A low standing wave leaky coaxial cable and a radio frequency coaxial cable

Abstract

This application belongs to the technical field of communication transmission cables. More specifically, it relates to a low standing wave leaky coaxial cable and a radio frequency coaxial cable. This application makes corresponding optimized designs for the corrugation pitch of the copper tubes of the outer conductor and the inner conductor and the synchronous phase difference between the two, minimizing the standing wave ratio of the finished radio frequency coaxial cable and leaky coaxial cable. Meeting the requirements of YD / T 1092 standard and YD / T 2491 standard, this application can reduce the average voltage standing wave ratio of the leaky coaxial cable to 1.21 and the average voltage standing wave ratio of the radio frequency coaxial cable to 1.11, while having the advantages of being easy to operate and high adjustment accuracy.

Description

Technical Field

[0001] This application belongs to the technical field of communication transmission cables, and more specifically, relates to a low standing-wave leaky coaxial cable and a radio frequency coaxial cable. Background Art

[0002] As common types of coaxial cables, radio frequency coaxial cables and leaky coaxial cables have been widely used in many fields such as communication, radio and television, and satellite communication. Existing radio frequency coaxial cables and leaky coaxial cables generally include structures such as an inner conductor, a foamed insulation layer, an outer conductor, and a sheath layer from the inside to the outside. Among them, radio frequency coaxial cables are mostly used for radio frequency signal transmission between mobile base stations and antennas, and leaky coaxial cables are mostly used for wireless signal coverage in narrow areas such as tunnels.

[0003] Voltage Standing Wave Ratio (VSWR) is an important indicator to measure the impedance matching degree between the transmission line and the load in a radio frequency transmission system, and has a significant impact on the cable transmission effect. The closer the VSWR is to 1, the better the impedance matching between the transmission line and the load, the smaller the reflected power, and the higher the signal transmission efficiency; a high VSWR means more signal reflection and transmission loss. This reflected signal will not only reduce the signal strength, but may also cause damage to the transmitting device. Therefore, how to effectively reduce the voltage standing wave ratio of coaxial cables has always been one of the hot technical topics in this field.

[0004] In the prior art, whether it is a radio frequency coaxial cable or a leaky coaxial cable, in order to ensure the consistency of the cable impedance during the processing and prevent the standing wave ratio from increasing due to signal reflection caused by impedance mutation, the conventional method is to control the equipment to run according to fixed parameters as much as possible during the manufacturing process, so as to manufacture a cable with uniform and stable dimensions.

[0005] However, further research shows that due to unstable factors such as equipment or raw materials during the production process of radio frequency cables, the system often experiences periodic failures. This periodic effect on the cable is manifested as periodic structural dimension fluctuations of the cable, and the periodic structural dimension fluctuations are extremely likely to cause peak values of the standing wave ratio of the cable. Correspondingly, there is an urgent need for further research in this field to better meet the high-quality control requirements for reducing the voltage standing wave ratio of radio frequency coaxial cables. Summary of the Invention

[0006] In view of the above deficiencies or improvement requirements of the prior art, the present application provides a low standing-wave leaky coaxial cable and a radio frequency coaxial cable. By making targeted improvements in aspects such as the pitch design of specific structures such as the inner conductor and the outer conductor and the pitch change model, it is not only possible to more accurately and effectively reduce the voltage standing wave ratio of various coaxial cables, but also to simultaneously improve the cable bending stress and reduce the high-frequency signal attenuation. At the same time, it has the advantages of being easy to process and control, high reliability, etc., and is particularly suitable for high-frequency signal transmission application scenarios such as 5G communication base stations.

[0007] To achieve the above object, in a first aspect, the present application provides a low standing-wave leaky coaxial cable, which includes an inner conductor, an insulating medium, an outer conductor, and a protective sheath from the inside to the outside:

[0008] The inner conductor is composed of a spiral corrugated copper tube for transmitting signals and its thread direction remains right-handed. The corrugation pitch of the inner conductor is continuously gradually changed in a segmented distribution along the cable length direction, and adjacent segments each have different gradual change characteristics;

[0009] The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube, and periodic openings or slits are processed on its surface for uniformly radiating and receiving signals. The corrugation pitch of the outer conductor is also continuously gradually changed in a segmented distribution along the cable length direction, and adjacent segments each have different gradual change characteristics, and the pitch change of the inner conductor and the outer conductor maintain a synchronous phase difference.

