JP2010103685A - Leakage coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively and stably form slots to be perforated on outer conductors in a leakage coaxial cable. <P>SOLUTION: The leakage coaxial cable 1 includes: an inner conductor 3; an insulating body 5 provided at the outer periphery of the inner conductor 3; the outer conductor 7 provided at the outer periphery of the insulating body 5; and an outer cover 9 provided at the outer periphery of the outer conductor 7. The outer conductor 7 includes: two first outer conductors 11, 13 wound with the same pitch intervals in the opposite directions, each other, at the outer periphery of the insulating body 5; and a second outer conductor 15 wound with such intervals that a plurality of slots 17 are formed within the pitch intervals of the first outer conductors 11, 13 at the outer periphery of the two first outer conductors 11, 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a leaky coaxial cable that can be applied to various fields mainly for wireless communication, and in particular, can form a slot for an external conductor inexpensively and stably.

  Conventionally, a leaky coaxial cable that leaks radio waves in the longitudinal direction of the cable in order to ensure communication with moving objects such as train radios and automobile radios of high-speed cars in places where radio waves are difficult to propagate, such as tunnels and expressways (Referred to as “LCX”) has been developed.

  In general, a conventional leaky coaxial cable is formed in a cylindrical shape, and is used by being laid along a road or a track because of its controllability and stability. In addition to being used as an antenna for communication with an antenna installed in a vehicle, in recent years it is also used as an antenna for a wireless LAN.

  7 and 8, a conventional leaky coaxial cable 101 includes an inner conductor 103, an insulator 105 provided on the outer periphery of the inner conductor 103, and a slot 107 provided on the outer periphery of the insulator 105. This is a long cable composed of an outer conductor 109 having a hole called “a” and an outer jacket 111 covering the outer periphery of the outer conductor 109.

  As shown in FIG. 9, the outer conductor 109 includes a slot 107A in which a metal tape 109A such as a copper tape or an aluminum tape is elongated to the right (upwardly to the right) with respect to the longitudinal direction. Slots 107B, which are long in the lower right direction (downwardly to the right), are alternately punched in a so-called zigzag shape, for example, by punching. As shown in FIGS. 10 and 11, the metal tape 109A in which a plurality of slots 107 including the slots 107A and the slots 107B are formed is fed in the processing line direction and pressed by the uneven processing roller 113 from above and below. As a result, an unevenness 115 is applied. Further, the metal tape 109A subjected to the uneven processing 115 is sent out in the processing line direction (right direction in FIGS. 10 and 11) and is cylindrically attached to the outer periphery of the insulator 105 by the cylindrical forming portion 117. Molded into a shape.

  At this time, when the outer conductor 109 is vertically attached to the outer periphery of the insulator 105, an overlapping mark 119 is formed.

  Therefore, in the leaky coaxial cable 101, the electromagnetic field of the electromagnetic wave passing through the slot 107 is radiated to the outside as a leaked radio wave. Currently, it is used in a specific frequency range (for example, several tens of MHz to 900 MHz, 900 MHz to 2400 MHz, etc.) with a frequency of about several tens of MHz to 2.5 GHz. Has been.

  As a method of providing the slot 107 in the outer conductor 109, for example, in the leaky coaxial cable of Patent Document 1, the outer conductor is vertically attached to the outer periphery of the insulator with a gap between the first conductive tape. Then, the second conductive tape is spirally wound around the outer periphery of the first conductive tape, so that a slot is provided on one side of the outer conductor.

Further, in the leaky coaxial cable of Patent Document 2, a slot is formed by winding the metal wire of the first outer conductor and the metal wire of the second outer conductor in two layers while changing the winding direction in the opposite direction so as to provide a gap. is doing.
JP-A-9-198941 JP 2003-123555 A

  By the way, in the conventional leaky coaxial cable 101 of FIG.7 and FIG.8, since one metal tape 109A was longitudinally attached to the longitudinal direction of a cable, there existed a problem that flexibility was bad. Further, when the cable 101 is bent, there is a problem that a crack is derived from the slot 107 of the outer conductor 109.

