Leaky coaxial cable

Abstract

The present application relates to a kind of leak coaxial cable, including cable body and the three-dimensional helical antenna being arranged in the end of the cable body, the cable body includes sheath, outer conductor, insulating layer and inner conductor, the outer side of the inner conductor is sequentially arranged insulating layer, outer conductor and sheath;Wherein, the outer conductor is provided with several helical grooves along the axial direction, and the helical grooves are periodically arranged.This application sets helical groove structure on outer conductor, so that it has stronger radiation signal strength and more uniform signal coverage, so as to reduce signal blind area in enclosed space, so that it has stronger radiation signal strength and more uniform signal coverage, so as to reduce signal blind area in enclosed space, while the leak cable end of cable body is provided with three-dimensional helical antenna, increases signal radiation distance, expands signal radiation range.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a leaky coaxial cable. Background Technology

[0002] Leaky coaxial cable is a special type of transmission line that uses periodic slots in its outer conductor to directionally radiate and receive electromagnetic waves, thus providing wireless signal coverage within enclosed spaces. This type of cable is widely used in applications requiring stable wireless communication, such as traffic tunnels, subway systems, and mines.

[0003] Traditional leaky cables typically employ straight, figure-eight, or U-shaped slot structures. While these slot structures can achieve basic signal coupling, they have some significant drawbacks and limitations: The linear slots result in strong directionality of electromagnetic wave radiation, which can easily create signal blind spots in enclosed spaces, especially in curved or complex scenarios, where the continuity of signal coverage is poor.

[0004] Due to the limitations of traditional slot shapes, the radiated signal strength is relatively weak and may not meet the signal strength requirements of modern wireless communication systems.

[0005] The existing leaky cable end design cannot effectively enhance the signal radiation distance and range, resulting in insufficient signal coverage in the area near the leaky cable end, which affects the overall performance of the communication system. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a leaky coaxial cable. By setting a spiral slot structure on the outer conductor, it has a stronger radiation signal intensity and a more uniform signal coverage, thereby reducing the signal dead zone in the enclosed space. At the same time, a three-dimensional spiral antenna is set at the end of the leaky cable to increase the signal radiation distance at the end of the leaky cable and expand the signal radiation range.

[0007] To solve the above-mentioned technical problems, the present invention provides a leaky coaxial cable, including a cable body and a three-dimensional helical antenna disposed at the end of the cable body. The cable body includes a sheath, an outer conductor, an insulation layer and an inner conductor. The insulation layer, the outer conductor and the sheath are disposed sequentially on the outer side of the inner conductor. The outer conductor is provided with a plurality of helical slots along the axial direction and the helical slots are arranged periodically.

[0008] In one embodiment of the present invention, the helical slot includes at least two equiangular helical arms, and the equiangular helical arms include two equiangular helical lines connected end to end.

[0009] In one embodiment of the present invention, the helical slot includes at least one Archimedean spiral arm, which includes two Archimedean spirals connected end to end.

[0010] In one embodiment of the invention, the three-dimensional helical antenna is formed by an inner conductor extending in a helical shape toward the side away from the cable body.

[0011] In one embodiment of the present invention, the period of the helical slot is expressed as follows: , Where P is the period; m is a constant; c is the speed of light in a vacuum; f is the minimum operating frequency of the cable; and ε is the equivalent relative permittivity of the foamed insulation of the leaky cable.

[0012] In one embodiment of the present invention, a wrapping layer is further provided between the sheath and the outer conductor, the wrapping layer being made of mica tape, non-woven fabric or other tape.

[0013] In one embodiment of the present invention, the sheath is made of materials such as halogen-free low-smoke flame-retardant polyolefin or low-density linear polyolefin.

[0014] In one embodiment of the present invention, the outer conductor is manufactured by a copper strip corrugated longitudinal wrapping process.

[0015] In one embodiment of the invention, the insulating layer is made of physically foamed polyethylene material.

[0016] In one embodiment of the invention, the inner conductor is made of copper-clad aluminum.

[0017] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: (1) The leaky coaxial cable of the present invention adopts a spiral slot structure on the outer conductor, which can more effectively enhance the intensity of the radiated signal and make the electromagnetic wave radiate in a more uniform way, thereby reducing the signal blind zone in the enclosed space and improving the continuity and uniformity of signal coverage. This improvement is particularly important for ensuring communication quality, especially in curved or complex environments such as tunnels and subways.

