JPH0951226A - Leaky coaxial cable - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To effectively and effectively use radio waves by simply and reliably suppressing the emission of radio waves to a space where the use of radio waves is not necessary. A leaky coaxial cable includes a center conductor.
And the outer conductor 16 with the slots 18A and 18B provided on the central conductor 12 via the insulator 14, and the slots 18A and 18B on the inner coating 24 provided on the outer conductor 16. Shield 2 arranged to cover
0 and an outer coating 26 provided on the shield 20. This shield 20 is cut open only in the length portion L that radiates radio waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a leaky coaxial cable used in, for example, a mobile radio communication system, a radio control system or the like.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 7, a leaky coaxial cable used in a mobile radio communication system or the like has a center conductor 12 and a radio wave provided on the center conductor 12 via an insulator 14. An external conductor 16 with a slot 18 for radiating the external conductor and an external coating 26 provided on the external conductor 16 are provided. In this leaky coaxial cable 10, as shown in FIG. 7, the slot 18 of the outer conductor 16 is formed in a specific direction.
Depending on the position, the electric wave is emitted with a certain directivity within the cross section of the leaky coaxial cable 10 to realize stable wireless communication.

However, it is useless to radiate the radio wave even in a section where the use of the radio wave is not necessary in the entire length of the installed leaky coaxial cable, and there is a problem that the attenuation amount of the leaky coaxial cable becomes large. As described above, it is not preferable to radiate a radio wave to a space where the use of the radio wave is not necessary from the viewpoint of effective use of the radio wave.

Therefore, a superconductor is provided in the slot portion of the outer conductor of the leaky coaxial cable to prevent radio wave leakage,
There is also provided means for suppressing unnecessary radiation by setting a normal conducting state by a superconducting magnet attached to a moving body only at a necessary position (see Japanese Patent Laid-Open No. 2-66086). According to this conventional technique, unnecessary radiation of radio waves can be suppressed even in an open space, but in order to receive radio waves, a superconducting magnet that destroys this superconducting state in an antenna or the like on the receiving side. Since it is necessary to provide means such as
Radio wave reception equipment becomes complicated, and unlike moving bodies such as elevators, moving bodies such as trucks do not always move at a constant interval with respect to the leaky coaxial cable. There is a possibility that radio waves cannot be stably received without being affected by the magnetic field of the superconducting magnet or the like attached to the moving body.

When the section using the radio wave is distant, the general shielded coaxial cable is laid in the section where the use of the radio wave is not necessary, and the leaky coaxial cable is laid only in the necessary section. It is possible to relay both, but in this case, there is a possibility that long-term reliability may be deteriorated due to an increase in the number of connection points such as connectors.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the object of the present invention is to suppress the increase of the attenuation amount by simply and surely suppressing the emission of the radio wave to the space where the use of the radio wave is unnecessary. The purpose of the present invention is to provide a leaky coaxial cable that can effectively use radio waves.

[0007]

As a means for solving the above problems, the present invention comprises a center conductor and an outer conductor with a slot provided on the center conductor via an insulator. The leaky coaxial cable further comprises a shield provided so as to cover the slot of the outer conductor, and the shield is provided with a leaky coaxial cable characterized in that only a length portion for radiating radio waves is cut open. It is provided.

As described above, when the shield is provided so as to cover the slot in the section where the use of the radio wave is not necessary, unnecessary radiation of the radio wave from the slot is sufficiently suppressed and the leaky coaxial cable is normally shielded. The same function as a coaxial cable can be suppressed and the increase in attenuation due to leakage can be suppressed, but the shield is cut open only in the section where radio wave emission is necessary, and the radio wave is emitted from this part. , The radio waves can be used effectively.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail with reference to the drawings. FIGS. 1 to 3 show a leaky coaxial cable 10 according to the present invention.
Is the center conductor 12 and the insulator 1 on the center conductor 12.
4 and an outer conductor 16 provided via the outer conductor 4.

The central conductor 12 is made of an appropriate conductor such as a copper wire or an aluminum wire, and the insulator 14 is made of an insulating material such as polyethylene or fluororesin having a stable insulating property and formability. The insulator 14 is formed so as to cover the entire length of the center conductor.

As shown in FIG. 1, the outer conductor 16 is provided with a group of slots 18, and in the illustrated embodiment, the group of slots 18 is arranged in a so-called "H" shape in which the inclination is directed in the opposite direction. It is composed of a plurality of slots 18A, 18B that are formed. These slot groups 18 are appropriately provided over the entire length of the leaky coaxial cable 10 at places where radio wave emission is necessary or at predetermined intervals. Radio waves radiated by the slot group 18 provided in the outer conductor 16 are radiated with a certain directivity within the cross section of the leaky coaxial cable 10. Therefore, the leaky coaxial cable 10 is usually laid so that the slot group 18 faces the antenna (not shown) of the moving body that should receive radio waves. Of course, the slots 18A and 18B may be arranged other than the so-called “H” shape shown in FIG. 1, if necessary.

