JP7700509B2 - Vehicle antenna device - Google Patents

Description

The present invention relates to a vehicle antenna device.

In recent years, there has been a trend in vehicles to have various electronic devices, such as visible light cameras, radars, and sensors, concentrated in a bracket, especially in the windshield. Conventionally, an antenna pattern (antenna) made of a conductor for receiving broadcast waves has been placed on vehicle window glass such as the windshield. In such cases, the electronic device and the antenna are placed close to each other in the windshield so as not to block the view of the vehicle occupants more than necessary. However, when the electronic device and the antenna are placed close to each other, there is a risk that the operation of the antenna will become unstable due to noise emitted from the electronic device, etc., and the desired antenna gain will not be obtained.

Therefore, technology has been developed to reduce noise that occurs when electronic devices and antennas are placed close to each other on vehicle window glass (for example, Patent Documents 1 and 2). Patent Document 1 discloses that an opening is formed using a conductive pattern larger than the sensor to reduce noise superimposed on an antenna located outside the sensor. Patent Document 2 discloses a configuration in which a noise removal line made of a conductor is placed around the radar device to reduce noise that occurs during the operation of the radar device.

JP 2015-095794 A JP 2016-063416 A

The technologies disclosed in Patent Documents 1 and 2 reduce noise generated by electronic devices, but do not take into account coupling to the antenna caused by resonance caused by the wiring connecting the electronic devices to the ECU, etc. Therefore, even if the technologies disclosed in Patent Documents 1 and 2 are used, the receiving sensitivity of the antenna will be reduced due to resonance caused by the wiring connecting the electronic devices to the ECU, etc.

The present invention aims to provide a vehicle window antenna device that suppresses the reduction in antenna reception sensitivity caused by the wiring of an electronic device when the electronic device and the antenna are placed in close proximity.

A vehicle antenna device according to one aspect of the present invention comprises an electronic device, an antenna arranged in the vicinity of the electronic device and configured to transmit and receive radio waves in a predetermined frequency band, a transmission line connecting the electronic device to an ECU installed in the vehicle, and at least one stub connected to the electronic device and being a conductor having a predetermined length L _S , wherein the length L _S of the at least one stub is set in accordance with the length of the transmission line so as to suppress a reduction in antenna gain of radio waves included in the frequency band transmitted and received by the antenna.

In the above-mentioned vehicle antenna device, the electronic device may be attached to a vehicle window glass and acquire external information about the vehicle through the vehicle window glass.

In the above-mentioned vehicle antenna device, the antenna may be mounted near the vehicle window glass.

In the above-mentioned vehicle antenna device, the antenna may be attached to the surface of the vehicle window glass or may be enclosed within the vehicle window glass.

In the above-mentioned vehicle antenna device, the vehicle window glass may include a windshield.

In the above-mentioned vehicle antenna device, the vehicle window glass may include a rear window.

In the above-mentioned vehicle antenna device, the at least one stub may be electrically connected to the earth potential portion of the electronic device.

In the vehicle antenna device described above, the at least one stub may extend from the electronic device as a single wire.

In the above-described vehicle antenna device, the at least one stub may include a short stub having an end opposite to the electronic device that is connected to earth, and a length LSS of the short stub may satisfy (0.05×(λ/2)+(λ/2)×N)×k≦ _LSS ≦(1.0×(λ/2)+(λ/2)×N)×k, where λ is a frequency band of radio waves transmitted and received by the antenna, k is a wavelength shortening rate of a _dielectric around the short stub, and N is an integer greater than or equal to 0.

In the vehicle antenna device described above, the short stub may be wired in the air.

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

In the above-described vehicle antenna device, the at least one stub may include an open stub whose end opposite to the electronic device is an open end, and a length L OS of the open stub may satisfy (0.1×(λ/4)+(λ/2)×M)×k≦L _OS ≦(1.0×(λ/4)+(λ/2)×M)×k, where λ is a frequency band of radio waves transmitted and received by the antenna, k is a wavelength shortening rate of a _dielectric around the open stub, and M is an integer greater than or equal to 0.

In the above-mentioned vehicle antenna device, the open stub may be disposed on a vehicle window glass on which the electronic device is mounted, and k may be the wavelength shortening rate of the vehicle window glass.

In the above-mentioned vehicle antenna device, the electronic device may include a heating wire that heats the vehicle window glass, and the open stub may extend from the heating wire.

In the vehicle antenna device described above, the open stub may extend away from the antenna.

In the above-mentioned vehicle antenna device, the open stub may be capacitively coupled to the metal body of the vehicle.

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

In the vehicle antenna device described above, the at least one stub may include a first stub and a second stub, and the length of the first stub may be different from the length of the second stub.

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

In the vehicle antenna device described above, the antenna may be capable of receiving radio waves with frequencies in the VHF to UHF bands.

In the vehicle antenna device described above, the antenna may be capable of receiving at least one of DAB Band III and terrestrial digital broadcasting waves.

According to one aspect of the present invention, a vehicle antenna device can be provided that suppresses a decrease in the antenna reception sensitivity due to the wiring of the electronic device when the electronic device and the antenna are placed in close proximity.

