JP2013126096A - Leakage coaxial cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LCX easy to manufacture, in which a coupling loss in the longitudinal direction of a cable is stabilized by clarifying a setting basis (design basis) for satisfactorily flattening variations of the coupling loss in the longitudinal direction of the cable.SOLUTION: In this leakage coaxial cable, a central conductor 102, an insulator 103 coating the central conductor 102, an external conductor 104 covering the outside of the insulator 103 are formed into a coaxial structure, a plurality of slot parts 101 for forming a leakage electromagnetic field are formed in the external conductor 104, and the external conductor 104 is covered with a sheath 105. When the length of the slot part 101 is set as L, and its angle to the longitudinal direction of the cable is set as θ, [log(Lsin2θ)] is changing at a fixed ratio in the longitudinal direction of the cable, and the leakage amount of the leakage magnetic field continuously increases as the leakage magnetic field gets away from a power supply side in the longitudinal direction of the cable, a loss in the leakage coaxial cable is compensated, and a reception level in the longitudinal direction of the cable is fixed.

Description

  The present invention relates to a leaky coaxial cable, and more particularly to a leaky coaxial cable with a stabilized coupling loss.

  As shown in FIG. 6, the leaky coaxial cable (hereinafter referred to as “LCX”) includes an inner conductor 102, an insulator 103, an outer conductor 104, and a jacket (sheath) 105 and is configured in a coaxial shape. Conventionally, this LCX is installed along the Shinkansen and used for wireless communication between the train and the ground, or it is installed in the subway yard and underground mall and used for communication between the ground and fire and radio. Has been. In such an LCX 1, periodic slot portions 101 are provided on the outer conductor 104 in order to leak the electromagnetic energy inside the coaxial to the outside.

  That is, the outer conductor 104 of the LCX 1 is provided with a plurality of slot-like slot portions 101 per cycle for every fixed cycle with respect to the cable axis. Each slot 101 is inclined at some angle with respect to the cable axis. In addition, when the half of the interval between the slot portions 101 coincides with the half wavelength of the use frequency or becomes an integral multiple of the half wavelength, the resonance state is established. This frequency is called a resonance frequency.

  In order to manufacture such an LCX, first, a cylindrical insulator 103 is formed around the inner conductor 102. The inner conductor 102 is inserted along the central axis of the insulator 103. Next, a metal tape is wound around the outer peripheral surface of the insulator 103 in a vertically attached shape. The metal tape is provided with an opening that becomes the slot portion 101. This metal tape becomes the outer conductor 104. Then, by forming the jacket 105 on the outer conductor 104, the LCX is completed.

  In LCX, there is a problem that received power decreases as the distance from the power feeding side increases due to the effect of transmission loss. That is, when the antenna is moved while keeping the distance from the LCX constant, the received power of the antenna decreases as the antenna moves away from the power feeding side due to the transmission loss of the LCX. In order to prevent this, it is required to stabilize the coupling loss in the cable length direction.

  Regardless of the distance from the power supply side, in order to reduce the fluctuation of the signal level, the radiation efficiency from the slot portion 101 may be changed as described in Non-Patent Document 1. This technique is generally called grading. That is, if LCX having a small coupling loss (a large amount of electromagnetic wave leakage) is used in a portion far from the power supply side so as to compensate for transmission loss by combining LCXs having different coupling losses, LCX having the same coupling loss is used. It is possible to configure a communication system that is longer than that configured only with a small reception level fluctuation range.

  Non-Patent Document 1 (Section 2.4.2, p27) includes a “step grading type” using four types of LCX (A, B, C, D) having different coupling losses as shown in FIG. LCX is described. In order to change the coupling loss, it is necessary to change the shape (length, width, angle, etc.) of the slot portion 101.

  In Patent Document 1 and Patent Document 2, instead of connecting LCXs with different coupling losses, the cable itself has a grading function by gradually changing the coupling loss of the cable itself in the longitudinal direction. Is described. Patent Document 1 describes that in order to reduce the change in the received power level in the longitudinal direction of the cable, the coupling loss is gradually changed by gradually changing the slot angle, and the change in the coupling loss is alleviated. Yes. Patent Document 2 describes that the change in coupling loss is mitigated by changing the size and density of the slot.

