Low standing wave radio frequency coaxial cable

Abstract

The invention belongs to the technical field of communication transmission cables, and particularly relates to a low standing wave radio frequency coaxial cable. An outer conductor of the radio frequency coaxial cable is composed of an annular corrugated copper pipe or a spiral corrugated copper pipe, the corrugated pitch of the outer conductor is processed to be continuously and gradually changed in a segmented distribution mode in the length direction of the cable, and adjacent segments have different gradual change characteristics. According to the radio-frequency coaxial cable, the voltage standing wave ratio of the radio-frequency coaxial cable can be reduced in a more accurate and convenient-to-control mode, the bending stress of the cable is improved, the attenuation of high-frequency signals is reduced, and the like, so that the radio-frequency coaxial cable is particularly suitable for high-frequency signal transmission application scenes such as 5G communication base stations and the like. According to the 50-12 feeder line, on the basis of meeting the YD / T1092 standard, the standing-wave ratio is kept between 1.11 and 1.14 when the frequency band is 700 MHz to 2700 MHz, and compared with the prior art, the mean value is optimized by about 0.21.

Description

Technical Field

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

[0002] RF coaxial cable is a high-performance cable used to transmit RF signals. It is widely used in communications, broadcasting, satellite communications, etc. Existing RF coaxial cables generally include inner conductor, foam insulation layer, outer conductor and sheath layer from inside to outside. Its key electrical parameters mainly include characteristic impedance, attenuation and voltage standing wave ratio.

[0003] Voltage standing wave ratio (VSWR) is an important indicator to measure the impedance matching degree between the transmission line and the load in the RF 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; high VSWR means more signal reflection and transmission loss. This reflected signal will not only reduce the signal strength, but also may cause damage to the transmitting equipment. Therefore, how to effectively reduce the voltage standing wave ratio of coaxial cable has always been one of the hot technical topics in this field.

[0004] The search found that some research ideas on how to reduce the voltage standing wave ratio of coaxial cables have been proposed in the prior art. For example, Ding Weilin et al. pointed out in the article "Analysis of the Impact of Structural Parameter Changes of RF Coaxial Cables for Mobile Communications on the Voltage Standing Wave Ratio" (Communication World, March 2014, pp. 11-12) that by analyzing the structural parameters of RF coaxial cables, it was found that changes in parameters such as the diameter of the inner conductor and the outer conductor, and the dielectric constant of the insulating layer will affect the voltage standing wave ratio. CN202110539194.2 discloses a device and method for manufacturing a twisted inner conductor pushing RF coaxial cable, wherein the density of the molded core wire, that is, the insulating layer, is non-periodically changed by changing the mold gap I0 during the pushing process, thereby eliminating the peak value of the voltage standing wave ratio. In addition, CN202210163073.7 discloses a spiral corrugated copper tube outer conductor radio frequency coaxial cable and a manufacturing method thereof, wherein an outer skin layer is arranged between the foamed insulation layer and the corrugated copper tube outer conductor for bonding connection, thereby correspondingly improving electrical performance parameters such as the maximum voltage standing wave ratio.

[0005] However, further research shows that the above-mentioned prior art focuses more on improving structures such as the insulation layer. However, the insulation layer is a double-layer or multi-layer polyolefin polymer structure that is continuously and concentrically extruded on the inner conductor and mainly composed of a foam layer. Its processing process is difficult to accurately control and is prone to instability after aging. In addition, improvement measures such as adjusting the thickness parameters of the insulation layer have relatively limited effects on reducing the peak value of the voltage standing wave ratio, which may be more prominent under high-frequency signal transmission conditions. Accordingly, further research is urgently needed in this field to better meet the high-quality control requirements for reducing the voltage standing wave ratio of RF coaxial cables. Summary of the invention

[0006] In response to the above-mentioned defects or improvement needs of the prior art, the present application provides a low standing wave RF coaxial cable, in which targeted improvements are made by selecting the pitch design of specific structures such as the external conductor and its pitch variation model, and matching high-precision processing methods. Accordingly, not only can the voltage standing wave ratio of the RF coaxial cable be reduced in a more accurate and easy-to-control manner, but the effect achieved is more significant compared with the prior art. At the same time, it helps to simultaneously improve the cable bending stress and reduce the attenuation of high-frequency signals, and is therefore particularly suitable for high-frequency signal transmission application scenarios such as 5G communication base stations.

