A railway communication leaky cable

Abstract

The invention discloses a railway communication leaky cable, belonging to the technical field of leaky cables. The railway communication leaky cable includes, from inside to outside, an inner conductor, an insulating layer, an outer conductor and an outer sheath; the inner conductor adopts a spiral corrugated copper tube; the outer conductor is a corrugated structure formed by a smooth copper strip longitudinally wrapped on the insulating layer through corrugation, and a periodic slot group is provided on the outer conductor, and the slots in the slot group are of unequal length; the long side of the slot forms an inclination angle with the direction of electromagnetic wave travel in the leaky cable; and the outer sheath is extruded with a color strip corresponding to the position and direction of the slot. The railway communication leaky cable disclosed by the invention fully considers the stability of signal transmission, coverage capacity, heat dissipation performance and convenience of installation and maintenance in structural design, and has high practical value and broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of leaky cables and relates to a leaky cable for railway communications. Background Art

[0002] With the rapid development of mobile communication technology, railways are gradually moving towards digitalization and intelligence. The railway-specific mobile communication system has entered the 5G-R era from GSM-R. Therefore, the railway 5G-R wireless communication system has significant differences from the railway GSM-R wireless communication system in terms of requirements, functions, and architecture.

[0003] Railway 5G-R wireless communication coverage scenarios include railway main lines, railway stations, and railway tunnels. Railway 5G-R leaky coaxial cables are laid along the tunnels to provide wireless coverage of signals in narrow and enclosed spaces, ensuring the reliability requirements of the new generation of railway wireless communication systems.

[0004] The application frequency band of the railway 5G-R wireless communication system is 400MHz-2100MHz, which is compatible with the 1.9GHz / 2.1GHz frequency band of 5G, the 900MHz frequency band of GSM-R and the 400MHz frequency band of digital wireless modulation. At present, the railway-specific leaky cable frequency band is divided into 450MHz leaky cable, 450MHz and 900MHz leaky cable, and 900MHz leaky cable. The leaky cable for the public network is divided into 75MHz-960MHz leaky cable and 700MHz-2700MHz frequency band leaky cable. Therefore, it is not compatible with the railway 5G-R wireless communication system application frequency band. The existing 5G medium-frequency radiating leaky coaxial cable has the problem of low radiation performance and does not meet the requirements of the railway 5G-R communication system application frequency band. Summary of the invention

[0005] The purpose of the present invention is to provide a railway communication leaky cable, which can be compatible with the 1.9GHz / 2.1GHz frequency band of 5G, the 900MHz frequency band of GSM-R and the 400MHz frequency band of digital wireless modulation on the same leaky cable to ensure the stability of signal transmission, solve the problems of large coupling loss at low frequency and large transmission at high frequency, and in the railway-specific GSM-R application band, the comprehensive loss of 1.5km length is below 105dB.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a railway communication leaky cable, which comprises, from inside to outside, an inner conductor, an insulating layer, an outer conductor and an outer sheath;

[0008] The inner conductor is a spiral corrugated copper tube;

[0009] The outer conductor is a corrugated structure formed by a smooth copper strip longitudinally wrapped on an insulating layer through corrugation. The outer conductor is provided with periodically arranged slot groups, each of which includes four forward slots and four reverse slots, and the four forward slots and the four reverse slots are symmetrically arranged to form four eight-shaped slot pairs; the slots in each slot group are of unequal length; the long side of the slot forms an inclination angle α with the length direction of the leaky cable;

[0010] The slot lengths of the four positive slots in each slot group are L1, L2, L3, and L4 respectively, and the slot lengths of the four reverse slots are L5, L6, L7, and L8 respectively. The slot lengths of the four positive slots satisfy: L1=L2+W=L3-δ=L4+W-δ, and the slot lengths of the four reverse slots satisfy: L5=L6+W+δ=L7+δ=L8+W+δ, where L1=L5-γ, γ is a constant, δ is a constant, γ=0.2mm, δ=0.1mm-0.2mm; W is the slot width of the slot.

