JP2001345631A - Converter method in electric wave environment, reflection structure body, and on-road communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain low-cost counter measures in electric wave environment for reflecting secondary reflection waves in a desired direction without affecting a system for applying primary reflection waves from a road surface to a reflection structure body. SOLUTION: A plurality of reflection plates having the angle of a reflection surface that is related by distance depending on positions between a road-side antenna and the reflection structure body, or the incidence angle of incidence waves to the reflection structure body are mounted on the reflection structure body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-stop automatic toll collection system (hereinafter referred to as an ETC system) and a driving support road system (hereinafter referred to as an ETC system) for communication between a roadside antenna installed on a road and an on-vehicle device. , AHS), etc., in a DSRC (Dedicated Short Range Communication) roadside communication system, suppresses the influence on roadside communication due to radio wave reflection from structures installed around the installation location of the roadside antenna The present invention also relates to a radio wave environment measure for improving a radio wave environment and a road communication system.

[0002]

2. Description of the Related Art FIG. 7 is an external view showing an installation structure of a radio wave absorbing wall proposed as a conventional radio wave environment measure. This is an example described in Japanese Utility Model Publication No. 6-72297. FIG. 8 is an external view showing an example of a real environment in which a radio wave environment measure is taken.

[0003] In Fig. 8, 1 is a road surface, 2 is a roadside antenna, 3 is a vehicle entering the roadside antenna 1 toward the roadside antenna 2, 4 is an on-vehicle device mounted on the vehicle 3;
Reference numeral 5 denotes an on-board unit ground position at which the on-board unit 4 is located; 6, a communication area at the on-board unit ground position 5; 7, a direct wave emitted from the roadside antenna 2; 8, a primary reflected wave from the road surface 1; Is a reflecting structure existing in front of the roadside antenna 2, and 11 c is a secondary reflected wave from the reflecting structure 9. 7, reference numeral 14 denotes a wall base such as the reflective structure 9, 15 denotes a radio wave reflector attached to the wall base 14, 16 denotes a radio wave absorber provided as a pair with the radio wave reflector 15, and 17 denotes a radio wave absorber. Radio wave reflector 15 and radio wave absorber 1
6 is a front panel that covers the front panel 6. The reflecting structure 9 is
For example, a gantry such as a roof (ceiling) of a tollgate or an electric bulletin board on an expressway, and a viaduct or a road existing in the sky in the communication area 6 and its vicinity.

Next, the operation will be described. When there is a reflective structure 9 such as a tollgate roof above the communication area 6 or in the vicinity of the same, radio waves emitted from the roadside antenna 2 and reaching the vehicle-mounted device 4 include primary waves generated by the road surface 1 in addition to the direct waves 7. There is a secondary reflected wave 11c in which the reflected wave 8 is reflected again by the reflecting structure 9. DSRC (Dedicated Sho) such as ETC system
In an rt Range Communication (dedicated narrow-range communication) system, it is desired that the vehicle-mounted device 4 be non-responsive except in the communication area 6.
A shaped beam (for example, a sector beam) having a low side lobe characteristic in which radiation is suppressed is generally used in a region other than the angle at which the beam is projected. However, actually, the roadside antenna 2
In a toll booth where a vehicle is installed, there is a reflective structure 9 such as a roof (ceiling) or a gantry, and the road surface 1 and the reflective structure 9 are provided.
Is the propagation path of the radio wave. For this reason, a radio wave reaches beyond the communication area 6 and an unstable system may be obtained.
Therefore, measures are taken to prevent the generation of the secondary reflected wave 11c by mounting a radio wave absorbing wall (see FIG. 7) described in, for example, Japanese Utility Model Laid-Open Publication No. 6-72297 on the entire lower surface of the reflecting structure 9. In this case, the primary reflected wave 8 from the road surface 1 passes through the front panel 17, is guided to and absorbed by the radio wave absorber 16 by the radio wave reflector 15, and the secondary reflected wave 1
It acts to suppress the generation of 1c.

[0005]

In the conventional radio wave environment countermeasures, since the radio wave absorbing wall configured as described above is provided for the reflecting structure, approximately 20 dB is required to absorb the primary reflected wave from the road surface. An extremely large number of expensive radio wave absorbers having the above-described return loss are required, and there has been a problem that the radio wave environment is expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and alleviates the influence on the system of a secondary reflected wave generated when a primary reflected wave from a road surface enters a reflecting structure. It aims to realize low-cost radio wave environment measures. Another object is to realize a low-cost radio wave environment measure that reduces the intensity of the secondary reflected wave without using an expensive radio wave absorber. Furthermore,
It is another object of the present invention to implement a low-cost radio wave environment measure that reduces the influence of primary reflected waves that are two-dimensionally emitted from a roadside antenna and reflected to the surroundings by a road surface, as well as the vehicle's approach direction.