  Further, the leaky coaxial cables of Patent Document 1 and Patent Document 2 have a problem in that unnecessary electric field components in the longitudinal direction of the cable cannot be suppressed because slots can be arranged only in a predetermined slot direction on the cable. It was.

  Further, since only the slots having a constant length can be formed, the same slots are uniformly arranged in the longitudinal direction of the cable, so that a stable coupling loss cannot be obtained in the longitudinal direction of the cable. there were.

  An object of the present invention is to stably and inexpensively form a slot opened in an outer conductor in a leaky coaxial cable.

In order to solve the above problems, a leaky coaxial cable of the present invention includes an inner conductor, an insulator provided on the outer periphery of the inner conductor, an outer conductor provided with a slot on the outer periphery of the insulator, and the outer conductor. In a long leaky coaxial cable provided with a jacket provided on the outer periphery of
The outer conductor includes two first outer conductors wound around the outer periphery of the insulator in opposite directions at the same pitch interval, and the outer periphery of the two first outer conductors within the pitch interval of the first outer conductor. And a second outer conductor wound at intervals to form a plurality of slots.

  Further, in the leaky coaxial cable according to the present invention, in the leaky coaxial cable, the first outer conductor is preferably a strip-like or linear metal body, and the second outer conductor is preferably a strip-like or linear metal body. .

  As can be understood from the means for solving the above problems, according to the present invention, the outer conductor includes two first outer conductors wound around the outer periphery of the insulator in the opposite directions to each other at the same pitch interval. The outer periphery of the two first outer conductors is composed of a second outer conductor wound at intervals to form a plurality of slots within the pitch interval of the first outer conductor. The effect of.

(1) Since the plurality of slots are formed by the plurality of first outer conductors and the second outer conductor, the flexibility of the cable itself can be improved.

(2) Since the plurality of slots arranged in the cable are alternately changed at intervals of ½ pitch between the plurality of slots that rise to the right and the plurality of slots that rise to the left with respect to the longitudinal direction of the cable. Unnecessary electric field components can be suppressed.

(3) Since the slot length of each of the plurality of slots rising to the right and the plurality of slots rising to the left can be changed periodically, the intensity of the electromagnetic waves to be radiated can be changed periodically. The coupling loss in the longitudinal direction can be stabilized.

  Embodiments of the present invention will be described below with reference to the drawings.

  Referring to FIGS. 1A, 1B, and 2, a leaky coaxial cable 1 according to this embodiment includes an inner conductor 3, an insulator 5 provided on the outer periphery of the inner conductor 3, and this insulation. This is a long cable provided with an outer conductor 7 provided on the outer periphery of the body 5 and an outer jacket 9 covering the outer periphery of the outer conductor 7.

  Further, the outer conductor 7 includes two first outer conductors 11 and 13 wound around the outer periphery of the insulator 5 at the same pitch interval P in opposite directions, and outer peripheries of the two first outer conductors 11 and 13. And a second outer conductor 15 wound around at intervals S (see FIG. 3) so as to form a plurality of slots 17 within the pitch interval P (see FIG. 2) of the first outer conductor.

  More specifically, in this embodiment, as shown in FIG. 2, for example, two metal tapes as the first outer conductors 11 and 13 are opposite to each other on the outer periphery of the insulator 5. 2 are wound at the same pitch interval P, the two first outer conductors 11 and 13 intersect at the same pitch interval P in the longitudinal direction on the front side of the insulator 5 in FIG. In FIG. 2 of the body 5, the two first outer conductors 11, 13 intersect in the middle of the two intersecting positions on the front side on the back side of the paper surface, and intersect at the same pitch interval P in the longitudinal direction.