[0010] As a further preference of the present application, a synchronous phase difference of 0.6 times to 0.8 times of pitch change is maintained between the inner conductor and the outer conductor.

[0011] As a further preference of the present application, the inner conductor and the outer conductor include at least three adjacent sections along the cable length direction, and the corrugation pitches in the first to third sections change according to the following first to third functional formulas respectively:

[0012] First functional formula: P i =g + t×func

[0013] Second functional formula: P j =g - t×func

[0014] Third functional formula: P r =g + t×sinα

[0015] Wherein, P i represents the corrugation pitch when the i-th change occurs in the first section, with the unit of mm; P j represents the corrugation pitch when the j-th change occurs in the second section, with the unit of mm; Pr r represents the pitch of the corrugation when the r-th change occurs in the third section, in mm; g represents the preset reference value of the corrugation pitch, in mm; t represents the preset tolerance value of the corrugation pitch, in mm; func represents a preset random function for randomly outputting a value between (0, 1) each time; α represents the period of change of the corrugation pitch in the third section, and its value range is (0, π).

[0016] As a further preference of the present application, the first to third sections are repeatedly distributed along the length direction of the cable, and are repeatedly distributed at least twice or more.

[0017] As a further preference of the present application, the inner and outer conductors are processed for the corrugation pitch in the following manner:

[0018] The smooth copper strip is longitudinally wrapped through a forming table, and then a corrugated copper tube is formed by welding at the joint of the smooth copper strip using argon arc welding or laser welding;

[0019] The corrugated copper tube is fed into a grooving machine for processing at a speed corresponding to the above first to third functional formulas under the clamping and traction of a servo motor, thereby forming the continuously varying corrugation pitch as described above.

[0020] As a further preference of the present application, the insulating medium is a double-layer insulating structure of a polyolefin bonding layer / polyolefin closed-cell foam layer, or a three-layer insulating structure of a polyolefin bonding layer / polyolefin closed-cell foam layer / polyolefin outer skin layer.

[0021] As a further preference of the present application, the protective sheath is made of polyethylene sheath material or halogen-free low-smoke flame-retardant polyolefin sheath material.

[0022] In a second aspect, a low standing-wave radio frequency coaxial cable is further provided. The radio frequency coaxial cable includes an inner conductor, an insulating layer, an outer conductor, and a protective sheath from the inside to the outside. The inner conductor is composed of a spiral corrugated copper tube for transmitting signals and its thread direction remains right-handed. The corrugation pitch of the inner conductor is continuously varying in a segmented distribution along the length direction of the cable, and adjacent segments each have different gradient characteristics;

[0023] The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube. The corrugation pitch of the outer conductor is also continuously varying in a segmented distribution along the length direction of the cable, adjacent segments each have different gradient characteristics, and the pitch change of the inner conductor and the outer conductor maintain a synchronous phase difference.

[0024] Generally speaking, compared with the prior art through the above technical solutions conceived by the present application, the following beneficial effects are obtained:

[0025] (1) By specifically improving the design form of the corrugation pitch of specific structures such as the outer conductor and the inner conductor, the present application can not only make full use of the characteristics that the corrugation structures of both are more sensitive to the interference of the electromagnetic field distribution to break the resonance effect with the wavelength of high-frequency signals and reduce signal reflection, but also effectively avoid the superposition of the peak values of the standing wave ratio in the cable length direction, thereby further improving the reduction effect of the voltage standing wave ratio.

[0026] (2) By specifically improving the design method of the corrugation pitch, the present application can better achieve processing control in terms of precision and quality compared with solutions such as improving the insulating layer, and it is not easy to lose the low standing wave performance due to reasons such as aging. In addition, this zoned continuous gradient design realizes the differentiation of the bending performance at different positions of the same section of cable during the production process, thus better meeting the comprehensive requirements of the radio frequency coaxial cable for both low standing wave and special bending performance. Compared with other methods of adjusting the standing wave by adjusting the density or dielectric constant of the insulating layer, the method of the present application is more suitable for batch on-line production and is convenient for on-line monitoring and rapid on-line precise adjustment, with higher stability.

[0027] (3) The present application further optimizes the design of the change model of the corrugation pitch. A large number of actual tests show that even in the application scenario of high-frequency signal transmission, this change model can still successfully avoid the appearance of peak values of the standing wave ratio of the cable. Taking the 50-12 feeder in the YD / T 1092 standard as an example, when used in the frequency band of 700 MHz to 3700 MHz, the standing wave ratio can be reduced from 1.5 to 1.2. By adjusting the change law of the pitch of each section of the cable and calculating the optimal section design according to the cable use frequency band and cable loss, it is possible to more effectively avoid the generation of new standing wave peaks caused by the continuous use of an algorithm.

