JP2009004948A - Leakage coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage coaxial cable (LCX), of which the outer conductor of the coaxial cable comprises a plurality of slot areas at row for leakage electromagnetic field formation, which can be manufactured easily, can have sufficient mechanical durability, can be bent easily, can be used in a long, slender and meandering space, can reduce joint loss and strengthen radiation wave intensity, and also can acquire characteristics optimal to each frequency band even if the operating frequencies cover a plurality of bands. <P>SOLUTION: In a leakage coaxial cable, of which the outer conductor 4 of the coaxial cable includes a plurality of slot areas 1 at row for leakage electromagnetic field formation, a multiple of a half of the peripheral length for each slot area 1 matches with a multiple of half-wave length of a frequency between two operating frequency bands. Alternatively, each slot area 1 is composed of those having a plurality of different peripheral lengths, and a multiple of a half of this peripheral length matches with a multiple of half-wave length of a plurality of operating frequencies. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a leaky coaxial cable, and more particularly, to a wide band of a leaky coaxial cable.

  A leaky coaxial cable (hereinafter referred to as “LCX”) is composed of an inner conductor, an insulator, an outer conductor, and a jacket, and is conventionally laid along the Shinkansen for wireless communication between the train and the ground. It is used, or it is installed in subway premises and underground shopping malls, and is used for communication of the fire radio and police radio with the ground. In such an LCX, as described in Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1 to Patent Document 3, in order to leak electromagnetic energy inside the coaxial to the outside, a period is formed on the outer conductor. Slot is provided.

  In other words, the outer conductor of the leaky coaxial cable is provided with a plurality of slots having a long hole per cycle at regular intervals with respect to the cable axis. Each slot is inclined at some angle to the cable axis. It should be noted that the resonance state occurs when half of the circumference of each slot coincides with the half wavelength of the used frequency or becomes an integral multiple of the half wavelength. This frequency is called the resonance frequency.

LCX Communication System (First Edition 1982.8.20) (Corona) Chapter 2 "Antenna Engineering Handbook (1 edition, 1 print, 1980.10.30)" (Ohm) Chapter 3 JP-A-7-131236 JP 2003-51713 A Japanese Patent No. 2641944

  By the way, the LCX described in Non-Patent Document 1 uses a slot portion in a non-resonant state. In such an LCX, the intensity of the radiated wave is weak and the coupling loss is generally 60 dB or more.

  The LCX described in Non-Patent Document 2 is basically an antenna and is not a coaxial cable type, so it is difficult to bend, the use length is short, and it is difficult to use it in a slender and winding space.

  In the LCX described in Patent Document 1, since the size of the slot portion is shorter than the resonance wavelength, strong radiation cannot be obtained, and the coupling loss is about 65 dB.

  In the LCX described in Patent Document 2, since it is necessary to form a large number of slot portions on the outer conductor, the manufacturing is complicated, and the outer conductor is cut when the cable is bent or twisted. There is a risk that the mechanical durability may be insufficient.

  The LCX described in Patent Document 3 uses the slot portion in a resonance state, and has a small coupling loss at the resonance frequency, but is optimal for each frequency band when the use frequency extends over a plurality of bands. The special characteristics cannot be obtained.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and its purpose is to be easy to manufacture, have sufficient mechanical durability, bend easily in an elongated space. To provide an LCX that can be used, has a low coupling loss and has a strong radiated wave, and can obtain optimum characteristics for each frequency band even when the used frequency extends over a plurality of bands. It is in.

  The leaky coaxial cable according to the present invention has any one of the following configurations.

[Configuration 1]
In a leaky coaxial cable in which a plurality of slot portions for forming a leakage electromagnetic field are provided in a row on the outer conductor of the coaxial cable, each slot portion has an integral multiple of half the circumference of each of the two used frequency bands. It is characterized by coincident with an integral multiple of a half wavelength of the frequency in between.

[Configuration 2]
In a leaky coaxial cable in which a plurality of slot portions for forming a leakage electromagnetic field are provided in a row on the outer conductor of the coaxial cable, each slot portion is configured with a plurality of different circumferential lengths. The integral multiple of the half of the length is equal to the integral multiple of the half wavelength of the plurality of operating frequencies.

  In the leaky coaxial cable according to the present invention having the configuration 1, each slot portion has an integral multiple of a half of the circumference of the slot portion and an integral multiple of a half wavelength of the frequency between the two used frequency bands. Thus, it is possible to obtain optimum characteristics for a plurality of use frequency bands, to reduce the coupling loss, and to increase the intensity of the radiated wave.

  In the leaky coaxial cable according to the present invention having the configuration 2, each slot portion is configured to have a plurality of different circumferential lengths, and an integral multiple of a half of the circumferential length is an integral multiple of a half wavelength of a plurality of operating frequencies. Since they match, the resonance state is obtained for a plurality of use frequency bands, and the coupling loss can be reduced and the intensity of the radiated wave can be increased.

  That is, the present invention is easy to manufacture, has sufficient mechanical durability, can be used in a space that is easy to bend, is long and slender, and has a low coupling loss and a strong radiated wave. Further, it is possible to provide an LCX that can obtain optimum characteristics for each frequency band even when the used frequency is in a plurality of bands.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a sectional view and a side view showing the configuration of the LCX according to the first embodiment of the present invention.