[0007] To achieve the above object, the present application provides a low standing wave radio frequency coaxial cable, which includes an inner conductor, an insulating layer, an outer conductor and a protective sleeve from inside to outside: The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube, the corrugation pitch of the corrugated copper tube is processed to be a continuous gradient distributed in segments along the length direction of the cable, and adjacent segments each have different gradient characteristics; The outer conductor includes 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 rrepresents 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).

[0008] Through the above ideas, first of all, considering that the wrinkle structure on the surface of the outer conductor is more sensitive to the interference of the electromagnetic field distribution, and the outer conductor production link is one of the processes that is most likely to produce standing wave peaks in the actual manufacturing process of the radio frequency coaxial cable due to its particularity of processing and structural complexity, the corresponding application selects a design of continuous gradual change of its wrinkle pitch, which is more conducive to breaking the resonance effect with the wavelength of the high-frequency signal, reducing signal reflection, and effectively avoiding the appearance of a high standing wave ratio peak in the length direction of the cable; Secondly, after the introduction of the continuous and gradual wrinkle pitch, when the RF coaxial cable is produced in a long length, unpredictable periodic changes may be formed again in the length direction and cause new standing wave problems; in this case, considering that each cable has its corresponding attenuation value at the corresponding frequency point, when the attenuation value reaches a certain level, both the system signal and the periodic interference signal strength will be weakened (that is, the standing wave will no longer be superimposed or increased), so the present application specifically designs the outer conductor wrinkle pitch as a segmented variation control form, so that even if a periodic standing wave ratio peak is generated along the length direction of the cable, it will not be superimposed due to signal attenuation, and the voltage standing wave ratio reduction effect is further improved accordingly; Finally, since the size of the wrinkle pitch directly affects the bending performance of the cable, the present application accordingly adopts the above partitioned continuous gradient design, so that in the production process, it is convenient to adopt phased pitch changes according to actual needs to meet the differentiation of bending performance at different positions of the same section of cable, thereby better meeting the comprehensive needs of RF coaxial cables for low standing waves and special bending performance. As a further preferred embodiment 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.

[0009] As a further preferred embodiment of the present application, when the first to third sections are repeated along the length direction of the cable, an intermediate section is provided as a spacing area.

[0010] As a further preferred embodiment of the present application, the length L of the middle section is designed according to the following relationship: L<A÷A min Wherein, L is defined as the total length of all corrugation pitches in the middle section divided by 1000, in m; A represents the cable system loss value within the corresponding length when the actual voltage standing wave V1 of a coaxial cable is tested to be reduced to the target voltage standing wave V2, in dB; A min Represents the attenuation value of the coaxial cable at the lowest frequency point within the standard frequency band, in dB / 100m.

[0011] As a further preferred embodiment of the present application, the inner conductor is composed of copper-clad aluminum wire, a smooth copper tube or a spiral corrugated copper tube; in the case of a spiral corrugated copper tube, the corrugation pitch of the inner conductor is also processed into a continuous gradient that is distributed in segments along the length direction of the cable as a whole, and adjacent segments each have different gradient characteristics.

[0012] As a further preferred embodiment of the present application, the pitch variation of the inner conductor maintains a synchronous phase difference with that of the outer conductor, and the former is 0.6 to 0.8 times of the latter.

[0013] As a further preferred embodiment of the present application, the outer and inner conductors are processed with the following method 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.