[0011] As a further improvement of the present invention, the inner conductor is made of smooth copper strip through longitudinal welding and corrugation;

[0012] The spiral corrugated copper tube has wave crests, wave troughs and spiral corrugation pitches; the spiral corrugated copper tube is a spiral structure formed by an annular corrugating knife deflecting along the outer diameter of the wave trough at an angle consistent with the spiral rise angle, wherein the inner diameter of the annular corrugating knife is 1.20-1.25 times the outer diameter of the wave crest, and the thickness of the annular corrugating knife is 1 / 5 times the spiral corrugation pitch.

[0013] As a further improvement of the present invention, the spiral wrinkles of the inner conductor form an angle θ with the normal cross section of the inner conductor, and the angle θ satisfies: , where p is the spiral corrugation pitch, d is the inner diameter of the annular corrugating knife, is the correction factor, The value is 0.2-0.5, π is the ratio of a circle to a circle, and arcsin() is the inverse sine function.

[0014] As a further improvement of the present invention, the insulating layer is a physical foaming insulating structure, the insulating layer is tightly fitted to the inner conductor, and the adhesion force is ≥400N; the foaming degree of the insulating layer is ≥82%, and the insulation eccentricity is ≤3%.

[0015] As a further improvement of the present invention, the overlap width of the corrugated structure of the outer conductor is 9mm-12mm, the corrugations of the corrugated structure are arc structures, the corrugation depth is 0.3mm-0.5mm, and the corrugation width is 2mm-4mm.

[0016] As a further improvement of the present invention, the pitch of two adjacent slot groups is set to P, and P is 350mm-450mm; in each slot group, the slot spacing between two adjacent slots is P1, P2, P3, P4, P5, P6, and P7 respectively, and satisfies: P1=P3=P5=P7=P / 10, P2=P6=3P / 50, P4=6P / 25.

[0017] As a further improvement of the present invention, the cutting cross section S of each slot on the outer conductor satisfies: S=(L i -W)×W+πW 2 / 4,L i is the length of the i-th slot, i=1,2,3…,8, the cutting section S is 105mm 2 ~120mm 2 π is the ratio of circumference to diameter of a circle, and the groove width W is 3.4mm-3.8mm.

[0018] As a further improvement of the present invention, the inclination angle α is 13°~18°.

[0019] As a further improvement of the present invention, color strips corresponding to the positions and directions of the slots are extruded on the outer sheath.

[0020] As a further improvement of the present invention, the outer sheath is made of halogen-free, low-smoke, flame-retardant polyolefin material.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] A railway communication leaky cable of the present invention has slots of unequal lengths on the outer conductor; the inner conductor adopts a spiral corrugated copper tube, which helps to enhance the mechanical strength and flexibility of the inner conductor, and at the same time has a certain electromagnetic shielding effect, which helps to improve the stability of signal transmission. The insulating layer is located between the inner conductor and the outer conductor, and plays a role of electrical isolation. The insulating layer also has certain properties such as heat resistance, cold resistance, and aging resistance to ensure the long-term stable operation of the leaky cable under various environmental conditions. The outer conductor is formed by a smooth copper strip that is longitudinally wrapped on the insulating layer through corrugation to form a corrugated structure, on which a periodic slot group is opened. The slots in the slot group are of unequal length, and the long sides of the slots form an inclination angle with the direction of travel of the electromagnetic wave in the leaky cable. The unequal length slots help to achieve a more complex electromagnetic field distribution, which may improve the bandwidth and efficiency of signal transmission, while reducing interference between signals and improving radiation performance. The inclination angle design can guide the propagation direction of electromagnetic waves in the leaky cable, realize directional radiation or reception, and enhance the coverage capability of the signal in a specific direction. The corrugated structure increases the surface area of ​​the outer conductor, which helps to dissipate heat and improves the mechanical strength and bending resistance of the outer conductor. The outer sheath is extruded with color strips corresponding to the position and direction of the slots. The color strips with visual identification serve as intuitive identification of the slots, making it easier for installation and maintenance personnel to quickly identify the position and direction of the slots, thereby improving work efficiency.

