High temperature resistant low loss radio frequency coaxial cable, leaky coaxial cable and manufacturing method thereof

Abstract

The present application belongs to the technical field of communication transmission cables, and more specifically, to high temperature resistant and low loss radio frequency coaxial cables, leaky coaxial cables and methods for making the same. The radio frequency coaxial cable and leaky coaxial cable provided in the present application include an inner conductor, an insulating layer, an outer conductor and a sheath arranged in sequence from the inside to the outside. The present application can prepare radio frequency coaxial cables and leaky coaxial cables with excellent heat resistance by optimizing the structure and insulation process of the coaxial cable, while reducing the attenuation value, which helps the coaxial cable to operate stably under high power. Under the premise of meeting the requirements of standing wave testing and time domain fault point testing, that is, in the case of excellent heat resistance, compared with existing products, the 2700MHz attenuation test value of the radio frequency coaxial cable produced by the present application can be optimized by about 22.6%, and the 2700MHz attenuation test value of the leaky coaxial cable can be optimized by about 14.7%.

Description

Technical Field

[0001] The present application belongs to the technical field of communication transmission cables, and more specifically, to a high temperature resistant and low loss radio frequency coaxial cable, a leaky coaxial cable and a manufacturing method thereof. Background Art

[0002] In mobile communication systems, in order to expand the coverage of signals, the communication system needs to provide the antenna with a higher power transmission signal. However, the higher the signal power of the communication system, the greater the heat generated by the cables in the system during operation, and the higher the temperature between the inner and outer conductors inside the cable. The basic structure of the common RF coaxial cable currently includes an inner conductor, a physical foamed polyethylene insulation layer, an outer conductor and a sheath. When the operating temperature of the cable reaches above 80°C, the physical foamed polyethylene insulation layer will soften and deform, causing the cable structure to deform and thus affect signal transmission, and in severe cases, signal interruption.

[0003] Using polytetrafluoroethylene to push and sinter the polyethylene insulation layer can increase the heat resistance level of the insulation layer, allowing the RF coaxial cable to work at high power. However, due to the limitations of the blank volume and sintering process, this process cannot be used to continuously produce cables of large lengths, especially cables with large outer diameters, which is not conducive to mass production. In addition, although the use of polytetrafluoroethylene microporous film wrapped around the sintered insulation layer can increase the heat resistance of the insulation layer, the production efficiency of this process is low, and the attenuation of the produced RF coaxial cable is high.

[0004] Therefore, there is an urgent need to provide a high temperature resistant and low-loss radio frequency coaxial cable. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to provide a high-temperature resistant and low-loss RF coaxial cable, a leaky coaxial cable and a method for manufacturing the same, aiming to solve the problems of the existing RF coaxial cables and leaky coaxial cables, such as poor high-temperature resistance, high attenuation, high preparation cost and complex preparation process, while enabling the continuous production of long-length and large-diameter cables.

[0006] To achieve the above objectives, in a first aspect, the present application provides a high-temperature resistant and low-loss radio frequency coaxial cable, comprising an inner conductor, a composite insulation layer, an outer conductor and a sheath arranged in sequence from the inside to the outside, the composite insulation layer comprising an inner skin layer, a polyolefin resin layer and an outer skin layer in sequence from the inside to the outside, and the polyolefin resin layer comprising a heat-resistant resin layer and a low-loss resin layer in sequence from the inside to the outside.

[0007] Wherein, the heat-resistant resin layer and the low-loss resin layer are both foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer.

[0008] In a second aspect, the present application provides a high temperature resistant low loss leaky coaxial cable, comprising an inner conductor, a composite insulation layer, an outer conductor and a sheath arranged in sequence from the inside to the outside, wherein the composite insulation layer comprises an inner skin layer, a polyolefin resin layer and an outer skin layer in sequence from the inside to the outside, and the polyolefin resin layer comprises a heat resistant resin layer and a low loss resin layer in sequence from the inside to the outside,

[0009] Wherein, the heat-resistant resin layer and the low-loss resin layer are both foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer.

[0010] Preferably, the crosslinking degree of the heat-resistant resin layer is 75% to 80%.

[0011] Preferably, the cross-linking degree of the low-loss resin layer is 50% to 60%.

[0012] Preferably, the total thickness of the heat-resistant resin layer and the low-loss resin layer is 3 mm to 13.5 mm, wherein the thickness of the low-loss resin layer is greater than or equal to the thickness of the heat-resistant resin layer.

[0013] Preferably, the ratio of the thickness of the low-loss resin layer to the thickness of the heat-resistant resin layer is (1~1.5):1.

[0014] Preferably, the thickness of the heat-resistant resin layer is 1.5 mm to 5.5 mm, the thickness of the low-loss resin layer is 1.5 mm to 8 mm, and the thickness of the low-loss resin layer is greater than or equal to the thickness of the heat-resistant resin layer.

