JP7285801B2 - Communication device and electronic toll collection system - Google Patents

Description

The present disclosure relates to communication devices and electronic toll collection systems.

In the ETC (registered trademark, Electronic Toll Collection) system, tolls on toll roads are settled by communication between the wireless antenna installed at the toll gate and the ETC on-board device installed in the vehicle. be done. ETC in-vehicle equipment in which the following vehicle is equipped with a radio antenna by reflecting the radio waves transmitted by the radio antenna to the preceding vehicle from the road or other vehicle when the preceding and following vehicles are entering the toll gate. Incorrect communication may occur. That is, multipath may occur. In this case, the ETC system erroneously recognizes that the vehicle equipped with the ETC on-board device is the preceding vehicle, and the following vehicle erroneously recognizes that the vehicle is not equipped with the ETC on-board device. was
Therefore, a technology has been put into practical use to prevent this phenomenon from occurring by installing radio wave absorbers on the roof of the toll gate, the blocking wall between the lanes, or the like. However, as the period in which the radio wave absorber is installed becomes longer, the absorption performance of the radio wave absorber gradually deteriorates due to adhesion of exhaust gas, dust, etc. to the surface of the radio wave absorber. Also, the appropriate range for installing the radio wave absorber varies depending on road conditions and the like. Therefore, it is difficult to define this range.
Patent Literature 1 discloses a technique for preventing multipath without installing a radio wave absorber. According to the present technology, the radio wave arrival angle detection unit detects the angle corresponding to the radio wave transmission source.

JP 2012-247958 A

According to the technique disclosed in Patent Document 1, erroneous communication may be caused by the detection of an erroneous angle by the radio wave arrival angle detector. As a specific example, according to the present technology, when a radio wave arrival angle detection unit detects an erroneous angle with respect to a radio wave arriving from within the communication area, the radio wave may be determined to be a radio wave from outside the communication area. be. The communication area is an area in which communication devices provided in the ETC system should communicate. When the radio wave arrival angle detection unit determines in this way, communication cannot be performed between the ETC vehicle-mounted device located within the communication area and the radio antenna installed at the tollgate.

An object of the present disclosure is to prevent multipath by receiving radio waves from an ETC vehicle-mounted device located within the communication area without transmitting the radio waves from the ETC vehicle-mounted device located outside the communication area.

A communication device according to the present disclosure includes:
a dielectric layer comprising a dielectric plate;
a first transmission layer located on the surface of the dielectric layer, which transmits an electromagnetic wave having a transmission frequency as a first layer transmission wave and does not transmit an electromagnetic wave having a frequency different from the transmission frequency;
Located on the back surface of the dielectric layer, the incident angle of the first layer-transmitted wave to the first transmission layer falls within the second layer transmission range indicating the range of the incident angle of the electromagnetic wave to the first transmission layer. the first layer transmitted wave is transmitted as a second layer transmitted wave, and the first layer transmitted wave is transmitted when the angle of incidence on the first transmission layer does not fall within the second layer transmission range. a radome having a second transmissive layer that does not transmit light;
An antenna facing the second transmission layer and receiving the second layer transmitted wave,
The incident angle of the first layer transmitted wave to the first transmission layer falls within the first layer transmission range indicating the range of the incident angle of the electromagnetic wave to the first transmission layer,
The second layer transmission range is included in the first layer transmission range,
The second layer transmission range is smaller than the first layer transmission range.

According to the present disclosure, the second transmission layer transmits the electromagnetic wave when the incident angle of the electromagnetic wave to the first transmission layer falls within the second layer transmission range, and the incident angle of the electromagnetic wave to the first transmission layer is is not within the second layer transmission range, it does not transmit electromagnetic waves.
Therefore, according to the present disclosure, multipath can be prevented by receiving radio waves from the ETC vehicle-mounted device located within the communication area without transmitting the radio waves from the ETC vehicle-mounted device located outside the communication area.

1 is a configuration example of a communication device 100 according to Embodiment 1; 3 is a configuration example of a radome 200 and an antenna 310 according to Embodiment 1; 1 shows a configuration example of a radome 200 according to Embodiment 1, in which (a) is an example in which a first transmission layer 210 and a second transmission layer 220 transmit electromagnetic waves, and (b) is an example in which the first transmission layer 210 transmits electromagnetic waves. An example in which the second transmission layer 220 does not transmit electromagnetic waves, and (c) is an example in which the first transmission layer 210 does not transmit electromagnetic waves. An example in which multipath does not occur at a toll booth equipped with the communication device 100 according to the first embodiment. An example in which multipath occurs at a tollgate equipped with the communication device 100 according to the first embodiment. An example in which multipath occurs in the free flow ETC provided with the communication device 100 according to the first embodiment. An example of a toll booth with radio wave absorbers installed.

Embodiment 1.
Hereinafter, this embodiment will be described in detail with reference to the drawings.

*** Configuration description ***
FIG. 1 shows a configuration example of a communication device 100 according to this embodiment. The communication device 100 includes a radome (radome) 200 and a wireless device 300, as shown in the figure.

The communication device 100 is installed in a place through which a mobile object can pass or around a place through which a mobile object can pass. The communication device 100 can communicate with equipment provided in a mobile object, or equipment possessed by the mobile object. Specific examples of locations where the communication device 100 is installed are roads, roadsides, parking lots, harbors, and airports. The communication device 100 may be mounted on a mobile object. A moving object is, for example, an automobile, a ship, an air vehicle, a robot, or a human being. The communication device 100 may communicate with a communication device such as a smartphone owned by a person. Any information may be communicated between the communication device 100 and the mobile object. As a specific example, the communication device 100 transmits to and receives from the mobile device information for collecting charges from the user of the mobile device. The communication device 100 is an ETC (registered trademark, Electronic
Toll Collection, electronic toll collection) system 90 . When referring to the ETC system 90, it is assumed that the ETC system 90 includes the communication device 100 unless otherwise specified. The ETC system 90 consists of a communication device 100 and an ETC vehicle-mounted device.

The outside of communication device 100 is typically a container that covers wireless device 300 . The container does not have to be sealed. The shape of the container is, as a specific example, substantially cuboid, polyhedron, or substantially cylindrical. The front face of communication device 100 is radome 200 . The sides and back of the communication device 100 are typically made of a material that does not allow electromagnetic waves to pass through or that makes it difficult for electromagnetic waves to pass through.

Wireless device 300 can wirelessly communicate with a mobile object. The wireless device 300 can receive electromagnetic waves transmitted through the radome 200 and transmit electromagnetic waves transmitted through the radome 200 to a moving object. Wireless device 300 does not have to be capable of transmitting electromagnetic waves. Electromagnetic waves are radio waves as a specific example. The frequency of electromagnetic waves may be any value.

Radio apparatus 300 includes an antenna 310, a DIP 320, a transmitter 330, a receiver 340, and a modulator/demodulator 350, as shown in the figure.

Antenna 310 faces second transmissive layer 220 . Antenna 310 receives electromagnetic waves that have passed through radome 200 . Antenna 310 can be any antenna. Antenna 310 is, as a specific example, a loop antenna.

A DIP (Diplexer) 320 electrically separates the transmission path and the reception path. DIP 320 is connected to antenna 310 , transmitter 330 , and receiver 340 .

The transmitter 330 instructs the antenna 310 to transmit electromagnetic waves.

The receiving section 340 transmits the electromagnetic waves received by the antenna 310 to the modem section 350 .

The modulation/demodulation unit 350 has a function of modulating an electrical signal into an electromagnetic wave and a function of demodulating the electromagnetic wave into an electrical signal.

Wireless device 300 may not receive electromagnetic waves when the intensity of the electromagnetic waves partially passing through second transmission layer 220 is below a certain level.

