JP2008219879A - Leaky coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leaky coaxial cable which is highly reliably and can leak an electromagnetic field of stable strength over a length direction. <P>SOLUTION: A leaky coaxial cable is equipped with: an inner conductor; an insulator layer formed along an outer circumference of the inner conductor; an external conductor layer which is formed along an outer circumference of the insulator layer and includes slots disposed in a predetermined cycle in the length direction; an external coating layer formed along an outer circumference of the external conductor layer; and a non-metal rigid wire which is disposed within the external coating layer over the length direction and has a Young's modulus higher than that of the external coating layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a leaky coaxial cable provided with an outer conductor layer having slots arranged at a predetermined period in the longitudinal direction.

  The leaky coaxial cable is a coaxial cable that transmits an electric signal while leaking a part of the electric signal transmitted inside the cable to the outside, and is used for, for example, wireless communication with a moving body such as a train or an automobile. The leaky coaxial cable has a spiral slit in the outer conductor (see Patent Document 1), and has a slot (hole) arranged in the outer conductor at a predetermined cycle in the longitudinal direction (see Patent Document 2). There is. In particular, when the operating frequency band is a VHF band or a UHF band, a slot-type leaky coaxial cable that has a high degree of design freedom and can increase the stability of the electromagnetic field to be leaked is mainly used.

  Moreover, as a leaky coaxial cable laid outside, a self-supporting type cable having a support line extending in the longitudinal direction as described in Patent Document 1 is mainly used so as to withstand the tension applied by wind or the like. It was done. On the other hand, as a leaky coaxial cable for laying in a relatively short distance such as indoors, a non-self-supporting leaky coaxial cable that does not include the above-described support wire has also been used.

JP 2002-314328 A JP 2003-273461 A

  However, since the conventional non-self-supporting leaky coaxial cable does not include a support wire, it tends to be twisted and residual stress is likely to occur after laying. As a result, the probability of breakage of the leaky coaxial cable is increased and the reliability may be lowered.

  In order to prevent this twisting, it is conceivable to incorporate a support line in the coating layer of the leaky coaxial cable. However, in the case of a slot-type leaky coaxial cable, if the metal body is near or on the slot, it leaks. There has been a problem that the electromagnetic field strength may be disturbed.

  The present invention has been made in view of the above, and an object of the present invention is to provide a leaky coaxial cable that is highly reliable and can leak an electromagnetic field having a stable strength in the longitudinal direction.

  In order to solve the above-described problems and achieve the object, a leaky coaxial cable according to the present invention is formed with an inner conductor, an insulator layer formed on the outer periphery of the inner conductor, and an outer periphery of the insulator layer. An outer conductor layer having slots arranged in a predetermined cycle in the longitudinal direction, an outer coating layer formed on the outer periphery of the outer conductor layer, and the outer coating layer disposed in the outer coating layer in the longitudinal direction. And a non-metallic rigid wire having a higher Young's modulus.

  The leaky coaxial cable according to the present invention is characterized in that, in the above invention, the slot of the outer conductor layer is formed over an angle of 180 degrees or more in the outer peripheral direction of the outer conductor layer.

  The leaky coaxial cable according to the present invention is characterized in that, in the above invention, the rigid wire is made of an insulator.

  The leaky coaxial cable according to the present invention is characterized in that, in the above invention, the rigid wire is made of a fiber reinforced resin.

  Moreover, the leaky coaxial cable according to the present invention is characterized in that, in the above invention, two of the rigid wire rods are disposed at positions facing each other with the inner conductor interposed therebetween.

  The leaky coaxial cable according to the present invention includes a support wire core wire and a support wire coating layer formed on an outer periphery of the support wire core wire in the above invention, and is disposed outside the outer coating layer in a longitudinal direction. And a neck portion connecting the support line and the outer covering layer.

