Low-loss radio frequency coaxial cable and manufacturing method thereof

Abstract

The invention belongs to the field of wireless communication, and particularly relates to a low-loss radio frequency coaxial cable and a manufacturing method thereof. The inner conductor of the radio frequency coaxial cable is subjected to surface treatment, so that the adhesive force between the inner conductor and the insulating layer is improved, the transmission loss is reduced, and the signal transmission performance is improved. After the surface of the inner conductor is subjected to proper process treatment, the contact performance can be improved, and signal reflection and loss increase can be avoided. On the premise of meeting the test requirements of insulation adhesive force, standing wave and insulation voltage resistance, the surface of the inner conductor of the radio-frequency coaxial cable is moderately processed, so that the attenuation index of the radio-frequency coaxial cable is integrally optimized by 3.3%-6.0% under the frequency bands of 900MHz, 1800MHz, 2700MHz and the like compared with that of an existing product.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communications, and more specifically, relates to a low-loss radio frequency coaxial cable and a manufacturing method thereof. Background Art

[0002] RF coaxial cable is a cable used to transmit electromagnetic energy in the radio frequency range. It is widely used in radio communications, broadcasting, television, radar, navigation and other fields. Existing RF coaxial cables are usually composed of an inner conductor, an insulating layer, an outer conductor and a sheath layer. The inner conductor is usually made of high-purity copper or silver and is responsible for transmitting radio frequency signals; the insulating layer is located between the inner conductor and the outer conductor to isolate the two and act as a supporting structure; the outer conductor is used to transmit signals and shield external signals.

[0003] The product structure of conventional RF coaxial cable complies with the industry standard YD / T1092 "50 Ω Foamed Polyolefin Insulated Corrugated Copper Tube Outer Conductor RF Coaxial Cable for Communication Cable and Wireless Communication". Its insulation layer is usually divided into three layers. The solid thin insulation layer close to the inner and outer conductors of the cable is mainly made of low-density polyethylene (LDPE) or high-density polyethylene (HDPE), mixed with ethylene-vinyl acetate (EVA) resin with bonding effect; the foam insulation layer in the middle is thicker, and its material composition is mainly LDPE and HDPE mixture mixed with nucleating agent, and is made by physical foaming continuous extrusion process. This kind of insulation structure can better take into account the requirements of attenuation, cost and production efficiency. However, there are problems in the prior art that the dielectric constant of the solid insulation layer is large and the cable transmission attenuation is too high. The commonly used insulation layer between the inner and outer conductors is a polyolefin physical foaming structure with a dielectric constant of about 1.25. However, the physical foaming layer cannot be well bonded to the surface of the inner conductor, which will cause the insulation layer and the inner conductor to separate, causing changes in the cable structure and affecting normal transmission.

[0004] In order to solve the above problems, the usual practice is to first extrude a solid inner skin layer on the surface of the inner conductor, and then extrude a foam layer on the inner skin layer. The role of the solid inner skin layer is to bond the inner conductor and the foamed polyethylene layer. However, since the inner skin layer is generally a mixture of solid polyethylene and glue EVA, the comprehensive dielectric constant is about 2.4 (data at 1 MHz), compared with the dielectric constant of 1.25 of the physical foam layer, the existence of the inner skin layer greatly increases the transmission loss of the cable.

[0005] Therefore, an improved radio frequency coaxial cable structure is urgently needed to solve the above problems. Summary of the invention

[0006] In view of the defects of the prior art, the purpose of the present invention is to provide a low-loss radio frequency coaxial cable and a method for manufacturing the same. By roughening the surface of the inner conductor, the contact between the inner conductor and the insulating layer is improved, and the solid inner skin layer is omitted, thereby reducing cable losses and improving signal transmission performance, thereby solving the technical problems of the prior art such as poor contact between the inner conductor and the insulating layer and high transmission loss.

[0007] To achieve the above object, the present invention provides a low-loss radio frequency coaxial cable, comprising an inner conductor, a composite insulating layer, an outer conductor and an outer sheath which are concentrically nested from inside to outside; The composite insulating layer comprises a foamed resin layer and a solid outer skin layer; wherein the foamed resin layer is in direct contact with the inner conductor, and the solid outer skin layer is in direct contact with the outer conductor; The surface of the inner conductor directly contacting the foamed resin layer has a microscopic rough structure formed by roughening treatment, and the roughness thereof is 0.5 μm to 5.0 μm.