1 is a schematic diagram illustrating a configuration of a vehicle antenna device according to a first embodiment; FIG. 11 is a diagram showing frequency characteristics of the S11 parameter of the antenna. FIG. 11 is a diagram showing frequency characteristics of an S11 parameter of an electronic device. FIG. 11 is a diagram showing frequency characteristics of the S11 parameter of a transmission line. 10 is a diagram for comparing the antenna gain of an antenna in a vehicle antenna device with that in a default configuration. FIG. 10 is a diagram for comparing the antenna gain of an antenna in a vehicle antenna device with that in a default configuration. FIG. 11 is a diagram showing the relationship between the distance between an electronic device and an antenna and the value of the S11 parameter of the antenna at a frequency of 200 MHz. FIG. 11 is a diagram showing the relationship between the length of the stub and the value of the S11 parameter of the antenna. FIG. 11 is a schematic diagram showing a configuration of a vehicle antenna device according to a second embodiment. 10 is a diagram for comparing the antenna gain of an antenna in a vehicle antenna device with that in a default configuration. FIG. 10 is a diagram for comparing the antenna gain of an antenna in a vehicle antenna device with that in a default configuration. FIG. 11 is a diagram showing the relationship between the distance between an electronic device and an antenna and the value of the S11 parameter of the antenna at a frequency of 200 MHz. FIG. 11 is a diagram showing the relationship between the length of the stub and the value of the S11 parameter of the antenna. FIG. 11 is a diagram showing a configuration example of a vehicle antenna device according to a first modified example; FIG. 11 is a diagram showing a configuration example of a vehicle antenna device according to a second modified example.

Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. In order to clarify the description, the following description and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate descriptions will be omitted as necessary. In each embodiment, deviations in directions such as parallel, horizontal, and vertical are permitted to the extent that they do not impair the effects of the present invention. In addition, in drawings to explain the embodiments, unless a direction is specifically stated, it refers to the direction on the drawing.

(First embodiment)
A vehicle antenna device 100 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a vehicle antenna device according to a first embodiment. Fig. 1 is a view from inside a vehicle in a state in which a vehicle window glass 20 described later is attached to a vehicle, and is an enlarged view of a portion of the vehicle window glass 20 where an electronic device 30 and an 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 perpendicular to the horizontal direction. Although Fig. 1 will be described as a view from inside the vehicle, it may be referred to as a view from outside the vehicle.

As shown in FIG. 1, the vehicle antenna device 100 according to the 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.

The vehicle window glass 20 is a dielectric that constitutes a part of the vehicle in which the vehicle antenna device 100 is arranged, and may be entirely made of a glass plate. In addition, the dielectric near the electronic device 30 is not limited to the vehicle window glass 20, and may be partially or entirely made of resin, for example, a shark fin on the roof covered with 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 is fixed to a body flange formed on the vehicle housing. The upper part of the vehicle window glass 20 is fixed by 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 FIG. 1 is illustrated as a diagram showing the upper part of the vehicle window glass 20, but if the position where the electronic device 30 and the antenna 40 are arranged is, for example, the lower part, left part, or right part of the vehicle window glass 20, the end 10a may be interpreted as the end part corresponding to that position.

The electronic device 30 includes, for example, a visible light camera, a radar (including millimeter waves), and sensors such as an infrared sensor, a rain sensor, a temperature and humidity sensor, and a condensation sensor, as well as a heating wire that heats the vehicle window glass 20 in front of the camera to provide 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, or may be attached so as to be embedded in the ceiling, for example, in an overhead console. The electronic device 30 may be attached to the vehicle window glass 20 via the housing, or may be attached directly to the vehicle window glass 20. The electronic device 30 acquires information about the outside of the vehicle through the vehicle window glass 20, and information about the inside of the vehicle cabin.

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

Furthermore, the 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 a frequency band for satellite communication 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 5G (5th Generation Mobile Communication System) frequency band. An example of an antenna for 5G is an antenna capable of transmitting and receiving radio waves in a frequency band for narrow-area communication called DSRC (Dedicated Short Range Communication) (e.g., 5.8 GHz band) used for V2X (Vehicle to Everything) such as vehicle-to-vehicle communication and road-to-vehicle communication. In addition, the antenna 40 is not limited to one of the antennas exemplified above, and may include multiple antennas and be integrated and arranged in one place, or multiple antennas may be individually distributed and arranged near the vehicle window glass 20. Note that the term "transmitting and receiving" is used to mean that the antenna 40 can "transmit" or "receive" radio waves, or both "transmit" and "receive".

The antenna 40 may be arranged so that the distance from the electronic device 30 is, for example, 500 mm or less. If the distance is more than 500 mm, the antenna 40 is arranged sufficiently far from the electronic device 30, so that the two are isolated 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, layout restrictions arise, so if the distance is 500 mm or less and the decrease in the antenna sensitivity of the antenna 40 can be suppressed, the degree of freedom of arrangement is improved, which is preferable. In addition, the distance may be 350 mm or less, 200 mm or less, or 100 mm or less. Furthermore, the distance does not need to have a lower limit, but may be, for example, 0 mm or more, 5 mm or more, 10 mm or more, 30 mm or more, or 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 in the vicinity of the vehicle window glass 20.