[0018] (2) The leaky coaxial cable of the present invention is provided with a three-dimensional spiral antenna at the end of the leaky coaxial cable, which can increase the signal radiation distance at the end of the leaky cable and expand the signal radiation range. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0020] Figure 1This is a schematic diagram of the structure of the leaky coaxial cable in a preferred embodiment of the present invention; Figure 2 for Figure 1 The cross-sectional view of the leaky coaxial cable is shown. Figure 3 This is a schematic diagram of the spiral slots arranged periodically on the outer conductor in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the spiral groove hole in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the periodic arrangement of spiral slots on the outer conductor in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the spiral groove hole in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the structure of the leaky coaxial cable and the three-dimensional helical antenna of the present invention; Figure 8 This is a partial structural schematic diagram of the three-dimensional spiral antenna of the present invention; Explanation of reference numerals in the accompanying drawings: 1. Sheath; 2. Wrapping layer; 3. Outer conductor; 4. Insulating layer; 5. Inner conductor; 6. Spiral slot; 61. Equiangular spiral arm; 62. Archimedean spiral arm; 7. Three-dimensional spiral antenna. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention. Example 1

[0022] Reference Figure 1-3 As shown, the present invention provides a leaky coaxial cable, including a cable body and a three-dimensional helical antenna 7 disposed at the end of the cable body. The cable body includes a sheath 1, an outer conductor 3, an insulation layer 4 and an inner conductor 5. The insulation layer 4, the outer conductor 3 and the sheath 1 are disposed sequentially on the outer side of the inner conductor 5. The outer conductor 3 is provided with a plurality of helical slots 6 along the axial direction, and the helical slots 6 are arranged periodically.

[0023] The leaky cable structure of this invention is not limited to 50-12 leaky cables. The dimensions of the leaky cable structure can be adjusted according to specific application requirements. The helical radius of the spiral slot 6 and the pitch between the spirals can also be adjusted appropriately. This flexibility allows the invention to adapt to different usage environments and coverage requirements, improving the adaptability and versatility of the cable.

[0024] like Figure 4 As shown, the spiral groove 6 includes at least one equiangular spiral arm 61, and the equiangular spiral arm 61 includes two equiangular spirals 611 connected end to end.

[0025] The spiral slot 6 in this embodiment includes two centrally symmetrical equiangular spiral arms 61. By setting two centrally symmetrical equiangular spiral arms 61, it helps to distribute signals evenly in different directions, thereby improving the stability and reliability of the signals.

[0026] The equation of one of the equiangular spirals is:

[0027] The equation of the other equiangular spiral is:

[0028] Where r0 is the radius at the start of the spiral, i.e., the radius at t=0; a is the spiral growth rate, which determines the speed at which the spiral expands; t is a parameter, usually representing angle or time; δ is the phase difference, used to adjust the starting position of the second spiral relative to the first spiral.

[0029] In this embodiment, r0=1mm and a=0.08, but these values ​​can be adjusted according to specific needs in practical applications. By precisely adjusting the value of a, the performance of the leaky coaxial cable can be optimized, making it better suited to specific application environments and coverage requirements. The number of spiral turns can also be adjusted according to actual application needs.

[0030] Since the radius vector length of an equiangular helix increases exponentially with the increase of the angle, δ = π / 2 is generally set in order to form a self-complementing structure in the gap between the two helical arms.

[0031] Furthermore, the three-dimensional spiral antenna 7 is formed by the inner conductor 5 extending in a spiral shape towards the side away from the cable body, such as... Figure 7 and 8 As shown, the three-dimensional spiral antenna 7 is made by extending a spiral from the inner conductor 5. The diameter d1 of the three-dimensional spiral antenna 7 is the same as the diameter of the inner conductor 5, both being 4.8 mm. Its spiral diameter d2 is 42.6 mm, the pitch s is 30.5 mm, and the number of turns N is 10. The three parameters—spiral diameter d2, pitch s, and number of turns N—together determine the signal radiation characteristics of the leaky coaxial cable and can be adjusted according to actual needs.

[0032] The expression for the period of the spiral slot 6 described in this embodiment is as follows: ,

[0033] Where P is the period; m is a constant, m≤-1; c is the speed of light in a vacuum, which is 3×10⁸ m / s; f is the minimum operating frequency of the cable; and ε is the equivalent relative permittivity of the foamed insulation of the leaky cable.

[0034] In practical applications, the period of the spiral slot can be adjusted according to specific needs through the expression of the spiral slot period, thereby optimizing the cable performance. This adjustability enables the cable to adapt to different usage environments and frequency requirements, improving the cable's adaptability and versatility.