  Therefore, the crossing positions of the two first outer conductors 11 and 13 are alternately switched at the 1/2 pitch interval P (= P / 2) between the front side and the back side of the insulator 5 in FIG. As a result, the surface shape of the insulator 5 exposed from the two first outer conductors 11 and 13 is, for example, the intersection of the two first outer conductors 11 and 13 on the front side of the insulator 5 in FIG. Thus, the surface area gradually changes in the longitudinal direction. Similarly, the surface area of the insulator 5 on the back side in FIG. 2 gradually changes in the longitudinal direction.

  The two first outer conductors 11 and 13 are not limited to two metal tapes, and may be, for example, two metal wires. That is, the two first outer conductors 11 and 13 are band-shaped or linear metal bodies.

  Furthermore, in this embodiment, as shown in FIGS. 3 and 4, for example, one metal tape as the second outer conductor 15 is disposed on the outer periphery of the two first outer conductors 11, 13. The first outer conductors 11 and 13 are wound in a spiral shape with an interval S so as to form a plurality of slots 17 within the pitch interval P of the first outer conductors 11 and 13.

  Therefore, due to the pitch interval P between the two first outer conductors 11 and 13 and the interval S between the second outer conductors 15, the front side of the insulator 5 in FIG. A long slot 17A is formed in the diagonally upper right direction. On the other hand, on the back side of the insulator 5 in FIG. 4, a long slot 17 </ b> B is formed so as to be lowered to the right with respect to the longitudinal direction (in the diagonally downward direction in FIG. 4). That is, in the leaky coaxial cable 1 of this embodiment, a plurality of slots 17 including a plurality of slots 17A and a plurality of slots 17B are formed.

  In FIG. 4, the two first outer conductors 11 and 13 and the second outer conductor 15 are on the back side of the paper corresponding to FIG. 3, and are shown by dotted lines for easy understanding of this description. .

  The second outer conductor 15 is not limited to a metal tape, and may be a metal wire, for example. That is, the second outer conductor 15 is a band-shaped or linear metal body.

  For the inner conductor 3, for example, an annealed copper wire can be used, and in addition, a tin-plated or silver-plated one, a copper alloy-used one, a single wire, a stranded wire, a pipe, or the like Various materials and structures are applicable.

  Further, for example, polyethylene can be used for the insulator 5, and in addition, cross-linked polyethylene, foamed polyethylene, polypropylene, fluorine resin such as PTFE, PFA, and FEP (all of which includes foam) may be used.

  In addition, for the outer conductor 7, the metal tape or the metal wire, which is a good conductor for any of the first outer conductors 11 and 13 and the second outer conductor 15, can be an annealed copper tape or an annealed copper wire, for example. In addition, tin plating or silver plating may be used, or a copper alloy may be used.

  In addition, for example, PVC can be used for the jacket 9 described above, and various other resins may be used.

  With the configuration described above, the leaky coaxial cable 1 has a right-up (right oblique upward direction) with respect to the longitudinal direction of the cable due to the pitch interval P between the two first outer conductors 11 and 13 and the interval S between the second outer conductors 15. A plurality of slots 17A and a plurality of slots 17B that are lowered to the right (in the diagonally downward direction to the right) are formed, and the plurality of slots 17A and the plurality of slots 17B are interchanged at a ½ pitch interval P (= P / 2). Will be molded. Moreover, depending on the shape of the two first outer conductors 11 and 13 intersecting, the sizes of the plurality of slots 17A and the plurality of slots 17B also change periodically. As a result, the intensity of the electromagnetic wave radiated from the plurality of slots 17 can also be periodically changed.

  In other words, in the leaky coaxial cable 1, a plurality of slots 17 are formed with a right-up portion (slot 17A) and a right-down portion (slot 17B), and these are ½ pitch intervals P (= P / 2). ) Can be formed so as to be interchanged. In addition, since the size of the slot 17 can be periodically changed, the intensity of the electromagnetic wave radiated from the slot 17 can also be periodically changed.

  Further, by changing the pitch interval P between the two first outer conductors 11 and 13 and the interval S between the second outer conductors 15, the sizes of the slot 17A and the slot 17B can be easily changed. As a result, the intensity of the electromagnetic wave radiated from the slot 17 can also be changed.

