JP2012191402A - Leaky coaxial cable and method of manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide an LCX in which the coupling loss is stabilized in the cable length direction without increasing the manufacturing cost, and the LCX in which the coupling loss is stabilized in the cable length direction. An LCX manufacturing method that can be manufactured at a low cost is provided.
A center conductor, an insulator covering the center conductor, and an outer conductor covering the outside of the insulator have a coaxial structure, and the outer conductor has a plurality of slots for forming a leakage electromagnetic field. A leaky coaxial cable in which a portion 101 is formed and an outer conductor 104 is covered with a jacket 105. The outer conductor 104 is printed with resist ink to fix the shape of the hole that becomes the slot portion 101 and corrodes the metal. A metal tape having an opening formed by being passed through the liquid to be wound is configured to be wound around the outer peripheral surface of the insulator 103.
[Selection] Figure 6

Description

  The present invention relates to a leaky coaxial cable and a leaky coaxial cable manufacturing method, and more particularly to a leaky coaxial cable and a leaky coaxial cable manufacturing method in which processing of a slot portion is facilitated and coupling loss is stabilized. .

  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.

  Patent Document 1 describes that an opening is formed in a metal tape to be the outer conductor 104 by a punching method using a mold. Patent Document 2 describes that a hole is formed in a metal tape to be the outer conductor 104 by a cutting method using an end mill. Japanese Patent Application Laid-Open No. H10-228561 describes that a hole is formed in a metal tape to be the outer conductor 104 with a laser beam. Patent Document 4 describes that an opening is formed in a metal tape to be the outer conductor 104 by an etching method.

  In LCX, it is required to stabilize the coupling loss in the cable length direction. In order to stabilize the coupling loss, 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, 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, combining LCXs with different coupling losses and compensating for the transmission loss, if LCX with a small coupling loss (a large amount of electromagnetic wave leakage) is used in the part far from the power supply side, the same It is possible to configure a communication system that is longer than the LCX having the coupling loss and has a small reception level fluctuation range. Non-Patent Document 1 describes an example using three types of LCX having different coupling losses. In order to change the coupling loss, it is necessary to change the shape (size, thickness, angle, etc.) of the slot portion 101.

Japanese Patent Laid-Open No. 10-193001 JP 2010-073513 A Japanese Patent Application Laid-Open No. 2003-079415 JP 2008-278206 A

“LCX Communication System” (first edition, published in 1982) (written by Toshihiko Kishimoto and Shinji Sasaki, Corona) 27-P. 29

  By the way, as described above, when an opening is formed by a punching method using a mold on a metal tape to be the outer conductor 104, there is a problem that the manufacturing cost of the mold is expensive. Further, since the mold is worn as the number of punches increases, it is necessary to replace the mold, resulting in an increase in production cost. In addition, there is a problem that only the same shape determined by the shape of the mold or several types of shapes of holes can be produced.

  There is a problem in that the processing time is long when the hole is formed in the metal tape to be the outer conductor 104 by a cutting method using an end mill. Moreover, since the end mill wears as the cutting time increases, it is necessary to replace the end mill, resulting in an increase in production cost.

  Further, when a hole is formed in the metal tape to be the outer conductor 104 with a laser beam, there is a problem that the laser irradiation apparatus is extremely expensive, for example, about 100 million yen. As a result, the product cost increases significantly.

  And when producing an opening by the etching method in the metal tape used as the external conductor 104, since a process is complicated, there exists a problem that product cost will rise. In addition, since the photomask has to be manufactured with high accuracy and high accuracy is required for the arrangement of the photomask, the manufacturing cost has been increased. That is, as shown in FIG. 7, in the photoetching, first, a resist is applied to the entire surface of the metal tape to be the outer conductor of the LCX (step st101). Then, a separately prepared photomask aperture pattern master (steps st102 to st103) for photomask is arranged with high precision on a metal tape coated with a resist (step st104) and exposed from above the pattern master to obtain the necessary metal. Only the portion is baked and fixed (step st105). Thereafter, development is performed to remove the resist in the part that becomes the opening (step st106), and the metal part in the part that becomes the opening is removed by etching with a corrosive solution (step st107). . Further, unnecessary resist is removed (step st108), so that resources are wasted due to loss of resist material.