  The leaky coaxial cable according to the present invention includes a non-metallic rigid wire having a Young's modulus higher than that of the outer cover layer disposed in the longitudinal direction in the outer cover layer, so that twisting and disturbance of the leakage electromagnetic field are simultaneously caused. Since it is suppressed, there is an effect that the electromagnetic field with high reliability and stable strength over the longitudinal direction can be leaked.

  Hereinafter, embodiments of a leaky coaxial cable according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view schematically showing a leaky coaxial cable according to Embodiment 1 of the present invention. FIG. 2 is a schematic side view of the leaky coaxial cable shown in FIG. As shown in FIGS. 1 and 2, the leaky coaxial cable 10 according to the first embodiment is formed on the inner conductor 1, the insulator layer 2 formed on the outer periphery of the inner conductor 1, and the outer periphery of the insulator layer 2. The outer conductor layer 3, the outer coating layer 4 formed on the outer periphery of the outer conductor layer 3, and the rigid wire 5 disposed in the outer coating layer 4 in the longitudinal direction. A white stripe 6 is formed on the surface of the surface in the longitudinal direction. This will be specifically described below.

  The inner conductor 1 is a hollow pipe made of copper having low conductor resistance and good transmission loss characteristics, and has an outer diameter of about 8 mm. The insulator layer 2 is composed of a hollow polyethylene pipe with good insulation and a polyethylene string that supports the polyethylene pipe from the inner peripheral side, and has an outer diameter of about 20 mm.

  The outer conductor layer 3 is a laminated pleated aluminum tape which is wound vertically along the outer circumference of the insulator layer 2. FIG. 3 is a schematic cross-sectional perspective view showing a state in which the outer covering layer 4 is removed from the leaky coaxial cable 10 shown in FIG. 1 and the outer conductor layer 3 is exposed. As shown in FIG. 3, the outer conductor layer 3 has rectangular slots 3a arranged at a predetermined cycle in the longitudinal direction. That is, the leaky coaxial cable 10 is a slot-type leaky coaxial cable. The length, width, period and inclination angle of the rectangular slot 3a with respect to the longitudinal direction are appropriately designed according to the carrier frequency to be leaked and the electromagnetic field strength to be leaked in the transmission signal. Further, since the slot 3a is formed over an angle θ of 180 degrees or more in the outer circumferential direction of the outer conductor layer 3, for example, around 200 degrees, the leaky coaxial cable 10 leaks an electromagnetic field having a relatively high strength. It is possible to make it.

  The outer coating layer 4 is made of black polyethylene containing carbon and realizes water resistance and weather resistance that can withstand outdoor use. The outer diameter of the outer coating layer 4 is about 30 mm.

  And the rigid wire 5 is arrange | positioned over the longitudinal direction in the center of the thickness direction of the outer coating layer 4. Since the rigid wire 5 is made of a non-metallic material having a Young's modulus higher than that of the outer coating layer 4, the torsional rigidity of the leaky coaxial cable 10 is increased to suppress the occurrence of torsion, and the reliability of the leaky coaxial cable 10 is improved. High quality. In particular, as shown in FIG. 1, two rigid wire rods 5 are arranged at positions facing each other with the inner conductor 1 interposed therebetween, so that the leaky coaxial cable 10 is connected to the two rigid wire rods 5 while increasing torsional rigidity. When bending in a direction perpendicular to the surface including the, it can be easily bent without applying excessive force.

  Further, since the rigid wire 5 is made of a non-metallic material, the electric conductivity is extremely low as compared with the case of being made of a metal material. Therefore, there is very little risk of disturbing the strength of the electromagnetic field leaked from the leaky coaxial cable. FIG. 4 is a schematic cross-sectional view showing the circumferential projection angle of the slot 3a when the leaky coaxial cable 10 is viewed from the vertical direction. As shown in FIG. 4, in the leaky coaxial cable 10, the circumferential projection angle of the slot 3 a extends over an angle θ that is 180 degrees or more, so that it is in the outer coating layer 4 at a position facing the inner conductor 1. When two rigid wire rods 5 are disposed, the rigid wire rod 5 is positioned on the surface of the slot 3a in any direction. At this time, when the rigid wire 5 is a metal material, the slot 3a and the rigid wire 5 may interact with each other to disturb the strength of the electromagnetic field leaked from the leaky coaxial cable. However, since the rigid wire 5 is a non-metallic material and has an extremely low electric conductivity as compared with the metal material, the electromagnetic field leaked from the leaky coaxial cable 10 due to the interaction between the slot 3a and the rigid wire 5. There is very little risk of disturbance in the strength.