The leaky coaxial cable 10 of the present invention, as shown in FIG. 1 and FIG.
A shield 20 is provided so as to cover 18B. This shield 20, as shown in FIGS.
Of the entire length of the leaky coaxial cable 10, only the length portion L (see FIG. 1) that radiates radio waves is cut open, and the slots 18A and 18B are covered in other portions.

Therefore, unnecessary radiation of radio waves from the slots 18A and 18B is sufficiently suppressed, and in the section of the total length of the leaky coaxial cable 10 where the use of radio waves is not required, the leaky coaxial cable 10 is normally shielded. The same function as a type coaxial cable can be suppressed to suppress the increase in attenuation due to leakage, but the radio wave is radiated from the cut-out portion 22 of the shield 20 only in the section where the radio wave needs to be used. , The radio waves can be used effectively.

In this case, in particular, even when the section where the use of the radio wave is required (that is, the length portion L for radiating the radio wave: see FIG. 1) is distant, it is possible to lay one leaky coaxial cable 10. It is possible to achieve effective use of radio waves easily without laying the wires.
Since connection with a connector or the like is not required, long-term reliability can be ensured. Further, unlike the prior art, since the leaky coaxial cable 10 itself includes the shield 20 that suppresses unnecessary radiation of radio waves, not only in a place having a wall surface such as a tunnel, but also in an open space. It is advantageous in that the radio waves can be effectively utilized. Furthermore, for example, a mobile body that does not always move at a constant distance from the leaky coaxial cable 10 such as a truck is surely receiving radio waves, and the mobile body has a complicated superconducting magnet or the like. This is advantageous in that effective use of radio waves can be easily achieved without providing special equipment.

In the embodiment shown in FIGS. 1 to 3, this shield 20 is provided with a slot 18 as shown in FIG.
It is provided so as to cover the entire circumference of the outer conductor 16 including A and 18B, and suppresses unnecessary radiation of radio waves in the entire circumference of the leaky coaxial cable 10. Therefore, in particular, since the cross-sectional diameter of the leaky coaxial cable 10 is smaller than the wavelength of the radio wave, even in the leaky coaxial cable 10 in which the radio wave tends to be radiated in all the circumferential directions of the leaky coaxial cable 10, It is possible to reliably suppress unnecessary radiation. In addition,
In this case, the shield 20 is formed with as little space as possible from the outer conductor 16 so as to cover the slots 18A and 18B to such an extent that the radiation of radio waves from the slots 18A and 18B can be surely suppressed.

The shield 20 is preferably formed on an inner coating 24 provided on the outer conductor 16, as shown in FIGS. The inner coating 24 is provided on the central conductor 1 at the portion 22 where the shield 20 is cut open.
2 and the external conductor 16 have a role of protecting them from the external environment so that they are not directly exposed to the outside. Even if the inner coating 24 is provided in this manner, the inner coating 24 usually has a thickness such that a space is provided between the outer conductor 16 and the shield 20 to the extent that a large amount of radio wave radiation is allowed. Therefore, the slots 18A and 18B are not covered by the shield 20.
Is sufficiently covered by the above, and there is no problem as there is no effect on the suppression of radio wave radiation itself.

The shield 20 can be formed of, for example, a metal, and any metal can be used as long as it shields radio waves. Specifically, it can be formed from copper or aluminum. In the illustrated embodiment, the shield 20 is formed by winding a copper tape, an aluminum tape, or the like on the inner coating 24 in consideration of the flexibility of the leaky coaxial cable 10 to some extent. It is not limited to this,
For example, it may be formed by another appropriate method such as vertical attachment. It should be noted that, on the shield 20, as shown in FIGS.
As shown in FIG. 3, an outer coating 26 is provided, and the outer coating 26 protects the leaky coaxial cable 10 from the external environment in a section where the use of radio waves is not required (a portion other than the portion 22 where the shield 20 is cut open). To do.

The shield 20 is cut open by cutting off the length portion L (see FIG. 1) for radiating radio waves by an appropriate means such as a cutter. Further, in the illustrated embodiment, as shown in FIGS. 1 and 3, the outer covering 26 is cut open together with the shield 20, but the outer covering 26 does not necessarily need to be cut open. That is, the shield 20 may be formed and the length portion L (see FIG. 1) for radiating radio waves may be cut open, and then the outer coating 26 may be provided over the entire length of the leaky coaxial cable 10. In this case, the shield 20
Even in the portion 22 where the cutout is opened, the outer coating 26
Since the outer conductor 16 and the like are protected by the above, the above-described inner coating 24 is not necessarily provided. This also applies to other embodiments described below.