The antenna 40 may be attached to the surface of the vehicle window glass 20. Alternatively, the antenna 40 may be enclosed inside the vehicle window glass 20. Alternatively, the antenna 40 may be arranged inside an aerodynamic part made of resin, such as a rear spoiler, if it is on a dielectric, or the dielectric may be air and the antenna 40 may be air-wired. Alternatively, the antenna 40 may be arranged on metal. An example of an antenna 40 arranged on metal may be an antenna (so-called shark fin antenna) inside a protruding resin radome installed on the metal roof of a vehicle. Since shark fin antennas are often arranged on the rear of a vehicle roof, examples of electronic devices include a high-mounted stop lamp and a visible light camera (back camera) installed near the rear window.

The antenna 40 is disposed in a position that does not impair the visibility of the occupants of the vehicle in which the vehicle antenna device 100 is disposed. In this embodiment, the antenna 40 is described as being disposed above the vehicle window glass 20, but is not limited to this.

In FIG. 1, the antenna 40 includes a power supply unit 41 and a linear element 42. The antenna 40 shown in FIG. 1 is a so-called monopole antenna. The antenna 40 may also be a so-called dipole antenna that further includes an earth unit (not shown) and a linear element connected to the earth unit. The power supply unit 41 is disposed close to the metal body 10. The power supply unit 41 (and the earth unit) is connected to a communication device (not shown) via a transmission line such as a coaxial cable (not shown).

The line element 42 is an antenna element made of a conductor. One end of the line element 42 is connected to the power supply unit 41, and the other end is an open end. The line element 42 is, for example, L-shaped. The line element 42 is connected to the power supply unit 41 at point 42a, with point 42a as the connection point, and extends from point 42a to point 42b in the negative direction of the Y axis. The line element 42 extends from point 42b to point 42c in the positive direction of the X axis. Note that in FIG. 1, the shape of the line element 42 is L-shaped, but it may be arbitrarily set, such as forming a closed loop with the line element, depending on the vehicle in which the vehicle antenna device 100 is installed.

The transmission line 50 connects the electronic device 30 and the ECU 60 installed in the vehicle in which the vehicle antenna device 100 is arranged. The transmission line 50 is, for example, an AV line, 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 the position where the transmission line 50 intersects with the end (end 10a) of the metal body of the vehicle. The range of the length L can be exemplified as 1800 mm to 5000 mm. The upper and lower limits of the length L vary depending on the vehicle, but may be, for example, 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. Furthermore, the length d may be 300 mm or less, 200 mm or less, or 150 mm or less.

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 installed may be provided with ECUs for engine control, brake control, and safety control.

The stub 70, which is a conductor (conductor wire) whose one end is connected to the electronic device 30 and extends therefrom, may be a short stub whose other end is connected to the ground, or an open stub whose other end is an open end. The stub 70 is a conductor that is connected to the electronic device 30 at a point 70a (connection point 70a) and has a predetermined length _Ls . It can be connected to a terminal having the same potential as the ground of the electronic device 30 or to a terminal having a DC potential of more than 0 [V], but it is preferable to connect to a terminal having the same potential as the ground because it is more stable. In other words, it is preferable for the stub 70 to be connected to the ground potential part of the electronic device 30 because it is more electrically stable. In addition, the stub 70 is preferably a conductor that extends from the electronic device 30 as a single wire without forming a branch or a closed loop.

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 placed near the antenna 40, it couples with the electronic device 30 to radio waves of a specific frequency band transmitted and received by the antenna 40, causing a decrease in the sensitivity of the antenna 40. In other words, when the electronic device 30 has a frequency that resonates within the same frequency band transmitted and received by the antenna 40, it causes a decrease in the gain of the antenna 40. Therefore, the vehicle antenna device 100 according to the first embodiment includes a stub 70 having a length L _s , and by adjusting the length L _s according to the wavelength λ of the radio waves transmitted and received by the antenna 40, 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 the point 70a. In this embodiment, the stub 70 is described as a short stub. Moreover, since the stub 70 is a short stub, in the following description, the length _Ls may be described as the length _Lss .

The stub 70 has an end opposite to the electronic device 30 connected to the metal body 10 (earth). The stub 70 may be formed from the earth wire of the electronic device 30. In other words, the stub 70 may be common to the earth wire of the electronic device 30. In addition, at least a portion of the stub 70 from the end connected to the electronic device 30 to the opposite end may be air-wired.

ここで、Ｎ≧０の整数である。 The length _Lss 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 material around the stub 70 satisfies the following formula (1).

Here, N is an integer greater than or equal to 0.

A more preferable range for the length _Lss of the stub 70 is within the range of expression (2).

A more preferable range for the length _Lss of the stub 70 is within the range of expression (3).

In this manner, under the above conditions, by setting the length _Lss of the stub 70 so as 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 the antenna 40.