  In addition, if this rigid wire 5 consists of an insulator, since disturbance of the intensity | strength of the electromagnetic field to leak is reliably prevented, it is preferable if it consists of fiber reinforced resin (FRP). Is sufficient because the Young's modulus is sufficiently high, and a fiber-reinforced thermoplastic resin (FRTP) is preferable because it is easier to mold. As FRP or FRTP, for example, glass fiber, carbon fiber, polyester fiber, aramid fiber, polyamide fiber, etc. are appropriately used as reinforcing fiber, and epoxy resin, unsaturated polyester resin, polyamide resin, phenol resin, polyethylene resin, polypropylene as matrix A resin, polyethylene terephthalate resin or the like appropriately used is used.

  As shown in FIGS. 1 and 2, the stripe 6 is formed in a direction perpendicular to the surface including the two rigid wires 5, that is, in a direction in which the leaky coaxial cable 10 can be easily bent. As a result, the operator can easily confirm the bending direction when the leaky coaxial cable 10 is bent or wound around the drum from the outside, so that workability is improved.

  As described above, the leaky coaxial cable 10 according to the first embodiment has the nonmetallic rigid wire 5 having a higher Young's modulus than the outer covering layer 4 disposed in the outer covering layer 4 in the longitudinal direction. Since the twisting and the disturbance of the strength of the leakage electromagnetic field are suppressed at the same time, the electromagnetic field with high reliability and stable strength can be leaked in the longitudinal direction. Further, the leaky coaxial cable 10 has an outer diameter as small as about 30 mm and a weight as light as about 1 kg / m, and is easy to handle and easy to lay.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples. Note that the present invention is not limited to the embodiments.

As Example 1 of the present invention, a leaky coaxial cable having the structure shown in FIGS. 1 to 3 and including a rigid wire having a circular cross section with a diameter of 2 mm made of FRP was produced. The rigid wire material contained glass fibers and unsaturated polyester resin, and the Young's modulus was 25 N / mm ² . On the other hand, as a comparative example, a leaky coaxial cable having a structure shown in FIGS. 1 to 3 and including a wire rod having a circular shape with a diameter of 2 mm made of a galvanized steel wire was produced. Furthermore, as a reference example, a leaky coaxial cable having a structure similar to that shown in FIGS. And the leaky coaxial cable of Example 1, the comparative example, and the reference example was spread on concrete, and the CW signal wave having a frequency of 400 MHz was transmitted, and the half was installed at a position 1.5 m directly above each leaky coaxial cable. The reception level of the electromagnetic field intensity leaked from each leaky coaxial cable was measured by the wavelength dipole antenna.

  FIGS. 5-7 is a figure which shows the receiving level of the electromagnetic field intensity | strength leaked from the leaky coaxial cable of a reference example, Example 1, and a comparative example, respectively, and a horizontal axis is the length of the leaky coaxial cable of a half-wavelength dipole antenna. The position with respect to the direction is shown, and the vertical axis shows the reception level at that position. The direction of the received polarization of the half-wave dipole antenna is the reception of the circumferential electric field polarization component of the leaky coaxial cable.

  As shown in FIG. 5, in the leaky coaxial cable of the reference example, since no wire material is disposed, a stable reception level is obtained in the longitudinal direction. On the other hand, as shown in FIG. 6, the leaky coaxial cable of Example 1 includes a rigid wire made of FRP, and thus a stable reception level in the longitudinal direction was obtained as in the reference example. However, as shown in FIG. 7, the leaky coaxial cable of the comparative example includes a rigid wire made of a galvanized steel wire, and thus the obtained reception level fluctuates in the longitudinal direction.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. The leaky coaxial cable according to the second embodiment has a self-supporting structure having a support line in the longitudinal direction.