[0023] Furthermore, different color strips can be used to further distinguish leaky cables of different models, specifications or uses, reducing the risk of misuse and confusion. The railway communication leaky cable disclosed in the present invention fully considers the stability of signal transmission, coverage capability, heat dissipation performance, and convenience of installation and maintenance in structural design. The railway communication leaky cable provided by the present invention is compatible with the 1.9GHz / 2.1GHz frequency band of 5G, the 900MHz frequency band of GSM-R, and the 400MHz frequency band of digital wireless modulation, providing safe and reliable 5G-R wireless network coverage for high-speed railways. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a leaky cable for 5G-R communication provided by a specific embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a slot type provided for a specific embodiment of the present invention;

[0026] Among them, 1. inner conductor; 2. insulation layer; 3. outer conductor; 31. slot; 4. outer sheath; 41. color strip. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Terminology explanation:

[0029] GSM-R: GSM for Railways, is an integrated dedicated digital mobile communications system designed specifically for railway communications;

[0030] 5G-R: is a new generation of railway mobile communication system based on 5G technology.

[0031] Corrugation longitudinal wrapping: It is a commonly used technology in material processing, especially in the manufacturing process of optical cables, electrical cables and other communication lines. Corrugation longitudinal wrapping refers to embossing metal strips (such as steel strips, aluminum strips or copper strips) through a corrugating machine to form a specific texture, and then wrapping these textured metal strips longitudinally around the outer layer of the optical cable or electrical cable to provide mechanical protection and enhance performance.

[0032] Spiral wrinkle copper tube: It is a copper tube with a specific structure, whose inner or outer surface presents spiral wrinkles. Spiral wrinkle copper tube refers to the copper tube surface formed with spiral wrinkles through a specific process, and this wrinkle can be on the inner surface or the outer surface.

[0033] Insulation eccentricity: refers to the degree of deviation between the center of the insulation material in the winding and the geometric center of the winding, expressed as a percentage. In power cables, insulation eccentricity also refers to the unevenness of the thickness of the cable insulation layer in the cross section.

[0034] Foaming degree: refers to the percentage of gas contained in the foam, usually expressed as a percentage. It is an important parameter to measure the performance of foam materials and is closely related to the density, mechanical properties, thermal insulation properties, etc. of the material.

[0035] like Figure 1 As shown, the present invention provides a railway communication leaky cable, comprising an inner conductor 1, an insulating layer 2, an outer conductor 3 and an outer sheath 4, wherein the inner conductor 1, the insulating layer 2, the outer conductor 3 and the outer sheath 4 are arranged in sequence from the inside to the outside. The outer conductor 3 is provided with a plurality of slots 31 of unequal lengths; and the outer sheath 4 is extruded with a color strip 41.

[0036] Among them, the inner conductor 1 adopts a spiral corrugated copper tube; the outer conductor 3 is a corrugated structure formed by a smooth copper strip being corrugated and longitudinally wrapped on the insulating layer 2, and a plurality of slot groups are periodically opened on the outer conductor 3, each slot group includes a plurality of slots 31, and the slots 31 in each slot group are of unequal length; the long side of the slot 31 forms an inclination angle α with the direction of electromagnetic wave propagation in the leaky cable (that is, the length direction of the leaky cable); and the outer sheath 4 is extruded with a color strip 41 corresponding to the position and direction of the slot 31.

[0037] In the above structure, the inner conductor 1 adopts a spiral corrugated copper tube, which helps to enhance the mechanical strength and electrical performance of the conductor, and may also take into account the stability and efficiency of signal transmission. The insulating layer 2 is located between the inner conductor 1 and the outer conductor 3, which plays an electrical isolation and protection role to ensure the purity and safety of signal transmission. The outer conductor 3 is made of a smooth copper strip that is corrugated and longitudinally wrapped on the insulating layer 2 to form a corrugated structure, which enhances the mechanical strength and signal shielding effect of the outer conductor 3. The unequal length slots 31 opened on the outer conductor 3 are the key to the signal leakage of the leaky cable. The outer sheath 4 protects the entire leaky cable structure from erosion by the external environment. At the same time, the extruded color strips 41 correspond to the slots 31, which are convenient for identification and positioning during installation and maintenance.

