JPS6076802A - Leak cable - Google Patents

Abstract

PURPOSE:To reduce both the processing cost and the transmission loss by setting coaxially a cylindrical external conductor having a continuous slit in its lengthwise direction and twisted and paired leak lines consisting of paired spiral conductors which are insulated from each other. CONSTITUTION:A cylindrical external conductor 10 having a continuous slit 11 in its lengthwise direction and twisted and paired leak lines 20 are set coaxially to each other. These lines 20 consist of spiral conductor pairs 21 and 22 which are insulated from each other. For instance, a cylindrical external conductor 10 is put into a polyethylene jacketing 12 and conductor pairs 21 and 22 covered with jacketings 23 and 24 are twisted inside the conductor 10. The twisted steel wires 13 are provided to the jacketing 12 for the tension resistance purpose.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to leaky cables.

Conventional technology and problems In recent years, the need for wireless communication has increased even in areas where radio waves cannot reach, such as tunnels and underground malls, and for this purpose, various types of leaky cables such as leaky coaxial cables and twisted pair leaky cables are being used. has been developed.

A leaky coaxial cable has a structure in which slots are opened at a predetermined period on the outer conductor of the coaxial cable at a predetermined angle with the cable axis. The drawback is that lamination processing costs are high. In addition, since it is difficult to solder the second seam of ordinary leaky coaxial cables that use aluminum as the outer conductor, they are wrapped with nylon thread, etc., and due to thermal expansion and contraction, vibration, etc. There is also the problem that the radiation characteristics of radio waves fluctuate as the state of contact with the eyes changes over time.

On the other hand, twisted pair leaky cables consist of a pair of spiral conductors that are insulated from each other, but unlike leaky coaxial cables, most of the electromagnetic field propagating along the cable is distributed inside the outer conductor. Because it does not have a structure that allows for a leaky coaxial cable, it has the disadvantage that its transmission characteristics vary significantly due to the influence of the outside world, and because its conductor surface area is small, its transmission loss is greater than that of a leaky coaxial cable of the same diameter.

Another type of VL spiral coaxial cable is known, which has a structure in which the outer conductor of the coaxial cable is provided with a longitudinal line 1-, and the inner conductor is a tightly wound spiral conductor wire. Difficult to use in higher frequency bands than Mllz
tt, and since the helical pinch of the internal conductor is small, the wire speed during processing is low and processing costs are high.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a stable leakage cable with low processing costs, low transmission loss, and little change over time. It is in.

Composition of the invention The leaky cable of the present invention achieves the above object.

A cylindrical outer conductor having a continuous slit in the longitudinal direction and a pair-type leaky line consisting of a pair of mutually insulated spiral conductors are arranged coaxially.

That is, one aspect of the present invention utilizes the advantages of a coaxial leaky cable while using an inexpensive twisted pair leaky line (inner conductor) as a radiation wave source instead of the expensive pickpocket on the outer conductor 7). The above object has been achieved by combining the advantages of the coaxial type and the twisted pair type.

The present invention will now be explained in more detail by way of examples.

Embodiment of the Invention FIG. 1 is a perspective view showing the basic configuration of an embodiment of the present invention. Reference numeral 10 denotes a cylindrical outer conductor having a longitudinally continuous line 1 to 11, and 20 denotes a twisted pair type leaky line consisting of a pair of spiral conductors 21 and 22 insulated from each other. Outer g(<Conductor 10.!: Twisted pair type leaky line 20 and are arranged coaxially with each other.

The outer conductor 10 is typically formed by winding a thin aluminum plate in a vertically aligned manner without having a ninth seam. This is because a loop circuit is formed by the external conductor in the cross section of the cable, and a current that cancels out the magnetic flux generated in the paired leakage line 20 that interlinks with the loop circuit and becomes a leakage wave is generated in the external conductor. This is to prevent this from occurring.

The twisting pitch p of the pair-type leaky line 20 is as follows.

It is set to satisfy the linear equation like a normal twisted pair leaky cable.

(c, /p) (ν/(1+ν)) < f < (c/
p)× [ν/(1−ν)] where C is the speed of light, ν is the wavelength shortening rate, and f is the frequency.

FIG. 2 is a sectional view showing a specific configuration of an embodiment of the present invention, and the same components as in FIG. 1 are given the same reference numerals. Reference numeral 12 designates an outer sheath 213 made of polyethylene or the like, which is a steel stranded wire for tensile strength, and 23 and 24 an outer sheath for the conductor pair 21 and 22. Each jacket 12, 23 and 24 is constructed from a low loss insulating material. If necessary, open the air gap 1
A may be filled with a low-loss insulating inclusion.

Preferably, the outer conductor 10 may be reinforced by pasting a plastic film or may be corrugated to increase pressure strength.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention comprises a cylindrical outer conductor having five longitudinally continuous slits and a twisted pair type leaky line consisting of a pair of mutually insulated spiral conductors, which are coaxially disposed. Since the cable is configured to do so, it is possible to provide a stable leaky cable with low processing costs (low transmission loss and little change over time).

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a basic configuration of an embodiment of the present invention, and FIG. 2 is a sectional view showing a specific configuration of an embodiment of the present invention. 10. Cylindrical outer conductor, 11. Slit, 20.
・Twisted pair type leaky line, 21.22...L pair, 12,
23.24... Outer covering. Patent applicant Sumitomo Electric Industries Co., Ltd. Representative Patent attorney Gobe Tamamushi

Claims (1)

[Claims] A cylindrical outer part 81 having a continuous slit in the longitudinal direction;
A leaky cable characterized in that a conductor and a pair-type leaky line consisting of a pair of vI spiral conductors insulated from each other are coaxially arranged.