the length L vary depending on the vehicle. For example, it may be 1900 mm or more, 2000 mm or more, 4000 mm or less, 3500 mm or less, 3000 mm or less, or 2500 mm or less. The length d may be, for example, 5 mm or more, 10 mm or more, 50 mm or more, or 100 mm or more. Further, the length d may be 300 mm or less, 200 mm or less, or 150 mm or less.

[0043] The ECU 60 is a control device that controls the electronic device 30. In addition to the ECU 60, the vehicle in which the vehicle antenna device 100 is disposed may be provided with ECUs for engine control, brake control, and safety control.

[0044] The stub 70, which is a conductor (wire) having one end connected to the electronic device 30 and extending, may be a short stub having the other end connected to the ground, or an open stub having the other end as an open end. The stub 70 is connected to the electronic device 30 at the point 70a (connection point 70a) and has a predetermined length L s and is a conductor that can be connected to a terminal at the same potential as the ground of the electronic device 30 or a terminal having a DC potential exceeding 0 [V]. However, it is preferable to connect to a terminal at the same potential as the ground because it is more stable. That is, it is preferable that the stub 70 is connected to the ground potential portion of the electronic device 30 because it is electrically more stable. Further, the stub 70 is preferably a wire extending from the electronic device 30 in a single line without forming a branch or a closed loop.

[0045] Here, when the electronic device 30 is attached to the vehicle window glass 20 and connected to the ECU via the transmission line 50, the electronic device 30 also functions as a pseudo antenna. Therefore, when the electronic device 30 is arranged in the vicinity of the antenna 40, the electronic device 30 couples with the radio waves in a specific frequency band transmitted and received by the antenna 40, causing a decrease in the sensitivity of the antenna 40. That is, when the electronic device 30 has a frequency that resonates within the same frequency band as that transmitted and received by the antenna 40, the gain of the antenna 40 decreases. Thus, the vehicle antenna device 100 according to the first embodiment includes a stub 70 having a length L s and, depending on Wavelength λ of radio wave transmitted and received by antenna 40 , by adjusting the length L s , it is possible to suppress a decrease in the antenna gain of the radio waves included in the frequency band transmitted and received by the antenna 40. The length L s is the length from the point 70a where the stub 70 is connected to the electronic device 30 to the end opposite to the point 70a. In the present embodiment, the stub 70 is described as a short stub. Also, since the stub 70 is a short stub, in the following description, the length L s may be described as the length L ss .

[0046] One end of the stub 70 opposite to the electronic device 30 is connected to the metal body 10 (ground). The stub 70 may be constituted by the ground wire of the electronic device 30. In other words, the stub 70 may be common with the ground wire of the electronic device 30. Also, at least a part of the stub 70 from the end connected to the electronic device 30 to the end opposite thereto may be aerial wiring.

[0047] The length L ss of the stub 70 is set so that the relationship between the wavelength λ [mm] of the radio waves transmitted and received by the antenna 40 and the wavelength shortening rate k of the dielectric around the stub 70 satisfies the following formula (1).

Equation

[0048] More preferable length L of stub 70 ss falls within the range of formula (2).

Equation

[0049] Even more preferable length L of stub 70 ss falls within the range of formula (3).

Equation

[0050] Thus, under the above conditions, by setting the length L of stub 70 ss to satisfy the above formula (1), it is possible to suppress a decrease in the antenna gain of radio waves included in the frequency band transmitted and received by antenna 40.

[0051] Next, the antenna gain of antenna 40 in vehicle antenna device 100 will be described. To evaluate the antenna gain of antenna 40 in vehicle antenna device 100, the antenna gain of antenna 40 in vehicle antenna device 100 including stub 70 and in a configuration without stub 70 with respect to vehicle antenna device 100 was compared. In the present embodiment, a configuration obtained by removing only stub 70 from vehicle antenna device 100 is referred to as the "default configuration".

[0052] To compare the antenna gain of antenna 40 between vehicle antenna device 100 and the default configuration, the S11 parameter of antenna 40 was evaluated by simulation.

[0053] First, before showing the evaluation results, the frequency characteristics of the S11 parameters of antenna 40, electronic device 30, and transmission line 50 used in the simulation will be described.

[0054] Using FIG. 2, the frequency characteristics of the S11 parameter of the antenna 40 will be described. Here, in the power feeding unit 41, the S11 parameter of the antenna 40 was calculated by simulating the ratio between the input power and the reflected power of the antenna 40. In the figures showing the frequency characteristics of the S11 parameter shown hereinafter, similar to FIG. 2, the horizontal axis represents the frequency [MHz], and the vertical axis represents the value of the S11 parameter [dB].

[0055] As shown in FIG. 2, for the antenna 40 used in the simulation, the length of the strip element 42 was set so as to resonate at a frequency of 200 MHz. Also, the antenna 40 is set such that the value of the S11 parameter becomes -7.1 dB at a frequency of 200 MHz.

