JP4835653B2 - Radio wave leakage limiting wall used in road-to-vehicle communication systems - Google Patents

Description

  The present invention includes an ETC system (Electronic Toll Collection System) for communication between a roadside antenna and an on-board device having an automatic toll collection function, a parking lot system applying a road-to-vehicle communication technology, a drive-through system, a gas station system, etc. The present invention relates to a radio wave environment countermeasure for improving a radio wave environment due to a reflection structure such as a surrounding or a vehicle shape depending on the installation location of the roadside antenna in the road-vehicle communication system.

  FIG. 12 is an external view showing a radio wave environment in the vicinity of a conventional toll gate on a highway or toll road. In FIG. 12, 1a is an ETC lane, 1b is a non-ETC lane adjacent to the ETC lane 1a, 2 is a roadside antenna installed in the ETC lane 1a, and 3a is an ETC traveling on the non-ETC lane 1b toward the toll gate. Vehicle 3b is a non-ETC vehicle traveling on the ETC lane 1a toward the toll booth, 4 is an ETC vehicle-mounted device that is mounted on the ETC vehicle 3a and communicates with the roadside antenna 2, and 5 is a roadside antenna 2 and an ETC vehicle-mounted device. 4 is a direct communication wave radiated from the roadside antenna 2, 7a is a primary reflected wave that bounces off the body of the non-ETC vehicle 3b and jumps in front of the communication region 5, and 7b is a non-ETC vehicle. The primary reflected wave bounces off the vehicle body 3b and jumps into the adjacent non-ETC lane 1b, 8 receives the primary reflected wave 7b by the ETC vehicle-mounted device 4 and receives the roadside antenna. 2 is a vehicle detector for detecting vehicle entry that detects that the vehicle has entered the communication area 5, and 9 b is a vehicle exit detection that detects that the vehicle has exited the communication area 5. The vehicle detector 10 is a gantry for installing the roadside antenna 2.

  Normally, when the ETC vehicle 3a equipped with the ETC vehicle-mounted device 4 enters the ETC lane 1a of the toll gate and the ETC vehicle 3a passes through the vehicle detector 9a for detecting vehicle entry, the road-side antenna 2 moves toward the communication area 5. Before the ETC vehicle 3a passes through the vehicle exit detection vehicle detector 9b, information necessary for toll collection is exchanged with the ETC vehicle-mounted device 4 until the radio wave is emitted.

  However, since ETC vehicles and non-ETC vehicles are mixed on the road, for example, as shown in FIG. 12, the non-ETC vehicle 3b enters the ETC lane 1a and the ETC vehicle 3a enters the non-ETC lane 1b. May enter. At this time, the direct wave 6 radiated from the roadside antenna 2 hits the road surface of the ETC lane 1a, roadside devices such as the vehicle detectors 9a and 9b, and the non-ETC vehicle 3b passing through the communication area 5, before the communication area 5. Bounce around the next lane. The primary reflected wave 7b bounced off to the adjacent non-ETC lane 1b reaches the ETC vehicle-mounted device 4 of the ETC vehicle 3a traveling on the non-ETC lane 1b.

  FIG. 13 shows the electric field strength characteristics in the adjacent lanes when a vehicle is present in the ETC lane 1a and when there is no vehicle. When a vehicle is present on the ETC lane 1a, the electric field strength is higher than when no vehicle is present due to the influence of the primary reflected wave 7b from the vehicle. Therefore, the electric field strength rises to about −66 dBm, which is higher than the level at which the ETC onboard device 4 reacts, −70.5 dBm, and is received by the ETC onboard device 4 mounted on the ETC vehicle 3a passing through the non-ETC lane 1b. May end up. The ETC vehicle-mounted device 4 erroneously determines that the vehicle is passing through the ETC lane 1a, and performs communication with the roadside antenna 2. The ETC system erroneously determines the non-ETC vehicle 3b that is passing through the ETC lane 1a as the ETC vehicle 3a. I let it pass. On the other hand, the ETC vehicle 3a is charged twice. Here, the range in which the ETC vehicle-mounted device 4 traveling on the adjacent non-ETC lane 1b reacts is from 0 m directly below the antenna to 6 m immediately below the antenna, which is longer than the communication area 5 of the ETC lane 1a as shown in FIG. is there.

