JP2000286632A - Leakage waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive leakage waveguide which can perform communication with another leakage waveguide and also with a roadside antenna via a single on-vehicle antenna by arraying the leakage holes in the lengthwise direction of a tube with spaces secured to satisfy the intra- waveguide wavelength reduction rate and the wavelength of carrier frequency used for the communication under a specific condition. SOLUTION: In regard to a leakage waveguide which is laid along a road to perform communication between a passing vehicle and the ground, the leakage holes are arrayed in the lengthwise direction of the waveguide with a space P/2 that is decided by an expression I or II where ν shows the intra-waveguide wavelength reduction rate with λ showing the wavelength of carrier frequency used for the communication respectively. Then the radio waves radiated through the leakage holes can be set almost in the same direction as the radio waves radiated from a roadside antenna. A radiation pattern which radiates obliquely the radio waves to the waveguide is obtained from the array of leakage holes. Thus, it is possible to perform communication via a simple on-vehicle antenna even with use of a roadside antenna.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leaky waveguide laid along a road, and more particularly, to a simple and inexpensive on-vehicle antenna for communication with the leaky waveguide and communication with a roadside antenna. The present invention relates to a leaky waveguide that enables communication.

[0002]

2. Description of the Related Art A road-to-vehicle communication system for mutually communicating between a passing vehicle such as an automobile and the ground has been put into practical use for the purpose of improving the efficiency of road use and improving safety. In this road-vehicle communication system, a leaky waveguide, which can be regarded as an equivalently continuous antenna, is laid along a road to transmit a high-frequency signal such as a microwave.

As shown in FIG. 5, for example, a leaky waveguide mainly includes a hollow conductor (tube) 2 formed by processing a copper material and having a substantially elliptical cross section. This hollow conductor 2
Has a leak hole (through hole) 3 for generating a leak radio wave.
Are provided at regular intervals in the longitudinal direction of the tube.

[0004] By arranging the leak holes 3 at appropriate intervals, the radiation angle of the leaked radio wave can be arbitrarily determined. Assuming that the radiation angle is θ and the leak hole interval is P / 2, the relationship between the leak hole interval and the radiation angle is expressed by the following equation. However, the angle perpendicular to the leaky waveguide is θ = 0 °.

[0005]

(Equation 3)

Here, λ is the wavelength of the carrier frequency, and ν is the wavelength shortening rate of the waveguide.

Normally, a value close to 0 ° is selected as the radiation angle from the leaky waveguide.
From equation (1),

[0008]

(Equation 4)

The following P is selected. This leak hole interval P / 2
FIG. 6 shows an example of the directivity of the leaky waveguide having the leak hole 3 provided in the above. The horizontal direction in the figure corresponds to the longitudinal direction of the leaky waveguide. Thus, the leaky waveguide having the leak holes 3 provided at the leak hole interval P / 2 has directivity perpendicular to the leak waveguide.

In the road-to-vehicle communication system, not only the leaky waveguide is laid along the road as described above, but also the antenna is periodically installed at appropriate intervals on the road side and used in combination with the leaky waveguide. Sometimes. FIG. 7 shows a road-vehicle communication system using both a leaky waveguide and a roadside antenna. In the figure,
Arrows indicate the direction of radio wave radiation. In the road (not shown), the left-right direction in the figure is the longitudinal direction. A transceiver 4 is connected to one end of the leaky waveguide 1. The transceiver 4 is also connected to the roadside antenna 7. The signal from the transceiver 4 is transmitted from the leaky waveguide 1 and the roadside antenna 7. By receiving the signal from the leaky waveguide 1 or the roadside antenna 7 with the vehicle-mounted antenna 6 or the vehicle-mounted antenna 8, communication between the ground and the vehicle 5 becomes possible.

[0011]

As described above, the conventional leaky waveguide 1 radiates radio waves almost perpendicular to the road. On the other hand, since the roadside antenna 7 is installed periodically, it radiates radio waves obliquely to the road in order to secure a long communication area in the longitudinal direction of the road. When the two radio waves are to be received by the vehicle 5, a plurality of antennas 8 that receive a radio wave arriving from a direction perpendicular to the side surface of the vehicle 5 and a plurality of antennas 6 that receive a radio wave arriving from an oblique front direction of the vehicle 5 Antennas are required. Alternatively, an antenna having complicated directivity for receiving both radio waves is required. For this reason, there is a problem that the in-vehicle antenna becomes expensive.

Accordingly, an object of the present invention is to solve the above-mentioned problems and provide a leaky waveguide which enables communication with a leaky waveguide and communication with a roadside antenna with a single, inexpensive vehicle-mounted antenna. To provide.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a leaky waveguide laid along a road for communication between a passing vehicle and the ground. When the rate is ν and the wavelength of the carrier frequency used for communication is λ,

[0014]

(Equation 1)

Or

[0016]

(Equation 2)

The leak holes are arranged in the longitudinal direction of the pipe at the interval P / 2 given by

The radiation direction of the radio wave from the leak hole may be substantially the same as the radiation direction of the radio wave from the roadside antenna provided on the roadside of the road.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the directivity of a leaky waveguide according to the present invention. The horizontal direction in the figure corresponds to the longitudinal direction of the leaky waveguide. The leaky waveguide having this directivity radiates radio waves not obliquely but vertically to the leaky waveguide. In the illustrated example, the radio wave is emitted in a direction inclined approximately 45 ° to the right from the vertical direction 0 °. To obtain such a radiation pattern,

[0021]

(Equation 1)

Or

[0023]

(Equation 2)

The leak hole 2 at the leak hole interval P / 2 given by
Are arranged.