[0056] Next, using FIG. 3, the frequency characteristics of the S11 parameter of the electronic device 30 will be described. Here, the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was set to 100 mm, and at the point 50a, the S11 parameter of the electronic device 30 was calculated by simulating the ratio between the input power and the reflected power of the electronic device 30. As shown in FIG. 3, the electronic device 30 used in the simulation is set to resonate at a frequency of 180 MHz. Also, the electronic device 30 is set such that the value of the S11 parameter becomes -27.4 dB at a frequency of 180 MHz.

[0057] Using FIG. 4, the frequency characteristics of the S11 parameter of the transmission line 50 will be described. FIG. 4 is a diagram showing the frequency characteristics of the S11 parameter of the transmission line. The transmission line 50 used in the simulation was modeled such that the length L in the transmission line 50 was set to 2870 mm, and two signal lines were terminated at 60 Ω from a position 1 mm away from the ECU 60 side from point 50a. At point 50a, the S11 parameter of the transmission line 50 was calculated by simulating the ratio of the input power to the reflected power of the transmission line 50. As shown in FIG. 4, the transmission line 50 is a model in which the frequencies at which the S11 parameter becomes a minimum value (about -12 dB) are periodic. Note that at the frequency at which the S11 parameter is about -12 dB, the transmission line 50 is matched to 50 Ω.

[0058] Next, the comparison result of the antenna gain of the vehicle antenna device 100 and the antenna 40 in the default configuration will be described. First, using FIG. 5, the comparison result of the vehicle antenna device 100 and the default configuration when the distance between the electronic device 30 and the antenna 40 is set to 200 mm and the length L ss of the stub 70 is set to 550 mm will be described. FIG. 5 is a diagram for comparing the antenna gains of the vehicle antenna device and the antenna in the default configuration. Note that in FIG. 5, the length L ss of the stub 70 is set to 550 mm for the purpose of suppressing the reduction of the antenna gain at the frequency 200 MHz which is the resonance frequency of the antenna 40.

[0059] FIG. 5 is a diagram showing the frequency characteristics of the S11 parameter of the antenna 40 in the power supply unit 41 in the vehicle antenna device 100 and the S11 parameter of the antenna 40 in the power supply unit 41 in the default configuration. Note that in the simulation, the electronic device 30, the antenna 40, and the transmission line 50 having the characteristics shown in FIGS. 2 to 4 were used. Also, the stub 70 was arranged as aerial wiring, and the wavelength shortening rate k around the stub 70 was set to 1.0.

[0060] In FIG. 5, the dotted line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the vehicle antenna device 100. As shown in FIG. 5, in the case of the default configuration, at 200 MHz which is the resonance frequency of the antenna 40, the value of the S11 parameter is -4.5 dB. That is, in the case of the default configuration, due to the resonance of the electronic device 30 and the transmission line 50, the value of the S11 parameter of the antenna 40 at a frequency of 200 MHz deteriorates from -7 dB to -4.5 dB. Note that the lower the S11 parameter, the more the reduction in the antenna gain given to the antenna 40 due to the resonance of the electronic device 30 and the transmission line 50 can be suppressed.

[0061] On the other hand, in the case of the vehicle antenna device 100, at 200 MHz which is the resonance frequency of the antenna 40, the value of the S11 parameter is -6.2 dB. Also, at a frequency of 205 MHz, the S11 parameter becomes -6.4 dB which is the minimum value. That is, since the vehicle antenna device 100 has a configuration including the stub 70, the reduction in the reception sensitivity of the antenna 40 due to the resonance of the electronic device 30 and the transmission line 50 can be suppressed.

[0062] Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening ratio k is 1.0, the frequency of the radio wave transmitted and received by the antenna 40 is 200 MHz (λ≒1499 mm), and the length L of the stub 70 ss is 550 mm. When calculated using these values, the length L of the stub 70 ss satisfies equations (1) to (3) when the integer N is 0. That is, the vehicle antenna device 100 includes the stub 70, and furthermore, since the length L of the stub 70 ss satisfies equations (1) to (3), the reduction in the reception sensitivity of the antenna 40 can be suppressed as compared with the default configuration.

[0063] Next, using FIG. 6, the distance between the electronic device 30 and the antenna 40 is 200 mm, and the length L of the stub 70 ssThe comparison result of the antenna gain between the vehicle antenna device 100 when the length L is 550 mm and the default configuration will be described. FIG. 6 is a diagram for comparing the antenna gains of the antenna in the vehicle antenna device and in the default configuration.

[0064] FIG. 6 is a diagram showing the frequency characteristics of the S11 parameter of the antenna 40 in the power feeding unit 41 in the vehicle antenna device 100 and the S11 parameter of the antenna 40 in the power feeding unit 41 in the default configuration. In the simulation, the antenna 40 and the transmission line 50 having the characteristics shown in FIGS. 2 and 4 were used. For the electronic device 30, the characteristics when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was 50 mm were used. Also, the wavelength shortening rate k around the stub 70 was set to 1.0. The length L of the stub 70 ss is 550 mm.