[0014] As a further preferred embodiment of the present application, in the above processing, the following formula is used to realize automatic control: P=(V×K×1000) / R Among them, P represents the pitch of each wrinkle during online production, in mm; V represents the instantaneous forward speed of the corrugating traction, in meters per minute; K represents the compression coefficient of the smooth copper strip during the processing; R represents the instantaneous speed of the corrugator during the corrugating process, in revolutions per minute.

[0015] As a further preferred embodiment of the present application, the tolerance of each wrinkle pitch is controlled within ±0.05 mm.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: (1) The present application makes targeted improvements by selecting the corrugation pitch design form of a specific structure such as an outer conductor. This not only makes full use of the characteristic that the corrugation structure is more sensitive to electromagnetic field distribution interference to break the resonance effect with the wavelength of the high-frequency signal and reduce signal reflection, but also can more effectively avoid the superposition of the standing wave ratio peak in the length direction of the cable, and accordingly further improves the effect of reducing the voltage standing wave ratio; (2) The present application makes targeted improvements by selecting the wrinkle pitch design form of specific structures such as the outer conductor. Compared with solutions such as improving the insulation layer, it can better achieve processing control in terms of precision and quality, and is not prone to losing low standing wave performance due to aging and other reasons. In addition, this partitioned continuous gradient design achieves differentiated bending performance at different positions of the same cable section during the production process, which better meets the comprehensive requirements of RF coaxial cables for low standing wave and special bending performance. Compared with other methods of adjusting standing wave by adjusting the density or dielectric constant of the insulation layer, the method of the present application is more suitable for batch online production and is convenient for online monitoring and rapid online precise adjustment, with higher stability. (3) This application further optimizes the design of the variation model of the corrugation pitch. Many actual tests have shown that the variation model can successfully avoid the high peak value of the cable's standing wave ratio even in high-frequency signal transmission application scenarios; taking the 50-12 feeder in the YD / T1092 standard as an example, when the frequency band is 700MHz~3700MHz, the standing wave ratio can be reduced from 1.5 to 1.2; by adjusting the pitch variation law of each section of the cable and calculating the optimal segmentation design based on the cable's 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; (4) The present application further adopts similar corrugation pitch processing for the inner conductor of the spiral corrugated copper tube, and makes a matching optimization design for the synchronous phase difference between the two, so as to minimize the standing wave ratio of the finished RF coaxial cable; wherein, the processing of the outer and inner conductors is fully compatible with the standard production process of YD / T 1092, thereby expanding the adaptability; the inner and outer conductors are produced by the same method at the same time, and the problem of standing wave superposition that may be caused by the periodicity of the two layers of the cable conductors is effectively prevented; (5) The present application further optimizes the design of the precision processing method of the outer and inner conductors, and accordingly can realize automatic control of the manufacturing process of the partitioned variable pitch according to the input variation function, thereby having the advantages of high precision, good quality control, and being suitable for large-scale batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1It is a schematic diagram for showing that the outer conductor includes at least three sections along the length direction of the cable according to a preferred embodiment of the present application, wherein the corrugation pitch changes continuously and gradually in each section and each section has a different gradual change feature; Figure 2 is a schematic diagram for exemplarily showing the structure of a radio frequency coaxial cable according to the present application; In all the drawings, the same reference numerals are used to represent the same structures or elements, wherein: 1-inner conductor; 2-insulating layer; 3-outer conductor; 4-protective sheath. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0019] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0021] As analyzed in the previous "Background Technology" section, the existing RF coaxial cable generally includes an inner conductor, a foamed insulation layer, an outer conductor and a sheath layer from the inside to the outside. In order to reduce the voltage standing wave ratio, the existing technology usually improves the specific composition of the insulation layer or its thickness and other processing parameters. However, it still has relatively poor effects under high-frequency transmission conditions, difficult to accurately control the quality, and insufficient stability after aging.