[0028] (4) The present application further makes corresponding optimized design for the synchronous phase difference between the outer conductor and the inner conductor, so as to minimize the standing wave ratio of the finished radio frequency coaxial cable to the greatest extent. In addition, the processing of the outer and inner conductors is fully compatible with the standard production process of YD / T 1092, thus expanding the adaptability. When the outer and inner conductors are produced using this method at the same time, it can more effectively prevent the standing wave superposition problem that may occur in the two layers of conductors of the cable due to periodicity. Brief Description of the Drawings

[0029] Figure 1 is a schematic diagram for showing that the outer conductor / inner conductor includes at least three sections along the cable length direction according to the preferred embodiment of the present application, wherein the corrugation pitch continuously changes in each section and each has different gradient characteristics.

[0030] Figure 2It is a schematic structural diagram for exemplarily showing a leaky coaxial cable according to the present application;

[0031] Figure 3 It is a schematic structural diagram for exemplarily showing a radio frequency coaxial cable according to the present application;

[0032] Wherein, in all the drawings, the same reference numerals are used to represent the same structures or elements, and among them:

[0033] 1 - Inner conductor; 2 - Insulating medium; 3 - Outer conductor; 4 - Protective sheath; 5 - Periodic openings or slits; 11 - Inner conductor; 12 - Insulating layer; 13 - Outer conductor; 14 - Protective sheath. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with 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.

[0035] It should be understood that expressions such as "including" and "may include" used in the present application indicate the existence of disclosed functions, operations or constituent elements, and do not limit the existence of one or more additional functions, operations and constituent elements. In the present application, terms such as "including" and / or "having" can be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but cannot be interpreted as excluding the existence or possibility of addition of one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0037] As analyzed in the "Background Art" section above, the existing leaky coaxial cables generally include structures such as an inner conductor, a foamed insulating layer, an outer conductor and a sheath layer from the inside to the outside. In order to reduce the voltage standing wave ratio, in the prior art, improvements are usually made to the specific composition form of the insulating layer or processing parameters such as its thickness, etc., but there are still problems such as relatively poor effects under high-frequency transmission conditions, difficult precise control of quality, and insufficient stability after aging.

[0038] In view of the above technical problems, according to the first aspect of the present application, a low standing wave leaky coaxial cable is provided. Refer to Figure 2, the basic composition structure of the leaky coaxial cable is similar to that of the RF coaxial cable. Both have a similar nested structure. The main difference is that the outer conductor of the leaky coaxial cable has periodic openings or slots 5, allowing signals to leak out for specific coverage areas.

[0039] As the most critical improvement point, in this application, specific designs are made for both the inner conductor and the outer conductor. Specifically, the inner conductor 1 is composed of a spiral corrugated copper tube for transmitting signals, and the thread direction thereof remains right-handed. The corrugation pitch of the inner conductor 1 is continuously gradually changed in a segmented distribution along the cable length direction, and adjacent segments each have different gradual change characteristics.

[0040] In cooperation with this, the outer conductor 3 is composed of an annular corrugated copper tube or a spiral corrugated copper tube, and periodic openings or slots are processed on its surface for evenly radiating and receiving signals. The corrugation pitch of the outer conductor 3 is also continuously gradually changed in a segmented distribution along the cable length direction, and adjacent segments each have different gradual change characteristics. Moreover, a synchronous phase difference is maintained between the pitch change of the inner conductor 1 and the outer conductor 3.

[0041] The reason for such a design is that each cable has its corresponding attenuation value at a corresponding frequency point. When the attenuation value reaches a certain level, both the system signal and the periodic interference signal intensity will be weakened (i.e., the standing wave no longer superposes / increases). In view of the above theoretical support, in this application, the characteristics that the corrugation structure is more sensitive to the electromagnetic field distribution interference are first fully utilized, and the corrugation pitches of the inner conductor and the outer conductor are both designed as different periodic changes in a segmented distribution. This not only breaks the resonance effect with the wavelength of the high-frequency signal, reduces signal reflection, and can more effectively avoid the superposition of the periodic standing wave ratio peaks in the cable length direction, but also helps to achieve processing control in terms of accuracy and quality, and is not easily lose the low standing wave performance due to reasons such as aging.