  FIG. 8 is a schematic cross-sectional view schematically showing a leaky coaxial cable according to Embodiment 2 of the present invention. 8, the same or corresponding components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. As shown in FIG. 8, the leaky coaxial cable 20 according to the second embodiment includes an inner conductor 1, an insulator layer 2, an outer conductor layer 3 having a slot 3 a, and an outer sheath, similar to the leaky coaxial cable 10. A layer 4 and a rigid wire 5 are provided. 8, for the sake of explanation, the circumferential projection angle of the slot 3a is shown as in FIG. The circumferential projection angle of the slot 3a is an angle θ that is 180 degrees or more.

  The leaky coaxial cable 20 further includes a support wire 7 disposed in the longitudinal direction in the vicinity of the outside of the outer covering layer 4 and a neck portion 8 connecting the support wire 7 and the outer covering layer 4. The support wire 7 includes a support wire core wire 7a and a support wire covering layer 7b formed on the outer periphery of the support wire core wire 7a. FIG. 9 is a schematic perspective view of the leaky coaxial cable 20. As shown in FIG. 9, a plurality of neck portions 8 are provided apart from each other in the longitudinal direction of the leaky coaxial cable 20. Therefore, the leaky coaxial cable 20 has a so-called SSW type self-supporting structure. The gap between the neck portions 8 is called a window portion.

  The supporting wire core wire 7a consists of a 7 / 1.4 stranded steel wire, and its outer diameter is 4.2 mm. In addition, as the support wire core wire 7a, for example, a non-metallic material such as FRP or FRTP, or a metal material such as a steel wire or a steel stranded wire may be used. Further, like the outer coating layer 4, the support wire coating layer 7 b and the neck portion 8 are made of black polyethylene containing carbon and have water resistance and weather resistance. In addition, the outer diameter of the support wire 7 is about 9 mm. The neck 8 has a width of about 3 mm and a height of about 3 mm.

  Like the leaky coaxial cable 10, the leaky coaxial cable 20 includes the rigid wire 5. Therefore, since the twist and the disturbance of the leak electromagnetic field are suppressed at the same time, the electromagnetic field is highly reliable and has a stable strength in the longitudinal direction. Can be leaked. Further, since the leaky coaxial cable 20 includes the support wire 7, it is not necessary to use a separate suspension wire when laying aerial, and the laying is easy and twisting is further suppressed. Since the support wire 7 is separated from the slot 3a by the neck portion 8, there is no possibility of disturbing the leaked electromagnetic field even if the support wire core wire 7a is a metal material. Furthermore, in the leaky coaxial cable 20, since the formation direction of the slot 3a does not overlap the arrangement direction of the support wire 7, the disturbance of the leaking electromagnetic field is more reliably suppressed.

  Further, the leaky coaxial cable 20 is easily wound around the drum because the rigid wire 5 is disposed on the line connecting the inner conductor 1 and the support wire core wire 7a. In addition, since the leaky coaxial cable 20 includes the two rigid wire rods 5, even when the neck portion 8 is cut off at the end of the leaky coaxial cable 20 at the time of laying and the support wire 7 is cut off, the twist is suppressed, so that it is high. Reliability can be maintained.

  The leaky coaxial cable 20 according to the second embodiment has an SSW type self-supporting structure in which a plurality of neck portions 8 are provided apart in the longitudinal direction. However, the present invention is not limited to this, and the leaky coaxial cable may be an SSD type without a window portion provided with a neck portion continuous in the longitudinal direction.

  Next, as Example 2 of the present invention, a leaky coaxial cable having the structure shown in FIG. 8 and comprising a rigid wire with a circular cross section of 2 mm in diameter and made of the same FRP as in Example 1 was produced. Then, the leaky coaxial cable of Example 2 was spread on concrete, and the reception level of the electromagnetic field strength leaked from the leaky coaxial cable was measured by the same method as in Example 1.