  Such miscommunication problems may also occur when ETC lanes are adjacent to each other, and unaccounted for charges at the time of toll collection due to miscommunication with ETC on-board devices in such adjacent lanes. Heavy billing and incorrect amount of money are fatal problems in operating the ETC system.

  As described above, the conventional road-to-vehicle communication system has a problem that erroneous communication occurs between adjacent lanes.

  The present invention has been made to solve such problems, and has an object to limit erroneous communication between adjacent lanes in a road-vehicle communication system.

The radio wave leakage limiting wall according to the present invention includes a first lane provided with a roadside antenna for communicating with an in-vehicle device mounted on a passing vehicle, and a second lane adjacent to the first lane. An in-vehicle device mounted on a vehicle passing through the second lane and a metal wall that restricts communication between the roadside antenna, and a radio wave absorber portion and a metal portion on the metal wall Are alternately arranged, and the centers of the widths of the radio wave absorber portions are respectively arranged at a plurality of ground heights to which the vehicle-mounted device in a normal vehicle and a large vehicle is attached.

The ground height to which the vehicle-mounted device in the ordinary vehicle is attached is about 1 m, and the ground height to which the vehicle-mounted device in the large vehicle is attached is about 2 m.

The road-to-vehicle communication system according to the present invention includes the above-described radio wave leakage limiting wall.

  According to the radio wave leakage limiting wall according to the present invention, it is possible to limit erroneous communication between the roadside antenna provided in the first lane and the vehicle-mounted device mounted on the vehicle passing through the second lane. .

  Further, by making the radio wave leakage restriction wall into a lattice shape, it is possible to further check the vehicles traveling in adjacent lanes with excellent visibility.

  Further, by configuring the radio wave leakage limiting wall to have a radio wave absorber, the first lane provided with the roadside antenna is hardly affected by the reflected wave from the radio wave leakage limiting wall. .

  Further, the radio wave leakage limiting wall is composed of a plurality of flat plates, and the adjacent flat plates are connected to each other at an angle smaller than 180 degrees to pass through the roadside antenna provided in the first lane and the second lane. It is possible to limit the erroneous communication with the vehicle-mounted device mounted on the vehicle, and to obtain the effect of being hardly affected by the reflected wave from the radio wave leakage limiting wall even in the first lane at low cost. it can.

  Moreover, according to the road-to-vehicle communication system according to the present invention, it is possible to limit erroneous communication between the roadside antenna provided in the first lane and the vehicle-mounted device mounted on the vehicle passing through the second lane. it can.

Embodiment 1 FIG.
In the road-to-vehicle communication system according to the first embodiment, in order to prevent radio wave leakage to the adjacent lane, a metal flat wall for limiting radio wave leakage is provided on the island between the ETC lane 1a and the adjacent lane 1b. It is characterized by that.

  1 is an external view showing a radio wave environment in the vicinity of a toll gate such as a highway in Embodiment 1 of the present invention, and FIG. 2 is an external view of a metal flat plate wall in Embodiment 1. In FIG. 1 and 2, 1a is an ETC lane that is the first lane, 1b is a non-ETC lane that is a second lane adjacent to the ETC lane 1a, and 2 is installed in a traffic vehicle installed in the ETC lane 1a. A roadside antenna for communicating with the vehicle-mounted device, 3a is an ETC vehicle traveling on the non-ETC lane 1b toward the toll gate, 3b is a non-ETC vehicle traveling on the ETC lane 1a toward the toll gate, 4 is an ETC vehicle-mounted device that is mounted on the ETC vehicle 3 a and communicates with the roadside antenna 2, 5 is a communication area in which communication is possible between the roadside antenna 2 and the ETC vehicle-mounted device 4, and 6 is a direct radiation emitted from the roadside antenna 2. A wave 7a hits the body of the non-ETC vehicle 3b and bounces back to the front of the communication area 5, and 7b hits the body of the non-ETC vehicle 3b and moves toward the adjacent non-ETC lane 1b. The primary reflected wave that rebounds, 9a is a vehicle detector for vehicle entry detection that detects that the vehicle has entered the communication area 5, 9b is a vehicle detector for vehicle exit detection that detects that the vehicle has exited from the communication area 5, Reference numeral 10 denotes a gantry for installing the roadside antenna 2, and the above is the same as in a conventional radio wave environment.