[0042] In addition, the inventor of this application also realized that after introducing the continuously gradually changed corrugation pitch, when the RF coaxial cable is produced in a large length, unforeseen periodic changes may be formed again in the length direction, resulting in new standing wave problems. In this case, considering that each cable has its corresponding attenuation value at a corresponding frequency point, when the attenuation value reaches a certain level, both the system signal and the periodic interference signal intensity will be weakened. In view of the above theoretical support, the corrugation pitch of the outer conductor in this application is specifically designed as a segmented variation control form. In this way, even if periodic standing wave ratio peaks are generated along the cable length direction, they cannot be superposed due to the passive attenuation of the signal, further improving the reduction effect of the voltage standing wave ratio.

[0043] In a preferred embodiment of this application, see Figure 1, the inner conductor and the outer conductor include at least three adjacent sections along the cable length direction, where the corrugation pitches in the first to third sections change according to the following first to third functional formulas respectively:

[0044] First functional formula: Pi = g + t × func

[0045] Second functional formula: Pj = g - t × func

[0046] Third functional formula: Pr = g + t × sinα

[0047] Where, P i represents the corrugation pitch when the i-th change occurs in the first section, with the unit of mm; P j represents the corrugation pitch when the j-th change occurs in the second section, with the unit of mm; P r represents the corrugation pitch when the r-th change occurs in the third section, with the unit of mm; g represents the preset corrugation pitch reference value, with the unit of mm; t represents the preset corrugation pitch tolerance value, with the unit of mm; func represents a preset random function for randomly outputting a value between (0, 1) each time; α represents the corrugation pitch change period in the third section, and its value range is (0, π).

[0048] Through the above design, a large number of actual tests show that even in the high-frequency signal transmission application scenario, this pitch change model can still successfully avoid the peak value of the standing wave ratio of the cable; taking the 50-12 feeder in the YD / T1092 standard as an example, when used in the frequency band of 700 MHz to 3700 MHz, the standing wave ratio can be reduced from 1.5 to 1.2, and it also has the advantages of being easy to control and high adjustment accuracy. For example, the random function can be a pseudo-random number generation function that follows a uniform distribution.

[0049] In another preferred embodiment of the present application, the first to third sections are repeatedly distributed along the cable length direction and are repeated at least twice.

[0050] In another preferred embodiment of the present application, when the first to third sections repeatedly appear along the cable length direction, an intermediate section is set as an interval area, and the length L of this intermediate section is designed according to the following relational formula:

[0051] L < A ÷ A min

[0052] Where, L is defined as the total length of all corrugation pitches in the intermediate section divided by 1000, with the unit of m; A represents the actual voltage standing wave V 1 of a current coaxial cable is reduced to the target voltage standing wave V 2The loss value of the cable system within the corresponding length, with the unit of dB; A min represents the attenuation value at the lowest frequency point within the standard operating frequency band of the coaxial cable, with the unit of dB / 100m.

[0053] The present application also provides a manufacturing method for the corresponding low standing-wave leaky coaxial cable, including the following steps:

[0054] (1) Processing the inner conductor 1;

[0055] (2) Preparing the insulating medium 2 on the surface of the inner conductor;

[0056] (3) Coating the outer conductor 3 outside the insulating medium 2;

[0057] (4) Preparing the protective sleeve 4 on the surface of the outer conductor 3.

[0058] Among them, during the forming process of the inner conductor and the outer conductor, their corrugation pitches are simultaneously designed to be continuously gradually changed as a whole along the cable length direction, and adjacent segments each have different gradual change characteristics.

[0059] In another preferred embodiment of the present application, the inner and outer conductors are processed to achieve the corrugation pitch in the following manner:

[0060] Longitudinally wrap the smooth copper strip through the forming table, and then use argon arc welding or laser welding to weld at the seam of the smooth copper strip to form a corrugated copper tube;

[0061] Under the clamping and traction of the servo motor, feed the corrugated copper tube into the grooving machine for processing at a speed corresponding to the above first to third functional formulas, thereby forming the above continuously gradually changed corrugation pitch.

[0062] More specifically for explanation, compared with the traditional spiral corrugated copper tube production line, the following functional modules can be adopted in the present application to achieve the corresponding functions: such as the main grooving traction module, the grooving processing module, and the grooving processing module, etc. Among them, the main grooving traction module is used to adjust the linear speed in real time according to the preset input change function; the grooving processing module is used to adjust the motor speed according to the preset input change function, and then groove the conductor to output the set pitch.