[0008] Further preferably, the surface roughness of the inner conductor is 1 μm to 3 μm.

[0009] Further preferably, the inner conductor surface roughening treatment method is laser roughening, chemical etching, mechanical grinding or electrochemical treatment.

[0010] According to another aspect of the present invention, there is provided a method for manufacturing the radio frequency coaxial cable, comprising the following steps: (1) The inner conductor is subjected to surface roughening treatment so that its roughness is controlled within the range of 0.5 μm to 5.0 μm; (2) double-layer co-extrusion is performed on the surface of the roughened inner conductor to prepare a foamed resin layer and a solid outer skin layer; (3) An outer conductor and an outer sheath are sequentially prepared outside the solid outer skin layer.

[0011] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art: (1) The present invention significantly improves the contact between the inner conductor and the insulating layer by roughening the surface of the inner conductor, while omitting the solid inner cortex layer and reducing the transmission loss of the cable. Experimental tests show that, under the same other process conditions, the inner conductor surface of the RF coaxial cable is moderately roughened and the inner cortex layer is removed. The attenuation index is overall optimized (reduced) by 3.3% to 6.0% in the 900MHz, 1800MHz, and 2700MHz frequency bands compared to the prior art that is not roughened and contains an inner cortex layer.

[0012] (2) The optimized cable structure of the present invention has better signal transmission performance and anti-interference ability, and is suitable for radio frequency communication scenarios.

[0013] (3) The surface roughness of the low-loss RF coaxial inner conductor provided by the present invention is controlled within the range of 0.5 μm to 5.0 μm, which can not only improve the contact between the inner conductor and the insulating layer, but also avoid signal reflection and loss increase.

[0014] (4) The low-loss RF coaxial cable manufacturing method provided by the present invention is simple and easy to implement, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the end face structure of the radio frequency coaxial cable of comparative example 1 of the present invention.

[0016] Figure 2 It is a schematic diagram of the side structure of the radio frequency coaxial cable of comparative example 1 of the present invention.

[0017] Figure 3 This is a schematic diagram of the end face structure of the radio frequency coaxial cable according to Example 1 of the present invention.

[0018] Figure 4 This is a schematic diagram of the side structure of the radio frequency coaxial cable according to Example 1 of the present invention.

[0019] Figure 5 This is a schematic diagram of the microstructure of the roughened surface of the inner conductor in Example 1 of the present invention.

[0020] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 1 - inner conductor; 2 - composite insulation layer; 3 - outer conductor; 4 - outer sheath; 21 - solid inner skin layer; 22 - foamed resin layer; 23 - solid outer skin layer. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0022] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0023] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0024] In the present invention, unless otherwise specified and / or described, all numerical values ​​involving the amounts of components are "parts by weight" from beginning to end. The process parameters in the following examples without specifying specific conditions are usually based on conventional conditions.

[0025] Prior art radio frequency coaxial cables, such as Figure 1 and Figure 2 As shown, it includes an inner conductor 1, a composite insulation layer 2, an outer conductor 3 and an outer sheath 4 which are concentrically nested from the inside to the outside. The composite insulation layer is composed of a solid inner skin layer 21, a foamed resin layer 22 and a solid outer skin layer 23; wherein the solid inner skin layer is used to bond the metal inner conductor and the thermoplastic foamed polyolefin resin insulation layer. In order to improve the bonding effect, the solid inner skin layer is usually mixed with a resin with a bonding effect. However, the addition of a bonding resin will cause the solid inner skin layer to have a high dielectric constant, which increases the transmission loss of the cable; on the other hand, directly connecting the metal surface of the inner conductor to the thermoplastic resin has poor contact due to the different types of materials. Poor contact can also easily lead to a decrease in the electrical performance of the cable. In view of these technical defects, the present invention provides a low-loss radio frequency coaxial cable, and its end face and side structure schematic diagrams are shown as follows: Figure 3 and Figure 4 As shown, it includes an inner conductor 1, a composite insulation layer 2, an outer conductor 3 and an outer sheath 4 which are concentrically nested from the inside to the outside. The composite insulation layer is composed of a foamed resin layer 22 and a solid outer skin layer 23; the foamed resin layer 22 is in direct contact with the inner conductor 1, and the solid outer skin layer 23 is in direct contact with the outer conductor 3. The surface of the inner conductor 1 in direct contact with the foamed resin layer 22 also has a microscopic rough structure formed by roughening treatment, and its roughness (Ra) ranges from 0.5 μm to 5.0 μm.