[0035] In addition, a wrapping layer 2 is provided between the sheath 1 and the outer conductor 3. The wrapping layer 2 enhances the mechanical strength and durability of the cable, making it more suitable for use in harsh environments.

[0036] In this embodiment, the wrapping layer 2 is made of mica tape, non-woven fabric, or other tape. The wrapping layer also helps improve the flame-retardant properties of the cable, increasing safety.

[0037] In this embodiment, the sheath 1 is made of halogen-free, low-smoke, flame-retardant polyolefin or low-density linear polyolefin. The choice of material for sheath 1 improves the flame-retardant performance and environmental characteristics of the cable, helping to reduce the release of harmful gases in the event of a fire, thus protecting personnel safety and the environment.

[0038] The outer conductor 3 is manufactured using a copper strip corrugated longitudinal wrapping process.

[0039] Insulation layer 4 is made of physically foamed polyethylene material. The choice of material for insulation layer 4 helps to reduce the weight of the cable while maintaining good insulation performance.

[0040] In this embodiment, the inner conductor 5 is made of copper-clad aluminum. Using a copper-clad aluminum inner conductor ensures that signal transmission loss in the cable is minimized, thereby guaranteeing the signal quality of the communication system.

[0041] In this embodiment, the thickness of the sheath 1 is generally 1.9±0.2mm, the thickness of the wrapping layer 2 is generally 0.13±0.01mm, the outer diameter of the outer conductor 3 is generally 13.8±0.2mm, the thickness of the copper strip of the outer conductor 3 is generally 0.08mm, the outer diameter of the insulation layer 4 is generally 12.3±0.2mm, the equivalent dielectric constant ε of the insulation is determined to be 1.248 based on the physical foaming properties of polyethylene, and the outer diameter of the inner conductor 5 is generally 4.8±0.1mm.

[0042] Example 2 like Figure 5-6 As shown, the spiral slot 6 includes at least one Archimedean spiral arm 62, and the Archimedean spiral arm 62 includes two Archimedean spirals 621 connected end to end.

[0043] In this embodiment, the spiral slot 6 includes two centrally symmetrically arranged Archimedean spiral arms 62. The two Archimedean spiral arms 62 can complement each other. The linear growth characteristic of the Archimedean spiral arms 62 helps to control the radiation range of the signal, making it adaptable to different coverage requirements.

[0044] The equation of one Archimedean spiral is:

[0045] The equation for the other Archimedes spiral is:

[0046] r0 and r1 are the radii of the starting points of the two helices, respectively; a is the linear growth rate of the helix, which determines the speed of helical expansion; t is a parameter, usually representing angle or time. In this embodiment, r0 = 0.5 mm, a = 0.0005, and r1 = r0 + 0.5 mm.

[0047] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A leaky coaxial cable, characterized in that, The system includes a cable body and a three-dimensional helical antenna disposed at the end of the cable body. The cable body includes a sheath, an outer conductor, an insulation layer, and an inner conductor. The insulation layer, the outer conductor, and the sheath are sequentially disposed on the outer side of the inner conductor. The outer conductor has a plurality of helical slots arranged along the axial direction, and the helical slots are periodically arranged. The period of the helical slots is expressed as follows: ； Where P is the period; m is a constant and m≤-1; c is the speed of light in a vacuum; f is the minimum operating frequency of the cable; and ε is the equivalent relative permittivity of the foamed insulation of the leaky cable.

2. The leaky coaxial cable according to claim 1, characterized in that: The spiral slot includes at least one equiangular spiral arm, which includes two equiangular spiral lines connected end to end.

3. The leaky coaxial cable according to claim 1, characterized in that: The spiral slot includes at least one Archimedean spiral arm, which includes two Archimedean spirals connected end to end.

4. A leaky coaxial cable according to claim 1, characterized in that: The three-dimensional spiral antenna is formed by the inner conductor extending in a spiral shape toward the side away from the cable body.

5. A leaky coaxial cable according to claim 1, characterized in that: A wrapping layer is provided between the sheath and the outer conductor, and the wrapping layer is made of mica tape, non-woven fabric or other tape.

6. A leaky coaxial cable according to claim 1, characterized in that: The sheath is made of materials such as halogen-free low-smoke flame-retardant polyolefin or low-density linear polyolefin.

7. A leaky coaxial cable according to claim 1, characterized in that: The outer conductor is manufactured using a copper strip corrugated longitudinal wrapping process.

8. A leaky coaxial cable according to claim 1, characterized in that: The insulation layer is made of physically foamed polyethylene material.

9. A leaky coaxial cable according to claim 1, characterized in that: The inner conductor is made of copper-clad aluminum.

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