[0022] In view of the above technical problems, the present application proposes a low standing wave radio frequency coaxial cable, see Figure 2The basic component structure of the radio frequency coaxial cable is similar to that of existing products, that is, from the inside to the outside, it includes an inner conductor 1, an insulating layer 2, an outer conductor 3 and a protective sleeve 4, and may also include some other supporting functional structural layers; the main difference is that in this application, an outer conductor 3 composed of an annular corrugated copper tube or a spiral corrugated copper tube is optimized and designed, wherein the corrugation pitch of the corrugated copper tube is processed into a continuous gradient that is distributed in segments as a whole along the length direction of the cable, and adjacent segments each have different gradient characteristics.

[0023] The reason for this design is mainly based on the following technical discoveries and theoretical support.

[0024] First of all, the inventors of the present application realized that the wrinkle structure on the surface of the outer conductor is more sensitive to the interference of the electromagnetic field distribution, and the outer conductor production process is one of the processes that is most likely to produce standing wave peaks in the actual manufacturing process of RF coaxial cables due to its special processing and structural complexity; accordingly, the present application chooses to design a continuous gradual change in the wrinkle pitch, which is more conducive to breaking the resonance effect with the wavelength of the high-frequency signal, reducing signal reflection, and effectively avoiding the appearance of a high standing wave ratio peak in the length direction of the cable.

[0025] Secondly, the inventor of the present application realized that after introducing the continuous gradual change of the corrugation pitch, when the RF coaxial cable is produced in a long length, it may form unpredictable periodic changes in the length direction again, and cause new standing wave problems; in this case, considering that each cable has its corresponding attenuation value at the corresponding frequency point, when the attenuation value reaches a certain level, both the system signal and the periodic interference signal strength will be weakened (that is, the standing wave will no longer be superimposed or increased). In view of the above theoretical support, the present application specifically designs the outer conductor corrugation pitch as a segmented variation control form, so that even if a periodic standing wave ratio peak is generated along the length of the cable, it will not be superimposed due to the passive attenuation of the signal, which further improves the effect of reducing the voltage standing wave ratio.

[0026] Finally, since the size of the wrinkle pitch will directly affect the bending performance of the cable, the corresponding application, through the above-mentioned partitioned continuous gradient design combined with the relevant change model, is also convenient for adopting phased pitch changes according to actual needs during the production process to meet the differentiated bending performance of different positions of the same section of cable, thereby better meeting the comprehensive needs of RF coaxial cables for low standing waves and special bending performance.

[0027] In a preferred embodiment of the present application, see Figure 1 The outer conductor includes 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: Pi =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).

[0028] Through the above design, many actual tests have shown that the pitch variation model of the above optimization design can successfully avoid the high peak value of the cable's standing wave ratio even in high-frequency signal transmission application scenarios; taking the 50-12 feeder in the YD / T1092 standard as an example, when the frequency band is 700MHz~3700MHz, the standing wave ratio can be reduced from 1.5 to 1.2, and it has the advantages of easy control and high adjustment accuracy. For example, the random function can be a pseudo-random number generation function that obeys a uniform distribution.

[0029] In another preferred embodiment 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.

[0030] In another preferred embodiment of the present application, when the first to third sections appear repeatedly along the length direction of the cable, an intermediate section is provided as a spacing area.

[0031] In another preferred embodiment of the present application, the length L of the middle section is designed according to the following relationship: L<A÷A min Wherein, L is defined as the total length of all corrugation pitches in the middle section divided by 1000, in m; A represents the cable system loss value within the corresponding length when the actual voltage standing wave V1 of a coaxial cable is tested to be reduced to the target voltage standing wave V2, in dB; A min Represents the attenuation value of the coaxial cable at the lowest frequency point within the standard frequency band, in dB / 100m.

[0032] The design principle of the length L of the third section will be explained below with reference to an example.