[0007]

According to a first aspect of the present invention, there is provided a radio wave environment countermeasure method comprising: a distance depending on a position of a roadside antenna and a reflecting structure provided around the roadside antenna; A plurality of reflectors having a reflection surface angle related by an incident angle are attached to the reflection structure.

The reflecting structure of the second invention is based on a distance depending on the position of the roadside antenna and the reflecting structure provided around the roadside antenna and an incident angle of an incident wave on the reflecting structure. A reflector having a set reflection surface angle is attached to the lower surface. Things.

The reflecting structure according to a third aspect of the present invention includes a reflecting plate provided with the reflecting surface facing in a direction of reflecting a primary reflected wave from a road surface to the communication area. Things.

A fourth aspect of the present invention is a reflective structure, wherein a plurality of reflectors are arranged in parallel in a road width direction.

In the reflection structure according to a fifth aspect of the present invention, an absorber for reducing the amount of radio wave reflection is mounted on the reflection surface of the reflection plate, around the reflection plate including the reflection surface, and on a part of the support structure. Things.

A sixth aspect of the present invention is a reflective structure in which a plurality of reflectors are attached to the reflective structure so as to surround reflected waves radiated from the roadside antenna and reflected around the roadside antenna by a road surface or the like. It is.

A road communication system according to a seventh aspect of the present invention
A road communication system for performing wireless communication with a specific narrow area communication area, comprising: a road antenna for communicating with a vehicle; and the reflecting structure according to any one of the second to sixth inventions. It is.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an external view showing a radio wave environment measure according to the first embodiment of the present invention, FIG. 2 is an external view of a reflector attached to a reflective structure according to the first embodiment, and FIG. FIG. 4 is a correlation diagram showing the relationship between the angle of the reflection plate and the position where the reflection point on the reflection structure is lowered on the road surface. FIG. 4 is a distribution diagram showing the relative power with respect to the vehicle-mounted device position in the first embodiment.
9 to 11 are the same as those of the conventional radio wave environment countermeasures.

Next, the operation when this radio wave environment measure is taken will be described. The radio wave emitted from the roadside antenna 2 includes a primary reflected wave 8 from the road surface 1 in addition to the direct wave 7. In general, in a tollgate such as a highway, a reflection structure 9 such as a roof (ceiling) or a gantry is often installed above or near the communication area 6, and a part of the primary reflected wave 8 is sky. However, the rest reaches the reflective structure 9. The primary reflected waves 8 reaching the reflecting structure 9 are reflected by the reflectors 10a, 10a attached to the reflecting structure 9.
b is reflected again as secondary reflected waves 11a and 11b, respectively. Here, a plurality of the reflectors 10 are arranged side by side so that the longitudinal direction of the long plate is parallel to the road width direction, and is attached to the reflector 9 by the support structures 12a and 12b at an angle α. The direction of the secondary reflected wave 11 can be arbitrarily controlled by setting the angle α. In general, the electric field strength of the secondary reflected wave 11 is larger than the non-response level of the vehicle-mounted device 4 and cannot be ignored.
By returning the primary reflected wave 8 to the inside, the level rise in the non-response area can be suppressed. To return the primary reflected wave 8 to the inside of the communication area 6, the angle α of the reflecting surface of the reflecting plate 10 is set as follows:

[0016]

(Equation 1)

The angle may be set to satisfy the above. here,
The angles αa and αb are angles at which the primary reflected wave 8 returns to the ends a and b of the communication area 6, respectively, and are given by the following equations (Equations 2 and 3).

[0018]

(Equation 2)

[0019]

(Equation 3)

Here, θ is the angle of incidence of the radio wave radiated from the roadside antenna 2 on the road surface 1, and the radio wave primarily reflected from the road surface 1 enters the reflector 10 at an angle θ. Also,
P is a distance from a point 0 m directly below the roadside antenna 2 to a projection point onto the road surface 1 from a representative reflection point appropriately set on the reflection plate 10 attached to the reflection structure 9, Ca and Cb.
Is the distance from the point 0m directly below the roadside antenna 2 to the end a and end b of the communication area 6, and Hb is the mounting lower surface (reflection surface) of the support structure 12a in the reflection structure 9 from the road surface 1.
And Δh is the difference between the height of the reflection surface of the reflection structure 9 and the height of the reflection point of the reflection plate 10 from the road surface. FIG. 3 shows an example in which the angle α of the reflecting plate 10 is shown as a function of the position of the reflecting structure 9 where the reflection point is lowered on the road surface. This curve varies depending on the relationship between the height of the reflection point of the roadside antenna 2 and the reflection point of the reflection structure 9. For example, when the primary reflected wave 8 on the road surface 1 is incident on the reflective structure 9 installed at a position 6 m from the position directly below the roadside antenna 2 in the vehicle approach direction (position of 6 m on the horizontal axis in FIG. 3), By setting the angle α at which the plate 10 is attached to the reflecting structure 9 to an angle of about 25 ° to 38 °, the secondary reflected wave 1
1 acts to return it to the inside of the communication area 6. Conversely, by setting the angle α to an angle smaller than 25 °, the secondary reflected wave 11 is moved further away from the end b (more than 4 m) to 38 °.
The larger angle acts to return the primary reflected wave 8 to a region before the end a (point 0m).