[0026] The present invention provides a radio frequency coaxial cable that improves the contact between the inner conductor and the insulating layer by improving the surface structure of the inner conductor and omitting the inner cortex layer. Traditional radio frequency coaxial cables require the surfaces of the inner conductor and the outer conductor to remain smooth to prevent reflection of the cable due to defects in the conductor surface, which affects the use. However, the inventors of the present application unexpectedly discovered that when the surface of the inner conductor is moderately roughened, it does not actually affect the electrical performance of the product within the standard range. Moreover, the roughened inner conductor surface also improves its adhesion to the foamed polyolefin layer insulation layer. At the same time, since the roughened inner conductor surface increases the contact with the foamed insulation layer, the original solid inner cortex structure can be directly omitted. Omitting this structure means that the transmission loss of the original solid inner cortex to the cable is also avoided at the same time, so the transmission loss of the coaxial cable can be further reduced.

[0027] The roughness (Ra) of the inner conductor surface ranges from 0.5 μm to 3.0 μm, and the preferred range is from 1.0 μm to 3.0 μm. This roughness range can ensure good contact between the inner conductor and the insulation layer, while avoiding increased signal reflection and loss due to excessive roughness.

[0028] The inner conductor surface roughening treatment method of the present invention can adopt laser roughening, chemical etching, mechanical grinding or electrochemical treatment to form a uniform concave-convex structure on the surface of the inner conductor and increase the contact area with the insulating layer. However, the roughening degree of the inner conductor surface must be strictly controlled to avoid the conductor surface size fluctuation due to excessive roughening affecting signal transmission, or the electric field concentration effect caused by the sharp metal edges due to excessive roughening causing electrical breakdown.

[0029] The surface of the inner conductor of the present invention is roughened to form a microscopic rough structure. It is understandable that the present application does not limit the shape or material type of the inner conductor and the outer conductor themselves, and the inner conductor and the outer conductor reported in the prior art are all applicable to the present application. In some embodiments, the above-mentioned inner conductor includes but is not limited to copper-clad aluminum wire, spiral corrugated copper tube, smooth copper tube, etc., and high-purity silver material can also be used in other embodiments. The above-mentioned outer conductor is one of a spiral corrugated metal outer conductor, an annular corrugated metal outer conductor or a metal wire braided outer conductor. In some embodiments, the above-mentioned metal inner conductor and outer conductor are both copper conductors.

[0030] Compared with the prior art, the insulating layer between the inner conductor and the outer conductor of the radio frequency coaxial cable of the present invention omits the original solid inner skin layer used to bond the inner conductor and the foamed insulating layer, and the remaining foamed resin layer and the solid outer skin layer can adopt the insulating layer materials reported in the prior art. For example, the foamed resin layer can be a foamed polyolefin, including but not limited to foamed polyethylene, with a foaming degree of 40%-85% and a thickness of 3mm-15mm, and the solid outer skin layer is a solid polyolefin, such as low-density polyethylene LDPE (density range of 0.910 g / cm³ - 0.930 g / cm³) or high-density polyethylene HDPE (density range of 0.940 g / cm³ - 0.976 g / cm³), with a thickness of 0.05mm~0.15mm.

[0031] In some embodiments, the outer sheath is a polyolefin sheath, including but not limited to polyethylene resin, polypropylene resin, polystyrene resin, etc., and the thickness of the outer sheath is 0.3mm~4mm.

[0032] The improved radio frequency coaxial cable of the present invention has a composite insulating layer composed of a foamed resin layer and a solid outer skin layer, omitting the traditional solid inner skin layer. After the surface roughening treatment, the surface of the inner conductor directly contacts the foamed resin layer, which significantly improves its contact and reduces signal transmission loss.

[0033] The present invention also provides a method for manufacturing the radio frequency coaxial cable, comprising the following steps: (1) The inner conductor is subjected to surface roughening treatment so that its roughness is controlled within the range of 0.5 μm to 5.0 μm; (2) double-layer co-extrusion is performed on the surface of the roughened inner conductor to prepare a foamed resin layer and a solid outer skin layer; (3) An outer conductor and an outer sheath are sequentially prepared outside the solid outer skin layer.