[0065] In FIG. 6, the dotted line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the vehicle antenna device 100. In the case of the default configuration, the value of the S11 parameter has a characteristic that it rises steeply as the frequency increases with the vicinity of the frequency 198 MHz as the first inflection point, and rises gently as the frequency further increases with the vicinity of the frequency 211 MHz as the second inflection point. That is, in the vicinity of the frequency 210 MHz, it shows that the reception sensitivity of the antenna 40 is reduced due to the influence of the resonance of the electronic device 30 and the transmission line 50.

[0066] On the other hand, in the vehicle antenna device 100, in the vicinity of the frequency 210 MHz, the value of the S11 parameter becomes lower than that in the default configuration, and the slope of the S11 parameter becomes substantially constant. That is, the length L of the stub 70 ss is set to a length (550 mm) that can suppress the decrease in the reception sensitivity of the antenna 40 in the vicinity of the frequency 210 MHz, so the vehicle antenna device 100 can suppress the reduction in the reception sensitivity of the antenna 40.

[0067] Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening ratio k is 1.0, and the length L of the stub 70 ss is 550 mm. Also, in an example shown in FIG. 6, the frequency of the radio wave transmitted and received by the antenna 40, and the target frequency for reducing the reduction in the reception sensitivity of the antenna 40 is 210 MHz. When calculated using these values, the length L of the stub 70 ss satisfies the equations (1) to (3) when the integer N is 0. That is, the vehicle antenna device 100 includes the stub 70, and further, since the length L of the stub 70 ss satisfies the equations (1) to (3), it is possible to suppress the reduction in the reception sensitivity of the antenna 40 as compared with the default configuration.

[0068] Next, with reference to FIG. 7, the relationship between the distance between the electronic device 30 and the antenna 40 and the S11 parameter of the antenna 40 at a frequency of 200 MHz will be described. FIG. 7 is a diagram showing the relationship between the distance between the electronic device 30 and the antenna and the S11 parameter of the antenna at a frequency of 200 MHz. In the simulation, the electronic device 30, the antenna 40, and the transmission line 50 having the characteristics shown in FIGS. 2 to 4 were used. Also, the wavelength shortening ratio k around the stub 70 was set to 1.0, and the length L of the stub 70 ss was set to 550 mm.

[0069] In FIG. 7, the horizontal axis indicates the distance [mm] between the electronic device 30 and the antenna 40, and the vertical axis indicates the value [dB] of the S11 parameter. The solid line is the S11 parameter at a frequency of 200 MHz and represents the S11 parameter of the antenna 40 in the vehicle antenna device 100. The dotted line is the S11 parameter at a frequency of 200 MHz and represents the S11 parameter of the antenna 40 in the default configuration.

[0070] As shown in FIG. 7, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 400 mm, the S11 parameter is lower for the vehicle antenna device 100 than the default configuration. That is, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 400 mm, it can be seen that the vehicle antenna device 100 is such that the antenna 40 is not affected by the resonance from the electronic device 30 and the transmission line 50 more than the default configuration. Thus, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 400 mm, the vehicle antenna device 100 can suppress the decrease in the reception sensitivity of the antenna 40 more than the default configuration.

[0071] Next, using FIG. 8, the length L of the stub 70 ss and the relationship with the S11 parameter of the antenna 40 of the vehicle antenna device 100 at a frequency of 200 MHz will be described. FIG. 8 is a diagram showing the relationship between the length of the stub and the S11 parameter of the antenna. In the simulation, the electronic device 30, the antenna 40, and the transmission line 50 having the characteristics shown in FIGS. 2 to 4 were used. Also, the wavelength shortening rate k around the stub 70 was set to 1.0.

[0072] In FIG. 8, the horizontal axis represents the length L of the stub 70 ss [mm], and the vertical axis represents the value [dB] of the S11 parameter. The solid line represents the value [dB] of the S11 parameter of the antenna 40 of the vehicle antenna device 100 at a frequency of 200 MHz. In FIG. 8, the length L at which the S11 parameter becomes the maximum value (extreme value), ss [mm], and the length L at which the S11 parameter becomes the minimum value (extreme value), ss [mm], etc., the length L at which the S11 parameter becomes substantially the same value ss [mm], it can be seen that it has periodicity. For example, the length L of the stub 70 at which the S11 parameter shows the minimum value ss [mm] is 550 mm and 1300 mm. Here, since the frequency is 200 MHz, the half wavelength (1 / 2 wavelength) [mm] is the speed of the radio wave, which is 3.0×10 8 [m / s] divided by 200×10 6The value obtained by dividing by [Hz] and 2 is 750 [mm] (= 0.75 [m]). That is, the length L of the stub 70 ss [mm] can suppress the reduction in the reception sensitivity of the antenna 40 every time the distance increases by half the wavelength λ [mm] of the radio wave transmitted and received by the antenna 40. Therefore, the length L of the stub 70 ss When satisfies the expressions (1) to (3), the vehicle antenna device 100 can suppress the reduction in the reception sensitivity of the antenna 40.