  Reference numeral 11 denotes a metal flat plate wall which is a radio wave leakage limiting wall, and is installed on an island between the ETC lane 1a and the non-ETC lane 1b. The metal flat plate wall 11 may be formed of steel, but is preferably formed of aluminum for weight reduction. 11a is a steel support that supports the flat metal plate wall 11 and has a diameter of about 20 cm so that it does not break even if the vehicle hits it. Reference numeral 12 denotes a secondary reflected wave that bounces off the metal plate wall 11. Here, the size of the metal flat plate wall 11 is set to 6 m in length to block the range in which the ETC vehicle-mounted device 4 reacts in the adjacent lane 1b as shown in FIG. The value is 3.8 m.

  Next, the operation of the present invention will be described. When the non-ETC vehicle 3b passes the vehicle detector 9a, the direct wave 6 radiated from the roadside antenna 2 toward the communication area 5 hits the vehicle body of the vehicle 3b, and the primary reflected wave 7b tries to jump into the adjacent lane 1b. Since it hits the metal flat plate wall 11 on the island and bounces off as the secondary reflected wave 12, the radio wave of the roadside antenna 2 does not jump into the adjacent lane 1b.

  3 is an electric field strength characteristic diagram in the own lane and the adjacent lane depending on the presence or absence of the metal plate wall 11 having the dimension and shape shown in FIG. 2, and (1) is an electric field strength characteristic diagram in the ETC lane 1a which is the own lane. (2) is an electric field strength characteristic diagram in the adjacent lane 1b. As described in (2) of FIG. 3, when the metal flat plate wall 11 which is a radio wave leakage restriction wall is installed, the electric field strength is a reception sensitivity level of −70.5 dBm or less at which the ETC onboard device 4 reacts. Therefore, road-to-vehicle communication is not established between the ETC vehicle-mounted device 4 mounted on the ETC vehicle 3a traveling in the adjacent lane 1b and the roadside antenna 2. As a result, erroneous communication with the ETC vehicle 3a traveling in the adjacent lane 1b can be prevented, and charge exchange with an erroneous vehicle can be prevented.

  Here, it is considered that the secondary reflected wave 12 that bounces off the metal plate wall 11 and the direct wave 6 from the roadside antenna 2 may be combined to increase the electric field strength before the communication area 5. However, as shown in FIG. 3 (1), the electric field strength characteristics in the vicinity of the communication region 5 of the ETC lane 1a are almost the same with and without the metal flat plate wall 11, so that the metal flat plate wall It can be determined that the level of the secondary reflected wave 12 reflected by 11 is weak. Therefore, even if the ETC vehicle 3a enters the ETC lane 1a, communication is not started before the communication area 5, and information necessary for toll collection can be exchanged within the communication area 5.

Embodiment 2. FIG.
4 is an external view showing a radio wave environment in the vicinity of a toll gate such as a highway in Embodiment 2 of the present invention, and FIG. 5 is an external view of a grid-like metal wall in Embodiment 2. In FIG. 4 and 5, reference numerals 1 to 12 are the same as those in the first embodiment, and reference numeral 13 denotes a lattice-shaped metal wall installed on the island as a radio wave leakage restriction wall. Here, the lattice-shaped metal wall 13 uses a stainless steel wire mesh to prevent corrosion due to exhaust gas or rain, and although not shown, it is attached to a steel frame and formed into a panel shape. . The material of the grid-shaped metal wall 13 may be aluminum for weight reduction, or steel or the like if waterproof coating is applied. Further, as shown in FIG. 13, the size of the grid-shaped metal wall 13 is set such that the length is 6 m and the height is the vehicle height regulation value in order to block the range in which the ETC vehicle-mounted device 4 reacts in the adjacent lane 1 b 3.8m.