Next, another embodiment of the present invention will be described.
This will be described with reference to FIGS. 4 to 6. First, in the embodiment shown in FIGS. 1 to 3, the shield 20 is provided with the slots 18A, 1
Although it is formed so as to cover the entire circumference of the outer conductor 16 including 8B, if the radiation of the radio waves from the slots 18A and 18B is sufficiently suppressed, it is considered that the attenuation amount is not greatly affected. Therefore, the shield 20 has at least the slot 1
If 8A and 18B are covered, there is no problem because unnecessary radiation of radio waves from the outer conductor 16 can be efficiently suppressed, and as shown in FIG. 4, slots 18A and 18B
The part other than the part corresponding to may be opened as indicated by reference numeral 28.

On the other hand, in the length portion L (see FIG. 1) for radiating radio waves, in the embodiment shown in FIGS. 1 to 3, the shield 20 is cut out so as to open corresponding to the slots 18A and 18B. However, the present invention is not limited to this, and the shield 20 may be cut open over the entire circumference of the outer conductor 16 as shown in FIGS. 5 and 6.
Also by this, the radio wave can be effectively radiated only in the section where the use of the radio wave is necessary. In this case,
In FIG. 5, it is shown that the outer conductor 16 is entirely covered with the shield 20 in the section where the emission of the radio wave is not necessary. In the section 22 in which the shield 20 is cut open in the embodiment in which only the slots 18A and 18B are covered by the shield 20 in the section where the radio wave emission shown in FIG.
May be cut open all around.

The embodiment shown in FIG. 4 and FIG.
In the embodiment shown in FIG. 6, for example, the cross-sectional diameter of the leaky coaxial cable 10 is not significantly smaller than the wavelength of the radio wave, and the cross-section of the leaky coaxial cable 10 can exert some shielding effect. Etc., can be widely used.

The leaky coaxial cable 10 of the present invention is
It can be used for a wireless communication system and a wireless control system for various mobile objects such as trucks and elevators regardless of the type of the mobile object.

[0023]

As described above, according to the present invention, since the shield is provided so as to cover at least the slot in the section where the radio wave is not required to be used, the unnecessary emission of the radio wave from the slot is sufficient. The leakage coaxial cable works like a normal shielded coaxial cable to suppress the increase in attenuation due to leakage, but the shield is cut open only in the section where the use of radio waves is required. Since the radio waves are radiated from the part, there is a practical benefit that the radio waves can be effectively used.

In particular, according to the present invention, even if the section where the radio wave is required to be used (that is, the length portion for radiating the radio wave) is distant, it is possible to cope with the installation of one leaky coaxial cable. In addition, the effective use of the radio waves can be easily realized without laying time and the connection with a connector or the like is not required. Therefore, long-term reliability can be secured. Further, compared to the conventional technology, the leaky coaxial cable itself has a shield that suppresses unnecessary radiation of radio waves, so that radio waves can be emitted not only in a place having a wall surface such as a tunnel but also in an open space. It is advantageous in that it can be effectively utilized. Furthermore, for example, a mobile body that does not always move at a constant distance from the leaky coaxial cable such as a truck is surely receiving radio waves, and the mobile body has a complicated structure such as a superconducting magnet. This is advantageous in that effective use of radio waves can be easily achieved without providing equipment.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a leaky coaxial cable according to the present invention.

2 is a cross-sectional view of the leaky coaxial cable taken along the line AA in FIG.

3 is a cross-sectional view of the leaky coaxial cable taken along the line BB in FIG.

FIG. 4 is a sectional view of another embodiment of the leaky coaxial cable according to the present invention.

FIG. 5 is a schematic perspective view of still another embodiment of the leaky coaxial cable according to the present invention.

6 is a cross-sectional view of the leaky coaxial cable taken along the line AA in FIG.

FIG. 7 is a schematic perspective view of a conventional general leaky coaxial cable.

[Explanation of symbols]

 10 Leakage Coaxial Cable 12 Center Conductor 14 Insulator 16 Outer Conductor 18 Slot Group 18A, 18B Slot 20 Shield 20a Opening 22 Shield Cutout Part 24 Internal Coating 26 External Coating

Claims (1)

[Claims] 1. A leaky coaxial cable comprising a center conductor and an outer conductor with a slot provided on the center conductor via an insulator, the leaky coaxial cable being provided so as to cover at least the slot of the outer conductor. A leaky coaxial cable, further comprising a shield, wherein the shield is opened only in a length portion for emitting radio waves.