JP5189761B2 - Leaky coaxial cable and manufacturing method thereof - Google Patents

Description

  The present invention relates to a leaky coaxial cable that is laid in a high-rise building, a tunnel, an underground mall, or the like and used as a transmission / reception antenna of a wireless communication system.

For example, as disclosed in Patent Document 1, such a leaky coaxial cable includes an outer conductor formed in a corrugated shape on the outer periphery of an insulator having an inner conductor inserted and held in the center. The radio wave leakage holes for radiating and transmitting signal radio waves are formed in parallel at a predetermined pitch in the cable longitudinal direction, and the outer conductor is covered with a sheath made of a resin material.
JP 2006-302692 A (FIG. 5)

  In a leaky coaxial cable, the efficiency of radiation characteristics is determined by the size of the opening of the radio leak hole in the circumferential direction of the cable. However, in the conventional leaky coaxial cable described above, the radio leak hole formed in the outer conductor is cabled. Since it is inclined with respect to the longitudinal direction, it is necessary to form a radio wave leak hole that is longer (in the tilt direction) than the opening length in the cable circumferential direction, and radiation per unit length of the radio wave leak hole The amount will be small.

  Therefore, if the radio wave leakage hole is formed along the cable circumferential direction, the actual length of the radio wave leakage hole becomes equal to the radiation opening length, and the amount of radiation per unit length of the radio wave leakage hole becomes large. Efficient radiation can be performed through the holes. Further, it is advantageous in terms of strength that the width of the radio wave leakage hole is small.

  However, if the electromagnetic wave leakage hole is formed along the cable circumferential direction and the width thereof is reduced, the opening direction of the electromagnetic wave leakage hole varies depending on the cable longitudinal direction position of the corrugated outer conductor, and the radiation characteristic is reduced. Expected to get worse. For example, if the width of the electromagnetic wave leakage hole is set smaller than the corrugation pitch in the outer conductor, depending on the position of the outer conductor in the cable longitudinal direction, the electromagnetic wave leakage hole is located on one slope of the wave, or on the other slope, or A case occurs that is located at the top of a wave. Then, variation occurs in the opening direction of each radio wave leakage hole, and due to the variation in the opening direction, the radiation direction of the radio wave becomes uneven, and the radiation characteristics deteriorate.

  The present invention has been made paying attention to such points, and by adding a device to the formation of a radio wave leakage hole in the corrugated outer conductor, the leakage is high in radiation efficiency and excellent in radiation characteristics. An object is to provide a coaxial cable and a manufacturing method thereof.

  In order to achieve the above object, the present invention is configured as follows.

According to a first aspect of the present invention, an outer conductor formed in a corrugated shape is disposed on the outer periphery of an insulator through which an inner conductor is inserted and held, and radio wave leakage holes are formed in parallel at a predetermined pitch in the cable longitudinal direction on the outer conductor. A leaky coaxial cable,
The electromagnetic wave leakage hole is formed in a long hole along the cable circumferential direction,
The width w of the radio wave leakage hole in the cable longitudinal direction and the corrugation pitch p in the cable longitudinal direction of the outer conductor,
1p <w <10p
Set to the relationship.

  According to this configuration, any of the electromagnetic wave leakage holes formed in parallel in the cable longitudinal direction has a width larger than a mountain of waves, so that the electromagnetic wave leakage holes are less likely to be biased toward one wave slope, The radio wave leak holes are opened radially outwardly on average, and the radio wave radiation directions in the radio wave leak holes are aligned, so that the radiation characteristics are stabilized regardless of the position in the cable longitudinal direction.

  According to this configuration, since the radio wave leakage hole is formed along the cable circumferential direction, the actual length of the radio wave leakage hole is equal to the radiation opening length, and the amount of radiation per unit length of the radio wave leakage hole is increased. Thus, it is possible to perform efficient radiation with a short radio wave leakage hole.

According to a third invention, in the first invention,
The outer conductor is
A corrugated metal sheet in which the radio wave leakage hole is formed;
A resin protective layer that is attached to the outer peripheral surface of the metal sheet and closes the radio wave leakage hole;
Is provided.

  According to this configuration, in the step of continuously forming the sheath on the outer periphery of the outer conductor, the melted sheath material does not flow into the radio wave leakage hole, and the outer conductor does not lift from the outer periphery of the insulator and deform. It can be arranged correctly concentrically with respect to the central inner conductor.

According to a fourth invention, in the third invention,
A tape-like outer conductor material formed by attaching the resin protective layer to the outer peripheral surface of the metal sheet is wound into a cylindrical shape to form the outer conductor, and the metal is formed at both ends of the outer conductor material in the winding direction. The sheets are polymerized.

  According to this configuration, the outer conductor can be made into a completely cylindrical shape that is electrically continuous over the entire circumference, and the electrical characteristics in the circumferential direction are stabilized.