[0033] Based on the above design of the corrugation pitch according to the present application, it is assumed that the common cable standing wave requirement is VSWR≤1.20, which is converted into a return loss of 21dB, and the common cable standing wave system threshold is 1.50, which is converted into a return loss of 14dB. In this case, in order to reduce the voltage standing wave ratio of 1.50 to 1.20, at least 21-14=7dB of loss (attenuation) is required, that is, when the cable reaches the specific length calculated by the above relationship, its attenuation (loss) can just reach 7dB. At this time, even if there are periodic peaks along the length of the cable, they cannot be superimposed due to signal attenuation, and will not have an adverse effect on the standing wave.

[0034] In another preferred embodiment of the present application, the inner conductor of the radio frequency coaxial cable can be composed of copper-clad aluminum wire, smooth copper tube or spiral corrugated copper tube; when copper-clad aluminum wire and smooth copper tube are used, it is necessary to refer to the technical standard YD / T 1092 for processing of parameters such as average diameter, average outer diameter, average wall thickness and roundness.

[0035] In the case of a spiral corrugated copper tube, the pitch of the corrugation of the inner conductor is also processed to be a continuous gradient distributed in segments along the length of the cable, and adjacent segments each have different gradient characteristics. In addition, the pitch change of the inner conductor maintains a synchronous phase difference with the outer conductor, and the former is 0.6 to 0.8 times that of the latter.

[0036] The present application also provides a method for manufacturing a corresponding low standing wave radio frequency coaxial cable, comprising the following steps: (1) Processing the inner conductor 1; (2) preparing an insulating layer 2 on the surface of the inner conductor 1; (3) wrapping an outer conductor 3 outside the insulating layer 2; (4) A protective cover 4 is prepared on the surface of the outer conductor 3.

[0037] In the forming process of the inner conductor and / or the outer conductor, in the case of a corrugated copper tube, the corrugation pitch is designed to be a continuous gradient distributed in segments along the length direction of the cable as a whole, and adjacent segments each have different gradient characteristics.

[0038] In another preferred embodiment of the present application, the outer and inner conductors are processed with the following method 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.

[0039] In another preferred embodiment of the present application, in the above processing, the following formula is used to achieve automatic control: P=(V×K×1000) / R Among them, P represents the pitch of each wrinkle during online production, in mm; V represents the instantaneous forward speed of the corrugating traction, in meters per minute; K represents the compression coefficient of the smooth copper strip during the processing; R represents the instantaneous speed of the corrugator during the corrugating process, in revolutions per minute.

[0040] Through the above design, not only can the dynamic processing process of the above-mentioned corrugation pitch be realized with higher precision and more automation, but also the tolerance of each corrugation pitch can be ensured to be controlled within ±0.05mm, which is more conducive to improving the final performance of the coaxial cable product to a certain extent.

[0041] To explain more specifically, compared with the traditional corrugated copper tube production line, the present application can use the following functional modules to implement the corresponding functions: such as corrugation main traction module, corrugation processing module and corrugation processing module, etc. The corrugation main traction module is used to adjust the line speed in real time according to the preset input change function; the corrugation processing module is used to adjust the motor speed according to the preset input change function, and then corrugate the conductor output to set the pitch.

[0042] A specific example is given below to better explain the present application.

[0043] Specific example 1 In this specific example, the provided RF coaxial cable is applied to the HHTAY-50-42 RF coaxial cable (cable specification is -42) in the YD / T1092 standard, and the specific processing steps are as follows: 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. A polyolefin foam layer is extruded on the surface of the inner conductor to form an insulating semi-finished product with a diameter of 42.7 mm; After the smooth copper strip is formed, it is welded by argon arc welding to become a copper tube. The semi-finished insulation product is inserted into the copper tube. According to the above control method, the main traction clamp moves forward and enters the corrugation box for high-speed corrugation to form a semi-finished outer conductor of the corrugated copper tube with a diameter of 46.5mm. A layer of polyethylene sheath material is extruded on the surface of the outer conductor to form a finished sheath with a diameter of 49.3 mm.