FIG. 6 is a characteristic diagram showing a shielding effect for preventing radio wave leakage due to the spacing (mesh size) a and b of the metal grid having the dimensions shown in FIG. 5, and has a conductivity of 5.65 × as a conductor constituting the metal grid. 10 ⁷ [S / m] copper is used, the thickness of the wire net itself is 2σ (σ = λ / 20, λ: wavelength), and a and b are calculated at the same interval. As shown in the figure, the shielding effect increases when the lattice spacings a and b are narrowed, and the shielding effect decreases when the lattice spacings a and b are widened. Therefore, if the intervals a and b of the metal grating are set to intervals equivalent to 3λ / 4, λ / 2, λ / 4, etc., which are about 50 mm, which is about the same as the wavelength λ, the shielding effect is 10 dB or more. Can be secured.

  Next, the operation of the present invention will be described. When the non-ETC vehicle 3b passes the vehicle detector 9a, the direct wave 6 radiated from the roadside antenna 2 toward the communication area 5 hits the vehicle body of the vehicle 3b, and the primary reflected wave 7b tries to jump into the adjacent non-ETC lane 1b. However, since it hits the grid-shaped metal wall 13 on the island and bounces off as the secondary reflected wave 12, the radio wave of the roadside antenna 2 does not jump into the adjacent non-ETC lane 1b. Therefore, as shown in (2) of FIG. 3, since the electric field strength in the adjacent non-ETC lane 1b is equal to or less than the reception sensitivity level of −70.5 dBm to which the ETC onboard device 4 reacts, the vehicle is traveling in the non-ETC lane 1b. Road-to-vehicle communication is not established between the ETC vehicle-mounted device 4 mounted on the ETC vehicle 3a and the roadside antenna 2. Thereby, it is possible to prevent erroneous communication with the ETC vehicle 3a traveling in the adjacent lane 1b, and to prevent fee exchange with the wrong vehicle.

  Here, the level of the secondary reflected wave 12 bounced off upon hitting the lattice-shaped metal wall 13 is weak as shown in (1) of FIG. 3 as in the first embodiment, and the electric field intensity in the ETC lane 1a. Since there is almost no difference depending on the presence or absence of the grid-shaped metal wall 13, communication does not start before the communication area 5 even if the ETC vehicle 3 a enters the ETC lane 1 a, and it is necessary for toll collection within the communication area 5 Exchange information.

  In addition, since it is a lattice-shaped wall, it has excellent visibility, so that a vehicle traveling in the adjacent lane 1b can be confirmed from within the vehicle traveling on the ETC lane 1a, and the vehicle touches when the vehicles merge after passing through the toll gate lane. The effect of preventing accidents is obtained. In the above description, almost all of the radio wave leakage restriction wall is a metal grid, but a part thereof may be constituted by the metal flat plate described in the first embodiment or a radio wave absorber described later.

Embodiment 3 FIG.
FIG. 7 is an external view showing a radio wave environment near a toll gate such as a highway in Embodiment 3 of the present invention. In the figure, reference numerals 1 to 10 are the same as those in the first embodiment, and reference numeral 14 denotes a radio wave absorber wall installed on the island as a radio wave leakage limiting wall. Here, the electromagnetic wave absorber is preferably outdoor because it is an outdoor type, but in the case of an indoor type electromagnetic wave absorber, it is used by covering it with an incombustible or flame-retardant material such as an acrylic plate or a reinforced vinyl sheet. it can. The size of the radio wave absorber wall 14 is the same as that of the metal flat plate wall 11 in the first embodiment shown in FIG.