[0015] Preferably, the thickness of the endothelial layer is 0.05 mm to 0.15 mm.

[0016] Preferably, the thickness of the outer skin layer is 0.05 mm to 0.15 mm.

[0017] In a third aspect, the present application provides a method for manufacturing the above-mentioned coaxial cable, comprising the following steps:

[0018] S1, using molten polyolefin resin to extrude and wrap around the outer side of the inner conductor to form an inner skin layer;

[0019] S2, uniformly mixing the molten cross-linked polyolefin resin and the foaming gas to form an aerosol, then extruding the aerosol and wrapping it on the outside of the inner skin layer to form a first foaming layer, and performing radiation cross-linking to form a heat-resistant resin layer;

[0020] S3, continue to use the aerosol and the molten polyolefin resin to perform double-layer co-extrusion on the outside of the heat-resistant resin layer to form a second foaming layer and an outer skin layer covering the outside of the second foaming layer, and then perform radiation cross-linking to form a low-loss resin layer and an outer skin layer covering the outside of the low-loss resin layer;

[0021] S4. An outer conductor and an extruded sheath are sequentially prepared on the outside of the outer skin layer to obtain a high temperature resistant and low loss RF coaxial cable or a leaky coaxial cable.

[0022] Preferably, in step S1, the extrusion temperature is 145°C to 210°C.

[0023] Preferably, before extrusion in step S1, the inner conductor is heated to 100°C-110°C.

[0024] Preferably, in step S2, the foaming gas is nitrogen or carbon dioxide.

[0025] Preferably, in step S2, the extrusion temperature is 160° C. to 190° C., and the radiation cross-linking dosage is 18 Mrad to 20 Mrad.

[0026] Preferably, in step S3, the temperature of the double-layer co-extrusion is 160° C. to 190° C., and the dose of the radiation cross-linking is 12 Mrad to 15 Mrad.

[0027] Preferably, in step S4, the temperature of the extruded sheath is 115°C to 165°C.

[0028] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art:

[0029] (1) The present application utilizes the fact that when a radio frequency coaxial cable or a leaky coaxial cable transmits a high-power signal, the heat inside the cable presents a temperature gradient state from high to low, and provides a radio frequency coaxial cable or a leaky coaxial cable with excellent high temperature resistance and low loss. The composite insulation layer includes an inner skin layer, a polyolefin resin layer and an outer skin layer from the inside to the outside, wherein the polyolefin resin layer is provided with a heat-resistant resin layer and a low-loss resin layer from the inside to the outside, and both the heat-resistant resin layer and the low-loss resin layer are foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer. The heat-resistant resin layer with a relatively high cross-linking degree provided near the inner conductor in the above-mentioned composite insulation layer can well withstand the high temperature near the inner conductor, improve the overall heat resistance of the composite insulation layer, and prevent the composite insulation layer from aging and degradation at high temperatures; at the same time, a low-loss resin layer with a relatively low cross-linking degree is provided on the outside of the heat-resistant resin layer, which can even out the electric field and make the electric field distribution smooth, thereby reducing the loss of electric energy in the composite insulation layer and improving the electrical performance of the cable. Through the synergistic effect of the heat-resistant resin layer and the low-loss resin layer in the composite insulation layer, it is possible to effectively reduce the attenuation of RF coaxial cables and leaky coaxial cables while ensuring excellent heat resistance, and has excellent transmission performance.

[0030] (2) In the RF coaxial cable and leaky coaxial cable provided in the present application, the composite insulation layer is made of polyolefin. Compared with the prior art, the composite insulation layer provided in the present application has a simple formula, low cost, and is easy to obtain. It can also prepare high-temperature resistant and low-loss RF coaxial cables and leaky coaxial cables with excellent heat resistance.

[0031] (3) This application uses melting, physical foaming, and electron irradiation to prepare cross-linked heat-resistant resin layers and low-loss resin layers. Compared with the prior art, this application has the advantages of simple preparation steps, low processing difficulty, and no need for multiple program temperature control, and can be manufactured on a factory scale. At the same time, it also has the advantage of preparing composite insulation layers of any specification wire diameter, especially preparing composite insulation layers with large wire diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the end face structure of the coaxial cable provided in the embodiments and comparative examples of the present application;

[0033] Figure 2 It is a schematic diagram of the side structure of the coaxial cable provided in the embodiments and comparative examples of the present application;