  As shown in FIG. 1, the LCX according to the present invention includes a central conductor 2, an insulator 3, an outer conductor 4, and an outer sheath (sheath) 5 that are coaxially formed. Slot portion 1 is provided.

  FIG. 2 is a graph showing the coupling loss indicating the radiation performance in LCX.

  The coupling loss in the LCX shown in FIG. 2 is the ratio between the power intensity in the LCX and the received power from the standard dipole antenna at a position 1.5 m away from the LCX. The smaller the absolute value, the stronger the radiation. Show.

  In FIG. 2, the characteristic indicated by a indicates the case where the length of each slot is 7 mm and the width is 3 mm, and the characteristic indicated by b indicates the case where the length of each slot is 14 mm and the width is 3 mm. ing.

  When the length of each slot is 7 mm, the coupling loss is about 70 dB at a frequency of 2 GHz to 5 GHz, and the radiation to the outside of the LCX is weak. The cut-off frequency of this LCX is in the vicinity of 1.6 GHz, and the intensity of the radiated wave having a frequency below this vicinity is rapidly attenuated.

  Even when the length of each slot is 14 mm, since the coupling loss is reduced only by about 5 dB, the radiation to the outside of the LCX is not so strong.

  In the LCX according to the present invention, the length of the slot portion 1 is 31 mm and 3 mm, for example. In each slot portion 1, an integral multiple of half of the circumference is equal to an integral multiple of a half wavelength of the frequency between the two used frequency bands. When half of the circumference of each slot 1 coincides with the half wavelength of the used frequency or becomes an integral multiple of the half wavelength, the resonance state occurs, the coupling loss is significantly reduced, and the radiation to the outside of the LCX is strong. Become. The resonance frequency when the length of the slot portion 1 is 31 mm is 3.8 GHz.

  FIG. 3 is a graph showing the coupling loss indicating the radiation performance of the LCX in the first embodiment of the present invention.

  In the LCX according to the present invention, as shown in FIG. 3, at the resonance frequency of 3.8 GHz, each slot 1 operates as a slot antenna, the coupling loss is remarkably reduced, and the radiation to the outside of the LCX is strong. Become.

  This resonance frequency is a frequency between 2.4 GHz and 5 GHz, which is the use frequency band of this LCX. Therefore, in this LCX, the coupling loss is as small as about 50 dB in the used frequency bands of 2.4 GHz and 5 GHz, and the radiation to the outside of the LCX becomes strong.

  Accordingly, this LCX can be suitably used as an LCX for so-called “wireless LAN” in which 2.4 GHz and 5 GHz are used frequency bands.

[Second Embodiment]
FIG. 4 is a sectional view and a side view showing the configuration of the LCX according to the second embodiment of the present invention.

  As shown in FIG. 4, the LCX according to the present invention may be configured such that each of the slot portions 1 a and 1 b has a plurality of different circumferential lengths. An integral multiple of half the circumference of each of the slot portions 1a and 1b is equal to an integral multiple of half wavelengths of a plurality of operating frequencies. The lengths of the slot portions 1a and 1b are, for example, 31 mm and 15.5 mm, and the width is 3 mm.

  FIG. 5 is a graph showing the coupling loss indicating the radiation performance of the LCX in the second embodiment of the present invention.

  The resonance frequencies of the slot portions 1a and 1b in the LCX are 3.8 GHz and 7.1 GHz. As shown in FIG. 5, the coupling loss is remarkably reduced at these resonance frequencies, and the radiation to the outside of the LCX is strong. Become. That is, in this LCX, resonance can be achieved for a plurality of use frequency bands, and the coupling loss can be reduced and the intensity of the radiated wave can be increased for each use frequency band. Even in the vicinity of these resonance frequencies, there is little coupling loss, and a strong radiated wave can be obtained outside the LCX.

  Therefore, in this LCX, a strong radiated wave can be obtained outside the LCX by reducing the coupling loss in a plurality of frequency bands or a wide frequency band.

It is sectional drawing and the side view which show the structure in 1st Embodiment of LCX which concerns on this invention. It is a graph which shows the coupling loss which shows the radiation performance in LCX. It is a graph which shows the coupling loss which shows the radiation performance of LCX in the 1st Embodiment of this invention. It is sectional drawing and the side view which show the structure in 2nd Embodiment of LCX based on this invention. It is a graph which shows the coupling loss which shows the radiation performance of LCX in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slot part 1a Slot part 1b Slot part 2 Center conductor 3 Insulator 4 Outer conductor 5 Outer sheath (sheath)

Claims (2)

In a leaky coaxial cable in which a plurality of slots for forming a leakage electromagnetic field are provided in a row on the outer conductor of the coaxial cable,
The slotted coaxial cable is characterized in that an integral multiple of a half of the circumference of each slot portion is an integral multiple of a half wavelength of a frequency between two used frequency bands. In a leaky coaxial cable in which a plurality of slots for forming a leakage electromagnetic field are provided in a row on the outer conductor of the coaxial cable,
Each of the slot portions is composed of a plurality of different perimeters, and an integral multiple of half of the perimeter coincides with an integral multiple of half wavelengths of a plurality of operating frequencies. Leaky coaxial cable.

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