FIG. 2 shows a configuration example of the radome 200 and the antenna 310. As shown in FIG. The radome 200 is a frequency selective plate (FSS: Frequency Selective Surface). The radome 200 has a plate that is planar or nearly planar. The surface of the radome 200 is the first transmission layer 210 . The back surface of the radome 200 is the second transmissive layer 220 . In this example, rectangular resonant elements are arranged two-dimensionally periodically in the first transmissive layer 210 and the second transmissive layer 220 .
Resonant elements are typically metal elements. A metal element is a small metal plate. The size and shape of the metal elements may be varied according to the transmission frequency 211 . The number of metal elements and the thickness of the metal elements may be changed as appropriate. The spacing between adjacent resonant elements may be changed as appropriate. The arrangement of the resonant elements does not have to be a two-dimensional periodic array.
In this example, the antenna 310 has patch antennas arranged in a two-dimensional periodic arrangement.

FIG. 3 shows a configuration example of the radome 200. As shown in FIG. (a) of this figure is an example in which the first transmission layer 210 and the second transmission layer 220 transmit electromagnetic waves. (b) of this figure is an example in which the first transmission layer 210 transmits electromagnetic waves and the second transmission layer 220 does not transmit electromagnetic waves. (c) of this figure is an example in which the first transmission layer 210 does not transmit electromagnetic waves.
The radome 200 has a first transmissive layer 210, a second transmissive layer 220, and a dielectric layer 230, as shown in this figure. The radome 200 may comprise other components and the like.

The first transmission layer 210 is located on the surface of the dielectric layer 230 and transmits the first layer transmission wave. The first layer transmitted wave is an electromagnetic wave whose frequency is the transmitted frequency 211 . The incident angle of the first layer transmitted wave to the first transmission layer 210 falls within the first layer transmission range 212 . The first layer transmission range 212 indicates the range of angles of incidence of electromagnetic waves on the first transmission layer 210 . The first transmission layer 210 transmits electromagnetic waves as transmission layer transmission electromagnetic waves. An incident angle refers to an angle at which an electromagnetic wave is incident on the first transmission layer 210 unless otherwise specified. The incident angle is the angle between the propagation path of the electromagnetic wave and the perpendicular to the plane tangential to the point at which the electromagnetic wave enters the first transmission layer 210 .
The first transmission layer 210 does not transmit electromagnetic waves having a frequency different from the transmission frequency 211 . The first transmission layer 210 does not transmit electromagnetic waves whose incident angles to the first transmission layer 210 do not fall within the first layer transmission range 212 .
The first transmission layer 210 has a resonant element as a first resonant element.

The second transmissive layer 220 is similar to the first transmissive layer 210 . Differences between the second transmissive layer 220 and the first transmissive layer 210 are described below.
The second transmission layer 220 is located on the back surface of the dielectric layer 230 and transmits the second layer transmitted wave incident angle. The second layer transmitted wave is the first layer transmitted wave and an electromagnetic wave whose incident angle to the first transmission layer 210 is within the second layer transmission range 213 . The second transmission layer 220 transmits the first layer transmission wave as the second layer transmission wave. A second layer transmission range 213 indicates a range of incident angles of electromagnetic waves to the first transmission layer 210 .
If the incident angle of the first layer transmitted wave to the first transmission layer 210 does not fall within the second layer transmission range 213, the second transmission layer 220 does not transmit the first layer transmitted wave incident angle. When the second transmission layer 220 reflects the first layer transmitted wave, the dielectric layer 230 may absorb the first layer transmitted wave.
The second transmission layer 220 has, as a second resonant element, a resonant element different from the first resonant element. The first resonant element and the second resonant element may have common parts. Each of the first resonant element and the second resonant element may be a plurality of resonant elements arranged periodically two-dimensionally. The first resonant element and the second resonant element may each be made of metal.

The second layer transmission range 213 is included in the first layer transmission range 212 . The second layer transmission range 213 is smaller than the first layer transmission range 212 . Examples of first layer transmission areas 212 and second layer transmission areas 213 are shown in FIG.