[0034] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 1 is an inner conductor; 2 is a composite insulating layer; 3 is an outer conductor; 4 is a sheath; 21 is an inner skin layer; 22 is a polyolefin resin layer; and 23 is an outer skin layer. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] In the description of this application, it should be understood that the term "and / or" is a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " herein indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0037] In the description of the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0038] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0039] High-power RF coaxial cables and leaky coaxial cables will generate a lot of heat when transmitting high-power signals, and the heat generally presents a temperature gradient state from high to low from the inside to the outside. Among them, the inner conductor is the main heat generating part. Due to the skin effect of high-frequency current, the current is mainly concentrated on the surface of the conductor, resulting in an increase in the resistance loss on the surface of the inner conductor, thereby generating more heat and forming a high-temperature area. The heat generated by the inner conductor is transferred to the insulation layer by heat conduction. Because the thermal conductivity of the insulation layer is relatively poor, the heat transfer speed in the insulation layer is slow, resulting in a large temperature gradient inside the insulation layer. Using this principle, the inventor tried to combine polyolefin resin layers (heat-resistant resin layers, low-loss resin layers) with different cross-linking degrees, wherein a heat-resistant resin layer with a relatively high cross-linking degree is set near the inner conductor in the composite insulation layer, which can well withstand the high temperature near the inner conductor, improve the overall heat resistance of the composite insulation layer, prevent the composite insulation layer from aging and degradation at high temperatures, and can also bear the high electric field strength near the inner conductor. Furthermore, a low-loss resin layer with a relatively low degree of cross-linking is provided outside the heat-resistant resin layer, which can further even out the electric field, make the electric field distribution smoother, avoid electric field concentration, and help reduce the loss of electric energy in the composite insulation layer, improve the electrical performance of the cable, and efficiently transmit electric energy. Through the synergistic effect of the heat-resistant resin layer and the low-loss resin layer in the composite insulation layer, the RF coaxial cable and the leaky coaxial cable can operate stably under high-power working conditions.

[0040] Specifically, the present application provides a high temperature resistant low loss radio frequency coaxial cable or a leaky coaxial cable, both of which have a similar nested structure, and the schematic diagram of the end face structure is as follows: Figure 1 As shown in the figure, the side structure diagram is as follows Figure 2 As shown, it includes an inner conductor, a composite insulating layer, an outer conductor and a sheath arranged in sequence from the inside to the outside; the composite insulating layer includes an inner skin layer, a polyolefin resin layer and an outer skin layer in sequence from the inside to the outside;

[0041] The polyolefin resin layer is provided with a heat-resistant resin layer and a low-loss resin layer in sequence from the inside to the outside;

[0042] The heat-resistant resin layer and the low-loss resin layer are both foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer.

[0043] The high temperature resistant and low loss RF coaxial cable and leaky coaxial cable provided in the present application have similar nested structures. The only difference from the RF coaxial cable is that the outer conductor of the leaky coaxial cable is provided with a plurality of openings for allowing signal leakage, which is used for specific coverage areas.

[0044] It is understandable that the present application does not limit the process of setting openings on the outer conductor of the above-mentioned leaky coaxial cable. Those skilled in the art can select a suitable opening process according to the actual production conditions and actual application scenarios of the leaky coaxial cable, all of which are within the protection scope of the present application.

[0045] In some embodiments, the cross-linking degree of the heat-resistant resin layer is 75% to 80%.

[0046] In some embodiments, the cross-linking degree of the low-loss resin layer is 50% to 60%.

[0047] In some embodiments, the thickness of the endothelial layer is 0.05 mm to 0.15 mm.

[0048] In some embodiments, the total thickness of the heat-resistant resin layer and the low-loss resin layer is 3 mm to 13.5 mm, wherein the thickness of the low-loss resin layer is greater than or equal to the thickness of the heat-resistant resin layer.

[0049] In some embodiments, the ratio of the thickness of the low-loss resin layer to the thickness of the heat-resistant resin layer is (1~1.5):1.

[0050] In some embodiments, the thickness of the heat-resistant resin layer is 1.5 mm to 5.5 mm, the thickness of the low-loss resin layer is 1.5 mm to 8 mm, and the thickness of the low-loss resin layer is greater than or equal to the thickness of the heat-resistant resin layer.

[0051] In some embodiments, the thickness of the outer skin layer is 0.05 mm to 0.15 mm.

[0052] It is understandable that the present application does not limit the shape or material type of the inner conductor, and the inner conductors reported in the prior art are applicable to the present application. In some embodiments, the inner conductor includes but is not limited to copper clad aluminum wire, spiral corrugated copper tube, smooth copper tube, etc.

[0053] In some embodiments, the outer conductor is one of a spiral corrugated metal outer conductor and an annular corrugated metal outer conductor. In some embodiments, the metal outer conductor is a copper conductor.

[0054] In some embodiments, the sheath is a polyolefin sheath.