  Next, in order to investigate the effect of the leaky coaxial cable 1 of the above-described embodiment, the example of FIG. 1 and FIG. 2 based on the configuration of this embodiment is created and further compared with this example. A conventional leaky coaxial cable 129 of FIG. 6A was prepared as a comparative example. The slot lengths of the slot 107A and the slot 107B of the leaky coaxial cable 129 are periodically changed with the slot pitch.

  When the coupling loss (dB) in the longitudinal direction of the cable in the above example and the comparative example was measured, the coupling loss change in the longitudinal direction of the leaky coaxial cable 1 of the example was as shown in the graph shown in FIG. became. On the other hand, the coupling loss change in the longitudinal direction of the leaky coaxial cable 129 of the comparative example of FIG. 6 (A) was as shown in the graph shown in FIG. 6 (B).

  As can be seen from the graphs of FIGS. 5 and 6B, in the example, the coupling loss in the longitudinal direction of the cable is stable as in the comparative example.

  From the above, the leaky coaxial cable 1 according to the embodiment of the present invention has the following effects.

(1) Since the plurality of slots 17 are formed by the plurality of first outer conductors 11 and 13 and the second outer conductor 15, the flexibility of the cable itself can be improved.

(2) As for the plurality of slots 17 arranged in the cable, a plurality of slots 17A that rise to the right and a plurality of slots 17B that rise to the left with respect to the longitudinal direction of the cable alternate with a 1/2 pitch interval P (= P / 2). Therefore, an unnecessary electric field component in the longitudinal direction of the cable can be suppressed.

(3) Since the slot lengths of the plurality of rightward rising slots 17A and the plurality of leftward rising slots 17B can be changed periodically, the intensity of the radiated electromagnetic waves can be changed periodically. The coupling loss in the longitudinal direction of the cable can be stabilized.

(A) is a longitudinal cross-sectional view including the partially broken surface of the leaky coaxial cable according to the embodiment of the present invention, and (B) is a cross-sectional view of (A). It is a front view which shows the state which wound the two 1st outer conductors on the outer periphery of the insulator. It is a front view which shows the state which wound the 2nd outer conductor around the outer periphery of FIG. It is explanatory drawing which shows the state which looked the back surface of FIG. 3 transparently from the front side. It is a graph which shows the coupling loss in the longitudinal direction of the leaky coaxial cable of an Example. (A) is a schematic explanatory drawing of the leaky coaxial cable of a comparative example, (B) is a graph which shows the coupling loss in the longitudinal direction of the cable of (A). It is a longitudinal cross-sectional view including the partial fracture surface of the conventional leaky coaxial cable. It is a cross-sectional view of FIG. It is a top view before the process of the outer conductor of the conventional leaky coaxial cable. It is a front view which shows the manufacturing state which provides an outer conductor in the outer periphery of an insulator in the conventional leaky coaxial cable. It is the top view which looked at FIG. 10 from the top.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Leaky coaxial cable 3 Inner conductor 5 Insulator 7 Outer conductor 9 Outer jacket 11 First outer conductor 13 First outer conductor 15 Second outer conductor 17 Slot P Pitch interval S Distance

Claims (2)

In a long leaky coaxial cable comprising an inner conductor, an insulator provided on the outer periphery of the inner conductor, an outer conductor provided on the outer periphery of the insulator, and a jacket provided on the outer periphery of the outer conductor ,
The outer conductor includes two first outer conductors wound around the outer periphery of the insulator in opposite directions at the same pitch interval, and the outer periphery of the two first outer conductors within the pitch interval of the first outer conductor. A leaky coaxial cable comprising: a second outer conductor wound at intervals to form a plurality of slots.   2. The leaky coaxial cable according to claim 1, wherein the first outer conductor is a band-shaped or linear metal body, and the second outer conductor is a band-shaped or linear metal body.

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