  In the stabilization of the coupling loss by connecting LCXs having different coupling losses, the coupling loss changes in a sawtooth shape in the length direction of the LCX by about 10 dB. In this case, although the coupling loss is stabilized as compared with the case where only LCX having a constant coupling loss is used, it is not complete stabilization. Therefore, there is a possibility that the communication speed may be reduced between the LCX and a wireless mobile terminal that is a communication partner existing around the LCX, and between the LCX and the wireless mobile terminal in a place where the coupling loss is large. If a radio wave obstruction enters into the antenna, the coupling loss may increase rapidly and communication may become impossible.

  In addition, in order to connect LCXs with different coupling losses, many types of LCXs must be transported to the installation site, and connectors are required for LCX connections. And installation work is also required. Therefore, such a coupling loss stabilization technique causes an increase in costs such as transportation costs, material costs, and construction costs.

  Accordingly, the present invention has been proposed in view of the above-described circumstances, and its purpose is to provide an LCX that does not increase the manufacturing cost and has a stable coupling loss in the cable length direction. Another object of the present invention is to provide an LCX manufacturing method capable of manufacturing an LCX whose coupling loss is stabilized in the cable length direction at a low cost.

  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. A leaky coaxial cable, in which the outer conductor is a metal tape in which the shape of the opening serving as the slot portion is printed with a resist ink and fixed, and then passed through a liquid that corrodes the metal. Is formed by being wound around the outer peripheral surface of the insulator.

[Configuration 2]
The leaky coaxial cable having the configuration 1 is characterized in that the leakage amount of the leakage electromagnetic field from the slot portion continuously changes over the entire length of the cable.

[Configuration 3]
In the leaky coaxial cable having the configuration 1 or the configuration 2, the shape of the slot portion is continuously changed in the cable length direction, and the leakage amount of the leakage electromagnetic field is separated from the power feeding side in the cable length direction. It increases continuously and the change in the magnitude of the leakage electromagnetic field in the cable length direction is suppressed.

[Configuration 4]
In the leaky coaxial cable having the configuration 3, the cable length is equal to or shorter than the distance corresponding to the distance in which the leakage amount of the leakage electromagnetic field that continuously increases as the distance from the power feeding side increases in the cable length direction. It is characterized by being.

[Configuration 5]
The leaky coaxial cable having the configuration 1 is characterized in that the attenuation of the cable is selectively changed at a desired location.

  Moreover, the manufacturing method of LCX which concerns on this invention has the following structures.

[Configuration 6]
A step of covering the central conductor with an insulator, a step of printing and fixing the shape of the openings serving as a plurality of slot portions for forming a leakage electromagnetic field on the metal tape with a resist ink, and a solution for corroding the metal tape with the metal. A step of forming an opening in the metal tape by passing it through, a step of winding the metal tape around the outer peripheral surface of the insulator to form an external conductor, and a step of covering the external conductor with a jacket To do.

  In the LCX according to the present invention having the configuration 1, the outer conductor is opened by passing the shape of the opening serving as the slot portion into a solution that corrodes the metal after being printed and fixed with resist ink. Since the formed metal tape is wound around the outer peripheral surface of the insulator, the manufacturing cost is reduced.

  In the LCX according to the present invention having the configuration 2, since the leakage amount of the leakage electromagnetic field from the slot portion continuously changes over the entire length of the cable, the coupling loss is stabilized in the length direction of the cable. be able to.