Next, the antenna gain of the antenna 40 in the vehicle antenna device 100 will be described. To evaluate the antenna gain of the antenna 40 in the vehicle antenna device 100, the antenna gain of the antenna 40 in the vehicle antenna device 100 including the stub 70 was compared with that in a configuration of the vehicle antenna device 100 that does not include the stub 70. In this embodiment, the configuration of the vehicle antenna device 100 excluding only the stub 70 is referred to as the "default configuration."

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

First, before showing the evaluation results, we will explain the frequency characteristics of the S11 parameter of the antenna 40, electronic device 30, and transmission line 50 used in the simulation.

The frequency characteristics of the S11 parameter of antenna 40 will be explained using Figure 2. Here, the S11 parameter of antenna 40 was calculated by simulating the ratio of the input power to the reflected power of antenna 40 in power supply unit 41. Note that in the diagrams showing the frequency characteristics of the S11 parameter shown below, the horizontal axis represents frequency [MHz] and the vertical axis represents the value of the S11 parameter [dB], just like Figure 2.

As shown in FIG. 2, the length of the line element 42 of the antenna 40 used in the simulation was set so that it would resonate at a frequency of 200 MHz. The antenna 40 was also set so that the value of the S11 parameter was -7.1 dB at a frequency of 200 MHz.

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

The frequency characteristic of the S11 parameter of the transmission line 50 will be described with reference to FIG. 4. FIG. 4 is a diagram showing the frequency characteristic of the S11 parameter of the transmission line. The transmission line 50 used in the simulation was a model in which the length L of 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 point 50a toward the ECU 60. The S11 parameter of the transmission line 50 was calculated by calculating the ratio of the input power to the reflected power of the transmission line 50 at the point 50a by simulation. As shown in FIG. 4, the transmission line 50 is a model in which the frequency at which the S11 parameter becomes a minimum value (approximately -12 dB) is periodic. At the frequency at which the S11 parameter becomes approximately -12 dB, the transmission line 50 is matched to 50 Ω.

Next, a comparison result of the antenna gain of the antenna 40 in the vehicle antenna device 100 and the default configuration will be described.
First, a comparison result of the antenna gain between 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 _Lss of the stub 70 is set to 550 mm will be described with reference to Fig. 5. Fig. 5 is a diagram for comparing the antenna gain of the vehicle antenna device with that of the default configuration. In Fig. 5, the length _Lss of the stub 70 is set to 550 mm in order to suppress the reduction in the antenna gain at the frequency of 200 MHz, which is the resonant frequency of the antenna 40.

Figure 5 shows the S11 parameter of the antenna 40 at the power feeder 41 in the vehicle antenna device 100, and the frequency characteristics of the S11 parameter of the antenna 40 at the power feeder 41 in the default configuration. In the simulation, the electronic device 30, antenna 40, and transmission line 50 having the characteristics shown in Figures 2 to 4 were used. The stub 70 is wired in the air, and the wavelength shortening rate k around the stub 70 is set to 1.0.

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

In contrast, in the case of the vehicle antenna device 100, the value of the S11 parameter is -6.2 dB at 200 MHz, which is the resonant frequency of the antenna 40. Furthermore, at a frequency of 205 MHz, the S11 parameter is at a minimum value of -6.4 dB. In other words, because the vehicle antenna device 100 is configured to include the stub 70, it is possible to suppress a reduction in the receiving sensitivity of the antenna 40 due to resonance of the electronic device 30 and the transmission line 50.

Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening rate k is 1.0, the frequency of the radio waves transmitted and received by the antenna 40 is 200 MHz (λ≈1499 mm), and the length _Lss of the stub 70 is 550 mm. When calculated using these values, the length _Lss of the stub 70 satisfies the formulas (1) to (3) when the integer N is 0. That is, since the vehicle antenna device 100 includes the stub 70 and furthermore the length _Lss of the stub 70 satisfies the formulas (1) to (3), the reduction in the receiving sensitivity of the antenna 40 can be suppressed compared to the default configuration.

Next, a comparison result of the antenna gain of the vehicle antenna device 100 in a case where the distance between the electronic device 30 and the antenna 40 is 200 mm and the length _Lss of the stub 70 is 550 mm and the default configuration will be described with reference to Fig. 6. Fig. 6 is a diagram for comparing the antenna gain of the antenna in the vehicle antenna device with that in the default configuration.

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

In FIG. 6, the dotted line indicates the frequency characteristic of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristic 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 first inflection point near a frequency of 198 MHz, and rises steeply as the frequency increases, and has a second inflection point near a frequency of 211 MHz, and rises more gradually as the frequency increases. In other words, at a frequency of around 210 MHz, the antenna 40 is affected by the resonance of the electronic device 30 and the transmission line 50, and the reception sensitivity of the antenna 40 decreases.

In contrast, in the vehicle antenna device 100, the value of the S11 parameter is lower than that of the default configuration at a frequency of about 210 MHz, and the slope of the S11 parameter is generally constant. In other words, since the length _Lss of the stub 70 is set to a length (550 mm) that can suppress a decrease in the reception sensitivity of the antenna 40 at a frequency of about 210 MHz, the vehicle antenna device 100 can suppress a decrease in the reception sensitivity of the antenna 40.

Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening rate k is 1.0, and the length _Lss of the stub 70 is 550 mm. In addition, in the example shown in FIG. 6, the target frequency for reducing the decrease in the reception sensitivity of the antenna 40, which is the frequency of the radio waves transmitted and received by the antenna 40, is 210 MHz. When calculated using these values, the length _Lss of the stub 70 satisfies the formulas (1) to (3) when the integer N is 0. That is, since the vehicle antenna device 100 includes the stub 70 and furthermore, the length _Lss of the stub 70 satisfies the formulas (1) to (3), the decrease in the reception sensitivity of the antenna 40 can be suppressed compared to the default configuration.

Next, 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 with reference to Fig. 7. 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. In addition, the wavelength shortening rate k around the stub 70 was set to 1.0, and the length _Lss of the stub 70 was set to 550 mm.

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 of the S11 parameter [dB]. 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.

As shown in FIG. 7, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 400 mm, the S11 parameter is lower in the vehicle antenna device 100 than in the default configuration. In other words, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 400 mm, the vehicle antenna device 100 shows that the antenna 40 is less affected by resonance from the electronic device 30 and the transmission line 50 than in the default configuration. In this way, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 400 mm, the vehicle antenna device 100 is able to suppress the decrease in the receiving sensitivity of the antenna 40 more than in the default configuration.

Next, the relationship between the length _Lss of the stub 70 and the S11 parameter of the antenna 40 of the vehicle antenna device 100 at a frequency of 200 MHz will be described with reference to Fig. 8. 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.

In Fig. 8, the horizontal axis represents the length _Lss [mm] of the stub 70, 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, when checking the length _Lss [mm] at which the S11 parameter is substantially the same value, such as the length _Lss [mm] at which the S11 parameter is the maximum value (maximum value) and the length Lss [mm] at which the S11 parameter is the minimum value ₍ minimum value), it is found that there is a periodicity. For example, the length _Lss [mm] of the stub 70 at which the S11 parameter shows a minimum value is 550 mm and 1300 mm. Here, since the frequency is 200 MHz, the half wavelength (1/2 wavelength) [mm] is 750 [mm] (=0.75 [m]), which is the value obtained by dividing the speed of the radio wave, 3.0×10 ⁸ [m/s], by 200×10 ⁶ [Hz] and 2. In other words, the length L _ss [mm] of the stub 70 can suppress the reduction in the reception sensitivity of the antenna 40 every time the length L ss [mm] of the stub 70 increases by half the wavelength λ [mm] of the radio wave transmitted and received by the antenna 40. Therefore, when the length L _ss of the stub 70 satisfies the formulas (1) to (3), the vehicle antenna device 100 can suppress the reduction in the reception sensitivity of the antenna 40.

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

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 with a stub 80. 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, so descriptions of these configurations that are common to the first embodiment will be omitted as appropriate.

The stub 80 is an open stub with one end of the conductor being an open end. The stub 80 is a conductor that is connected to the electronic device 30 at a point 80a and has 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 described as L _os , but the length of the stub 80 may be described as L _s , which is a generalized description, as in the first embodiment.

The stub 80 extends from the electronic device 30 as a single wire without forming a branch or a closed loop. The stub 80 is, for example, L-shaped, extending from point 80a in the positive direction of the Y axis to point 80b, and extending from point 80b to point 80c in the negative direction of the X axis. In particular, the stub 80 extends away from the antenna 40. Point 80c, which is the end of the stub 80 opposite the electronic device 30, is an open end, and constitutes an open stub. Note that in FIG. 9, the stub 80 is not limited to an L-shape, and can be any shape that can constitute an open stub.

The portion of the stub 80 from point 80b to point 80c may be close to the end 10a of the metal body 10. The portion of the stub 80 from point 80b to point 80c may be 5 mm to 30 mm away from the end 10a of the metal body 10. In other words, the metal body 10 and the portion of the stub 80 from point 80b to point 80c are configured as a capacitive coupling portion. The capacitive coupling portion is capacitively coupled to the conductor portion by a predetermined capacitance value. The portion of the stub 80 from point 80b to point 80c forms a line having a specific characteristic impedance. The stub 80 may be arbitrarily set to have or not have a capacitive coupling portion, and the length of the capacitive coupling portion when it has one. In addition, the connection point 80a of the stub 80 with the electronic device 30 may be the earth potential portion of the electronic device 30.

ここで、Ｍ≧０の整数である。

The length L _os of the stub 80 is 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 wavelength λ of the radio waves transmitted and received by the antenna 40. The length L _os of the stub 80 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, the wavelength shortening rate k in the following formula (4) is the wavelength shortening rate of the vehicle window glass 20, and when the stub 80 is an aerial wiring, it is the wavelength shortening rate of air (k=1.0).

Here, M is an integer greater than or equal to 0.

A more preferable range for the length L _os of the stub 70 is within the range of expression (5).