FIG. 4 shows the vehicle-mounted device 4 when several types of reflectors 10 are attached to the lower part of the roof so as to return the primary reflected wave 8 to the inside of the communication area 6 (area 0 m to 4 m immediately below the roadside antenna 2). The distribution of the relative power measured at the position is shown. By attaching the reflector 10, the relative power level in the non-response area beyond the communication area 6 can be reduced by about 10 dB. In the conventional radio wave environment countermeasures as shown in FIG. 8, the electric wave intensity level of the secondary reflected wave 11 itself is reduced only by the expensive radio wave absorption band 16 having a large return loss. The cost of countermeasures is enormous. On the other hand, in the radio wave environment countermeasure of this embodiment, the angle of the reflection plate 10 is simply set to a desired range using the plate-shaped reflection plate 10 having a simple structure which is cheaper than the radio wave absorber, and the secondary By controlling the direction of the reflected wave 11 to a desired direction such as in the communication area, it is possible to suppress an increase in the power distribution in areas other than the communication area. In particular, in a road communication system for performing wireless communication between the road antenna 2 and the vehicle-mounted device 4 mounted on the vehicle in the communication area 6, in a wall such as a roof or a gantry installed above a road around the road antenna 2, By installing the reflection structure 9 provided with the reflection plate 10, when the vehicle-mounted device 4 passes through the non-response area in front of the communication area 6, unstable communication with the road antenna 2 is achieved. The communication can be prevented from being performed, and stable communication within the communication area can be performed.

Embodiment 2 FIG. FIG. 5 is an external view of a reflection plate attached to a reflection structure according to the second embodiment. In the second embodiment, a radio wave absorbing material 13 for reducing the amount of radio wave reflection is attached to the reflection surface of the reflection plate 10, the periphery of the reflection plate 10 including the reflection surface, and a part of the support structures 12a and 12b. is there. The appearance of the radio wave environment countermeasure in the second embodiment is the same as that of FIG. 1, and the correlation diagram showing the relationship between the angle of the reflector 10 and the position where the reflection point on the reflection structure 9 is lowered to the road surface is shown in FIG. It is the same as FIG.

As described above, according to the radio wave environment countermeasures according to the second embodiment, the reflection surface of the reflection plate 10, the periphery of the reflection plate 10 including the reflection surface, and a part of the support structure 12 are provided on the order of several dB. By applying a low-cost radio wave absorbing paint or mounting a radio wave absorber having a reflection attenuation amount, it is possible to reduce the influence of the electric field strength of the secondary reflected wave 11 and the irregular reflection by the support structure 12 by about several dB, For example, the effect of reducing the amount of deterioration depending on the actual mounting mechanism of the reflection plate 10 on the reflection structure 9 such as the support structure 12 can be obtained.

Embodiment 3 FIG. FIG. 6 is a zenith perspective view showing the third embodiment with a reflector attached. In the third embodiment, a plurality of reflectors 10 c to 10 c are emitted from the roadside antenna 2 so as to surround the primary reflected wave 8 from the road surface 1 or the like.
10 g is attached to the reflection structure 9. In addition,
The correlation diagram showing the relationship between the angle of the reflection plate 10 and the position where the reflection point of the reflection structure 9 is lowered on the road surface in the third embodiment is the same as FIG.

As described above, according to the radio wave environment measures according to the third embodiment, the radio wave emitted from the roadside antenna 2 is reflected by the road surface 1 and reaches the reflecting structure 9 so as to surround the roadside antenna 2. However, a plurality of reflecting plates 10c to 10g having a reflecting surface angle α related by a distance depending on the position of the roadside antenna 2 and the reflecting structure 9 or an incident angle of an incident wave to the reflecting structure 9 are formed. The two-dimensionally reflecting structure 9 surrounds the roadside antenna 2.
, The effect of avoiding the propagation of the secondary reflected wave 11 not only to the own lane but also to an adjacent oblique line is obtained.