JP 2003-51713 A JP-A-4-113708

"LCX Communication System" (First edition, published on August 20, 1982) (Toshihiko Kishimoto, Shinji Sasaki, Corona) Chapter 2 Basic Characteristics of LCX

  As described in Non-Patent Document 1, in the “step grading type” LCX in which LCXs with different coupling losses are combined, a large number of connectors are required to connect a plurality of LCXs. Takes time and effort. In addition, there is a problem that the reception level changes greatly in a stepped manner in a portion where LCXs having different coupling losses are connected.

  In the techniques described in Patent Literature 1 and Patent Literature 2, the “continuous grading type” is adopted, and the portion where the coupling loss greatly fluctuates is eliminated, but it is difficult to achieve good flatness. That is, in Patent Document 1 and Patent Document 2, the setting basis (design basis) for changing the slot angle to reduce the change in coupling loss is unclear, and each slot is changed with any profile. However, it is difficult to reduce the change in coupling loss due to the difficulty of manufacturing and the difficulty of manufacturing. For this reason, the “step grading type” as in Non-Patent Document 1 has become the mainstream for realizing grading, giving priority to manufacturability and ease of design.

  Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and the purpose thereof is to clarify the setting basis (design basis) for making the change in the coupling loss favorable in the cable length direction, and to manufacture the cable. It is an object of the present invention to provide an LCX in which the coupling loss is stabilized in the cable length direction.

  In order to solve the above-described problems and achieve the above object, the LCX according to the present invention has any one of the following configurations.

[Configuration 1]
The center conductor, the insulator covering the center conductor, and the outer conductor covering the outside of the insulator have a coaxial structure, and a plurality of slots for forming a leakage electromagnetic field are formed in the outer conductor, and the outer conductor is covered with a jacket. In a leaky coaxial cable, when the length of the slot is L and the angle with respect to the cable length direction is θ, [log (L ² sin2θ)] changes at a constant rate in the cable length direction. The amount of leakage electromagnetic field leakage increases continuously as the distance from the power supply side increases in the cable length direction, loss in the leaky coaxial cable is compensated, and the reception level is constant in the cable length direction. It is a feature.

[Configuration 2]
In the leaky coaxial cable having the configuration 1, the length of the slot portion, the angle of the slot portion, or both the length and the angle are continuously changed over the entire length of the cable. Is.

[Configuration 3]
In the leaky coaxial cable having the configuration 1 or the configuration 2, when the angle θ is in the range of 5 ≦ θ ≦ 30 (deg) and the length L is in the range of the outer diameter of the insulator, L ≦ D / 2 × sin (θ).

[Configuration 4]
In the leaky coaxial cable having any one of Configurations 1 to 3, the slot portion is formed by etching that chemically dissolves metal, cutting by laser, cutting by a rotary blade, or cutting by a cutting plotter. It is characterized by being.

In the LCX according to the present invention having the configuration 1, [log (L ² sin2θ)] is constant in the length direction of the cable when the length of the slot portion is L and the angle with respect to the length direction of the cable is θ. The amount of leakage electromagnetic field leakage increases continuously with distance from the power supply side in the cable length direction, loss in the leaky coaxial cable is compensated, and the reception level in the cable length direction is increased. It becomes constant.

  In the LCX according to the present invention having the configuration 2, the length of the slot portion, the angle of the slot portion, or both the length and the angle continuously change over the entire length of the cable. The reception level is constant in the length direction.

  In the LCX according to the present invention having the configuration 3, when the angle θ is in the range of 5 ≦ θ ≦ 30 (deg) and the length L is in the range of the outer diameter of the insulator as D, L ≦ D Since / 2 × sin (θ), the proportional relationship is obtained satisfactorily, and the reception level is constant in the cable length direction.

  In the LCX according to the present invention having the configuration 4, the slot portion is formed by etching that dissolves a metal chemically, cutting by a laser, cutting by a rotary blade, or cutting by a cutting plotter. Can be manufactured practically.