A more preferable range for the length L _os of the stub 70 is within the range of expression (6).

In this manner, by setting the length L _os of the stub 80 so as to satisfy the above formula (4) under the above conditions, 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.

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 was compared with that of a vehicle antenna device 200 without the stub 80. In this embodiment, the configuration of the vehicle antenna device 200 excluding only the stub 80 is referred to as the "default configuration."

To compare the antenna gain 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.

First, using FIG. 10, a comparison result of antenna gain between the vehicle antenna device 200 in the case where the distance between the electronic device 30 and the antenna 40 is 200 mm and the length L _os of the stub 80 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 FIG. 2 and FIG. 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 set to 50 mm were used. In addition, 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.

Figure 10 shows the S11 parameter of the antenna 40 in the power supply unit 41 in the vehicle antenna device 200, and the frequency characteristics of the S11 parameter of the antenna 40 in the power supply unit 41 in the default configuration.

In FIG. 10, the dotted line indicates the frequency characteristic of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristic 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 first inflection point near a frequency of 197 MHz, and rises steeply as the frequency increases, and has a second inflection point near a frequency of 211 MHz, and rises more gradually as the frequency increases. In other words, at a frequency of around 210 MHz, the antenna 40 is affected by the resonance of the electronic device 30 and the transmission line 50, and the receiving sensitivity of the antenna 40 is reduced.

In contrast, in the vehicle antenna device 200, the length L _os of the stub 80 is set to 190 mm in order to suppress the decrease in the reception sensitivity of the antenna 40 at 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 of the default configuration, and the slope of the S11 parameter becomes approximately constant. In other words, in the vehicle antenna device 200, the length L _os of the stub 80 is adjusted for 210 MHz, which is the target frequency at which the decrease in the reception sensitivity of the antenna 40 is reduced, so that the decrease in the reception sensitivity of the antenna 40 can be suppressed.

Here, the length L of the transmission line 50 is 2870 mm, the wavelength shortening rate k is 1.0, the frequency band of the radio waves transmitted and received by the antenna 40 is 210 MHz, and the length L _os of the stub 80 is 190 mm. When calculated using these values, the length L _os of the stub 80 satisfies the formulas (4) to (6) when M is 0. That is, since the vehicle antenna device 200 includes the stub 80 and furthermore the length L _os of the stub 80 satisfies the formulas (4) to (6), it is possible to suppress a decrease in the reception sensitivity of the antenna 40 compared to the default configuration.

Next, a comparison result of the antenna gain between the vehicle antenna device 200 and the default configuration when the distance between the electronic device 30 and the antenna 40 is 200 mm and the length L _os of the stub 80 arranged on the vehicle window glass 20 is 205 mm will be described with reference to Fig. 11. Fig. 11 is a diagram for comparing the antenna gain of the antenna in the vehicle antenna device and the default configuration.

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

In FIG. 11, the dotted line indicates the frequency characteristic of the S11 parameter of the antenna 40 in the default configuration, and the solid line indicates the frequency characteristic 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 a frequency of 197 MHz, and rises steeply as the frequency increases, and has a second inflection point near a frequency of 211 MHz, and rises more gradually as the frequency increases. In other words, at a frequency of around 210 MHz, the antenna 40 is affected by the resonance of the electronic device 30 and the transmission line 50, and the receiving sensitivity of the antenna 40 is reduced.

In contrast, in the vehicle antenna device 200, the length L _os of the stub 80 is set to 205 mm in order to suppress the decrease in the reception sensitivity of the antenna 40 at 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 of the default configuration, and the slope of the S11 parameter becomes approximately constant. In other words, in the vehicle antenna device 200, the length L _os of the stub 80 is adjusted for 210 MHz, which is the target frequency at which the decrease in the reception sensitivity of the antenna 40 is reduced, so that the decrease in the reception sensitivity of the antenna 40 can be suppressed.

Here, the length L of 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. In addition, in the example shown in FIG. 11, the target frequency λ, which is the frequency of the radio waves transmitted and received by the antenna 40 and which reduces the decrease in the reception sensitivity of the antenna 40, is 210 MHz. When calculated using these values, it is found that the length L _os of the stub 80 satisfies the formulas (4) to (6) when M is 0. That is, since the vehicle antenna device 200 includes the _stub 80 and furthermore satisfies the formulas (4) to (6), the decrease in the reception sensitivity of the antenna 40 can be suppressed compared to the default configuration. When the vehicle window glass 20 is a single pane, the wavelength shortening rate k can be exemplified as approximately 0.67, and when the vehicle window glass 20 is an exchange glass having an intermediate film sandwiched between two panes of glass, the wavelength shortening rate k can be exemplified as approximately 0.5.

Next, 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 with reference to Fig. 12. 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. In addition, 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. In addition, the length L _os of the stub 80 was 320 mm.

In FIG. 12, the horizontal axis indicates the distance [mm] between the electronic device 30 and the antenna 40, and the vertical axis indicates the value of the S11 parameter [dB]. 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.