[0063] According to the second aspect of the present application, a low standing-wave radio frequency coaxial cable is also proposed. Refer to Figure 3The basic component structure of the RF coaxial cable is similar to that of existing products, that is, from the inside to the outside, it includes an inner conductor 11, an insulating layer 12, an outer conductor 13 and a protective cover 14, and may also include some other supporting functional structural layers; the main difference is that in the present application, an optimized design is made for the inner conductor 11 composed of a spiral corrugated copper tube, wherein the inner conductor 11 is composed of a spiral corrugated copper tube for transmitting signals and its thread direction remains right-handed, and the corrugation pitch of the inner conductor 11 is a continuous gradient distributed in segments along the length direction of the cable as a whole, and adjacent segments each have different gradient characteristics.

[0064] In addition, the outer conductor 13 of the low standing wave RF coaxial cable can also be designed based on the above principle, and the corrugation pitch of the spiral corrugated copper tube is processed into a continuous gradient with segmented distribution along the length direction of the cable, and the adjacent segments each have different gradient characteristics. The above pitch variation model can also be applied to the processing of the outer conductor and the inner conductor.

[0065] A specific example is given below to better explain the present application, wherein all test samples are made from the same batch of copper strip raw materials and are manufactured on the same equipment, with only the wrinkle pitch control algorithm being changed to eliminate equipment error interference.

[0066] In this specific example, the coaxial cable provided is applied to the radio frequency coaxial cable model HHTAYZ-50-42 (cable specification is -42) in the YD / T1092 standard and the leaky coaxial cable model HLRHTYZ-50-42 in the YDT 2491-2013 standard. The processing steps are as follows:

[0067] The smooth copper strip is formed into a copper tube by argon arc welding, and then the surface of the copper tube is corrugated to form a corrugated copper tube inner conductor with a diameter of 17.6mm.

[0068] A polyolefin foam layer is extruded on the surface of the inner conductor to form an insulating semi-finished product with a diameter of 42.8 mm;

[0069] The semi-finished insulation product is inserted into a smooth copper tube formed by welding copper strips for corrugation. The cable core and the copper tube are tightly combined to obtain the outer conductor semi-finished product of the RF coaxial cable. A layer of low-smoke halogen-free flame-retardant sheath is extruded outside the outer conductor to obtain the HHTAYZ-50-42 finished product; or, the semi-finished insulation product is inserted into a copper tube formed by the longitudinal wrapping of the roller-corrugated copper strip, and a layer of low-smoke halogen-free flame-retardant sheath is directly extruded outside the outer conductor of the longitudinally wrapped copper tube after the drawing die is finalized, which is the HLRHTYZ-50-42 leaky coaxial cable.

[0070] The inner conductor and insulation processing steps of the above HHTAYZ-50-42 RF coaxial cable and HLRHTYZ-50-42 leaky coaxial cable are the same, and the inner conductor and insulation semi-finished products can be shared.

[0071] The processing and control process of the above-mentioned inner conductor / outer conductor are illustrated as follows:

[0072] A welding and corrugating device with a worn main traction gearbox is used to produce a 50-42 inner conductor. The speed of the worn main traction gearbox fluctuates periodically during forward traction. The insulated semi-finished products produced from the manufactured inner conductor are simultaneously applied to the HHTAY-50-42 radio frequency coaxial cable and the HLRHTYZ-50-42 leaky coaxial cable. The voltage standing wave ratios (i.e., VSWR) measured for the finished products of both cables show peak values, and the peak frequency points are at 1812 MHz.

[0073] The above control method of the present application is applied to the main traction of this welding and corrugating to control the continuous gradual change of the inner conductor pitch during production. 10 groups of insulated semi-finished products are produced respectively using the conventional technology and the control method of the present application. 5 groups are used to produce the HLRHTYZ-50-42 leaky coaxial cable, and 5 groups are used to produce the HHTAYZ-50-42 radio frequency coaxial cable. The test results of the VSWR of the finished products are shown in Table 1 and Table 2 below:

[0074] Table 1

[0075]

[0076] Table 2

[0077]

[0078] Comparing Table 1 and Table 2, it can be seen that the peak values of the standing wave of the radio frequency coaxial cable and the leaky coaxial cable produced using the present application have decreased significantly, and the decrease range is between 0.24 and 0.31. Correspondingly, it is confirmed that according to the present application, the voltage standing wave ratio peak value caused by systematic periodic faults due to equipment failures and other reasons during the production process of radio frequency coaxial cables and leaky coaxial cables can be improved.