[0038] More specifically, if Figure 2 As shown, each slot group includes a plurality of pairs of splayed slots. Figure 2, from left to right, the eight slots 31 in each slot group are numbered 1, 2, 3, 4, 5, 6, 7, 8. Each eight-shaped slot pair includes a forward slot and a reverse slot, the four on the left are forward slots, and the four on the right are reverse slots; the forward slots and the reverse slots are symmetrically arranged to form an eight-shaped slot pair, and the pitch of two adjacent slot groups is set to P, which is set to 350mm-450mm according to the application frequency band of the electromagnetic wave transmission frequency band. The slot spacing P1, P2, P3, P4, P5, P6, and P7 of two adjacent slots 31 meet: P1=P3= P5= P7=P / 10, P2=P6=3P / 50, P4=6P / 25. Suppress the resonance of a certain point in the application frequency band of electromagnetic wave transmission in the leaky cable and reduce the voltage standing wave ratio.

[0039] As a key solution of the present invention, the slot group includes four forward slots and four reverse slots, and all the slots 31 are of unequal lengths. The slot lengths of the four forward slots are L1, L2, L3, and L4, respectively, and the slot lengths of the four reverse slots are L5, L6, L7, and L8, respectively. Among them, the slot lengths of the four forward slots satisfy: L1=L2+W=L3-δ=L4+W-δ, and the slot lengths of the four reverse slots satisfy: L5=L6+W+δ=L7+δ=L8+W+δ, wherein L1=L5-γ, γ=0.2mm, δ=0.1mm-0.2mm. This structure can balance the influence of the size deviation of the slots 31 caused by corrugation on the transmission performance and radiation performance, and reduce the influence of resonance on the attenuation performance during leaky cable transmission.

[0040] In particular, the slot 31 design, the slots 31 in the slot group opened on the outer conductor 3 are not of equal length, and the long side of the slot 31 forms an inclination angle with the length direction of the leaky cable. This design can optimize the leakage mode of electromagnetic waves, so that the signal can propagate more evenly along the leaky cable direction, reduce the signal blind area, and improve the coverage effect. The inclination angle formed by the long side of the slot 31 and the length direction of the leaky cable helps to adjust the radiation direction and intensity of the electromagnetic wave, so that the signal can better adapt to complex environments such as tunnels and bridges, and improve the communication quality. By optimizing the design of the slot 31 and the frequency band compatibility, the leaky cable can provide more stable and uniform wireless communication signal coverage, reduce signal blind areas, and improve communication quality, especially the eight-shaped slot 31 design, which improves the radiation performance.

[0041] The layout and frequency band compatibility design principle of the slot group of the present invention is as follows: the slot group is arranged at a specific pitch P, which is set to 350mm-450mm according to the application frequency band of the electromagnetic wave transmission frequency band, so as to ensure that the leaky cable can cover and be compatible with multiple frequency bands, such as the 1.9GHz / 2.1GHz frequency band of 5G, the 900MHz frequency band of GSM-R and the 400MHz frequency band of digital wireless modulation. It has been verified that the fine design of the slot spacing helps to suppress the resonance of specific frequency points in the electromagnetic wave transmission in the leaky cable, thereby reducing the voltage standing wave ratio and improving the transmission efficiency.

[0042] The design principle of the eight-shaped slot pair is that the eight-shaped slot pair is composed of a forward slot and a reverse slot, which helps to balance the radiation direction of the electromagnetic wave and reduce the signal blind area. The unequal length design of the slots 31 and the specific length difference can balance the influence of the slot 31 size deviation caused by corrugation on the transmission performance and radiation performance, and further reduce the influence of resonance on the attenuation performance.