[0034] The roughening treatment in step (1) of the present invention is not limited to a specific roughening method, and may be, for example, laser roughening, chemical etching, mechanical grinding or electrochemical treatment. The preferred roughening method is a laser surface roughening process, which can ensure a high degree of consistency in the treatment process, and is easy to perform online synchronous processing, which is convenient for promotion.

[0035] In some embodiments, step (1) uses chemical etching to treat the surface of the inner conductor, the etching solution is a dilute nitric acid solution, the etching time is 5-10 minutes, and a uniform microscopic rough structure is formed, and the roughness is preferably controlled within the range of 1.0 μm to 3.0 μm.

[0036] In other embodiments, the surface of the inner conductor is processed by laser, specifically, the laser power is controlled at 10W-400W, the scanning speed is between 600mm / s and 1200mm / s, the scanning spacing is between 0.05mm and 0.12mm, and the roughness is preferably controlled within the range of 1.0 μm to 3.0 μm. The laser can be a common solid laser (365nm solid laser or 1064nm solid laser), a fiber laser, a gas laser (carbon dioxide laser or copper vapor laser) or a semiconductor laser, preferably a fiber laser.

[0037] In some embodiments, the inner conductor with roughened surface is a preheated inner conductor. The surface preheating temperature is usually controlled at 80° C.-120° C. according to different products, so that the foaming layer can better adhere to the conductor surface.

[0038] In some embodiments, step (2) specifically comprises: uniformly mixing molten polyolefin and foaming gas to form an aerosol, and co-extruding the aerosol and the molten polyolefin for preparing the solid outer skin layer on the surface of the inner conductor after roughening treatment to form the foamed resin layer and the solid outer skin layer coated on the outside of the foamed resin layer. The extrusion temperature is 130°C to 210°C to ensure that the foamed polyolefin material is tightly combined with the inner conductor to form the foamed resin layer.

[0039] In step (3) of the present invention, an outer conductor and an outer sheath are sequentially arranged outside the insulating layer according to conventional processes to complete the manufacture of the cable.

[0040] The following are examples and comparative examples: Comparative Example 1 The RF coaxial cable provided in this comparative example is applied to the traditional cable model HCAAY-50-12 in the YD / T1092 standard (cable specification is -12), and its end face and side face structure schematic diagrams are shown as follows: Figure 1 and Figure 2 As shown, an inner conductor 1, a composite insulating layer 2, an outer conductor 3 and an outer sheath 4 are coaxially arranged from the inside to the outside, wherein the composite insulating layer 2 includes a solid inner skin layer 21, a foamed resin layer 22 and a solid outer skin layer 23 from the inside to the outside, wherein the inner conductor is a solid copper-clad aluminum wire, the solid inner skin layer 21 and the solid outer skin layer 23 are low-density polyethylene, the foamed resin layer 22 is foamed polyethylene, the outer conductor 3 is a copper strip welded corrugated tube, and the outer sheath 4 is polyethylene. The preparation method of the radio frequency coaxial cable is carried out according to the following steps: (1) Low-density polyethylene and glue (EVA resin) are mixed in a ratio of 3:1 and extruded at 130-220°C, and evenly coated on the surface of a solid copper-clad aluminum inner conductor with a diameter of 4.8 mm to form a bonded solid inner skin layer with a thickness of 0.1 mm.

[0041] (2) High-density polyethylene, low-density polyethylene and nucleating agent (a mixture of cyclodextrin nanosponge (NS) and vinyl triethoxysilane (VTES), mass ratio of 1:1) were mixed in a mass ratio of 70:29:1, and after high-temperature plasticization at 130-195°C, high-pressure gas (carbon dioxide) was injected into the molten state. After being fully mixed in the screw, they were extruded at high pressure and attached to the inner skin layer for foaming and cooling to form an insulating foamed cable core with a diameter of 12.6 mm and a foaming degree of 75%.

[0042] (3) At the same time as the foaming layer in the previous step, a low-density polyethylene solid outer layer with a thickness of about 0.1 mm is extruded, which is evenly coated on the periphery of the foaming layer, so that the insulation layer has better sealing properties.