The first layer transmission range 212 is determined by the angular properties of the first transmission layer 210 . The second layer transmission range 213 is determined by the angular characteristics of the second transmission layer 220 . The first layer transmissive range 212 may be defined by the placement of the resonating elements in the first transmissive layer 210 . The second layer transmissive range 213 may be defined by the placement of the resonating elements in the second transmissive layer 220 .
The first transmissive layer 210 typically has transmissive properties. The transmission characteristics of the first transmission layer 210 are exhibited when the incident angle falls within the first layer transmission range 212 . The first layer transmission range 212 may be from 0° to 90°.
The second transmissive layer 220 typically has reflective properties. The reflection characteristics of the second transmission layer 220 are exhibited at least when the incident angle falls within the first layer transmission range 212 and when the incident angle does not fall within the second layer transmission range 213 . In the case where the incident angle of the electromagnetic wave to the second transmission layer 220 does not fall within the first layer transmission range 212, the second transmission layer 220 does not have to exhibit the reflection characteristics.
It is assumed that the first layer transmission range 212 is 0° or more and θ ₁ or less, and the second layer transmission range 213 is 0° or more and θ ₂ or less. The transmission characteristic of the first transmissive layer 210 decreases as the incident angle approaches θ ₁ and may reach a predetermined threshold when the incident angle is θ ₁ . The reflective properties of the second layer transmissive area 213 may increase as the incident angle approaches θ ₂ and may reach a predetermined threshold when the incident angle is θ ₂ .

The transmission frequency 211 is the frequency of electromagnetic waves that can be transmitted through the first transmission layer 210 and the second transmission layer 220 . The transmission frequency 211 may be a single frequency or a range of frequencies. The certain range does not have to be a continuous range. It should be noted that transmitting an electromagnetic wave includes attenuating and transmitting the electromagnetic wave. Impermeability of electromagnetic waves includes significantly attenuating the electromagnetic waves, scattering the electromagnetic waves, and partially reflecting the electromagnetic waves.

In (a) of FIG. 3 , the frequency of the electromagnetic wave is the transmission frequency 211 , and the incident angle of the electromagnetic wave to the first transmission layer 210 is within the first layer transmission range 212 . Therefore, the first transmission layer 210 transmits electromagnetic waves.
Also, the incident angle is within the second layer transmission range 213 . Therefore, the second transmission layer 220 transmits electromagnetic waves.

In (b) of this figure, the frequency of the electromagnetic wave is the transmission frequency 211 and the incident angle of the electromagnetic wave to the first transmission layer 210 is within the first layer transmission range 212 . Therefore, the first transmission layer 210 transmits electromagnetic waves.
However, the incident angle does not fall within the second layer transmission range 213 . Therefore, the second transmission layer 220 does not transmit electromagnetic waves.

In (c) of this figure, although the frequency of the electromagnetic wave is the transmission frequency 211 , the incident angle of the electromagnetic wave to the first transmission layer 210 does not fall within the first layer transmission range 212 . Therefore, the first transmission layer 210 does not transmit electromagnetic waves.

Dielectric layer 230 consists of a dielectric plate. The dielectric material is, for example, plastic or ceramic.

***Description of operation***
The operation of the ETC system 90 will be described separately for the case where multipath does not occur and the case where multipath occurs. A multipath is an erroneous communication by the communication device 100 . Multipath means that the communication device 100 communicates with the vehicle-mounted device located outside the ETC communication area 95 . The ETC communication area 95 is an area in which the communication device 100 provided in the ETC system 90 should communicate. The communication device 100 should properly communicate with the ETC on-board equipment within the ETC communication area 95 . The communication device 100 should not properly communicate with the ETC on-board equipment outside the ETC communication area 95 . The ETC communication area 95 may not be a fixed area. The ETC communication area 95 may be a three-dimensional space formed considering the position where the vehicle-mounted device is installed. An area outside the ETC communication area 95 and in which the communication device 100 provided in the ETC system 90 can communicate with the ETC vehicle-mounted device is called an ETC erroneous communication area 96 . Communication includes send-only and receive-only.

The ETC communication area 95 is typically an elliptical area. The ETC communication area 95 is determined according to the second layer transmission range 213 . The area outside the ETC communication area 95 is typically an area outside the ETC communication area 95 .
The second layer transmission range 213 is set so as to transmit radio waves within the ETC communication area 95 and not transmit radio waves from outside the ETC communication area 95 . The angle of incidence of radio waves transmitted from outside the ETC communication area 95 entering the first transmission layer 210 typically does not fall within the second layer transmission range 213 .