[0043] More specifically, compared with the slot structure of equal length in the prior art, the present invention adopts a symmetrical arrangement of forward slots and reverse slots and a design of unequal lengths, which helps to form a more uniform electromagnetic wave radiation field around the leaky cable. This design can reduce the signal blind area caused by the single radiation direction of the electromagnetic wave, improve the uniformity and continuity of the signal coverage, and achieve the purpose of balancing the radiation direction of the electromagnetic wave. Through the symmetrical arrangement of the eight-shaped slot pairs, the leaky cable can radiate electromagnetic waves in multiple directions, thereby effectively reducing the signal blind area. This is of great significance for improving the communication quality, especially the communication quality in complex environments. The design of unequal length and specific length difference of the slots 31 helps to balance the size deviation of the slots 31 caused by corrugation. This design can reduce the fluctuation of the transmission performance and radiation performance caused by the inconsistent size of the slots 31, thereby improving the overall performance stability of the leaky cable. Through the fine design of the slots 31 and the adjustment of the length difference, the leaky cable can reduce the possibility of resonance in a specific frequency band. This helps to reduce the signal attenuation caused by resonance and improve the transmission efficiency of the leaky cable. The design of 31 pairs of slots of unequal length enables the leaky cable to be compatible with multiple frequency bands at the same time, such as the 1.9GHz / 2.1GHz band of 5G, the 900MHz band of GSM-R, and the 400MHz band of digital wireless modulation. This frequency band compatibility makes the leaky cable have a wider application prospect in scenarios that require high-speed and reliable communication, such as high-speed railways. The inclination angle formed by the long side of the slot 31 and the length direction of the leaky cable helps to adjust the leakage mode of the electromagnetic wave so that the signal can propagate more evenly along the direction of the leaky cable. This design can further improve the uniformity and continuity of signal coverage and reduce signal blind spots.

[0044] The principle of the inclination angle between the long side of the slot 31 and the length of the leaky cable is that the inclination angle formed by the long side of the slot 31 and the length direction of the leaky cable helps to adjust the radiation direction and intensity of the electromagnetic wave, so that it can better adapt to complex environments such as tunnels and bridges. This design optimizes the leakage mode of the electromagnetic wave, allowing the signal to propagate more evenly along the direction of the leaky cable, improving the coverage effect and reducing the signal blind area.

[0045] Therefore, based on the above structure of the embodiment of the present invention, the unequal length design of the slots 31 of the present invention not only improves the radiation performance of the leaky cable, but also enhances its compatibility with signals of different frequency bands. Through the fine design of the slots 31 and the optimization of the frequency band compatibility, the leaky cable can provide more stable and uniform wireless communication signal coverage, especially in scenarios such as high-speed railways that require high-speed and reliable communication. This specially designed railway communication leaky cable achieves compatibility with signals of different frequency bands and optimizes transmission performance through the fine layout and size design of the slots 31, as well as the adjustment of the inclination angle between the long side of the slots 31 and the length of the leaky cable. This not only improves the communication quality, but also provides safe and reliable wireless communication signal coverage for complex environments such as high-speed railways.

[0046] Through experimental tests, it is found that the stability of signal transmission is compatible with the 1.9GHz / 2.1GHz band of 5G, the 900MHz band of GSM-R, and the 400MHz band of digital wireless modulation on the same leaky cable, solving the problem of large coupling loss at low frequency and large transmission at high frequency, especially in the railway-specific GSM-R application band, the comprehensive loss of 1.5km length is below 105dB, and the radiation performance is excellent. Therefore, the railway communication leaky cable of the present invention is compatible with the 1.9GHz / 2.1GHz band of 5G, the 900MHz band of GSM-R, and the 400MHz band of digital wireless modulation, providing safe and reliable 5G-R wireless network coverage for high-speed railways.

[0047] As an illustration, for those skilled in the art, for a 1.5km transmission line, if its comprehensive loss can be controlled below 105dB, this performance is usually ideal, especially in application scenarios that require long-distance, high-quality signal transmission. The loss level below 105dB means that the signal attenuates relatively little during the 1.5km transmission process, and can maintain high signal strength and clarity. This is crucial for applications that require long-distance transmission of high-quality signals. Low loss helps reduce signal distortion during transmission, thereby ensuring that the receiving end can accurately receive and restore the original signal. This is of great significance for ensuring communication quality, reducing bit error rates, etc. In high-speed railway communication systems, due to the high speed of trains and long communication distances, the quality and stability of signal transmission are extremely high. A 1.5km transmission line with a comprehensive loss of less than 105dB can meet this requirement and ensure unimpeded communication between the train and the ground control center.

[0048] Optionally, the inner conductor 1 is a spiral corrugated copper tube. For example, the outer diameter of the crest of the spiral corrugated copper tube is 17.5 mm. mm, the outer diameter of the trough is 14.5 mm, spiral wrinkle pitch 10.2 mm, made of smooth copper strip through longitudinal welding and corrugation.