According to a fifth aspect of the present invention, an outer conductor formed in a corrugated shape is provided on the outer periphery of an insulator having an inner conductor inserted and held in the center, and a radio wave leakage hole is formed in the longitudinal direction of the outer conductor at a predetermined phase in the circumferential direction. A method for manufacturing a leaky coaxial cable formed in a row at a predetermined pitch in a direction,
A radio wave leakage hole forming step in which the radio wave leakage holes are formed in parallel in the tape longitudinal direction at a predetermined interval in a tape-shaped metal sheet;
The external surface surface of the metal sheet in which the radio wave leakage hole is formed, an outer conductor material forming step of forming an outer conductor material was additionally provided a resin protective layer in a state of closing the microwave leakage hole,
The outer conductor material is placed in the longitudinal direction of the corrugated pitch p so that the width w of the electromagnetic wave leakage hole in the longitudinal direction of the tape and the corrugated pitch p of the outer conductor material have a relationship of 1p <w <10p. Corrugating process of corrugating and pressing,
An outer conductor forming step of forming the outer conductor by winding the outer conductor material subjected to the undulation process around the outer periphery of the insulator having the inner conductor inserted and held at the center;
including.

  According to this, the leaky coaxial cable provided with the outer conductor that exhibits the desired characteristics can be suitably manufactured.

  Thus, according to the present invention, it is possible to provide a leaky coaxial cable having high radiation efficiency and excellent radiation characteristics and a method for manufacturing the same.

  FIG. 1 is a perspective view showing a part of a leaky coaxial cable 1 according to the present invention, and FIG. 2 is a longitudinal front view thereof. In this leaky coaxial cable 1, an inner conductor 2 made of an aluminum pipe or a copper pipe is inserted and held in an insulated state through a spiral insulating spacer 4 made of polyethylene cordel string at the center of an insulator 3 made of polyethylene pipe. In addition, an outer conductor 5 in which a corrugated metal sheet is formed in a cylindrical shape is provided on the outer periphery of the insulator 3, and the outer conductor 5 is covered with a sheath 6 made of a resin material such as polyethylene. Are provided with a basic structure in which radio wave leakage holes 7 for radiating and transmitting signal radio waves are formed in parallel at a predetermined pitch q in the longitudinal direction of the cable.

  A cable support ridge 8 is formed integrally with the sheath 6 over the entire length of the cable at a predetermined phase portion different from the phase where the radio wave leakage holes are present in the outer periphery of the sheath 6, and the cable support ridge 8 is twisted around the cable support ridge 8. A support wire 9 made of a wire is embedded.

  The outer conductor 5 is formed by winding an outer conductor material 5 'formed by adding a resin protective layer (mylar layer) 5b made of a transparent resin material around the outer periphery of a metal sheet 5a made of aluminum and having a thickness of 0.2 mm. And is corrugated in a bellows shape at a predetermined pitch p in the longitudinal direction of the cable.

  The radio wave leakage hole 7 is formed as a long hole along the cable circumferential direction, and its circumferential length L is set to be several times the width w in the cable longitudinal direction. The arrangement pitch q in the direction is set to be approximately the same as the circumferential length L. Further, the corrugation pitch p of the outer conductor 5 is set to have a relationship of 1p <w <10p with respect to the width w of the radio wave leakage hole 7.

  According to such a setting, most of the radio wave leak holes 7 open radially outward, and the radio wave radiation directions in the radio wave leak holes 7 are aligned, so that the position in the longitudinal direction of the cable Regardless of the radiation characteristics are stable. For example, if the width w of the radio wave leak hole 7 is set to twice the wavy pitch p (w = 2p), the radio wave leak hole 7 may be formed at any position in the cable longitudinal direction as shown in FIG. At least one mountain wave will be opened.

  Incidentally, if the corrugation pitch p is larger than the width w of the radio wave leak hole 7 (1p> w), depending on the position in the longitudinal direction of the cable, most or the whole of the radio wave leak hole 7 may be opened on the wave slope, May be opened at the top of the antenna, and the opening direction of the radio wave leakage hole 7 varies depending on the installation position, and the radiation direction of the radio wave becomes uneven.

  Further, if the relationship between the corrugation pitch p of the outer conductor 5 and the width w of the radio wave leakage hole 7 is set to a state characteristic in the present invention described above, the mechanical strength of the cable and the radio wave radiation characteristics of the cable are deteriorated. In addition, the formation pitch q of the radio wave leakage holes 7 can be reduced. In general, in the case of a leaky coaxial cable, the radio wave radiation characteristic deteriorates at a frequency near the resonance frequency. Therefore, it is necessary to set the resonance frequency outside the use band of the leaky coaxial cable. The resonance frequency of the leaky coaxial cable 1 increases as the arrangement pitch q of the radio wave leakage holes 7 decreases. Therefore, if the present invention is adopted, the arrangement pitch q of the radio wave leak holes 7 can be reduced until the resonance frequency of the leaky coaxial cable 1 is driven to a high frequency range away from the use band. As a result, the radiation efficiency of the leaky coaxial cable can be increased. In addition, the resonance frequency can be adjusted without deteriorating the mechanical strength of the cable and the radio wave radiation characteristics of the cable.

  The leaky coaxial cable 1 having the above-described configuration is manufactured as follows.