[0043] (4) A 0.21 mm thick smooth copper strip is welded into a copper tube by forming argon arc welding and then inserted into the foam cable core for corrugation. The corrugation trough sinks into the cable core insulation layer, so that the outer conductor and the insulation layer fit tightly into a whole. The outer diameter of the corrugation peak is 13.85 mm.

[0044] (5) A layer of polyethylene sheath material is extruded on the surface of the outer conductor, and the sheath thickness is 0.8 mm.

[0045] Example 1 The radio frequency coaxial cable provided in this embodiment is applied to the traditional cable of model HCAAY-50-12 in the YD / T1092 standard (cable specification is -12), and its end face and side face structure schematic diagrams are shown as follows: Figure 3 and Figure 4 As shown, an inner conductor 1, a composite insulating layer 2, an outer conductor 3 and an outer sheath 4 are coaxially arranged from the inside to the outside, wherein the composite insulating layer 2 includes a foamed resin layer 22 and a solid outer skin layer 23 from the inside to the outside, wherein the inner conductor is a copper-clad aluminum wire with a surface roughness of 1 μm after roughening treatment, the solid outer skin layer 23 is low-density polyethylene with a thickness of 0.1 mm, the foamed resin layer 22 is foamed polyethylene, the outer conductor 3 is a corrugated copper strip, and the outer sheath 4 is polyethylene with a thickness of 0.8 mm. The preparation method of the radio frequency coaxial cable is carried out according to the following steps: (1) The copper-clad aluminum with a diameter of 4.8 mm was roughened by a fiber laser. The laser power was 50 W, the scanning speed was 1000 mm / s, the scanning spacing was 0.08 mm, and the surface roughness was controlled at 1 μm. The schematic diagram of the inner conductor surface after roughening is shown in the figure. Figure 5 Then it is preheated and the temperature before entering the foaming machine head is 80~120℃.

[0046] (2) High-density polyethylene, low-density polyethylene and a nucleating agent (a mixture of cyclodextrin nanosponge (NS) and vinyl triethoxysilane (VTES), mass ratio 1:1) were mixed in a mass ratio of 70:29:1, and after being plasticized at a high temperature of 130-195°C, high-pressure gas (carbon dioxide) was injected into the molten state. After being fully mixed in the screw, the mixture was directly attached to the inner conductor with a roughened surface by high-pressure extrusion for foaming and cooling to form an insulating foamed cable core with a diameter of 12.6 mm and a foaming degree of 75%, thereby obtaining a foamed resin layer.

[0047] (3) At the same time as the foaming layer in the previous step, a low-density polyethylene solid outer layer with a thickness of about 0.1 mm is extruded, which is evenly coated on the periphery of the foaming resin layer, so that the insulation layer has better sealing properties.

[0048] (4) A 0.21 mm thick smooth copper strip is welded into a copper tube by forming argon arc welding and then inserted into the foam cable core for corrugation. The corrugation trough sinks into the cable core insulation layer, so that the outer conductor and the insulation layer fit tightly into a whole. The outer diameter of the corrugation peak is 13.85 mm.

[0049] (5) A layer of polyethylene sheath material is extruded on the surface of the outer conductor, and the sheath thickness is 0.8 mm.

[0050] Example 2 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 2 μm.

[0051] Example 3 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 3 μm.

[0052] Example 4 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 4 μm.

[0053] Example 5 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 5 μm.

[0054] Comparative Example 2 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 6 μm.

[0055] Comparative Example 3 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 7 μm.

[0056] Comparative Example 4 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 8 μm.

[0057] Comparative Example 5 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 0.3 μm.

[0058] Comparative Example 6 The other aspects are the same as those of Example 1, except that the laser roughening process parameters are controlled so that the roughness of the inner conductor surface is 0.2 μm.

[0059] The RF coaxial cables of the above comparative examples and embodiments were verified and tested according to the test method in the YD / T1092 standard. The test items were: a. Adhesion test between the insulation layer and the inner conductor (considering the effect of the roughening process on the stability of the product structure); b. Standing wave test (considering the effect of the roughening process on the standing wave index); c. Insulation dielectric strength test (considering whether the surface roughness of the inner conductor after roughening will produce metal sharp corners to cause local electric field concentration, thereby causing abnormal insulation withstand voltage index); d. Loss / attenuation test (considering the effect of the roughening process on cable attenuation after removing the inner cortex layer). The measured results are shown in Table 1.