[0055] On the other hand, the present application also provides a method for manufacturing a high temperature resistant low loss radio frequency coaxial cable or a leaky coaxial cable, comprising the following steps:

[0056] S1, using molten polyolefin resin to extrude and wrap around the outer side of the inner conductor to form an inner skin layer;

[0057] S2, uniformly mixing the molten cross-linked polyolefin resin and the foaming gas to form an aerosol, then extruding the aerosol and wrapping it on the outside of the inner skin layer to form a first foaming layer, and performing radiation cross-linking to form a heat-resistant resin layer;

[0058] S3, continue to use the aerosol and the molten polyolefin resin to perform double-layer co-extrusion on the outside of the heat-resistant resin layer to form a second foaming layer and an outer skin layer covering the outside of the second foaming layer, and then perform radiation cross-linking to form a low-loss resin layer and an outer skin layer covering the outside of the low-loss resin layer;

[0059] S4. An outer conductor and an extruded sheath are sequentially prepared on the outside of the outer skin layer to obtain a high temperature resistant and low loss RF coaxial cable or a leaky coaxial cable.

[0060] In some embodiments, in step S1, the extrusion temperature is 140°C to 210°C.

[0061] In some embodiments, in step S1, the polyolefin resin includes but is not limited to one or more of polyethylene resin, polypropylene resin, and polystyrene resin.

[0062] In some embodiments, the polyethylene resin includes low-density polyethylene resin and / or high-density polyethylene resin.

[0063] In some embodiments, before the polyolefin is melt-extruded in step S1, the inner conductor is preheated, and the preheating temperature is lower than the extrusion temperature of the inner skin layer, so that the inner skin layer and the inner conductor are tightly bonded.

[0064] In some embodiments, in step S2, the foaming gas includes but is not limited to nitrogen or carbon dioxide.

[0065] In some embodiments, in step S2, the cross-linked polyolefin resin includes a polyolefin resin, a cross-linking agent, and a nucleating agent. The present application does not limit the source of the cross-linked polyolefin resin, which can be prepared in a laboratory or purchased from a commercial product.

[0066] In some embodiments, the polyolefin resin includes but is not limited to one or more of polyethylene resin, polypropylene resin, and polystyrene resin. In a specific embodiment, the polyolefin resin can be selected from but is not limited to low-density polyethylene with a brand name of XK1066L produced by Zibo Xianke Resin Co., Ltd. and high-density polyethylene with a brand name of XK1068H produced by Zibo Xianke Resin Co., Ltd.

[0067] It should be understood that the present application does not specifically limit the types of the above cross-linking agent and the above nucleating agent, and any cross-linking agent and nucleating agent reported in the prior art are applicable to the present application. In some embodiments, the above cross-linking agent includes but is not limited to triallyl isocyanurate, triallyl isocyanurate, etc.

[0068] In some embodiments, in the cross-linked polyolefin resin, the weight ratio of the polyolefin resin, the cross-linking agent and the nucleating agent is (90-100):(2-5):(1-2).

[0069] In some embodiments, the cross-linked polyolefin further includes an antioxidant and a photoinitiator, which can enhance the effect of radiation cross-linking.

[0070] In some embodiments, in step S2, the extrusion temperature is 160° C. to 190° C., and the radiation cross-linking dosage is 18 Mrad to 20 Mrad.

[0071] In some embodiments, in step S3, the temperature of the double-layer co-extrusion is 160° C. to 190° C., and the dose of the radiation cross-linking is 12 Mrad to 15 Mrad.

[0072] In some embodiments, in step S4, the temperature of the extruded sheath is 115°C to 165°C.

[0073] It is understandable that in order to meet the cross-linking requirements of the heat-resistant resin layer and the low-loss resin layer of high-temperature resistant and low-loss RF coaxial cables and leaky coaxial cables, technical personnel in this field can adaptively adjust the extrusion temperature, increase or decrease the radiation cross-linking dose and the thickness of the insulation layer according to the usage ratio of each component in the cross-linked polyolefin used in actual production, which are all within the scope of protection of this application.

[0074] The high temperature resistant and low loss radio frequency coaxial cable and leaky coaxial cable provided by the present application have good heat resistance and excellent attenuation performance. In actual work and application, they can operate stably at high power and have excellent transmission performance.

[0075] It should be understood that materials of the same or similar type, model, quality, nature or function as the reagents and instruments used in the following examples can be used to implement the present application. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0076] The following are examples and comparative examples:

[0077] Example 1

[0078] The radio frequency coaxial cable provided in this embodiment is applied to the cable model HCAAY-50-12 in the YD / T 1092 standard (cable specification is -12), and its end face structure schematic diagram is shown as follows: Figure 1 As shown in the figure, the side structure diagram is as follows Figure 2 As shown, from the inside to the outside, it includes an inner conductor 1, a composite insulation layer 2, an outer conductor 3 and a sheath 4, and the composite insulation layer 2 includes an inner skin layer 21, a polyolefin resin layer 22 and an outer skin layer 23 from the inside to the outside, wherein the above-mentioned polyolefin resin layer 22 is provided with a heat-resistant resin layer and a low-loss resin layer from the inside to the outside.