  (1) First, as shown in FIG. 5, long hole-shaped radio wave leak holes 7 are formed at a predetermined pitch on a 0.2 mm thick metal sheet 5a made of a continuous tape-like aluminum material slightly wider than the cable circumference. Punching is formed at q ′.

  (2) Next, as shown in FIG. 6, a resin protective layer (mylar layer) 5b made of a transparent resin material having a thickness of 0.1 mm is formed on the entire outer surface of the metal tape 5a in which the radio wave leakage hole 7 is punched and formed. In addition, a continuous tape-like outer conductor material 5 ′ is formed. As a result, the radio wave leakage hole 7 is blocked by the resin protective layer 5b. In this case, the resin protective layer 5b is narrower than the metal sheet 5a and is disposed so as to be aligned, and an overlap margin s of about 20 mm is formed at one end in the width direction of the metal sheet 5a.

  (3) Next, as shown in FIG. 7, the continuous tape-shaped outer conductor material 5 'is subjected to corrugation processing at a predetermined corrugation pitch p by roller pressing or the like.

  (4) Next, as shown in FIG. 8, a tubular outer conductor is wound by winding a corrugated tape-like outer conductor material 5 'around the outer periphery of an insulator 3 through which the inner conductor 2 is inserted and held at the center. 5 is formed. In this case, as shown in FIG. 4, the end portions of the metal sheet 5 a are overlapped with each other by overlapping the other end portion of the outer conductor material 5 ′ on the outer surface of the overlap margin s formed at one end of the outer conductor material 5 ′. A completely cylindrical outer conductor 5 in which the metal sheet 5a is conductively connected in the circumferential direction is formed by polymerization.

  (5) Although not shown, the sheath 6 is then formed on the outer periphery of the outer conductor 5 so that the leaky coaxial cable 1 shown in FIG. 1 is obtained.

[Other examples]
(1) As shown in FIG. 9, the radio wave leakage holes 7 may be formed in parallel at two locations in the circumferential direction.

  (2) The present invention can also be applied to a leaky coaxial cable having specifications that do not include the support wire 9.

It is a perspective view which shows a part of leaky coaxial cable. It is a vertical front view of a leaky coaxial cable. It is the vertical side view which expanded the electromagnetic wave leak hole formation location of an outer conductor. It is the vertical front view which expanded the circumferential direction part of the external conductor. It is a perspective view which shows an external conductor manufacturing process. It is a perspective view which shows an external conductor manufacturing process. It is a perspective view which shows an external conductor manufacturing process. It is a perspective view which shows an external conductor manufacturing process. It is a perspective view which shows another Example of an external conductor raw material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Leakage coaxial cable 2 Inner conductor 3 Insulator 5 Outer conductor 5 'Outer conductor material 5a Metal sheet 5b Resin protective layer 7 Electric wave leakage hole p Corrugation pitch q Arrangement pitch of electric wave leakage hole

Claims (4)

A leaky coaxial cable in which an outer conductor that is corrugated in the shape of a bellows is arranged on the outer periphery of an insulator through which the inner conductor is inserted and held, and radio leak holes are formed in parallel at a predetermined pitch in the cable longitudinal direction on the outer conductor. There,
The electromagnetic wave leakage hole is formed in a long hole along the cable circumferential direction,
The width w of the radio wave leakage hole in the cable longitudinal direction and the corrugation pitch p in the cable longitudinal direction of the outer conductor,
1p <w <10p
Set the relationship to
Leaky coaxial cable characterized by that. The outer conductor is
A corrugated metal sheet in which the radio wave leakage hole is formed;
A resin protective layer that is attached to the outer peripheral surface of the metal sheet and closes the radio wave leakage hole;
Comprising
The leaky coaxial cable according to claim 1 . A tape-like outer conductor material formed by attaching the resin protective layer to the outer peripheral surface of the metal sheet is wound into a cylindrical shape to form the outer conductor, and at both ends in the winding direction of the outer conductor material. Polymerize metal sheets,
The leaky coaxial cable according to claim 2 . An outer conductor that is corrugated in the shape of a bellows is arranged on the outer periphery of the insulator with the inner conductor inserted and held at the center, and radio leak holes are arranged in rows at a predetermined pitch in the longitudinal direction of the cable at a predetermined circumferential direction of the outer conductor. A method of manufacturing a leaky coaxial cable formed in
A radio wave leakage hole forming step in which the radio wave leakage holes are formed in parallel in the tape longitudinal direction at a predetermined interval in a tape-shaped metal sheet;
An outer conductor material forming step of forming an outer conductor material by attaching a resin protective layer to the outer surface of the metal sheet in which the radio wave leak hole is formed, so as to close the radio wave leak hole;
The outer conductor material is placed in the longitudinal direction of the corrugated pitch p so that the width w of the electromagnetic wave leakage hole in the longitudinal direction of the tape and the corrugated pitch p of the outer conductor material have a relationship of 1p <w <10p. Corrugating process of corrugating and pressing,
An outer conductor forming step of forming the outer conductor by winding the outer conductor material subjected to the undulation process around the outer periphery of the insulator having the inner conductor inserted and held at the center;
The manufacturing method of the leaky coaxial cable characterized by including.

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