FIGS. 2A to 2C show examples of the configuration of a leaky waveguide having such a leak hole spacing. FIG. 2 (a)
Shows that the leak holes 3 are arranged at intervals P / in the longitudinal direction of the pipe.
2, and these leakage holes 3 are alternately arranged at two different positions in the circumferential direction of the pipe. Each leak hole 3 is formed to be elongated parallel to the axis of the leak waveguide 1. This configuration is suitable for emitting vertically polarized waves.

In FIG. 2 (b), the leak holes 3 are arranged in the longitudinal direction of the tube at an interval P which is twice the interval P / 2 of the leak holes, and each leak hole 3 is arranged in the circumferential direction of the tube. Are arranged at the same position. Each leak hole 3 is formed to be elongated and perpendicular to the axis of the leak waveguide 1. This configuration is suitable for emitting horizontally polarized waves.

The structure shown in FIG. 2 (c) is formed to be elongated parallel to the axis of the leaky waveguide 1, as shown in FIG. 2 (a) and the structure shown in FIG. 2 (b). The leaked holes 3 are arranged at intervals of P / 2 in the longitudinal direction of the tube, and these leak holes 3 are alternately arranged at two different positions in the circumferential direction of the tube. Leakage holes 3 which are formed to be elongated and perpendicular to the axis are arranged at intervals P in the longitudinal direction of the tube, and the leakage holes 3 perpendicular to this axis are located at the same longitudinal position as every other leakage hole 3 parallel to the axis. It is arranged. This configuration is suitable for emitting circularly polarized waves.

With these leak hole arrangements, it is possible to obtain a radiation pattern that radiates radio waves obliquely to the leaky waveguide as shown in FIG.

FIG. 3 shows an embodiment in which the leaky waveguide of the present invention is laid along a road. In the figure, the arrows indicate the radiation direction of radio waves. In the road (not shown), the left-right direction in the figure is the longitudinal direction. In this road-to-vehicle communication system, as shown in the figure, a leaky waveguide 1 that radiates radio waves in an oblique direction to the leaky waveguide 1 is laid along the road so that Radio waves can be emitted in oblique directions. The roadside antenna 7 radiates radio waves obliquely to the road as in the related art. Therefore, the radio wave from the leaky waveguide 1 and the radio wave from the roadside antenna 7 reach the vehicle 5 at substantially the same angle.

On the other hand, it is assumed that a one-element microstrip antenna with a simple structure and low cost is used as the on-vehicle antenna 6, for example. FIG. 4 shows the directivity of the vehicle-mounted antenna 6. As shown in the figure, the on-vehicle antenna 6 has directivity having a spread of about ± 60 ° in the vehicle traveling direction, for example.
If the radio wave arrival direction is 50 ° as shown, radio waves can be received with sufficient intensity. Therefore, in the road-vehicle communication system shown in FIG. 3, the vehicle 5 having the on-vehicle antenna 6 having directivity as shown in FIG. 4 can receive the radio waves of both the leaky waveguide 1 and the roadside antenna 7 with sufficient strength. Can be.

Although the vehicle 5 is illustrated as a passenger car, the present invention can of course be applied to any type of vehicle. Further, the on-vehicle antenna 6 is installed on the front of the vehicle 5 so as to receive an oblique radio wave from the traveling direction of the vehicle, but radiates radio waves from the leaky waveguide 1 and the roadside antenna 7 toward the rear of the vehicle. Alternatively, the on-vehicle antenna 6 may be installed on the rear surface of the vehicle 5 to receive radio waves from behind.

[0032]

The present invention exhibits the following excellent effects.

(1) Since radio waves are radiated from the leaky waveguide to the leaky waveguide in an oblique direction, even when a roadside antenna is used together, communication can be performed with a simple vehicle-mounted antenna.

[Brief description of the drawings]

FIG. 1 is a directivity diagram of a leaky waveguide showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of a leaky waveguide showing an embodiment of the present invention.

FIG. 3 is a configuration diagram of a road-vehicle communication system using the leaky waveguide of the present invention.

FIG. 4 is a directivity diagram of a vehicle-mounted antenna.

FIG. 5 is a perspective view of a leaky waveguide.

FIG. 6 is a directivity diagram of a conventional leaky waveguide.

FIG. 7 is a configuration diagram of a conventional road-vehicle communication system using a leaky waveguide.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Leaky waveguide 2 Hollow conductor (tube) 3 Leakage hole 5 Vehicle 7 Roadside antenna

Continued on the front page. (72) Inventor Masahisa Kaneda 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Opto-System Research Laboratories (72) Inventor Tatsuri Watari 880, Sunasawa-cho, Hitachi City, Hitachi City, Hitachi Cable Inside the Takasago Plant, Inc. (72) Inventor Masato Nishiura 880, Sunasawa-cho, Hitachi City, Ibaraki Prefecture Inside the Takasago Plant, Hitachi Cable Co., Ltd. (72) Inventor Xiaofu 880 880, Sunasawa-cho, Hitachi City, Hitachi, Ltd.Hitachi Cable Co., Ltd. F-term in Takasago Plant (reference) 5J045 AA21 DA04 DA11 HA01 LA01 NA01

Claims (2)

[Claims] 1. In a leaky waveguide laid along a road for communication between a passing vehicle and the ground, a wavelength shortening rate in the pipe is ν, and a wavelength of a carrier frequency used for communication is λ. Then, Or A leakage waveguide in which leakage holes are arranged in the longitudinal direction of the tube at an interval of P / 2 given by: 2. The leaky waveguide according to claim 1, wherein the direction of radiation of the radio wave from the leak hole is substantially the same as the direction of radio wave radiation from the roadside antenna provided on the roadside of the road. .