[0079] The radio frequency coaxial cable provided in this embodiment uses a copper-clad aluminum wire with a diameter of 4.8 mm as the inner conductor 1; the thickness of the inner skin layer 21 is 0.1 mm; the cross-linking degree of the heat-resistant resin layer is 76%, the foaming degree is 70%, and the thickness is 1.6 mm; the cross-linking degree of the low-loss resin layer is 57%, the foaming degree is 70%, and the thickness is 2.3 mm; the thickness of the outer skin layer 23 is 0.1 mm; a ring-shaped corrugated copper tube with a diameter of 13.85 mm is used as the outer conductor 3, and the diameter of the sheath 4 is 17.8 mm and the thickness is 0.85 mm.

[0080] The method for preparing the radio frequency coaxial cable in this embodiment comprises the following steps:

[0081] Step 1: Use high-frequency heating to heat the inner conductor 1 to 105°C, heat the low-density polyethylene (density 0.921g / cm³) to a molten state, use an extrusion mold to process, extrude and coat the inner conductor 1, the extrusion temperature is 220°C, and after extrusion, use compressed air to cool and shape to obtain the inner skin layer 21.

[0082] Step 2: heat and melt the cross-linked polyethylene (27 parts by weight of XK1066L, 68 parts by weight of XK1068H, 1.6 parts by weight of cross-linking agent, 1.7 parts by weight of nucleating agent XK1198, 0.2 parts by weight of antioxidant 1076, and 1.5 parts by weight of photoinitiator 1173) in an extruder, and then introduce nitrogen with a purity of 99.99% (pressure of 370 bar), and stir and mix to form an aerosol. The aerosol is extruded and coated on the outside of the inner skin layer 21, and the extrusion temperature is 195°C to form a uniformly foamed first foaming layer, which is then cooled step by step by cooling water to facilitate the full cooling of the first foaming layer, thereby ensuring that the first foaming layer and the above-mentioned inner skin layer are fully combined, and finally blown dry with hot air from a wind pump. The above-mentioned first foaming layer is irradiated with an electron beam with an irradiation dose of 20 Mrad to obtain a heat-resistant resin layer.

[0083] Step 3: Heat and melt the cross-linked polyethylene in an extruder, then introduce nitrogen with a purity of 99.99% (pressure of 370 bar), stir and mix to form an aerosol. Extrude and coat the aerosol on the outside of the heat-resistant resin layer, and at the same time, the outer skin layer is made of low-density polyethylene (density of 0.921g / cm³) and melted and uniformly extruded through the die head of the extruder. The second foaming layer and the outer skin layer are extruded together on the outer surface of the heat-resistant resin layer. After cooling and drying, the second foaming layer is irradiated with an electron beam with an irradiation dose of 13Mrad to obtain a low-loss resin layer and an outer skin layer 23 coated on the outside of the low-loss resin layer.

[0084] Step 4: Processing the outer conductor 3 outside the outer skin layer 23 .

[0085] Step 5: Melt the irradiated cross-linked polyethylene material and extrude it to coat the outer side of the outer conductor 3 to form a sheath 4, thereby obtaining a high temperature resistant and low loss radio frequency coaxial cable.

[0086] Comparative Example 1

[0087] The end face structure diagram of the RF coaxial cable provided in this comparative example is as follows Figure 1 As shown, it includes an inner conductor 1, a composite insulating layer 2, an outer conductor 3 and a sheath 4 from the inside to the outside, wherein the composite insulating layer 2 includes an inner skin layer 21, a polyolefin resin layer 22 and an outer skin layer 23 from the inside to the outside.

[0088] In the RF coaxial cable provided in this comparative example, the crosslinking degree of the polyolefin resin layer 22 is set to 85%, 80%, 70%, 60%, 50%, and 45% respectively, the foaming degree is 70%, the thickness is 3.9 mm, and the parameter information of other structures is the same as that of Example 1.

[0089] Comparative Example 2

[0090] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 85%, and the cross-linking degree of the low-loss resin layer is 57%.

[0091] Comparative Example 3

[0092] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 76%, and the cross-linking degree of the low-loss resin layer is 65%.

[0093] Comparative Example 4

[0094] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 76%, and the cross-linking degree of the low-loss resin layer is 45%.

[0095] Comparative Example 5

[0096] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 70%, and the cross-linking degree of the low-loss resin layer is 57%.

[0097] Example 2

[0098] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 50%.

[0099] Example 3

[0100] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 60%.

[0101] Example 4

[0102] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 80%, and the cross-linking degree of the low-loss resin layer is 50%.

[0103] Example 5

[0104] The rest is the same as Example 1, except that the cross-linking degree of the heat-resistant resin layer is 80%, and the cross-linking degree of the low-loss resin layer is 60%.

[0105] Example 6

[0106] Different from Embodiment 1, this embodiment provides a leaky coaxial cable for use in closed places such as subways, tunnels and buildings where communication signals cannot be normally covered.