[0073] (Second Embodiment) Next, with reference to FIG. 9, the vehicle antenna device 200 according to the second embodiment will be described. FIG. 9 is a schematic diagram of the configuration of the vehicle antenna device 200 according to the second embodiment, and includes an electronic device 30, an antenna 40, a transmission line 50, an ECU 60, and a stub 80.

[0074] The vehicle antenna device 200 has a configuration in which the stub 70 in the vehicle antenna device 100 according to the first embodiment is replaced by a stub 80. Since the configurations of the electronic device 30, the antenna 40, the transmission line 50, and the ECU 60 are the same as those in the first embodiment, descriptions common to the first embodiment for these configurations will be omitted as appropriate.

[0075] The stub 80 is an open stub in which one end of the conductor is an open end. The stub 80 is connected to the electronic device 30 at the point 80a and has a conductor of a predetermined length L os The stub 80 may be disposed on the vehicle window glass 20. Since the stub 80 is an open stub, the length of the stub 80 is denoted as L os However, the length of the stub 80 may be described as the generalized L as in the first embodiment. s as described.

[0076] Stub 80 extends from the electronic device 30 in a single line without forming branches or closed loops. The stub 80 has, for example, an L shape, extends from point 80a in the positive Y-axis direction to point 80b, and extends from point 80b in the negative X-axis direction to point 80c. In particular, the stub 80 extends so as to move away from the antenna 40. The stub 80 has an open end at point 80c, which is the end opposite to the electronic device 30, and constitutes an open stub. Note that in FIG. 9, the stub 80 is not limited to an L shape and can have any shape that can form an open stub.

[0077] Among the stub 80, the portion from point 80b to point 80c may be close to the end 10a of the metal body 10. The distance between the portion from point 80b to point 80c of the stub 80 and the end 10a of the metal body 10 may be 5 mm to 30 mm. That is, the metal body 10 and the portion from point 80b to point 80c of the stub 80 are configured as a capacitive coupling portion. The capacitive coupling portion is capacitively coupled to the conductor portion with a predetermined capacitance value. The portion from point 80b to point 80c of the stub 80 forms a line having a specific characteristic impedance. Note that the presence or absence of the capacitive coupling portion and the length when the capacitive coupling portion is present can be arbitrarily set for the stub 80. Also, the connection point 80a of the stub 80 to the electronic device 30 may be the ground potential portion of the electronic device 30.

[0078] The length L of the stub 80 os is Wavelength λ of radio wave transmitted and received by antenna 40 set so as to suppress a decrease in the antenna gain of radio waves included in the frequency band transmitted and received by the antenna 40 according to. The length L of the stub 80 os is set so that the relationship between the wavelength λ [mm] of the radio waves transmitted and received by the antenna 40 and the wavelength shortening rate k of the dielectric around the stub 80 satisfies the following formula (4). When the stub 80 is disposed on the vehicle window glass 20, in the following formula (4), the wavelength shortening rate k is the wavelength shortening rate of the vehicle window glass 20, and when the stub 80 is an aerial wiring, the wavelength shortening rate of air (k = 1.0).

Equation

[0079] The more preferable length L of the stub 70 os falls within the range of formula (5).

Equation

[0080] The even more preferable length L of the stub 70 os falls within the range of formula (6).

Equation

[0081] Thus, under the above conditions, by setting the length L of the stub 80 os to satisfy the above formula (4), it is possible to suppress a decrease in the antenna gain of radio waves included in the frequency band transmitted and received by the antenna 40.

[0082] Next, the antenna gain of the antenna 40 in the vehicle antenna device 200 will be described. To evaluate the antenna gain of the antenna 40 in the vehicle antenna device 200, the antenna gain of the vehicle antenna device 200 including the stub 80 and the configuration of the vehicle antenna device 200 having no stub 80 were compared and evaluated. In the present embodiment, the configuration obtained by removing only the stub 80 from the vehicle antenna device 200 is referred to as the "default configuration".

[0083] To compare the antenna gains of the antenna 40 in the vehicle antenna device 200 and the default configuration, the S11 parameter of the antenna 40 was calculated and evaluated by simulation.

[0084] First, using FIG. 10, the distance between the electronic device 30 and the antenna 40 is 200 mm, and the length L of the stub 80 osThe comparison result of the antenna gain between the vehicle antenna device 200 when [the relevant parameter] is 190 mm and the default configuration will be described. In the simulation, the antenna 40 and the transmission line 50 having the characteristics shown in FIGS. 2 and 4 were used. For the electronic device 30, the characteristics when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was 50 mm were used. Also, the stub 80 was assumed to be a hollow wiring, and the wavelength shortening rate k around the stub 80 was set to 1.0.

[0085] FIG. 10 is a diagram showing the frequency characteristics of the S11 parameter of the antenna 40 in the power feeding unit 41 in the vehicle antenna device 200 and the S11 parameter of the antenna 40 in the power feeding unit 41 in the default configuration.

[0086] In FIG. 10, the dotted line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the vehicle antenna device 200. As shown in FIG. 10, in the case of the default configuration, the S11 parameter has a characteristic that it rises steeply as the frequency increases with the vicinity of the frequency 197 MHz as the first inflection point, and rises gently as the frequency further increases with the vicinity of the frequency 211 MHz as the second inflection point. That is, in the vicinity of the frequency of 210 MHz, the antenna 40 is affected by the resonance of the electronic device 30 and the transmission line 50, indicating that the reception sensitivity of the antenna 40 is reduced.

[0087] On the other hand, for the vehicle antenna device 200, in order to suppress the decrease in the reception sensitivity of the antenna 40 with respect to the frequency of 210 MHz at which the reception sensitivity of the antenna 40 is reduced, the length L of the stub 80 os is set to 190 mm. Therefore, in the vicinity of the frequency of 210 MHz, the value of the S11 parameter becomes lower than that in the default configuration, and the slope of the S11 parameter becomes substantially constant. That is, the vehicle antenna device 200 has the length L of the stub 80 osSince it is adjusted with respect to 210 MHz, which is the target frequency for reducing the reduction in the reception sensitivity of the antenna 40, it is possible to suppress the reduction in the reception sensitivity of the antenna 40.

[0088] Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening ratio k is 1.0, the frequency band of the radio wave transmitted and received by the antenna 40 is 210 MHz, and the length L of the stub 80 os is 190 mm. When calculated using these values, the length L of the stub 80 os satisfies equations (4) to (6) when M is 0. That is, the vehicle antenna device 200 includes the stub 80, and further, since the length L of the stub 80 os satisfies equations (4) to (6), it is possible to suppress the reduction in the reception sensitivity of the antenna 40 as compared with the default configuration.

[0089] Next, using FIG. 11, the comparison result of the antenna gain between the vehicle antenna device 200 when the distance between the electronic device 30 and the antenna 40 is 200 mm and the length L of the stub 80 disposed on the vehicle window glass 20 is 205 mm, and the default configuration will be described. FIG. 11 is a diagram for comparing the antenna gains of the antenna in the vehicle antenna device and the default configuration. os FIG. 11 is a diagram showing the frequency characteristics of the S11 parameter of the antenna 40 in the power feeding unit 41 in the vehicle antenna device 200 and the S11 parameter of the antenna 40 in the power feeding unit 41 in the default configuration. In the simulation, the antenna 40 and the transmission line 50 having the characteristics shown in FIGS. 2 and 4 were used. For the electronic device 30, the characteristics when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was 50 mm were used. The wavelength shortening ratio k around the stub 80 (vehicle window glass 20) was set to 0.67.

[0090] FIG. 11 is a diagram showing the frequency characteristics of the S11 parameter of the antenna 40 in the power feeding unit 41 in the vehicle antenna device 200 and the S11 parameter of the antenna 40 in the power feeding unit 41 in the default configuration. In the simulation, the antenna 40 and the transmission line 50 having the characteristics shown in FIGS. 2 and 4 were used. For the electronic device 30, the characteristics when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was 50 mm were used. The wavelength shortening ratio k around the stub 80 (vehicle window glass 20) was set to 0.67.

[0091] In FIG. 11, the dotted line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristics of the S11 parameter of the antenna 40 in the vehicle antenna device 200. In the case of the default configuration, the S11 parameter has a first inflection point near the frequency of 197 MHz, rises steeply as the frequency increases, has a second inflection point near the frequency of 211 MHz, and rises gently as the frequency further increases. That is, in the vicinity of the frequency of 210 MHz, the antenna 40 is affected by the resonance of the electronic device 30 and the transmission line 50, indicating that the reception sensitivity of the antenna 40 is reduced.

[0092] In contrast, the vehicle antenna device 200 sets the length L os of the stub 80 to 205 mm in order to suppress the decrease in the reception sensitivity of the antenna 40 with respect to the frequency of 210 MHz at which the reception sensitivity of the antenna 40 is reduced. Therefore, in the vicinity of the frequency of 210 MHz, the value of the S11 parameter becomes lower than that in the default configuration, and the slope of the S11 parameter becomes substantially constant. That is, since the length L os of the stub 80 of the vehicle antenna device 200 is adjusted with respect to 210 MHz, which is the target frequency for reducing the decrease in the reception sensitivity of the antenna 40, the reduction in the reception sensitivity of the antenna 40 can be suppressed.