  In the LCX according to the present invention having the configuration 3, the shape of the slot portion continuously changes in the cable length direction, and the leakage amount of the leakage electromagnetic field continuously increases as the distance from the power feeding side increases in the cable length direction. Since the change in the magnitude of the leakage electromagnetic field in the cable length direction is suppressed, the coupling loss can be stabilized in the cable length direction.

  In the LCX according to the present invention having the configuration 4, the cable length is equal to or shorter than the distance corresponding to the distance in which the leakage amount of the leakage electromagnetic field that continuously increases as the distance from the power feeding side increases in the cable length direction. Therefore, the coupling loss can be stabilized in the cable length direction.

  In the LCX according to the present invention having the configuration 5, since the attenuation amount of the cable is selectively changed at a desired location, the coupling loss can be set to a desired state in the cable length direction.

  In the LCX manufacturing method according to the present invention having the configuration 6, the shape of the openings serving as the plurality of slot portions for forming the leakage electromagnetic field is fixed on the metal tape by printing with resist ink, and the metal tape is attached to the metal tape. An opening is formed in the metal tape by passing it through the corrosive liquid, and this metal tape is wound around the outer peripheral surface of the insulator to form an outer conductor, so that the coupling loss is stabilized in the cable length direction. Can be manufactured at low cost.

  That is, the present invention provides an LCX in which the manufacturing loss is not increased, the coupling loss is stabilized in the cable length direction, and the coupling loss is stabilized in the cable length direction. It is possible to provide a method for manufacturing LCX that can manufacture LCX at low cost.

It is a flowchart which shows the manufacturing method of LCX which concerns on this invention. It is a side view which shows the structure of the external conductor of LCX based on this invention. It is a side view which shows the measuring system which measures the coupling loss of LCX. It is a graph which shows the antenna received power measured in LCX which concerns on this invention. It is a graph which shows the coupling loss of LCX which concerns on this invention. It is a side view which shows the structure of LCX. It is a flowchart which shows the manufacturing method of the conventional LCX.

  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 regular intervals with respect to the cable axis. Each slot 101 is inclined at some angle with respect to the cable axis.

  FIG. 1 is a flowchart showing a method for manufacturing LCX according to the present invention.

  In the present invention, as shown in FIG. 1, an etching method is used to form an opening serving as the slot portion 101 in the outer conductor 104. That is, the resist ink is printed on the metal tape that becomes the external conductor 104 in accordance with the target hole pattern. That is, an opening pattern diagram is prepared in step st1.

  FIG. 2 is a side view showing the configuration of the outer conductor of the LCX according to the present invention.

  Next, in step st <b> 2, as shown in FIG. 2, a resist pattern in which the opening 101 is drawn is printed on the metal tape to be the outer conductor 104 with the resist ink 106. At this time, since the resist pattern in which the opening 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, the resist ink 106 is printed (applied) only in a region excluding a portion that becomes the opening 101. In the conventional manufacturing method, a resist is applied to the entire surface of the metal tape, and the resist in the portion that is not exposed (portion that becomes the opening 101) is removed as an extra resist. In the present invention, since the resist ink 106 is not printed (applied) excessively on the portion to be the opening 101, resources are 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, as shown in FIG. 1, in step st3, the resist pattern is exposed, the resist ink is cured and baked on a metal tape. In step st4, the metal in the portion that becomes the opening where the metal portion is exposed is removed by etching to form the opening. In step st5, the resist ink remaining on the metal tape is removed. In step st6, the metal tape in which the holes are formed is completed. This metal tape is wound vertically on the insulator 103 to form the outer conductor 104.

  In the LCX manufacturing method according to the present invention, as shown in FIG. 2, the shape of the slot portion 101 formed as described above is continuously changed in the cable length direction, that is, continuous grading is performed. By doing so, the coupling loss can be continuously changed instead of stepwise, and the fluctuation range of the reception level can be minimized.