[0107] The leaky coaxial cable provided in this embodiment is applied to the cable model HLRCTYZ-50-32 (cable specification is -32) in the YD / T 2491 standard, and its end face structure schematic diagram is shown as follows: Figure 1 As shown in the figure, the side structure diagram is as follows Figure 2 As shown, from the inside to the outside, it includes an inner conductor 1, a composite insulation layer 2, an outer conductor 3 and a sheath 4, and the composite insulation layer 2 includes an inner skin layer 21, a polyolefin resin layer 22 and an outer skin layer 23 from the inside to the outside, wherein the polyolefin resin layer 22 is provided with a heat-resistant resin layer and a low-loss resin layer from the inside to the outside.

[0108] The leaky coaxial cable provided in this embodiment adopts a smooth copper tube with a diameter of 13.1 mm as the inner conductor 1; the thickness of the inner skin layer 21 is 0.15 mm; the crosslinking degree of the heat-resistant resin layer is 76%, the foaming degree is 76%, and the thickness is 4 mm; the crosslinking degree of the low-loss resin layer is 57%, the foaming degree is 76%, and the thickness is 5.8 mm; the thickness of the outer skin layer 23 is 0.1 mm; a smooth copper strip with a thickness of 0.1 mm is punched and longitudinally wrapped into a copper tube, and the insulating cable core mentioned in the present application is inserted into the copper tube. After drawing, the outer conductor copper tube (final size 33.5 mm) and the cable core are tightly fitted and then a layer of low-smoke halogen-free flame-retardant sheath with a thickness of 2.5 mm is extruded through the sheath together, and the diameter of the sheath 4 is 37 mm.

[0109] The method for preparing the leaky coaxial cable in this embodiment comprises the following steps:

[0110] Step 1: Use high-frequency heating to heat the inner conductor 1 to 105°C, heat the low-density polyethylene (density 0.921g / cm³) to a molten state, use an extrusion mold to process, extrude and coat the inner conductor 1, the extrusion temperature is 220°C, and after extrusion, use compressed air to cool and shape to obtain the inner skin layer 21.

[0111] Step 2: heat and melt the cross-linked polyethylene (27 parts by weight of XK1066L, 68 parts by weight of XK1068H, 1.6 parts by weight of cross-linking agent, 1.7 parts by weight of nucleating agent XK1198, 0.2 parts by weight of antioxidant 1076, and 1.5 parts by weight of photoinitiator 1173) in an extruder, and then introduce nitrogen with a purity of 99.99% (pressure of 370 bar), and stir and mix to form an aerosol. The aerosol is extruded and coated on the outside of the inner skin layer 21, and the extrusion temperature is 195°C to form a uniformly foamed first foaming layer, which is then cooled step by step by cooling water to facilitate the full cooling of the first foaming layer, thereby ensuring that the first foaming layer and the above-mentioned inner skin layer are fully combined, and finally blown dry with hot air from a wind pump. The above-mentioned first foaming layer is irradiated with an electron beam with an irradiation dose of 20 Mrad to obtain a heat-resistant resin layer.

[0112] Step 3: Heat and melt the cross-linked polyethylene in an extruder, then introduce nitrogen with a purity of 99.99% (pressure of 370 bar), stir and mix to form an aerosol. Extrude and coat the aerosol on the outside of the heat-resistant resin layer, and at the same time, the outer skin layer is made of low-density polyethylene (density of 0.921g / cm³) and melted and uniformly extruded through the die head of the extruder. The second foaming layer and the outer skin layer are extruded together on the outer surface of the heat-resistant resin layer. After cooling and drying, the second foaming layer is irradiated with an electron beam with an irradiation dose of 13Mrad to obtain a low-loss resin layer and an outer skin layer 23 coated on the outside of the low-loss resin layer.

[0113] Step 4: Use a 0.1mm thick smooth copper strip to punch holes and wrap it longitudinally into a copper tube. At the same time, insert the above-mentioned insulating cable core into the copper tube. After drawing, the outer conductor copper tube and the cable core are tightly fitted, and then a layer of low-smoke halogen-free flame-retardant sheath is extruded through the sheath to obtain a high-temperature resistant and low-loss leaky coaxial cable.

[0114] Comparative Example 6

[0115] The schematic diagram of the end face structure of the leaky coaxial cable provided in this comparative example is as follows Figure 1 As shown, it includes an inner conductor 1, a composite insulating layer 2, an outer conductor 3 and a sheath 4 from the inside to the outside, wherein the composite insulating layer 2 includes an inner skin layer 21, a polyolefin resin layer 22 and an outer skin layer 23 from the inside to the outside.

[0116] In the leaky coaxial cable provided in this comparative example, the crosslinking degree of the polyolefin resin layer 22 is set to 85%, 80%, 70%, 60%, 50%, and 45% respectively, the foaming degree is 76%, the thickness is 9.8 mm, and the parameter information of other structures is the same as that of Example 1.

[0117] Comparative Example 7

[0118] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 85%, and the cross-linking degree of the low-loss resin layer is 57%.