[0093] Here, the length L in the transmission line 50 is 2870 mm, the wavelength shortening rate k around the stub 80 (vehicle window glass 20) is 0.67, and the length L os of the stub 80 is 205 mm. Also, in an example shown in FIG. 11, the frequency of the radio wave transmitted and received by the antenna 40, that is, the target frequency λ for reducing the decrease in the reception sensitivity of the antenna 40 is 210 MHz. Using these values for calculation, it can be seen that the length L os of the stub 80 satisfies equations (4) to (6) when M is 0. That is, the vehicle antenna device 200 includes the stub 80, and further, the length L osSince the conditions of Formula (4) to Formula (6) are satisfied, it is possible to suppress the reduction in the reception sensitivity of the antenna 40 as compared with the default configuration. When the vehicle window glass 20 is a single plate, the wavelength shortening rate k can be exemplified by about 0.67. When the laminated glass with an intermediate film sandwiched between two glasses is used, the wavelength shortening rate k can be exemplified by about 0.5.

[0094] Next, with reference to FIG. 12, the relationship between the distance between the electronic device 30 and the antenna 40 and the value of the S11 parameter of the antenna 40 at a frequency of 200 MHz will be described. FIG. 12 is a diagram showing the relationship between the distance between the electronic device 30 and the antenna 40 and the value of the S11 parameter of the antenna at a frequency of 200 MHz. In the simulation, the electronic device 30, the antenna 40, and the transmission line 50 having the characteristics shown in FIGS. 2 to 4 were used. The stub 80 assumes a hollow wiring, and the wavelength shortening rate k around the stub 80 was set to 1.0. The length L of the stub 80 os is 320 mm.

[0095] In FIG. 12, the horizontal axis represents the distance [mm] between the electronic device 30 and the antenna 40, and the vertical axis represents the value [dB] of the S11 parameter. The solid line is the S11 parameter at a frequency of 200 MHz and represents the S11 parameter of the antenna 40 in the vehicle antenna device 200. The dotted line is the S11 parameter at a frequency of 200 MHz and represents the S11 parameter of the antenna 40 in the default configuration.

[0096] As shown in FIG. 12, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 200 mm, the S11 parameter is lower for the vehicle antenna device 200 than the default configuration. That is, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 200 mm, the vehicle antenna device 200 is such that the antenna 40 is not affected by the resonance from the electronic device 30 and the transmission line 50 more than the default configuration. When the distance between the electronic device 30 and the antenna 40 is 200 mm to 400 mm, the S11 parameter is slightly smaller for the default configuration than the vehicle antenna device 200, but is substantially the same value. This is presumably because, since the distance between the electronic device 30 and the antenna 40 is large, the antenna 40 is less likely to be affected by the resonance of the electronic device 30, so that the S11 parameter is substantially the same value for the vehicle antenna device 200 and the default configuration. As described above, in the range where the distance between the electronic device 30 and the antenna 40 is 50 mm to 200 mm, the vehicle antenna device 200 can suppress the decrease in the reception sensitivity of the antenna 40 more than the default configuration. Also, when the distance between the electronic device 30 and the antenna 40 is 200 mm to 400 mm, the vehicle antenna device 200 can suppress the decrease in the reception sensitivity of the antenna 40 in the same manner as the default configuration.

[0097] Next, using FIG. 13, the length L of the stub 80 os and the relationship with the S11 parameter of the antenna 40 of the vehicle antenna device 200 at a frequency of 210 MHz were evaluated. In the simulation, the antenna 40 and the transmission line 50 having the characteristics shown in FIGS. 2 and 4 were used. For the electronic device 30, the characteristics when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was 50 mm were used. The stub 80 was assumed to be a hollow wiring, and the wavelength shortening rate k around the stub 80 was set to 1.0.

[0098] In FIG. 13, the horizontal axis represents the length L of the stub 80 osrepresents [mm], and the vertical axis represents the value [dB] of the S11 parameter. The solid line represents the value [dB] of the S11 parameter of the antenna 40 of the vehicle antenna device 200 at a frequency of 210 MHz. In FIG. 13, the length L at which the S11 parameter reaches the maximum value (peak value) os [mm], and the length L at which the S11 parameter reaches the minimum value (trough value) os [mm], etc., the length L at which the S11 parameter is substantially the same value os [mm], it can be seen that it has periodicity. For example, the length L of the stub 80 at which the S11 parameter shows a minimum value os [mm] is 200 mm and 920 mm. That is, every time the length L os [mm] of the stub 80 increases by a distance equal to half of the wavelength λ of the radio wave transmitted and received by the antenna 40, the reduction in the reception sensitivity of the antenna 40 can be suppressed. Therefore, when the length L os of the stub 80 satisfies the formulas (4) to (6), the vehicle antenna device 200 can suppress the reduction in the reception sensitivity of the antenna 40.