[0049] As an example, a spiral corrugated copper tube is formed by deflecting the annular corrugating knife on the corrugating head along the outer diameter of the wave trough at an angle consistent with the spiral rise angle. The rolled spiral corrugated copper tube has the characteristics of beautiful texture, stable forming and better standing wave ratio. The inner diameter of the annular corrugating knife is designed to be 1.20-1.25 times the outer diameter of the wave peak, and the thickness of the annular corrugating knife is designed to be 1 / 5 times the pitch of the spiral corrugation.

[0050] For further example, the spiral wrinkles of the inner conductor 1 form a certain angle with the normal cross section of the inner conductor 1. θ , angle θ satisfy: , where p is the spiral corrugation pitch, d is the inner diameter of the annular corrugating knife, The correction coefficient is 0.2-0.5, and the actual calculation results are θ The angle range is 12°-14°.

[0051] As an example, the insulating layer 2 is a physical foaming insulating structure of skin-foam-skin, which fits tightly with the spiral corrugated copper tube, and the adhesion force is ≥400N.

[0052] Among them, the skin-foam-skin physical foaming insulation structure is an insulation technology widely used in the manufacture of wires and cables. The insulation layer 2 consists of a three-layer structure: an inner layer, a foam layer and an outer layer, and has excellent electrical properties, mechanical properties and environmental adaptability.

[0053] As an example, a skin-foam-skin insulation structure, including an inner layer, a foam layer and an outer layer, is illustrated as follows:

[0054] The inner layer is usually a solid layer, and the inner layer is tightly attached to the inner conductor 1, providing good adhesion and moisture resistance, ensuring the overall performance of the insulation layer 2. The foam layer adopts physical foaming technology to form a fine bubble structure. Reduce the dielectric constant and dielectric loss of the insulation layer 2, and improve the transmission performance of the cable; at the same time, the small and dense bubble structure of the foam layer can effectively prevent water molecules from penetrating, and improve the moisture resistance of the insulation layer 2. The outer layer material adopts high-density insulating material, such as high-density polyethylene. Provide good wear resistance, mechanical strength and environmental aging resistance, protect the inner layer and foam layer from external damage.

[0055] In the insulating layer 2 provided by the present invention, the foaming degree of the foaming layer is ≥82%, and the "immersion and spray cross" cooling method is adopted to ensure that the insulating bubbles are fine, uniform and consistent, the insulation eccentricity is ≤3%, and the total thermal shrinkage is not more than 4%. The advantages of this design are: the foaming degree of the foaming layer reaches or exceeds 82%, which means that the inside of the insulating layer 2 is filled with more bubbles, and these bubbles can more effectively isolate heat and current and improve insulation performance. Through the "immersion and spray cross" cooling method, it is ensured that the insulating layer 2 is heated evenly during the cooling process, avoiding the problem of uneven pore size and uneven distribution caused by local overheating or overcooling.

[0056] This cooling method helps to form a fine, uniform and consistent insulating foam cell structure, further improving the insulation performance. Insulation eccentricity ≤ 3%: This indicator is far lower than the national standard, indicating that the insulating layer 2 has extremely high precision and stability during the manufacturing process. Low eccentricity means that the insulating layer 2 can be more evenly wrapped around the conductor, reducing problems such as uneven electric field distribution and partial discharge caused by eccentricity, and improving the overall performance and safety of the cable. The total amount of thermal shrinkage is no more than 4%: This indicator reflects the dimensional stability of the insulating layer 2 after heating. By optimizing the foaming process and cooling method, the present invention can effectively control the total amount of thermal shrinkage of the insulating layer 2, ensuring that the cable can maintain stable size and performance in a high temperature environment. This is of great significance for improving the service life and reliability of the cable.

[0057] The insulating layer 2 provided by the present invention achieves the advantages of high foaming degree, fine and uniform insulating pores, low insulation eccentricity and small total thermal shrinkage by optimizing the foaming process and cooling method, which significantly improves the performance, service life and safety of the cable.

[0058] In the specific preparation process, the nucleating agent of the foaming layer in the insulating layer 2 is a non-polar molecular material with low dielectric loss, and its dielectric loss tangent is ≤5×10 -5 , does not change with temperature and frequency, reduces the dielectric loss of insulation, and ensures the stability of the performance of the insulation layer 2.