  Next, the operation of the present invention will be described. When the non-ETC vehicle 3b passes the vehicle detector 9a, the direct wave 6 radiated from the roadside antenna 2 toward the communication area 5 hits the vehicle body of the vehicle 3b, and the primary reflected wave 7b tries to jump into the adjacent non-ETC lane 1b. However, the radio wave of the roadside antenna 2 does not jump into the adjacent non-ETC lane 1b because it hits the radio wave absorber wall 14 on the island and is absorbed. Therefore, as shown in (2) of FIG. 3, since the electric field strength in the non-ETC lane 1b is equal to or less than the reception sensitivity level of −70.5 dBm to which the ETC on-board device 4 reacts, the ETC traveling on the non-ETC lane 1b Road-to-vehicle communication is not established between the ETC vehicle-mounted device 4 mounted on the vehicle 3a and the roadside antenna 2. Thereby, it is possible to prevent erroneous communication with the EC vehicle 3a traveling in the adjacent lane 1b, and to prevent fee exchange with the wrong vehicle.

  Here, since the primary reflected wave 7b is absorbed by the radio wave absorber wall 14, the electric field strength characteristic when there is no radio wave leakage restriction wall described in (1) of FIG. 3 is shown. Even if the vehicle 3a enters, communication is not started before the communication area 5, and information necessary for toll collection can be exchanged within the communication area 5.

Embodiment 4 FIG.
FIG. 8 is an external view showing a radio wave environment in the vicinity of a toll gate such as a highway in Embodiment 4 of the present invention, and FIG. 9 is an external view of a wall of a metal flat plate with a radio wave absorber in Embodiment 4. In the figure, reference numerals 1 to 11 are the same as those in the first embodiment. Reference numeral 15 denotes a metal wall with a radio wave absorber installed on the island as a radio wave leakage limiting wall, and is configured to have a radio wave absorber portion 15a and a metal portion 15b by attaching the radio wave absorber on a metal plate. Has been.

  FIG. 9 shows an external view of the metal wall 15 with a radio wave absorber. As shown in the figure, the size of the metal wall 15 with the radio wave absorber is the same as that of the metal flat plate wall in the first embodiment shown in FIG. 2, and the width of the radio wave absorber portion 15a and the metal portion 15b has a wavelength λ. The radio wave absorber portion 15a is arranged so that the center of the width of the radio wave absorber portion 15a is about 1 m and the ground height of about 2 m, and the radio wave absorber portions 15a and the metal portions 15b are alternately arranged. ing. Here, the ground height is about 1 m and the ground height is about 2 m so that the center of the width of the radio wave absorber portion 15a is located. In the case of a large vehicle such as a truck, it corresponds to the ground height of about 2 m. By arranging in this way, the reflected wave from the metal wall 15 with the radio wave absorber is mounted on the vehicle passing through the ETC lane 1a. It is possible to make it difficult to affect the installed vehicle-mounted device.

  Next, the operation of the present invention will be described. When the non-ETC vehicle 3b passes the vehicle detector 9a, the direct wave 6 radiated from the roadside antenna 2 toward the communication area 5 hits the vehicle body of the vehicle 3b, and the primary reflected wave 7b tries to jump into the adjacent non-ETC lane 1b. Is absorbed or reflected by the radio wave absorber portion 15a and the metal portion 15b of the metal wall 15 with the adjacent radio wave leakage blocking radio wave absorber on the island, so that the radio waves of the roadside antenna 2 are present in the adjacent non-ETC lane 1b. Will not jump in. Therefore, as shown in (2) of FIG. 3, since the electric field strength in the non-ETC lane 1b is equal to or less than the reception sensitivity level of −70.5 dBm to which the ETC on-board device 4 reacts, the ETC traveling on the non-ETC lane 1b Road-to-vehicle communication is not established between the ETC vehicle-mounted device 4 mounted on the vehicle 3a and the roadside antenna 2. Thereby, it is possible to prevent erroneous communication with the ETC vehicle 3a traveling in the adjacent lane 1b, and to prevent fee exchange with the wrong vehicle.

  Further, since the primary reflected wave 7b is absorbed or reflected by the metal wall 15 with the radio wave absorber, an electric field distribution in a state close to the case where there is no radio wave leakage restriction wall described in (1) of FIG. 3 is applied to the ETC lane 1a. Even if the ETC vehicle 3a enters the ETC lane 1a, communication is not started before the communication area 5, and information necessary for toll collection can be exchanged in the communication area 5.