[0099] (Modification Example 1) In the second embodiment, when the electronic device 30 includes a heating wire (for anti-fogging and anti-icing of the glass around the camera), the stub 80 may be arranged as shown below. FIG. 14 is a diagram showing a configuration example of a vehicle antenna device 300 according to Modification Example 1. The vehicle antenna device 300 includes an electronic device 30, an antenna 40, a transmission line 50, an ECU 60, and a stub 80. The electronic device 30 includes a heating unit 90 and a camera 150. The vehicle antenna device 300 has a configuration including a heating unit 90 and a camera 150 as a specific example of the electronic device 30 of the vehicle antenna device 200 according to the second embodiment. Note that the antenna 40, the transmission line 50, the ECU 60, and the stub 80 are the same as those in the second embodiment, and thus the description thereof will be omitted as appropriate. Also, in FIG. 14, for the sake of convenience, the heating unit 90 and the camera 150 in the electronic device 30 are shown separated from each other, but actually, the imaging unit of the camera 150 overlaps with the heating unit 90 in a plan view of the vehicle window glass 20.

[0100] The heating part 90 is the heating part of the vehicle window glass 20. The heating part 90 is provided, for example, for the purpose of anti-icing and anti-fogging of the transmission area of the vehicle window glass 20. The transmission area is an area where an electronic device 30 such as an information device installed inside the vehicle receives radio waves through the vehicle window glass 20 from the outside of the vehicle or transmits signals through the vehicle window glass 20 to the outside of the vehicle. The heating part 90 includes a heating wire 91, a power supply part 92, and a grounding part 93. At least a part of the heating wire 91 is arranged in the transmission area. The heating wire 91 is applied with a DC voltage from the power supply part 92 and is heated by the resistance of the heating wire 91 to heat the transmission area. Further, the power supply part 92 and the grounding part 93 are connected to a DC power supply arranged away from the vicinity of the transmission area via an electrical wiring (such as a harness) not shown in the figure. As shown in FIG. 14, at least one of the power supply part 92 and the grounding part 93 is connected to the camera 150. Note that the grounding part side electrical wiring on the side connected to the grounding part 93 may be arranged to take a ground connection near the DC power supply or may be arranged to take a ground connection at an arbitrary position of the metal body 10.

[0101] The camera 150 is a specific example of the electronic device 30 in the second embodiment and is, for example, a visible light camera. As described above, the camera 150 is connected to at least one of the power supply part 92 and the grounding part 93 of the heating part 90.

[0102] The stub 80 is, for example, an open stub. The stub 80 is connected to the heating wire 91 of the heating part 90 at the point 80a. In other words, the stub 80 extends from the ground potential part of the heating wire 91 with the point 80a as the ground potential part. The stub 80 extends in a single line from the point 80a, which is the ground potential part of the heating part 90, without forming a branch and a closed loop. The stub 80 has, for example, an L shape, extends from the point 80a in the positive Y-axis direction to the point 80b, and extends in the negative X-axis direction from the point 80b to the point 80c (open end). Note that the point 80a, which is the connection point between the stub 80 and the heating part 90, may be an arbitrary position of the heating wire 91. Further, the point where the stub 80 and the heating part 90 are connected is not limited to the ground potential part.

[0103] As described above, even when the heating unit 90 of the vehicle antenna device 300 according to the first modification includes the heating wire 91 and the stub 80 which is an open stub is configured to extend from the ground potential portion of the heating wire 91, the same effects as those of the second embodiment can be obtained.

[0104] (Second Modification) The following modifications may be made to the above-described first and second embodiments. In the first and second embodiments, the vehicle antenna device is configured to include one stub, but may be configured to include two or more stubs. FIG. 15 is a diagram showing a configuration example of a vehicle antenna device 400 according to the second modification. The vehicle antenna device 400 has a configuration in which a stub 110 is added to the vehicle antenna device 100 according to the first embodiment. As described above, the vehicle antenna device 400 includes the stub 110 in addition to the stub 70. In other words, the vehicle antenna device 400 includes the stub 70 which is the first stub and the stub 110 which is the second stub.

[0105] The stub 70 is the same as the stub 70 in the first embodiment. The stub 110 may be an open stub or a short stub. In the second modification, the stub 110 will be described as a short stub in the same manner as the stub 70.

[0106] The stub 110 is connected to the electronic device 30 at the point 110a. The point 110a may be at the same position as the point 70a or at a different position. The stub 110 has a different frequency from that of the stub 70 for suppressing the reduction in the reception sensitivity of the antenna 40. The stub 70 suppresses the reduction in the reception sensitivity of the antenna 40 at a first frequency such as 200 MHz, for example, and the stub 110 suppresses the reduction in the reception sensitivity of the antenna 40 at a second frequency such as 210 MHz, for example. Note that the frequencies at which the stub 70 and the stub 110 suppress the reduction in the reception sensitivity of the antenna 40 are not limited to the above and may be set as appropriate.

[0107] The lengths of the stubs 70 and 110 are set to satisfy the formulas (1) to (3). As described above, since the first frequency at which the stub 70 suppresses the reduction in the reception sensitivity of the antenna 40 is different from the second frequency at which the stub 110 suppresses the reduction in the reception sensitivity of the antenna 40, the length of the stub 70 may be set to be different from the length of the stub 110. In this way, the vehicle antenna device 400 may include two or more stubs, and each stub may suppress the reduction in the reception sensitivity of the antenna 40 in different frequency bands. In this way, the vehicle antenna device 400 can suppress the reduction in the reception sensitivity of the antenna 40 over a plurality of frequency bands, and thus over a wider bandwidth.