[0059] The outer conductor 3 provided by the present invention is a corrugated structure formed by a smooth copper strip longitudinally wrapped on the insulating layer 2 through corrugation. The overlap width of the corrugated structure is 9mm-12mm. The corrugation of the corrugated structure is an arc structure. The corrugation depth is 0.3mm-0.5mm, and the corrugation width is 2mm-4mm. This design can improve the bending performance of the leaky cable.

[0060] In addition, the outer sheath 4 has a color strip 41 with a width of not less than 8 mm extruded at the corresponding part of the notch, which has the following functions: first, it can be used to identify the corresponding direction of the slot 31, and second, it can more clearly distinguish the cable model, specification and purpose.

[0061] More specifically, the cutting section S of each slot 31 on the outer conductor 3 of the present invention is (Li -W)×W+πW 2 / 4, slot 31 cutting section S is 105mm 2 ~120mm 2 Between. i is the length of the i-th slot 31, i=1,2,3…,8, the cutting section S is 105mm 2 ~120mm 2 π is the ratio of circumference to diameter of a circle, and the groove width W is 3.4mm-3.8mm.

[0062] The inclination angle α of the slot 31 is the angle between the long side of the slot and the direction of travel of the electromagnetic wave in the leaky cable, which complements the slot length of the slot 31. The slot length needs to be determined after shaping to make the coupling loss more uniform. The inclination angle α of the slot 31 is 13°~18°, which can balance the coupling loss of the low frequency band and the 5G-R high frequency band.

[0063] In terms of material selection, the outer sheath 4 of the present invention is made of halogen-free low-smoke flame-retardant polyolefin material, which has extremely high flame retardant properties, low smoke emission and low corrosiveness.

[0064] As an example, the presence of the color strip 41 provides an intuitive visual mark, allowing the operator to quickly and accurately identify the specific position and direction of the slot 31. This is very convenient for cable routing, connection and subsequent maintenance and repair work, helping to reduce misoperation and improve work efficiency.

[0065] In the cable industry, there are cables of various models, specifications and uses. These cables may look very similar, but their performance, application scenarios and carrying capacity are different. By extruding color strips 41 of different colors at the corresponding positions of the outer sheath notches, each cable can be given a unique identity. This identification not only helps manufacturers to control quality and traceability during the production process, but also facilitates users to quickly and accurately identify the model, specifications and use of the cable during the purchase, installation and use, thereby avoiding potential risks caused by misuse or mixing.

[0066] As an example, the color strip 41 with a width of not less than 8 mm is extruded at the corresponding position of the notch of the outer sheath 4, which plays a vital role in the design and production of the cable. It is not only a powerful assistant for cable installation and maintenance, but also an important mark for distinguishing cable models, specifications and uses.

[0067] The product obtained by the railway communication leaky cable solution of the embodiment of the present invention has specific product parameters: the foaming degree of the foaming layer is 84%, the slot lengths of the four forward slots are L1=37.0mm, L2=33.6mm, L3=37.2mm, L4=33.8mm, the slot lengths of the four reverse slots are L5=37.2mm, L6=33.7mm, L7=37.1 mm, L8=33.6mm, and the inclination angle α is 15°; the data in Table 1 are obtained through testing:

[0068] Table 1 Performance test results

[0069]

[0070] It can be concluded from Table 1 that the special design of the foaming degree and slot 31 structure of the product can, firstly, balance the influence of the size deviation of the slot 31 caused by corrugation on the transmission performance and radiation performance, and reduce the influence of resonance on the attenuation performance during leaky cable transmission; secondly, it helps to form a more uniform electromagnetic wave radiation field around the leaky cable; thirdly, it ensures the stability of the performance of the application frequency band of the railway communication leaky cable, and provides safe and reliable 5G-R wireless network coverage for high-speed railways.