[0119] Comparative Example 8

[0120] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 65%.

[0121] Comparative Example 9

[0122] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 45%.

[0123] Comparative Example 10

[0124] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 70%, and the cross-linking degree of the low-loss resin layer is 57%.

[0125] Example 7

[0126] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 50%.

[0127] Example 8

[0128] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 75%, and the cross-linking degree of the low-loss resin layer is 60%.

[0129] Example 9

[0130] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 80%, and the cross-linking degree of the low-loss resin layer is 50%.

[0131] Example 10

[0132] The rest is the same as Example 6, except that the cross-linking degree of the heat-resistant resin layer is 80%, and the cross-linking degree of the low-loss resin layer is 60%.

[0133] The performance of the coaxial cables prepared in the embodiments and comparative examples was tested, and the test method was as follows:

[0134] 1) Heat resistance of composite insulation layer:

[0135] The semi-finished insulation products of the coaxial cables prepared in the examples and comparative examples, i.e., the composite insulation layer, were subjected to a heat extension test at a temperature of 200°C with reference to the standard GB / T2951.21-2008 "General test methods for insulation and sheath materials of electric and optical cables, Part 21: Special test methods for elastomer mixtures - ozone resistance test - heat extension test - mineral oil immersion test". The heat extension performance of the insulation reflects the heat resistance of the composite insulation layers of different structures after irradiation cross-linking. If the heat extension test is qualified, it is recorded as Pass; if the heat extension test is unqualified, it is recorded as Fail.

[0136] The finished cables made in the embodiment and the comparative example were respectively connected to the analog circuit system, and after continuous operation for 36 hours at rated power, attenuation, standing wave and time domain fault point tests were performed. If the standing wave and time domain fault point tests were qualified, it was recorded as Pass, indicating that the heat resistance of the composite insulation layer was excellent and could well withstand the heat generated when the cable was powered on and operated normally; if the standing wave and time domain fault point tests were unqualified, it was recorded as Fail, indicating that the heat resistance of the composite insulation layer did not meet the standards.

[0137] 2) Transmission performance of coaxial cable:

[0138] The transmission performance of the RF coaxial cable was tested with reference to YDT 1092-2013 "Communication Cable Wireless Communication 50Ω Foam Polyolefin Insulated Corrugated Copper Tube Outer Conductor RF Coaxial Cable", Part 5.6.8: Attenuation Constant Test".

[0139] The transmission performance of the leaky coaxial cable is tested with reference to YD / T 2491-2023 "Communication Cable Physical Foamed Polyethylene Insulation Longitudinal Copper Tape Outer Conductor Radiant Leaky Coaxial Cable".

[0140] This application reflects the transmission performance of the coaxial cable by testing its attenuation index at 2700MHz.

[0141] The test results are shown in Table 1, Table 2, Table 3 and Table 4.

[0142] Table 1 Heat resistance and attenuation performance of the RF coaxial cable prepared in Comparative Example 1

[0143]

[0144] Table 2 Heat resistance and attenuation performance of the RF coaxial cables prepared in Examples 1 to 5 and Comparative Examples 2 to 5

[0145]

[0146] Table 3 Heat resistance and attenuation performance of the leaky coaxial cable prepared in Comparative Example 6

[0147]

[0148] Table 4 Heat resistance and attenuation performance of leaky coaxial cables made in Examples 6 to 10 and Comparative Examples 7 to 10

[0149]

[0150] It can be seen from Tables 1 and 3 that a coaxial cable having both heat resistance and low loss performance cannot be prepared by simply adjusting the crosslinking degree of the polyolefin resin layer in the composite insulation layer.

[0151] It can be seen from Table 2 and Table 4 that when the cross-linking degree of the heat-resistant resin layer and the cross-linking degree of the low-loss resin layer in the composite insulation layer are not properly matched, the heat resistance or attenuation performance of the coaxial cable will be unqualified.

[0152] By comparing Table 1 and Table 2, it can be seen that under the condition that all heat resistance properties are qualified, the attenuation value of the RF coaxial cable produced in the present application can be optimized by 22.6% compared with the minimum attenuation value of the traditional RF coaxial cable (corresponding to the cable product with a cross-linking degree of 70% of the polyolefin resin layer in Example 1), which can significantly improve the transmission performance of the RF coaxial cable.

[0153] By comparing Table 3 and Table 4, it can be seen that under the condition that all heat resistance properties are qualified, the attenuation value of the leaky coaxial cable produced in the present application can be optimized by 14.7% compared with the minimum attenuation value of the traditional leaky coaxial cable (corresponding to the cable product with a cross-linking degree of 70% of the polyolefin resin layer in Example 6), that is, the leaky coaxial cable produced in the present application has excellent transmission performance.