Embodiment 5 FIG.
FIG. 10 is an external view showing a radio wave environment in the vicinity of a toll gate such as a highway in Embodiment 5 of the present invention. In the figure, 1 to 10 are the same as those in Embodiment 1 above. Reference numeral 16 denotes a folding-wall-shaped metal wall installed on the island as a radio wave leakage limiting wall. FIG. 11 shows an external view thereof and a view seen from above. 17a and 17b are secondary reflected waves that bounce off the folding-shaped metal wall 16, 17a is a secondary reflected wave to the ETC lane 1a, and 17b is a secondary reflected wave in an arbitrary direction. Here, the size of the folding screen-shaped metal wall 16 is the same as the metal flat plate wall 11 in the first embodiment shown in FIG. 2, and the width of each folding screen is about 50 cm, which is about 10 times the wavelength λ. The opening angle of the folding screen is set to 120 degrees which is 3π / 2. Further, the folding screen-shaped metal wall 16 ensures visibility as a lattice shape similar to the lattice-shaped metal wall 13 in the second embodiment. The intervals a and b of the grating are also the same as those of the grating-shaped metal wall 13 in the second embodiment, and are set to about 50 mm, which is about the same as the wavelength λ, and a shielding effect of 10 dB or more is ensured.

  Next, the operation of the present invention will be described. When the non-ETC vehicle 3b passes the vehicle detector 9a, the direct wave 6 radiated from the roadside antenna 2 toward the communication area 5 hits the vehicle body of the vehicle 3b, and the primary reflected wave 7b tries to jump into the adjacent non-ETC lane 1b. Is reflected on the folding-wall shaped metal wall 16 on the island, and is irregularly reflected by the metal wall developed in the folding screen shape and reflected separately into the secondary reflected wave 17a in the direction of the ETC lane 1a and the secondary reflected wave 17b in the arbitrary direction. The radio wave of the roadside antenna 2 does not jump into the adjacent non-ETC lane 1b. Therefore, as shown in (2) of FIG. 3, since the electric field strength in the non-ETC lane 1b is equal to or less than the reception sensitivity level of −70.5 dBm to which the ETC on-board device 4 reacts, the ETC traveling on the non-ETC lane 1b Road-to-vehicle communication is not established between the ETC vehicle-mounted device 4 mounted on the vehicle 3a and the roadside antenna 2. Thereby, it is possible to prevent erroneous communication with the ETC vehicle 3a traveling in the adjacent lane 1b, and to prevent fee exchange with the wrong vehicle.

  Here, the secondary reflected waves 17a and 17b diffused by the folding screen-shaped metal wall 16 jump into the ETC lane 1a, but the electric field in a state close to the case where there is no radio wave leakage restriction wall described in (1) of FIG. The distribution can be reproduced in the ETC lane, and even if the ETC vehicle 3a enters the ETC lane 1a, the communication is not started before the communication area 5, and information necessary for toll collection within the communication area 5 is exchanged. Can do. Moreover, the same effect can be obtained at a lower cost than using a radio wave absorber.

  In addition, since it is a metal grid-shaped wall, it has excellent visibility, and a vehicle traveling in the adjacent lane 1b can be confirmed from within the vehicle traveling on the ETC lane 1a, and when the vehicle merges after passing through the toll gate lane, The effect of preventing contact accidents is obtained.

  In the above description, the folding angle of the folding screen is 120 degrees. However, if the opening angle is smaller than 180 degrees, the same effect can be obtained even if the opening angle is set to 60 degrees, 90 degrees, or 150 degrees. It goes without saying that it is obtained.

  Further, in the above description, the folding screen-shaped metal wall 16 has a lattice shape, but a metal plate such as the metal plate wall 11 in the first embodiment may be connected in a folding screen, or the third embodiment, The same effect can be obtained by connecting a flat plate having a radio wave absorber as shown in 4 to form a folding screen-shaped radio wave leakage restriction wall.

  Further, the folding screen-shaped metal wall 16 may be formed in a curved wave shape (W shape). In short, if the primary reflected wave 7b is irregularly reflected by the radio wave leakage restriction wall, the reflected wave to the own lane. The same effect can be obtained. Further, the folding screen-shaped metal wall 16 can be formed in a folding screen shape in the vertical direction, but in this case, the reflected wave from the road surface may be affected.