[0071] Therefore, the present invention provides a railway communication leaky cable, which is to ensure the stability of signal transmission in the application frequency band on the same leaky cable at a frequency of 400MHz-2200MHz, and solve the problems of large coupling loss at low frequency and large transmission at high frequency. The railway communication leaky cable is in the railway-specific GSM-R application frequency band, and the comprehensive loss of 1.5km length is below 105dB.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A railway communication leaky cable, characterized in that: The device comprises, from inside to outside, an inner conductor (1), an insulating layer (2), an outer conductor (3) and an outer sheath (4); The inner conductor (1) is a spiral corrugated copper tube; The outer conductor (3) is a corrugated structure formed by a smooth copper strip longitudinally wrapped on an insulating layer (2) through corrugation. The outer conductor (3) is provided with periodically arranged slot groups, each of which includes four forward slots and four reverse slots, and the four forward slots and the four reverse slots are symmetrically arranged to form four pairs of splayed slots; the slots (31) in each slot group are of unequal length; the long sides of the slots (31) form an inclination angle α with the length direction of the leaky cable; The slot lengths of the four positive slots in each slot hole group are L1, L2, L3, and L4, respectively, and the slot lengths of the four reverse slots are L5, L6, L7, and L8, respectively. The slot lengths of the four positive slots satisfy: L1=L2+W=L3-δ=L4+W-δ, and the slot lengths of the four reverse slots satisfy: L5=L6+W+δ=L7+δ=L8+W+δ, wherein L1=L5-γ, γ is a constant, δ is a constant, γ=0.2mm, δ=0.1mm-0.2mm; and W is the slot width of the slot hole (31).

2. A railway communication leaky cable according to claim 1, characterized in that: The inner conductor (1) is made of a smooth copper strip that is longitudinally welded and corrugated; The spiral corrugated copper tube has wave crests, wave troughs and spiral corrugation pitches; the spiral corrugated copper tube is a spiral structure formed by an annular corrugating knife deflecting along the outer diameter of the wave trough at an angle consistent with the spiral rise angle, wherein the inner diameter of the annular corrugating knife is 1.20-1.25 times the outer diameter of the wave crest, and the thickness of the annular corrugating knife is 1 / 5 times the spiral corrugation pitch.

3. A railway communication leaky cable according to claim 1, characterized in that: The spiral wrinkles of the inner conductor (1) form an angle θ with the normal cross section of the inner conductor (1), and the angle θ satisfies: , where p is the spiral corrugation pitch, d is the inner diameter of the annular corrugating knife, is the correction factor, The value is 0.2-0.5, π is the ratio of a circle to a circle, and arcsin() is the inverse sine function.

4. A railway communication leaky cable according to claim 1, characterized in that: The insulating layer (2) is a physical foaming insulating structure, the insulating layer (2) is closely attached to the inner conductor (1), and the adhesion force is ≥400N; the foaming degree of the insulating layer (2) is ≥82%, and the insulation eccentricity is ≤3%.

5. The railway communication leaky cable according to claim 1, characterized in that: The overlap width of the corrugated structure of the outer conductor (3) is 9 mm to 12 mm, the corrugations of the corrugated structure are arc structures, the corrugation depth is 0.3 mm to 0.5 mm, and the corrugation width is 2 mm to 4 mm.

6. A railway communication leaky cable according to claim 1, characterized in that: The pitch of two adjacent slot groups is set to P, and P is 350mm-450mm; in each slot group, the slot spacings of two adjacent slots (31) are P1, P2, P3, P4, P5, P6, and P7 in sequence, and satisfy: P1=P3=P5=P7=P / 10, P2=P6=3P / 50, and P4=6P / 25.

7. The railway communication leaky cable according to claim 1, characterized in that: The cutting cross section S of each slot (31) on the outer conductor (3) satisfies: S=(L i -W)×W+πW 2 / 4,L i is the length of the i-th slot, i=1,2,3…,8, the cutting section S is 105mm 2 ~120mm 2 π is the ratio of circumference to diameter of a circle, and the groove width W is 3.4mm-3.8mm.

8. The railway communication leaky cable according to claim 1, characterized in that: The inclination angle α is 13°~18°.

9. The railway communication leaky cable according to claim 1, characterized in that: The outer sheath (4) is extruded with a color strip (41) corresponding to the position and direction of the slot hole (31).

10. The railway communication leaky cable according to claim 1, characterized in that: The outer sheath (4) is made of halogen-free, low-smoke, flame-retardant polyolefin material.

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