As shown in FIG. 12, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 200 mm, the S11 parameter is lower in the vehicle antenna device 200 than in the default configuration. In other words, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 200 mm, the antenna 40 is less affected by resonance from the electronic device 30 and the transmission line 50 in the vehicle antenna device 200 than in the default configuration. When the distance between the electronic device 30 and the antenna 40 is in the range of 200 mm to 400 mm, the S11 parameter is slightly smaller in the default configuration than in the vehicle antenna device 200, but the values are substantially the same. This is because the distance between the electronic device 30 and the antenna 40 is large, so the antenna 40 is less affected by the resonance of the electronic device 30, and therefore the S11 parameter is substantially the same in the vehicle antenna device 200 and the default configuration. As described above, when the distance between the electronic device 30 and the antenna 40 is in the range of 50 mm to 200 mm, the vehicle antenna device 200 is able to 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 in the range of 200 mm to 400 mm, the vehicle antenna device 200 is able to suppress the decrease in the reception sensitivity of the antenna 40 in the same way as the default configuration.

Next, the relationship between the length L _os of the stub 80 and the S11 parameter of the antenna 40 of the vehicle antenna device 200 at a frequency of 210 MHz was evaluated using Fig. 13. 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 were used when the distance between the electronic device 30 and the point 50a (the length d in the transmission line 50) was set to 50 mm. 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.

In Fig. 13, the horizontal axis represents the length L _os [mm] of the stub 80, 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, when the length L _os [mm] at which the S11 parameter is substantially the same value, such as the length L os [mm] at which the S11 parameter is the maximum value (local maximum value) and the length L _os [mm] at which the S11 parameter is the minimum value (local minimum value), it is found that there is a periodicity. For example, the length _{L os} [mm] of the stub 80 at which the S11 parameter shows a local minimum value is 200 mm and 920 mm. In other words, the reduction in the reception sensitivity of the antenna 40 can be suppressed every time the length L _os [mm] of the stub 80 increases by half the distance of the wavelength λ of the radio wave transmitted and received by the antenna 40. Therefore, when the length L _os of the stub 80 satisfies the formulas (4) to (6), the vehicle antenna device 200 can suppress a decrease in the receiving sensitivity of the antenna 40.

(Variation 1)
In the second embodiment, when the electronic device 30 includes a heating wire (for preventing fogging and icing of 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 the first modified example. 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 an electric heating unit 90 and a camera 150. The vehicle antenna device 300 includes an electric 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 therefore the description thereof will be omitted as appropriate. In addition, for the sake of convenience, FIG. 14 illustrates the electric heating unit 90 and the camera 150 in the electronic device 30 as being spaced apart, but in reality, the imaging unit of the camera 150 overlaps with the electric heating unit 90 in a plan view of the vehicle window glass 20 .

The electric heating unit 90 is an electric heating unit of the vehicle window glass 20. The electric heating unit 90 is provided, for example, for the purpose of deicing and defrosting the transparent area of the vehicle window glass 20. The transparent area is an area where an electronic device 30, such as an information device installed in the vehicle, receives radio waves from outside the vehicle through the vehicle window glass 20 and transmits signals to the outside of the vehicle through the vehicle window glass 20. The electric heating unit 90 includes a heating wire 91, a power supply unit 92, and an earth unit 93. At least a portion of the heating wire 91 is disposed in the transparent area. A direct current voltage is applied to the heating wire 91 from the power supply unit 92, and the heating wire 91 heats the transparent area by being heated by the resistance of the heating wire 91. The power supply unit 92 and the earth unit 93 are connected to a direct current power source disposed away from the vicinity of the transparent area via electrical wiring (such as a harness) not shown. As shown in FIG. 14, at least one of the power supply unit 92 and the earth unit 93 is connected to the camera 150. The electrical wiring on the earth unit side connected to the earth unit 93 may be arranged to be connected near a DC power source for earthing, or may be arranged to be connected to any position on the metal body 10 for earthing.

The camera 150 is a specific example of the electronic device 30 of the second embodiment, for example, a visible light camera. As described above, the camera 150 is connected to at least one of the power supply unit 92 and the earth unit 93 of the electric heating unit 90.

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 point 80a. In other words, the stub 80 extends from the earth potential part of the heating wire 91, with point 80a being the earth potential part. The stub 80 extends as a single wire from point 80a, which is the earth potential part of the heating part 90, without forming a branch or a closed loop. The stub 80 is, for example, L-shaped, and extends from point 80a in the Y-axis positive direction to point 80b, and from point 80b to point 80c (open end) in the X-axis negative direction. Note that point 80a, which is the connection point between the stub 80 and the heating part 90, may be any position on the heating wire 91. In addition, the point where the stub 80 and the heating part 90 are connected is not limited to the earth potential part.

In this way, even if the heating section 90 of the vehicle antenna device 300 according to the first modified example includes a heating wire 91 and the stub 80, which is an open stub, extends from the earth potential section of the heating wire 91, the same effect as in the second embodiment can be obtained.