  In other words, the shape of the opening can be changed in a complicated manner by making the opening to be the slot portion 101 as described above. By slightly changing the shape of the opening, the coupling loss in the LCX can be made constant in the cable length direction. A pattern of apertures whose shape changes slightly can be drawn by CAD or the like, and the data can be taken into a computer device and resist ink can be directly printed on a metal tape by an ink jet printer. And if the metal of the part used as an opening is removed by an etching process, the opening which a shape changes delicately about a cable length direction can be formed.

  Further, in this LCX manufacturing method, the shape of the opening can be freely changed, so that the leakage amount of the leakage electromagnetic field can be selectively changed at a desired location.

  As an example of the present invention, an LCX was produced using a cylindrical copper wire having an outer diameter of 2 mm as a central conductor. A foamed polyethylene insulator was formed by extrusion molding on the center conductor, and an insulator having an outer diameter of 5 mm was formed from the foamed polyethylene insulator.

  Next, 50 m of a copper tape with a plastic tape having a width of 20 mm was prepared as an external conductor. The copper tape with plastic tape is obtained by bonding a plastic tape with a thickness of 0.06 mm to a copper tape with a thickness of 0.01 mm for the purpose of improving the strength, and the thickness is 0.07 mm.

  On the copper tape side of the copper tape with plastic tape, a resist pattern in which apertures were drawn was printed and fixed using a resist ink that was fixed by light. And the opening used as a slot part was formed by the etching. This outer conductor was wound vertically on an insulator.

  Further, a flame-retardant non-halogen polyethylene resin having a thickness of 0.75 mm was extruded on the outer conductor, and a jacket having an outer diameter of about 7 mm was formed from the flame-retardant non-halogen polyethylene resin. The reason why the outer diameter is about 7 mm is that a slight air layer is formed between the insulator and the outer conductor or between the outer conductor and the jacket.

  The target characteristic of this LCX is that the coupling loss at a point 1.5 m away from the LCX is 80 dB and is constant in the cable length direction.

  As shown in FIG. 2, the resist pattern on which the opening printed on the copper tape is drawn has a length of 7 mm and a width of 2 mm in order to obtain a coupling loss of 80 dB at a position 1.5 m away from the LCX at the position 0 m. Were formed in a zigzag shape with an angle of 20 degrees with respect to the cable axis. At position 23m, in order to obtain 80 dB coupling loss at a distance of 1.5 m, the LCX coupling loss needs to be 70 dB to compensate for the attenuation of 23 m, so the shape of the elongated aperture is The length was 12 mm, the width was 2 mm, and the angle with respect to the cable axis was 20 degrees.

  That is, the change in coupling loss from the position 0 m to the position 23 m is compensated by gradually increasing the slot length. Since the LCX coupling loss needs to be 65 dB at the position 33 m, the shape of the elongated aperture is 12 mm in length, 2 mm in width, and the angle with respect to the cable shaft is 30 degrees. From the position 23 m to the position 33 m, the coupling loss was continuously reduced by gradually changing the angle of the opening with respect to the cable axis from 20 degrees to 30 degrees.

  FIG. 3 is a side view showing a measurement system for measuring the coupling loss of LCX.

  Next, in order to confirm the performance of the manufactured LCX, the coupling loss was measured using an experimental system as shown in FIG. The manufactured 50 m LCX1 was placed on a concrete floor 107 with a piece of wood 108 as a base and floated, and a signal of Pin (W) with a frequency of 2.4 GHz was input to the beginning of the LCX by the transmitter 109. A termination resistor 110 is attached to the end of LCX1. The half-wavelength standard dipole antenna 111 is arranged at a position immediately above the LCX 1 at a distance of 1.5 m so as to receive a polarized wave (Eθ polarized wave) in a direction perpendicular to the length direction of the LCX 1.