[0108] As described above, the present invention has been described based on the above embodiments. However, the present invention is not limited only to the configurations of the above embodiments, and of course includes various modifications, corrections, and combinations that can be made by those skilled in the art within the scope of the invention of the claims of the present application. For example, in the first and second embodiments, the vehicle antenna device may be configured to include two or more vehicle window glasses and stubs. In this case, one of the two vehicle window glasses may be a windshield, and the other may be a rear glass. Also, one of the two stubs may be an open stub, the other may be a short stub, both may be open stubs, or both may be short stubs.

Description of Reference Numerals

[0109] 10 Metal body 10a End 20 Vehicle window glass 30 Electronic device 40 Antenna 41, 92 Feeding unit 42 Strip element 50 Transmission line 60 ECU 70, 80, 110 Stub 90 Electric heating unit 91 Electric heating wire 93 Ground unit 100, 200, 300, 400 Vehicle antenna device 150 cameras

Claims

1. An electronic device, An antenna disposed in the vicinity of the electronic device and transmitting and receiving radio waves in a predetermined frequency band, A transmission line connecting the electronic device and an ECU installed in a vehicle, Connect to the electronic device and have a predetermined length L Ｓ and at least one stub, which is a conductor having the length, are provided. The length L of the at least one stub Ｓ A vehicle antenna device, which is set to suppress a decrease in antenna gain of radio waves included in a frequency band transmitted and received by the antenna, according to the wavelength λ of the radio waves transmitted and received by the antenna.

2. The vehicle antenna device according to claim 1, wherein the electronic device is attached to a vehicle window glass and acquires external information of the vehicle through the vehicle window glass.

3. The vehicle antenna device according to claim 2, wherein the antenna is attached in the vicinity of the vehicle window glass.

4. The vehicle antenna device according to claim 2 or 3, wherein the antenna is attached to the surface of the vehicle window glass or enclosed in the vehicle window glass.

5. The vehicle antenna device according to any one of claims 2 to 4, wherein the vehicle window glass includes a windshield.

6. The vehicle antenna device according to any one of claims 2 to 5, wherein the vehicle window glass includes a rear glass.

7. The vehicle antenna device according to any one of claims 1 to 6, wherein the at least one stub is electrically connected to the ground potential portion of the electronic device.

8. The vehicle antenna device according to any one of claims 1 to 7, wherein the at least one stub extends from the electronic device by a single wire.

9. The at least one stub includes a short stub in which an end opposite to the electronic device is electrically connected to the ground, When the wavelength of the radio wave transmitted and received by the antenna is λ, the wavelength shortening rate of the dielectric around the short stub is k, and N is an integer of N≧0, The length L of the short stub ＳＳ is (0.05×(λ / 2) + (λ / 2)×N)×k ≤ L ＳＳ ≤ (1.0×(λ / 2) + (λ / 2)×N)×k The vehicle antenna device according to any one of claims 1 to 8, which satisfies.

10. The vehicle antenna device according to claim 9, wherein the short stub is air-wired.

11. The vehicle antenna device according to claim 9 or 10, wherein the short stub is common to the ground wire of the electronic device.

12. The at least one stub includes an open stub in which an end opposite to the electronic device is an open end, When the wavelength of the radio wave transmitted and received by the antenna is λ, the wavelength shortening rate of the dielectric around the open stub is k, and M is an integer of M≧0, The length L of the open stub ＯＳ is (0.1×(λ / 4) + (λ / 2)×M)×k ≤ L ＯＳ ≤ (1.0×(λ / 4) + (λ / 2)×M)×k The vehicle antenna device according to any one of claims 1 to 11, which satisfies.

13. The open stub according to claim 12 is disposed on a vehicle window glass to which the electronic device is attached, and k is a wavelength shortening rate of the vehicle window glass.

14. The electronic device includes a heating wire that heats the vehicle window glass. The open stub according to claim 13 extends from the heating wire.

15. The open stub according to any one of claims 12 to 14 extends so as to move away from the antenna.

16. The open stub according to any one of claims 12 to 15 capacitively couples with a metal body of the vehicle.

17. The distance between a connection point of the electronic device and the at least one stub and a power feeding point of the antenna is 500 mm or less.

18. The at least one stub includes a first stub and a second stub. The length of the first stub is different from the length of the second stub.

19. The length of the transmission line includes a length L from a position where the transmission line intersects an end of a metal body of the vehicle to the ECU and a length d from the position to the electronic device. The range of the length L is 1800 mm to 5000 mm.

20. The antenna according to any one of claims 1 to 19 is capable of receiving radio waves having frequencies in a VHF band to a UHF band.

21. The antenna according to claim 20 is capable of receiving radio waves of at least one of DAB Band III and terrestrial digital broadcast waves.

Images