  In other words, the present invention clarifies the setting basis (design basis) for satisfactorily changing the coupling loss in the cable length direction, is easy to manufacture, and has a stable coupling loss in the cable length direction. LCX can be provided.

It is a side view which shows slot length L and slot angle (theta) in LCX. It is a graph showing an example of the relationship between the slot length L and the slot angle ^{θ (log (L 2 sin2θ)} ) and coupling loss Lc at LCX. It is a graph which shows the example of the change of the signal reception level in the cable longitudinal direction at the time of changing slot length L and slot angle (theta). It is a graph which shows the change of slot length L about the cable longitudinal direction in LCX of the Example of this invention. It is a graph which shows the change of the receiving level about the cable longitudinal direction in LCX of the Example of this invention. It is a side view which shows the structure of LCX. It is a graph which shows the example of the relationship between the signal level and distance from the electric power feeding side in the step grading type LCX used conventionally.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 6 is a side view showing the configuration of the LCX.

  As shown in FIG. 6, the LCX manufactured by the LCX manufacturing method according to the present invention has an inner conductor 102, an insulator 103, an outer conductor 104, and a jacket (sheath) 105 configured in a coaxial manner. . In this LCX 1, a periodic slot portion 101 is provided on the outer conductor 104 in order to leak electromagnetic energy inside the coaxial to the outside. The slot portion 101 is provided in the outer conductor 104 at a predetermined period with respect to the cable shaft. Each slot 101 is inclined at some angle with respect to the length direction of the cable (axial direction of the cable).

  FIG. 1 is a side view showing a slot length L and a slot angle θ in LCX.

The present invention provides an LCX in which a reception level in a wireless system using LCX can be flattened in the cable longitudinal direction. In general, in the zigzag slot type LCX, the relationship between the slot length L (mm) and the slot angle (θrad) shown in FIG. 1 and the coupling loss Lc (dB) is expressed by the following equation.
Lc∝log (L ² sin2θ) (where log is the common logarithm)

  In the present invention, the slot length L and the slot angle θ of each slot portion 101 are in accordance with the above equation so that the coupling loss gradually changes to compensate for the longitudinal reception level drop due to the transmission loss in LCX. Design and manufacture to be value. Only one of the slot length L and the slot angle θ may be changed, or both may be changed simultaneously.

The length L and the angle θ are limited to the range in which the above equation can obtain a proportional relationship, and are specifically as follows.
5 ≦ θ ≦ 30 (deg)
L ≦ D / 2 × sin (θ) (where D is the outer diameter of the insulator)

  Conventionally, many of the slot portions of the LCX were processed by pressing using a mold, but now, etching processing that chemically dissolves metal, cutting processing by laser, cutting processing by a rotary blade, and Since cutting with a cutting plotter has become practical and the degree of freedom in design has increased, it is possible to manufacture an LCX having the slot portion 101 as in the present invention by any one of these processing methods.

  When using the etching process, first, a resist ink is printed on a metal tape to be the external conductor 104 according to a target opening pattern. At this time, since the resist pattern on which the slot portion 101 is drawn is directly printed on the metal tape, it is not necessary to manufacture a high-precision photomask and it is not necessary to arrange the photomask on the resist surface with high accuracy. Moreover, since printing can be performed by an inkjet printer, it can be performed at low cost. Further, if the resist ink is printed only in the area excluding the portion that becomes the slot portion 101, resources can be saved.

  As resist ink used here, the thing made by Chisso Corporation described in Unexamined-Japanese-Patent No. 2009-35700, the thing made by Tokyo Ink Corporation described in Unexamined-Japanese-Patent No. 2010-53177, etc. should be used. Can do.

  Then, the resist pattern is exposed, and the resist ink is cured and baked on a metal tape. Next, the metal in the portion that becomes the slot portion 101 where the metal portion is exposed is removed by etching to form an opening, and the resist ink remaining on the metal tape is removed to form the opening. A metal tape is completed. This metal tape is wound vertically on the insulator 103 to form the outer conductor 104.