  The spectrum analyzer 112 received the output Pout from the half-wavelength standard dipole antenna 111. The coupling loss Lc is the ratio of the input power Pin to the LCX 1 and the output power Pout from the half-wavelength standard dipole antenna 111, and can be calculated by Lc = −10 log (Pout / Pin) (dB). That is, the coupling loss Lc indicates the radiation efficiency of the electromagnetic wave from LCX1. On the contrary, when receiving, it becomes receiving efficiency and the numerical value is the same.

  FIG. 4 is a graph showing antenna received power measured in the LCX according to the present invention.

  The half-wavelength standard dipole antenna 111 was moved from the start end (incident end at position 0 m) of LCX1 to the end end (position 50 m), and the coupling loss was continuously measured. Pin was set to 0 dB (1 mW). As shown in FIG. 4, when the horizontal axis is the position of LCX1 and the vertical axis is the output power Pout of the antenna, the output power Pout is -80 dBm on average although there is some variation. Therefore, it was confirmed that the coupling loss Lc was 80 dB as designed.

  FIG. 5 is a graph showing the coupling loss of the LCX according to the present invention.

  As shown in FIG. 5, the position of LCX1 is on the horizontal axis, and the vertical axis indicates the coupling loss and attenuation at each position, the power in the cable when 0 dBm is incident on LCX1, and the position 1.5 m away from LCX1. The characteristics of LCX1 were confirmed by taking the antenna output at.

  The position 0m (* 1) is an incident point of signal power to LCX1. Since the coupling loss is 80 dB as a design value, the coupling loss of LCX at this position is 80 dB (* 2). It can be seen that the power in the cable (* 4) decreases with the amount of attenuation (* 3) of the cable as the position of LCX1 advances. In order to compensate for this decrease, the coupling loss (* 5) of the cable is reduced. When the coupling loss exceeds 50 dB, the attenuation increases abruptly (* 6). Therefore, it can be seen that the use limit of LCX1 is up to about 50 m (* 7) at this position.

  Therefore, the cable length is equivalent to the distance at which the leakage amount of the leakage electromagnetic field that continuously increases as the distance from the power supply side increases in the cable length direction, before the cable attenuation increases rapidly. It is preferable that it is below the length to be.

  INDUSTRIAL APPLICABILITY The present invention is applied to a leaky coaxial cable and a method of manufacturing a leaky coaxial cable, and in particular, to a leaky coaxial cable and a method of manufacturing a leaky coaxial cable in which processing of a slot portion is facilitated and coupling loss is stabilized. Is done.

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

Claims (6)

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,
The outer conductor has a hole formed as a slot when the shape of the opening serving as the slot is printed and fixed with a resist ink and then passed through a liquid that corrodes the metal. A leaky coaxial cable characterized by being wound around an outer peripheral surface of a body. The leakage coaxial cable according to claim 1, wherein the leakage amount of the leakage electromagnetic field from the slot portion continuously changes over the entire length of the cable. The shape of the slot portion continuously changes in the cable length direction, and the leakage amount of the leakage electromagnetic field continuously increases as the distance from the power feeding side increases in the cable length direction, and leakage in the cable length direction. The leaky coaxial cable according to claim 1, wherein a change in the magnitude of the electromagnetic field is suppressed. The cable length is equal to or shorter than a distance corresponding to a distance in which the leakage amount of a leakage electromagnetic field that continuously increases as the distance from the power feeding side increases in the cable length direction. The leaky coaxial cable described. The leaky coaxial cable according to claim 1, wherein the attenuation amount of the cable is selectively changed at a desired location. Coating the central conductor with an insulator;
A process of printing and fixing the shape of the opening to be a plurality of slot portions for forming a leakage electromagnetic field on a metal tape with a resist ink;
Passing the metal tape through a solution that corrodes the metal to form openings in the metal tape;
Winding the metal tape around the outer peripheral surface of the insulator to form an outer conductor;
Covering the outer conductor with a jacket;
The manufacturing method of the leaky coaxial cable characterized by having.

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