The radio waves transmitted by the ETC on-board equipment are expressed as on-board equipment transmission waves. A radio wave transmitted by a radio is referred to as a radio transmission wave. The vehicle-mounted device transmission wave is a radio wave for the ETC vehicle-mounted device to communicate with the wireless device 300 . The frequency of the transmission wave from the vehicle-mounted device is the transmission frequency 211 . The radio transmission wave is a radio wave for the radio device 300 to communicate with the ETC vehicle-mounted device.

FIG. 4 shows an example of a case where multipath does not occur at a toll gate that includes the communication device 100. In FIG. A reference to a toll plaza means a toll plaza for a toll motorway unless otherwise specified. It is assumed that the vehicle is equipped with an ETC on-board device. The truck is running on vehicle lane L1.
The operation of the ETC system 90 when no multipath occurs will be described according to this figure.

First, the radio device 300 emits a radio transmission wave. The radio transmission wave passes through the radome 200 and reaches the ETC on-board equipment provided in the truck within the ETC communication area 95 .
Next, the ETC vehicle-mounted device provided in the truck receives the radio transmission wave from the radio device 300 and transmits the vehicle-mounted device transmission wave to the ETC system 90 according to the radio transmission wave.
Next, the first transmission layer 210 allows transmission waves from the vehicle-mounted device to pass therethrough. This is because the frequency of the vehicle-mounted device transmission wave is the transmission frequency 211 and the incident angle of the vehicle-mounted device transmission wave to the first transmission layer 210 is within the first layer transmission range 212 .
Next, the second transmission layer 220 allows transmission waves from the vehicle-mounted device to pass therethrough. This is because the incident angle of the transmission wave from the vehicle-mounted device is within the second layer transmission range 213 .
Next, the antenna 310 receives the vehicle-mounted transmission wave.

FIG. 5 shows an example in which multipath occurs at a toll gate that includes the communication device 100. In FIG. The truck is running on vehicle lane L1. The passenger car is traveling on the vehicle lane L2. The operation of the ETC system 90 when multipath occurs will be described according to this figure.

First, the radio device 300 emits a radio transmission wave. The radio transmission wave passes through the radome 200, is reflected by the truck within the ETC communication area 95, and reaches the ETC on-board equipment provided in the passenger car outside the ETC communication area 95.
Next, the ETC vehicle-mounted device provided in the passenger car receives the radio transmission wave from the radio device 300 and transmits the vehicle-mounted device transmission wave to the ETC system 90 in accordance with the radio transmission wave.
Next, the first transmission layer 210 allows transmission waves from the vehicle-mounted device to pass therethrough. This is because the frequency of the vehicle-mounted device transmission wave is the transmission frequency 211 and the incident angle of the vehicle-mounted device transmission wave to the first transmission layer 210 is within the first layer transmission range 212 .
Next, the second transmission layer 220 reflects the vehicle-mounted transmission wave. This is because the incident angle of the transmission wave from the vehicle-mounted device does not fall within the second layer transmission range 213 .
The reflected vehicle-mounted device transmission wave is converted into heat energy within the dielectric layer 230 .
In this example, the antenna 310 does not receive the vehicle-mounted device transmission wave.

FIG. 6 shows an example in which multipath occurs in free flow ETC provided with the communication device 100 . The free-flow ETC is a system in which the communication device 100 communicates with an on-board ETC device installed in a normally running vehicle to collect fees from the user of the vehicle. Also in this example, similarly to the example shown in FIG. 5, the first transmission layer 210 transmits the transmission wave of the vehicle-mounted device, and the second transmission layer 220 reflects the transmission wave of the vehicle-mounted device.