(Variation 2)
The above-described first and second embodiments may be modified as follows. 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 a second modification. The vehicle antenna device 400 is configured by adding a stub 110 to the vehicle antenna device 100 according to the first embodiment. In this way, 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 a first stub, and the stub 110, which is a second stub.

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 being a short stub, like the stub 70.

The stub 110 connects to the electronic device 30 at point 110a. Point 110a may be at the same position as point 70a or at a different position. The stub 110 and the stub 70 have different frequencies at which they suppress 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, and the stub 110 suppresses the reduction in the reception sensitivity of the antenna 40 at a second frequency, such as 210 MHz. Note that the frequencies at which the stubs 70 and 110 suppress the reduction in the reception sensitivity of the antenna 40 are not limited to the above and may be set appropriately.

The lengths of the stub 70 and the stub 110 are set to satisfy formulas (1) to (3). As described above, 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, so 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, each of which suppresses the reduction in the reception sensitivity of the antenna 40 in a different frequency band. In this way, the vehicle antenna device 400 can suppress the reduction in the reception sensitivity of the antenna 40 over multiple frequency bands, and ultimately over a wider band.

Although the present invention has been described above in accordance with the above embodiment, the present invention is not limited to the configuration of the above embodiment, and of course includes various modifications, corrections, and combinations that a person skilled in the art could make within the scope of the invention of the claims of this application. For example, in the first and second embodiments, the vehicle antenna device may be configured to include two or more vehicle window panes and stubs. In this case, one of the two vehicle window panes may be a windshield and the other may be a rear glass. In addition, one of the two stubs may be an open stub and the other a short stub, or both may be open stubs or both may be short stubs.

REFERENCE SIGNS LIST 10 Metal body 10a End portion 20 Vehicle window glass 30 Electronic device 40 Antenna 41, 92 Power supply portion 42 Line element 50 Transmission line 60 ECU
70, 80, 110 Stub 90 Heating portion 91 Heating wire 93 Earth portion 100, 200, 300, 400 Vehicle antenna device 150 Camera

Claims (21)

Electronic devices,
an antenna arranged near the electronic device for transmitting and receiving radio waves in a predetermined frequency band;
a transmission line connecting the electronic device and an ECU installed in a vehicle;
At least one stub connected to the electronic device and being a conductor having a predetermined length L _S ;
The length L _S of the at least one stub is set in accordance with a wavelength λ of the radio wave transmitted and received by the antenna so as to suppress a decrease in antenna gain of the radio wave included in a frequency band transmitted and received by the antenna. The vehicle antenna device according to claim 1, wherein the electronic device is attached to a vehicle window glass and acquires external information about the vehicle through the vehicle window glass. The vehicle antenna device according to claim 2, wherein the antenna is mounted near the vehicle window glass. 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 within the vehicle window glass. The vehicle antenna device according to any one of claims 2 to 4, wherein the vehicle window glass includes a windshield. The vehicle antenna device according to any one of claims 2 to 5, wherein the vehicle window glass includes a rear window. The vehicle antenna device according to any one of claims 1 to 6, wherein the at least one stub is electrically connected to a ground potential portion of the electronic device. The vehicle antenna device according to any one of claims 1 to 7, wherein the at least one stub extends from the electronic device as a single wire. the at least one stub includes a short stub whose end opposite the electronic device is electrically connected to a ground;
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 greater than or equal to 0.
The length _LSS of the short stub 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 the above. The vehicle antenna device according to claim 9, wherein the short stub is wired in the air. The vehicle antenna device according to claim 9 or 10, wherein the short stub is common to the ground wire of the electronic device. the at least one stub includes an open stub having an open end at an end opposite to the electronic device,
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 greater than or equal to 0.
The length L _OS of the open stub 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, wherein The vehicle antenna device according to claim 12, wherein the open stub is disposed on a vehicle window glass on which the electronic device is mounted, and k is the wavelength shortening rate of the vehicle window glass. The electronic device includes a heating wire that heats the vehicle window glass,
The vehicle antenna device according to claim 13, wherein the open stub extends from the heating wire. The vehicle antenna device according to any one of claims 12 to 14, wherein the open stub extends away from the antenna. The vehicle antenna device according to any one of claims 12 to 15, wherein the open stub is capacitively coupled to the metal body of the vehicle. The vehicle antenna device according to any one of claims 1 to 16, wherein the distance between the connection point between the electronic device and the at least one stub and the feeding point of the antenna is 500 mm or less. the at least one stub includes a first stub and a second stub;
The vehicle antenna device according to any one of claims 1 to 17, wherein a length of the first stub is different from a length of the second stub. the length of the transmission line includes a length L from a position where the transmission line intersects with an end of a metal body of the vehicle to the ECU, and a length d from the position to the electronic device,
The vehicle antenna device according to any one of claims 1 to 18, wherein the length L is in the range of 1800 mm to 5000 mm. The vehicle antenna device according to any one of claims 1 to 19, wherein the antenna is capable of receiving radio waves having frequencies in the VHF to UHF bands. The vehicle antenna device according to claim 20, wherein the antenna is capable of receiving at least one of DAB Band III and terrestrial digital broadcasting waves.

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