[0044] The design and verification process of the relevant comparative examples are as follows: During the normal production process of HHTAY-50-42 cable, the machine was shut down and the main traction gearbox of the welding process was replaced with a worn gearbox. The worn main traction gearbox had periodic defects in speed when traction was forward, and the voltage standing wave ratio (VSWR) of the produced HHTAY-50-42 cable showed frequency doubling peaks, with peak positions near 861MHz, 1722MHz, and 2583MHz respectively. The worn main traction was normally produced using conventional technology for 100-meter cable shutdown test (comparative example), and then the machine was restarted and the main traction transmission of the above-mentioned control method of this application was used to make the outer conductor pitch undergo continuous random gradient change, and the 100-meter cable was shut down for test.

[0045] The above steps were repeated 10 times to produce 10 groups of 100-meter cable control groups. The voltage standing wave ratio of the cables in the 10 control groups was tested, and the results are shown in Table 1 below.

[0046] Table 1

[0047] It can be seen from the test results in Table 1 above that the VSWR test results of the HHTAY-50-42 cable produced by the present application are significantly better than those of conventional cables produced using equipment with periodic defects, and the effective optimization (reduction) range of its VSWR test value is 0.17 to 0.29, and its VSWR test results meet the standard requirements.

[0048] In summary, compared with the prior art, the present application can not only reduce the voltage standing wave ratio of the RF coaxial cable in a more precise and easy-to-control manner, but also achieve more significant results compared with the prior art. At the same time, it helps to simultaneously improve the cable bending stress and reduce the high-frequency signal attenuation. The designed product structure and processing technology are fully compatible with the YD / T1092 standard production process, suitable for large-scale batch production, and therefore have good practical value and application prospects.

[0049] 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 low standing wave radio frequency coaxial cable, which comprises an inner conductor, an insulating layer, an outer conductor and a protective sleeve from inside to outside, characterized in that: The outer conductor is composed of an annular corrugated copper tube or a spiral corrugated copper tube, the corrugation pitch of the corrugated copper tube is processed to be a continuous gradient distributed in segments along the length direction of the cable, and adjacent segments each have different gradient characteristics; The outer conductor includes 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).

2. The low standing wave radio frequency coaxial cable according to claim 1, 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.

3. The low standing wave radio frequency coaxial cable according to claim 2, characterized in that: When the first to third sections are repeated along the length direction of the cable, an intermediate section is provided as a spacing area.

4. The low standing wave radio frequency coaxial cable according to claim 3, characterized in that: The length L of the middle section is designed according to the following relationship: L<A÷A min Wherein, L is defined as the total length of all corrugation pitches in the middle section divided by 1000, in m; A represents the cable system loss value within the corresponding length when the actual voltage standing wave V1 of a coaxial cable is tested to be reduced to the target voltage standing wave V2, in dB; A min Represents the attenuation value of the coaxial cable at the lowest frequency point within the standard frequency band, in dB / 100m.

5. The low standing wave radio frequency coaxial cable according to any one of claims 2 to 4, characterized in that: The inner conductor is composed of copper-clad aluminum wire, smooth copper tube or spiral corrugated copper tube; in the case of using spiral corrugated copper tube, the corrugation pitch of the inner conductor is also processed into a continuous gradient with segmented distribution along the length direction of the cable as a whole, and adjacent segments each have different gradient characteristics.

6. The low standing wave radio frequency coaxial cable according to claim 5, characterized in that: The outer and inner 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.

7. The low standing wave radio frequency coaxial cable according to claim 6, characterized in that: In the above processing, the following formula is used to achieve automatic control: P=(V×K×1000) / R Among them, P represents the pitch of each wrinkle during online production, in mm; V represents the instantaneous forward speed of the corrugating traction, in meters per minute; K represents the compression coefficient of the smooth copper strip during the processing; R represents the instantaneous speed of the corrugator during the corrugating process, in revolutions per minute.

8. The low standing wave radio frequency coaxial cable according to claim 7, characterized in that: The tolerance of each wrinkle pitch is controlled within ±0.05mm.

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