  In each of the above embodiments, the case where the ETC lane and the non-ETC lane are adjacent to each other has been described as an example. However, even when the ETC lanes are adjacent to each other, by providing a radio wave leakage restriction wall, Similar effects can be obtained.

Embodiment 6 FIG.
In each of the above embodiments, a road-to-vehicle communication system in a toll booth on a highway or a toll road has been described as an example, but roads such as a parking lot system, a drive-through system, a gas station system, etc. that apply road-to-vehicle communication technology. It can also be applied to an inter-vehicle communication system. For example, when there are multiple lanes adjacent to a parking lot, etc., and communication is performed between a roadside antenna installed on the lane and an on-board device equipped with an automatic toll collection function installed in the vehicle, radio wave leakage The restriction wall restricts the leakage of radio waves from the roadside antenna to the adjacent lanes, preventing unaccounted for charges, double billing, and incorrect charges.

  Further, the present invention can be applied not only to toll collection but also to a system in which only a vehicle having a passage permit can pass in advance by exchanging passage permission information between the roadside antenna and the vehicle-mounted device. In this case as well, the radio wave leakage restriction wall can restrict the leakage of radio waves from the roadside antenna to the adjacent lanes, and can prevent a vehicle that does not have a passage permit from passing by mistake. .

3 is an external view showing a radio wave environment near a toll gate in Embodiment 1. FIG. 3 is an external view of a radio wave leakage restriction wall according to Embodiment 1. FIG. FIG. 3 is a diagram showing electric field strength characteristics in the own lane and adjacent lanes depending on the presence or absence of a radio wave leakage restriction wall. 6 is an external view showing a radio wave environment in the vicinity of a toll gate in Embodiment 2. FIG. 6 is an external view of a radio wave leakage restriction wall according to Embodiment 2. FIG. FIG. 11 is a characteristic diagram showing a shielding effect of radio wave leakage by the interval between metal gratings of the radio wave leakage restriction wall in the second embodiment. 10 is an external view showing a radio wave environment in the vicinity of a toll gate in Embodiment 3. FIG. FIG. 10 is an external view showing a radio wave environment near a toll gate in a fourth embodiment. 10 is an external view of a radio wave leakage restriction wall according to Embodiment 4. FIG. 10 is an external view showing a radio wave environment near a toll gate in Embodiment 5. FIG. It is the external view and top view of the electromagnetic wave leakage restriction wall in Embodiment 5. It is an external view which shows the electromagnetic wave environment of the vicinity of the conventional toll gate. It is a figure which shows the electric field strength characteristic in an adjacent lane in the case where a vehicle exists in an ETC lane, and when it does not exist.

Explanation of symbols

  1a ETC lane, 1b non-ETC lane, 2 roadside antenna, 3a ETC vehicle, 3b non-ETC vehicle, 4 ETC on-board device, 5 communication area, 11 metal flat plate wall, 13 grid-shaped metal wall, 14 radio wave absorber wall, 15 radio wave Metal wall with absorber, 16 folding screen-shaped metal wall.

Claims (3)

Provided between a first lane provided with a roadside antenna for communicating with a vehicle-mounted device mounted on a passing vehicle and a second lane adjacent to the first lane, An on-vehicle device mounted on a vehicle to be passed and a metal wall that restricts communication between the roadside antenna, and a radio wave absorber portion and a metal portion are alternately arranged on the metal wall, and a normal vehicle and a large vehicle A radio wave leakage limiting wall, wherein the center of the width of the radio wave absorber portion is arranged at a plurality of ground heights to which the vehicle-mounted device in a vehicle is attached. The radio wave leakage limiting wall according to claim 1, wherein a height above ground where the on-vehicle device in the ordinary vehicle is attached is about 1 m, and a height above ground where the on-vehicle device in the large vehicle is attached is about 2 m. A road-to-vehicle communication system comprising the radio wave leakage restriction wall according to claim 1.

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