***Description of the effects of the first embodiment***
As described above, according to the ETC system 90 according to the present embodiment, the first transmission layer 210 transmits the first-layer transmitted wave. However, when the first layer-transmitted wave is incident on the first transmission layer 210 at an incident angle outside the second layer transmission range 213, the second transmission layer 220 does not transmit the first layer-transmitted wave. That is, the communication device 100 according to the present embodiment receives electromagnetic waves transmitted by ETC vehicle-mounted devices located within the ETC communication area 95, and transmits electromagnetic waves transmitted by ETC vehicle-mounted devices located outside the ETC communication area 95. do not receive. Therefore, the ETC system 90 according to the present embodiment can prevent multipath without using a radio wave absorber and without calculating an incident angle by linking a plurality of antennas.
Also, the ETC system 90 according to this embodiment does not use a radio wave absorber. FIG. 7 shows an example of a tollbooth in which radio wave absorbers are installed. FIG. 7 shows an example of installing a radio wave absorber on the roof of a toll gate and an example of installing a radio wave absorber on the gantry of the toll gate. In the ETC system 90 according to the present embodiment, construction work for installing the radio wave absorber is not required, and it is not necessary to close the tollbooth to install the radio wave absorber. Therefore, the ETC system 90 according to this embodiment can be installed at a relatively low cost and in a relatively short period of time.

***Other Configurations***
<Modification 1>
At least one of the first transmission layer 210 and the second transmission layer 220 may include multiple types of resonant elements.
As a specific example, the front surface of a partial area of the dielectric layer 230 is the resonant element A1, and the back surface corresponding to the area provided with A1 is the resonant element A2 corresponding to A1. The surface of the other regions of the dielectric layer 230 is the resonator element B1, and the back surface corresponding to the area with B1 is the resonator element B2 corresponding to the resonator element B1.
The communication device 100 according to this modification can support electromagnetic waves of multiple types of frequencies.

<Modification 2>
The appearance of the communication device 100 may be substantially polyhedral, and the radomes 200 may be installed on a plurality of surfaces.
In this modification, as a specific example, two outer surfaces of the communication device 100 are provided with radomes, the two radomes 200 face different vehicle lanes, and each radome 200 corresponds to each vehicle lane. An ETC communication area 95 is formed.
In this modification, the wireless device 300 may have multiple antennas 310 to support multiple ETC communication areas 95 .

***Other Embodiments***
Although Embodiment 1 has been described, a plurality of portions of this embodiment may be combined for implementation. Alternatively, one part of this embodiment may be implemented. In addition, the present embodiment may be modified in various ways as necessary, and may be implemented in any combination as a whole or in part.
It should be noted that the above-described embodiments are essentially preferable examples, and are not intended to limit the scope of the present disclosure, its applications, and uses.

90 ETC system, 95 ETC communication area, 96 ETC error communication area, 100 communication device, 200 radome, 210 first transmission layer, 211 transmission frequency, 212 first layer transmission range, 213 second layer transmission range, 220 second transmission Layers 230 dielectric layer 300 radio device 310 antenna 320 DIP 330 transmitter 340 receiver 350 modem L1 vehicle lane L2 vehicle lane.

Claims (5)

a dielectric layer comprising a dielectric plate;
a first transmission layer located on the surface of the dielectric layer, which transmits an electromagnetic wave having a transmission frequency as a first layer transmission wave and does not transmit an electromagnetic wave having a frequency different from the transmission frequency;
Located on the back surface of the dielectric layer, the incident angle of the first layer-transmitted wave to the first transmission layer falls within the second layer transmission range indicating the range of the incident angle of the electromagnetic wave to the first transmission layer. the first layer transmitted wave is transmitted as a second layer transmitted wave, and the first layer transmitted wave is transmitted when the angle of incidence on the first transmission layer does not fall within the second layer transmission range. a radome having a second transmissive layer that does not transmit light;
An antenna facing the second transmission layer and receiving the second layer transmitted wave,
The incident angle of the first layer transmitted wave to the first transmission layer falls within the first layer transmission range indicating the range of the incident angle of the electromagnetic wave to the first transmission layer,
The second layer transmission range is included in the first layer transmission range,
The communication device, wherein the second layer transmission range is smaller than the first layer transmission range. The first transmission layer has a resonant element as a first resonant element,
2. The communication device according to claim 1, wherein the second transmission layer has, as a second resonant element, a resonant element different from the first resonant element. 3. The communication device according to claim 2, wherein each of the first resonant element and the second resonant element is a plurality of resonant elements arranged two-dimensionally periodically. 4. The communication device according to claim 2, wherein the first resonant element and the second resonant element are each made of metal. An electronic toll collection system comprising the communication device according to any one of claims 1 to 4.

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