[0154] It can be seen from Tables 1 to 4 that, compared with the RF coaxial cable with qualified heat resistance prepared in Comparative Example 1 and the leaky coaxial cable with qualified heat resistance prepared in Comparative Example 6, Examples 1 to 5 and Examples 6 to 10 provide a heat-resistant resin layer and a low-loss resin layer in sequence from the inside to the outside of the polyolefin resin layer, and adjust the degree of cross-linking of the heat-resistant resin layer and the low-loss resin layer, thereby ensuring heat resistance while reducing the attenuation index of the coaxial cable and having excellent transmission performance.

[0155] In summary, the present application arranges a heat-resistant resin layer with a cross-linking degree of 75% to 80% near the inner conductor in the composite insulation layer of the coaxial cable, and arranges a low-loss resin layer with a cross-linking degree of 50% to 60% on the outside of the heat-resistant resin layer. Through the synergistic effect of the heat-resistant resin layer and the low-loss resin layer in the composite insulation layer, the manufactured RF coaxial cable and leaky coaxial cable can reduce the attenuation index while ensuring excellent heat resistance, which helps the coaxial cable to operate stably under high power.

[0156] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A high temperature resistant low loss radio frequency coaxial cable, comprising an inner conductor (1), a composite insulating layer (2), an outer conductor (3) and a sheath (4) arranged in sequence from the inside to the outside, wherein the composite insulating layer comprises an inner skin layer (21), a polyolefin resin layer (22) and an outer skin layer (23) in sequence from the inside to the outside, characterized in that: The polyolefin resin layer (22) is provided with a heat-resistant resin layer and a low-loss resin layer in sequence from the inside to the outside; Wherein, the heat-resistant resin layer and the low-loss resin layer are both foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer.

2. A high temperature resistant low loss leaky coaxial cable, comprising an inner conductor (1), a composite insulation layer (2), an outer conductor (3) and a sheath (4) arranged in sequence from the inside to the outside, wherein the composite insulation layer comprises an inner skin layer (21), a polyolefin resin layer (22) and an outer skin layer (23) in sequence from the inside to the outside, characterized in that: The polyolefin resin layer (22) is provided with a heat-resistant resin layer and a low-loss resin layer in sequence from the inside to the outside; Wherein, the heat-resistant resin layer and the low-loss resin layer are both foamed cross-linked polyolefin resins, and the cross-linking degree of the heat-resistant resin layer is higher than that of the low-loss resin layer.

3. The coaxial cable according to claim 1 or 2, characterized in that: The crosslinking degree of the heat-resistant resin layer is 75% to 80%.

4. The coaxial cable according to claim 1 or 2, characterized in that: The crosslinking degree of the low-loss resin layer is 50% to 60%.

5. The coaxial cable according to claim 1 or 2, characterized in that: The total thickness of the heat-resistant resin layer and the low-loss resin layer is 3 mm to 13.5 mm, wherein the thickness of the low-loss resin layer is greater than or equal to the thickness of the heat-resistant resin layer.

6. The coaxial cable according to claim 5, characterized in that: The thickness of the heat-resistant resin layer is 1.5 mm to 5.5 mm; and / or, The thickness of the low-loss resin layer is 1.5 mm to 8 mm; and / or, The thickness of the endothelial layer (21) is 0.05 mm to 0.15 mm; and / or, The thickness of the outer skin layer (23) is 0.05 mm to 0.15 mm.

7. A method for manufacturing a coaxial cable as claimed in claim 1 or 2, characterized in that: The steps include: S1, using molten polyolefin resin to extrude and wrap around the outer side of the inner conductor (1) to form an inner skin layer (21); S2, uniformly mixing the molten cross-linked polyolefin resin and the foaming gas to form an aerosol, then extruding the aerosol and wrapping it on the outside of the inner skin layer (21) to form a first foaming layer, and performing radiation cross-linking to form a heat-resistant resin layer; S3, continue to use the aerosol and the molten polyolefin resin to perform double-layer co-extrusion on the outside of the heat-resistant resin layer to form a second foaming layer and an outer skin layer covering the outside of the second foaming layer, and then perform radiation cross-linking to form a low-loss resin layer and an outer skin layer (23) covering the outside of the low-loss resin layer; S4. An outer conductor (3) and an extruded sheath (4) are sequentially prepared on the outside of the outer skin layer (23) to obtain a high temperature resistant and low loss radio frequency coaxial cable or a leaky coaxial cable.

8. The method according to claim 7, characterized in that: In step S1, the extrusion temperature is 145°C to 210°C.

9. The manufacturing method according to claim 7, characterized in that: In step S2, the foaming gas is nitrogen or carbon dioxide, the extrusion temperature is 160° C. to 190° C., and the radiation cross-linking dosage is 18 Mrad to 20 Mrad.

10. The manufacturing method according to claim 7, characterized in that: In step S3, the temperature of the double-layer co-extrusion is 160° C. to 190° C., and the dose of the radiation cross-linking is 12 Mrad to 15 Mrad.

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