FIG. 2 is a graph showing the relationship between the slot length L and slot angle θ (log (L ² sin2θ)) and the coupling loss Lc in LCX.

As shown in FIG. 2, when log (L ² sin 2θ) is taken on the horizontal axis and the coupling loss Lc is taken on the vertical axis, the relationship is almost linear (proportional relationship), and these are correlated one-to-one.

  FIG. 3 is a graph showing changes in the signal reception level in the cable longitudinal direction when the slot length L and the slot angle θ are changed.

As shown in FIG. 3, the slot length L and the slot angle θ are continuously graded so that log (L ² sin 2θ) changes at a constant ratio with respect to the cable longitudinal direction, and only the slot length L is changed to the cable longitudinal length. Signal reception level in the cable longitudinal direction for continuous grading so that it changes at a constant ratio in the direction and continuous grading so that only the slot angle θ changes at a constant ratio in the cable longitudinal direction. The change in level was calculated.

  The calculation conditions are as follows: LCX having the characteristics shown in FIG. 2 is used, the transmission output is 0 dBm, the cable attenuation is 0.5 dB / m, and the signal reception level (80 dBm) is equal at distances of 0 m and 40 m from the power supply side. It was made to become.

As can be seen from FIG. 3, when the slot length L and the slot angle θ are changed so that log (L ² sin2θ) changes at a constant ratio, the reception level becomes the flattest and a good result is obtained. There are differences in the longitudinal fluctuation level depending on the characteristics of the cable, the intended signal reception level, and the cable length, but when log (L ² sin2θ) changes at a constant rate, the reception level becomes flat. I understood it.

As an example of the present invention, LCX was prepared. A tape obtained by bonding copper foil and polyethylene terephthalate (PET) was used as the external conductor 104, and the slot portion 101 was formed in the external conductor 104 by etching. In this slot portion 101, log (L ² sin2θ) is changed at a constant ratio so that the signal reception level is constant from the power feeding side to the termination side over 40 m.

  FIG. 4 is a graph showing changes in the slot length L in the cable longitudinal direction in the LCX according to the embodiment of the present invention.

Specifically, in this LCX, the slot angle θ is set to a constant value of 30 degrees, and the slot length L is changed so that log (L ² sin2θ) changes at a constant ratio as shown in FIG. .

  FIG. 5 is a graph showing changes in the reception level in the cable longitudinal direction in the LCX according to the embodiment of the present invention.

  The reception level when a 0 dBm signal was input to this LCX was measured. As shown in FIG. 5, it was confirmed that the influence of attenuation in the LCX was compensated and the reception level was substantially constant in the cable longitudinal direction.

  The present invention is applied to a leaky coaxial cable, and in particular, to a leaky coaxial cable in which the coupling loss is stabilized.

1 LCX
101 Slot 102 Central conductor 103 Insulator 104 Outer conductor 105 Outer sheath (sheath)

Claims (4)

A center conductor, an insulator covering the center conductor, and an outer conductor covering the outside of the insulator are coaxially structured, and a plurality of slot portions for forming a leakage electromagnetic field are formed in the outer conductor, and the outer conductor A leaky coaxial cable whose conductor is covered with a jacket,
When the slot length is L and the angle with respect to the cable length direction is θ, [log (L ² sin2θ)] changes at a constant rate in the cable length direction, and leakage of the leakage electromagnetic field The leaky coaxial cable is characterized in that the amount continuously increases as the distance from the power feeding side increases in the cable length direction, the loss in the leaky coaxial cable is compensated, and the reception level is constant in the cable length direction. 2. The leaky coaxial cable according to claim 1, wherein the length of the slot portion, the angle of the slot portion, or both the length and the angle continuously change over the entire length of the cable. . L ≦ D / 2 × sin (θ) where 5 ≦ θ ≦ 30 (deg) as the range of the angle θ and the outer diameter of the insulator as D as the range of the length L. The leaky coaxial cable according to claim 1 or claim 2, wherein The slot portion is made by etching that chemically dissolves metal, cutting by laser, cutting by a rotary blade, or cutting by a cutting plotter. The leaky coaxial cable according to any one of the above.

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