[0060] It can be seen from the test data of test item d in Table 1 that, compared with comparative example 1, when other process procedures are the same, the attenuation index of embodiments 1 to 5 is overall optimized (reduced) by 3.3% to 6.0% after the inner conductor surface is roughened and the inner skin layer is removed.

[0061] From the test data of test item a in Table 1, it can be seen that the insulation adhesion index increases with the increase of the surface roughness of the inner conductor. When the surface roughness of the inner conductor drops to 0.3μm or less, after omitting the inner cortex, the adhesion between the conductor and the insulation layer cannot meet the normal requirements. In addition, when the adhesion index fails, it may be due to the unstable structure between the insulation layer and the inner conductor, which indirectly leads to the failure of the standing wave index of test item b.

[0062] It can be seen from the test data of test item c in Table 1 that when the surface roughness of the inner conductor exceeds 5μm, the electric field concentration effect caused by the sharp corners of the metal surface may cause the insulation dielectric strength test to fail. At the same time, according to experimental data, when the degree of roughening is too high (Comparative Example 2, Comparative Example 3 and Comparative Example 4), the insulation dielectric strength test fails, while the standing wave test meets the standard; because this indicator has problems before the standing wave indicator, the impact of the standing wave is not a priority consideration, which also shows that as long as the surface roughness of the inner conductor is controlled within an appropriate range, the standing wave test is usually up to standard.

[0063] Table 1

[0064] Based on the above test data, the present invention recommends that the surface roughness of the inner conductor of the radio frequency coaxial cable after the roughening process be controlled within the range of 0.5 μm to 5 μm, and the more preferred roughness range is 1 μm to 3 μm.

[0065] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-loss radio frequency coaxial cable, characterized in that: It includes an inner conductor, a composite insulation layer, an outer conductor and an outer sheath which are concentrically nested from the inside to the outside; The composite insulating layer comprises a foamed resin layer and a solid outer skin layer; wherein the foamed resin layer is in direct contact with the inner conductor, and the solid outer skin layer is in direct contact with the outer conductor; The surface of the inner conductor directly contacting the foamed resin layer has a microscopic rough structure formed by roughening treatment, and the roughness thereof is 0.5 μm to 5.0 μm.

2. The radio frequency coaxial cable according to claim 1, characterized in that: The surface roughness of the inner conductor is 1 μm to 3 μm.

3. The radio frequency coaxial cable according to claim 1, characterized in that: The inner conductor surface roughening treatment method is laser roughening, chemical etching, mechanical grinding or electrochemical treatment.

4. The radio frequency coaxial cable according to claim 1, characterized in that: The material of the foamed resin layer is foamed polyolefin; the foaming degree of the foamed polyolefin is 40%-85%; the thickness of the foamed resin layer is 3mm-15mm.

5. The radio frequency coaxial cable according to claim 1, characterized in that: The solid outer skin layer is solid polyolefin; the thickness of the solid outer skin layer is 0.05mm-0.15mm.

6. A method for preparing a radio frequency coaxial cable according to any one of claims 1 to 5, characterized in that: The steps include: (1) The inner conductor is subjected to surface roughening treatment so that its roughness is controlled within the range of 0.5 μm to 5.0 μm; (2) preparing the foamed resin layer and the solid outer skin layer by double-layer co-extrusion on the surface of the inner conductor after the roughening treatment; (3) The outer conductor and the outer sheath are sequentially prepared outside the solid outer skin layer.

7. The method according to claim 6, characterized in that The roughening treatment in step (1) is specifically laser roughening, chemical etching, mechanical grinding or electrochemical treatment.

8. The method according to claim 7, characterized in that When the roughening process is performed by laser roughening, the laser power is 10W-400W, the scanning speed is 600mm / s-1200mm / s, and the scanning interval is 0.05mm-0.12mm.

9. The method according to claim 6, characterized in that Step (2) specifically comprises: uniformly mixing molten polyolefin and foaming gas to form an aerosol, and co-extruding the aerosol and the molten polyolefin for preparing the solid outer skin layer on the surface of the inner conductor after the roughening treatment to form the foamed resin layer and the solid outer skin layer coated on the outside of the foamed resin layer.

10. The method according to claim 6, characterized in that The inner conductor in step (1) is an inner conductor that has been preheated at a temperature of 80°C-120°C.

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