[0079] In summary, compared with the prior art, the present application can not only more accurately and effectively reduce the voltage standing wave ratio of radio frequency coaxial cables, but also simultaneously improve the bending stress of the cables and reduce high-frequency signal attenuation. At the same time, it has the advantages of being easy to process and control, and high reliability; the designed product structure and processing technology are fully compatible with the production process of the YD / T 1092 standard, suitable for large-scale batch production, and thus have good practical value and application prospects.

[0080] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present application, and are not used to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application should be included within the protection scope of the present application.

Claims

1. A low standing wave leaky coaxial cable, the leaky coaxial cable comprising an inner conductor, an insulating medium, an outer conductor and a protective sleeve from inside to outside, characterized in that: The inner conductor is composed of a spiral corrugated copper tube for transmitting signals and its thread direction is kept rightward, wherein the corrugation pitch of the inner conductor is distributed in sections along the length direction of the cable and is continuously gradient, and adjacent sections each have a different gradient corrugation pitch; The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube and has periodic openings or gaps on its surface for uniformly radiating and receiving signals. The corrugation pitch of the outer conductor is also distributed in segments along the length of the cable and is continuously gradient. Adjacent segments each have a different gradient corrugation pitch, and the pitch change of the inner conductor maintains a synchronous phase difference with the outer conductor.

2. The low standing wave leakage coaxial cable according to claim 1, characterized in that: The inner conductor and the outer conductor maintain a synchronous phase difference of 0.6 to 0.8 times of the pitch change.

3. The low standing wave leakage coaxial cable according to claim 2, characterized in that: The inner conductor and the outer conductor include at least three adjacent sections along the length direction of the cable, wherein the corrugation pitches in the first to third sections change according to the following first to third functional expressions respectively: The first function: P i =g+t×func Second function: P j =gt×func The third function: P r =g+t×sinα Among them, P i represents the wrinkle pitch at the i-th change in the first section, in mm; P j represents the wrinkle pitch when the jth change occurs in the second section, in mm; P r represents the wrinkle pitch at the rth change in the third section, in mm; g represents the preset wrinkle pitch reference value, in mm; t represents the preset wrinkle pitch tolerance value, in mm; func represents a preset random function, which is used to randomly output a value between (0, 1) each time; α represents the wrinkle pitch change period in the third section, and its value range is (0, π).

4. The low standing wave leakage coaxial cable according to claim 3, characterized in that: The first to third sections are repeatedly distributed along the length direction of the cable, and are repeatedly distributed at least twice.

5. The low standing wave leakage coaxial cable according to claim 3 or 4, characterized in that: The inner and outer conductors are processed in the following manner to achieve the wrinkle pitch: The smooth copper strip is longitudinally wrapped through a forming table, and then the seams of the smooth copper strip are welded by argon arc welding or laser welding to form a corrugated copper tube; The corrugated copper tube is clamped and pulled by a servo motor and fed into a corrugating machine for processing at a speed corresponding to the first to third functional formulas, thereby forming the above-mentioned continuous and gradual corrugation pitch.

6. The low standing wave leakage coaxial cable according to claim 1, characterized in that: The insulating medium is a double-layer insulating structure of a polyolefin adhesive layer / a polyolefin closed-cell foam layer, or a three-layer insulating structure of a polyolefin adhesive layer / a polyolefin closed-cell foam layer / a polyolefin outer skin layer.

7. The low standing wave leakage coaxial cable according to claim 6, characterized in that: The protective sheath is made of polyethylene sheath material or halogen-free, low-smoke, flame-retardant polyolefin sheath material.

8. A low standing wave radio frequency coaxial cable, comprising an inner conductor, an insulating layer, an outer conductor and a protective sleeve from inside to outside, characterized in that: The inner conductor is composed of a spiral corrugated copper tube for transmitting signals and its thread direction is kept rightward, wherein the corrugation pitch of the inner conductor is distributed in sections along the length direction of the cable and is continuously gradient, and adjacent sections each have a different gradient corrugation pitch; The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube, wherein the corrugation pitch of the outer conductor is also distributed in segments along the length direction of the cable and continuously changes, and adjacent segments each have a different gradual corrugation pitch, and the pitch change of the inner conductor maintains a synchronous phase difference with the outer conductor.

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