  FIG. 10 is a diagram illustrating the reception level of the electromagnetic field intensity leaked from the leaky coaxial cable of the second embodiment, where the horizontal axis indicates the position of the half-wave dipole antenna in the longitudinal direction of the leaky coaxial cable, and the vertical axis indicates The reception level at that position is shown. As shown in FIG. 10, the leaky coaxial cable of Example 2 obtained a stable reception level in the longitudinal direction as in Example 1.

  In the above embodiment, the slot of the outer conductor layer is formed over an angle of 180 degrees or more in the outer peripheral direction of the outer conductor layer. However, even a leaky coaxial cable in which the slot is formed over an angle of less than 180 degrees is provided with the rigid wire according to the present invention, even if the rigid wire is disposed in the vicinity of the slot. The disturbance of the electromagnetic field strength is surely prevented. Further, since the rigid wire can be disposed at any position regardless of the position of the slot, the position and number of the rigid wires can be freely designed. Further, in the case where a leaky coaxial cable having a self-supporting structure as in the second embodiment is provided, when only one rigid wire is provided, it is provided at a position opposite to the support wire with the internal conductor interposed therebetween. This is preferable for preventing twisting.

It is the cross-sectional schematic which represented typically the leaky coaxial cable which concerns on Embodiment 1 of this invention. FIG. 2 is a schematic side view of the leaky coaxial cable shown in FIG. 1. It is a cross-sectional perspective schematic diagram which shows the state which removed the outer coating layer from the leaky coaxial cable shown in FIG. 1, and exposed the outer conductor layer. It is the cross-sectional schematic which shows the circumferential direction projection angle of the slot which looked at the leaky coaxial cable shown in FIG. 1 from the orthogonal | vertical direction. It is a figure which shows the reception level of the electromagnetic field intensity leaked from the leaky coaxial cable of the reference example of this invention. It is a figure which shows the reception level of the electromagnetic field intensity leaked from the leaky coaxial cable of Example 1 of this invention. It is a figure which shows the reception level of the electromagnetic field intensity leaked from the leaky coaxial cable of the comparative example of this invention. It is the cross-sectional schematic which represented typically the leaky coaxial cable which concerns on Embodiment 2 of this invention. FIG. 9 is a schematic perspective view of the leaky coaxial cable shown in FIG. 8. It is a figure which shows the reception level of the electromagnetic field intensity leaked from the leaky coaxial cable of Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner conductor 2 Insulator layer 3 Outer conductor layer 3a Slot 4 Outer coating layer 5 Rigid wire 6 Stripe 7 Support wire 7a Support wire core wire 7b Support wire coating layer 8 Neck part 10, 20 Leaky coaxial cable

Claims (6)

An inner conductor,
An insulator layer formed on the outer periphery of the inner conductor;
An outer conductor layer formed on the outer periphery of the insulator layer and having slots arranged at a predetermined period in the longitudinal direction;
An outer covering layer formed on the outer periphery of the outer conductor layer;
A non-metallic rigid wire having a higher Young's modulus than the outer coating layer disposed in the longitudinal direction in the outer coating layer;
A leaky coaxial cable comprising:   2. The leaky coaxial cable according to claim 1, wherein the slot of the outer conductor layer is formed over an angle of 180 degrees or more in an outer peripheral direction of the outer conductor layer.   The leaky coaxial cable according to claim 1, wherein the rigid wire is made of an insulator.   The leaky coaxial cable according to claim 1, wherein the rigid wire is made of a fiber reinforced resin.   5. The leaky coaxial cable according to claim 1, wherein two of the rigid wire rods are disposed at positions facing each other with the inner conductor interposed therebetween.   A support wire having a support wire core wire and a support wire coating layer formed on the outer periphery of the support wire core wire, and being disposed over the outer coating layer in the longitudinal direction, and the support wire and the outer coating layer. The leaky coaxial cable according to claim 1, further comprising a neck portion to be connected.

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