Although a plurality of reflectors 10c to 10g in the third embodiment are arranged linearly, the reflector 10 may have a curvature surrounding the roadside antenna 2.

[0027]

According to the first to fourth and seventh aspects of the present invention, the reflection plate attached to the reflection structure has a distance depending on the position of the roadside antenna and the reflection structure or an incident wave to the reflection structure. Since the angle of the reflecting surface is related by the incident angle of the, the primary reflected wave by the road surface in any positional relationship between the roadside antenna and the reflecting structure can be reflected in a desired direction such as in the communication area, The effect of suppressing an increase in power distribution outside the communication area can be obtained. In addition, since a plate-shaped reflector with a simple structure is used,
The effect of realizing low-cost radio wave environment measures can also be obtained.

According to the fifth aspect of the present invention, a low-cost radio wave absorbing material such as a radio wave absorbing paint or a radio wave absorber having a reflection attenuation of several dB is mounted on the reflecting surface of the reflecting plate. The intensity of the reflected wave is several d more than that of the reflector alone
The effect of realizing low-cost radio wave environment measures that can be reduced by about B can be obtained. In addition, since the radio wave absorbing material is also attached to the periphery of the reflector including the reflecting surface and the support structure, the influence of diffuse reflection by the support structure can be reduced by several dB. Also, the effect of reducing the amount of deterioration depending on the installation mechanism can be obtained.

According to the sixth aspect of the present invention, the reflector is attached to the reflecting structure so as to surround the reflected wave emitted from the roadside antenna and reflected around the roadside antenna by the road surface or the like. And the effect of avoiding the propagation of the secondary reflected wave to the adjacent oblique lines can be obtained.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a radio wave environment measure according to the present invention.
FIG.

FIG. 2 is an external view of a reflection plate attached to a reflection structure.

FIG. 3 is a correlation diagram showing a relationship between an angle of a reflector and a position where a reflection point on a reflection structure is lowered on a road surface.

FIG. 4 is a distribution diagram showing relative power with respect to a vehicle-mounted device position.

FIG. 5 is a second embodiment of a radio wave environment measure according to the present invention.
It is an external view of the reflection plate attached to the reflection structure shown in FIG.

FIG. 6 is a diagram showing a third embodiment of a radio wave environment measure according to the present invention;
FIG. 5 is a zenith perspective view of the reflector mounted state.

FIG. 7 is an external view showing a conventional radio wave environment measure.

FIG. 8 is an external view showing a real environment in which a radio wave environment measure is taken.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Road surface 2 Roadside antenna 3 Vehicle 4 Onboard equipment 5 Onboard equipment Ground height 6 Communication area 7 Direct wave 8 Primary reflected wave 9 Reflecting structure 10 Reflecting plate 11 Secondary reflected wave 12 Supporting structure 13 Radio wave absorber 14 Wall base 15 Radio wave Reflector 16 Radio wave absorber 17 Front panel

Continued on the front page (72) Inventor Yoshiaki Tsuda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5E321 BB02 BB21 GG05 GG11 5J020 EA00 EA10

Claims (7)

[Claims] A reflector having a distance depending on the position of a roadside antenna and a reflecting structure provided around the roadside antenna and an angle of a reflecting surface related by an incident angle of an incident wave to the reflecting structure. A radio wave environment countermeasure method, wherein a plurality of the radio wave environments are attached to the reflection structure. 2. A reflector having a distance dependent on the position of a roadside antenna and a reflecting structure provided around the roadside antenna and a reflecting surface angle set based on an incident angle of an incident wave on the reflecting structure. A reflecting structure comprising a plate attached to a lower surface. 3. A reflection structure comprising a reflection plate provided with a reflection surface directed in a direction of reflecting a primary reflected wave from a road surface to the communication area. 4. A reflecting structure, comprising a plurality of the reflecting plates according to claim 2 arranged in parallel in a road width direction. 5. The reflection structure according to claim 2, wherein the amount of radio wave reflection is reduced on the reflection surface of the reflection plate, around the reflection plate including the reflection surface, or on a part of the support structure. A reflective structure characterized by having an absorbing material attached thereto. 6. The reflection structure according to claim 2, wherein the reflection plate surrounds a reflection wave radiated from the roadside antenna and reflected by the road surface around the roadside antenna. A reflective structure, wherein a plurality of the reflective structures are mounted on the reflective structure. 7. A road communication system having a specific narrow-area communication area and performing wireless communication, comprising: a road antenna for communicating with a vehicle; and the reflection structure according to any one of claims 2 to 6. A road communication system, comprising: