A low standing wave radio frequency coaxial cable

Abstract

This application belongs to the technical field of communication transmission cables, and more specifically, relates to a low standing wave radio frequency coaxial cable. The outer conductor of the radio frequency coaxial cable is composed of a circular corrugated copper tube or a spiral corrugated copper tube, wherein the corrugation pitch of the outer conductor is processed to be continuously gradually changed in a segmented distribution along the cable length direction, and adjacent segments each have different gradual change characteristics. Through this application, not only can the voltage standing wave ratio of the radio frequency coaxial cable be reduced in a more accurate and convenient way, but also the cable bending stress is improved and the high-frequency signal attenuation is reduced, etc., so it is especially suitable for high-frequency signal transmission application scenarios such as 5G communication base stations. The 50-12 feeder of this application, on the basis of meeting the YD / T 1092 standard, when used in the frequency band of 700 MHz to 2700 MHz, the standing wave ratio remains between 1.11 and 1.14, which is optimized by about 0.21 compared with the average value of the prior art.

Description

Technical Field

[0001] This 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] A radio frequency coaxial cable is a high-performance cable used for transmitting radio frequency signals, and it is widely used in fields such as communication, radio and television, and satellite communication. The existing radio frequency 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, and its key electrical parameters mainly include characteristic impedance, attenuation, voltage standing wave ratio, etc.

[0003] The voltage standing wave ratio (VSWR) is an important indicator for measuring the impedance matching degree between the transmission line and the load in a radio frequency transmission system, and it 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 not only reduces 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] Searching found that some research ideas have been proposed in the prior art on how to reduce the voltage standing wave ratio of coaxial cables. For example, Ding Weilin et al. pointed out in the article "Analysis of the Influence of Structural Parameter Changes of Radio Frequency Coaxial Cables for Mobile Communication on Voltage Standing Wave Ratio" (Communications World, March 2014, Issue 3, pp. 11-12) that by analyzing the structural parameters of radio frequency coaxial cables, it was found that changes in parameters such as the diameters of the inner conductor and the outer conductor, and the dielectric constant of the insulation layer would affect the voltage standing wave ratio. CN202110539194.2 discloses a device and method for manufacturing a stranded inner conductor extruded radio frequency coaxial cable, in which the density of the formed core wire, that is, the insulation layer, is made to have an aperiodic change by changing the die gap I0 during the extrusion 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 its manufacturing method, in which an outer skin is provided between the foamed insulation layer and the corrugated copper tube outer conductor for bonding connection, and accordingly, electrical performance parameters such as the maximum voltage standing wave ratio can be improved.

[0005] However, further research shows that the above-mentioned existing technologies mainly focus on the improvement of structures such as the insulating layer. However, as a double-layer or multi-layer polyolefin polymer structure mainly composed of a foam layer that is continuously and concentrically extruded on the inner conductor, the insulating layer is difficult to precisely control during the processing, and it is prone to insufficient stability after aging. In addition, improvement measures such as adjusting the thickness parameters of the insulating 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, there is an urgent need in this field for further research to better meet the high-quality control requirements of radio frequency coaxial cables for reducing the voltage standing wave ratio. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement requirements of the existing technology, the present application provides a low standing wave radio frequency coaxial cable. By making targeted improvements in aspects such as the pitch design of specific structures such as the outer conductor and its pitch change model, and the supporting high-precision processing method, etc., not only can the voltage standing wave ratio of the radio frequency coaxial cable be reduced in a more accurate and convenient manner, but also the effect achieved is more significant compared with the existing technology. At the same time, it helps to synchronously improve the cable bending stress and reduce high-frequency signal attenuation, etc. Therefore, it is 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 the inside to the outside:

[0008] The outer conductor is composed of a circular corrugated copper tube or a spiral corrugated copper tube, and the corrugation pitch of the corrugated copper tube is processed to be continuously variable in a segmented manner along the cable length direction, and adjacent segments each have different variable characteristics;

[0009] The outer conductor includes 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:

[0010] First functional formula: P i =g + t × func

[0011] Second functional formula: P j =g - t × func

[0012] Third functional formula: P r =g + t × sinα

[0013] Wherein, P i represents the corrugation pitch when the i-th change occurs in the first section, with the unit of mm; P jRepresents 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 used to randomly output 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).

[0014] Based on the above concept, first, considering that the corrugation structure on the surface of the outer conductor is more sensitive to the interference of the electromagnetic field distribution, and due to the particularity of its processing and the complexity of its structure in the production process of the outer conductor, it is one of the processes most likely to generate standing wave peaks in the actual manufacturing process of the radio frequency coaxial cable. Correspondingly, in this application, by selecting a design with continuously varying corrugation pitch, it 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 high standing wave ratio peaks in the length direction of the cable;

[0015] Secondly, after introducing a continuously varying corrugation pitch, when the radio frequency coaxial cable is produced in a large length, unforeseen periodic changes may occur again in the length direction and lead to new standing wave problems; in this case, considering that each cable has its corresponding attenuation value for the corresponding frequency point, when the attenuation value reaches a certain level, both the system signal and the periodic interference signal intensity will be weakened (that is, the standing wave will no longer superimpose or increase). Therefore, in this application, the corrugation pitch of the outer conductor is specifically designed in a segmented variation control form, so that even if periodic standing wave ratio peaks occur along the length direction of the cable, they cannot be superimposed due to signal attenuation, correspondingly further improving the effect of reducing the voltage standing wave ratio;

[0016] Finally, since the size of the corrugation pitch will directly affect the bending performance of the cable, correspondingly, in this application, through the above-mentioned partitioned continuous variation design, it is convenient to adopt phased pitch changes according to actual needs during the production process to meet the differential bending performance requirements at different positions of the same section of the cable, thereby better meeting the comprehensive requirements of the radio frequency coaxial cable for low standing wave and special bending performance. As a further preference of this application, the first to third sections are repeatedly distributed along the length direction of the cable, and are repeated at least twice or more.

[0017] As a further preference of this application, when the first to third sections repeatedly appear along the length direction of the cable, an intermediate section is set as an interval area.

[0018] As a further preference of this application, the length L of the intermediate section is designed according to the following relationship:

[0019] L < A ÷ Amin

[0020] Wherein, L is defined as the total length of all the corrugation pitches in the middle section divided by 1000, with the unit of m; A represents the cable system loss value within the corresponding length when the actual voltage standing wave V1 of a current coaxial cable is reduced to the target voltage standing wave V2, 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.

[0021] As a further preference of the present application, the inner conductor is composed of copper-clad aluminum wire, smooth copper tube or spiral corrugated copper tube; wherein in the case of using a spiral corrugated copper tube, the corrugation pitch of the inner conductor is also processed to be continuously graded as a whole along the cable length direction, and adjacent segments each have different grading characteristics.

[0022] As a further preference of the present application, the pitch change of the inner conductor maintains a synchronous phase difference with the outer conductor, and the former is 0.6 times to 0.8 times of the latter.

[0023] As a further preference of the present application, the outer and inner conductors are processed to have corrugation pitches in the following manner:

[0024] The smooth copper strip is longitudinally wrapped through a forming table, and then welded at the joint of the smooth copper strip by argon arc welding or laser welding to form a corrugated copper tube;

[0025] The corrugated copper tube is fed into a grooving machine for processing at a speed corresponding to the first to third functional formulas under the clamping and traction of a servo motor, thereby forming the above-mentioned continuously graded corrugation pitches.

[0026] As a further preference of the present application, in the above processing process, the following formula is used to achieve automatic control:

[0027] P = (V × K × 1000) / R

[0028] Wherein, P represents each corrugation pitch during on-line production, with the unit of mm; V represents the instantaneous forward speed of grooving traction, with the unit of m / minute; K represents the compression coefficient of the smooth copper strip during processing; R represents the instantaneous rotational speed of the grooving machine during grooving processing, with the unit of revolutions per minute.

[0029] As a further preference of the present application, the tolerance of each of the above corrugation pitches is controlled within ±0.05 mm.

[0030] Generally speaking, compared with the prior art, the above technical solution conceived by the present application has the following beneficial effects:

[0031] (1) In this application, targeted improvements are made by selecting the design form of the corrugation pitch of specific structures such as the outer conductor. This not only makes full use of the characteristics that the corrugation structure is 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 can more effectively avoid the superposition of the standing wave ratio peak values in the cable length direction, and correspondingly further improve the reduction effect of the voltage standing wave ratio.

[0032] (2) In this application, targeted improvements are made by selecting the design form of the corrugation pitch of specific structures such as the outer conductor. Compared with the solution means such as improving the insulating layer, it can better achieve processing control in terms of accuracy and quality, and is not easily lose the low standing wave performance due to aging and other reasons. 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, and correspondingly better meets 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 insulation layer density or dielectric constant, the method of this application is more suitable for batch online production and is convenient for online monitoring and rapid online precise adjustment, with higher stability.

[0033] (3) In this application, the change model of the corrugation pitch is further optimized. 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 occurrence of high 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 pitch change law 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 peak values caused by the continuous use of an algorithm.

[0034] (4) In this application, similar corrugation pitch processing is further carried out on the inner conductor of the spiral corrugated copper tube, and a supporting optimization design is made for the synchronous phase difference between the two. In this way, the standing wave ratio of the radio frequency coaxial cable finished product can be reduced to the greatest extent. Among them, the processing of the outer and inner conductors is fully compatible with the standard production process of YD / T 1092, thus expanding the adaptability. The outer and inner conductors are produced using this method at the same time, effectively preventing the standing wave superposition problem that may occur due to periodicity between the two layers of conductors of the cable.

[0035] (5) In this application, the precision processing method of the outer and inner conductors is further optimized, and accordingly, the manufacturing process of the zoned variable pitch can be automatically controlled according to the input change function, thus having the advantages of high precision, good quality control, and being suitable for large-scale batch production. Brief Description of the Drawings

[0036] Figure 1is a schematic diagram showing that the outer conductor includes at least three sections along the cable length direction according to a preferred embodiment of the present application, where the corrugation pitch continuously varies in each section and each has a different variation characteristic;

[0037] Figure 2 is a schematic structural diagram of a radio frequency coaxial cable according to the present application for exemplary display;

[0038] Among them, in all the drawings, the same reference numerals are used to represent the same structures or elements, where:

[0039] 1 - inner conductor; 2 - insulating layer; 3 - outer conductor; 4 - protective sheath. Detailed implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the following further describes the present application in detail with reference to 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.

[0041] It should be understood that expressions such as "including" and "may include" used in the present application indicate the existence of the 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" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component or a combination 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 a combination thereof.

[0042] 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.

[0043] As analyzed in the "Background Art" section above, the existing radio frequency 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, the prior art usually improves the specific composition form of the insulating layer or processing parameters such as its thickness, but still has problems such as relatively poor effects under high-frequency transmission conditions, difficult precise control of quality, and insufficient stability after aging.

[0044] In view of the above technical problems, the present application proposes a low standing wave radio frequency coaxial cable, see Figure 2, the basic component structure of this 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. At the same time, it may also include some other supporting functional structure layers; the main difference is that in this application, an optimized design is carried out for the outer conductor 3 composed of a circular corrugated copper tube or a spiral corrugated copper tube, wherein the corrugation pitch of the corrugated copper tube is processed to be continuously gradually changed in a segmented manner along the cable length direction, and adjacent segments each have different gradual change characteristics.

[0045] The reason for such design is mainly based on the following technical discoveries and theoretical supports.

[0046] First of all, the inventors of this application realized that the corrugated structure on the surface of the outer conductor is more sensitive to the interference of the electromagnetic field distribution, and due to the particularity of its processing and the complexity of the structure in the production link of the outer conductor, it is one of the processes that are most likely to generate standing wave peaks in the actual manufacturing process of radio frequency coaxial cables; correspondingly, in this application, by choosing to design the corrugation pitch to be continuously gradually changed, it is more conducive to breaking the resonance effect with the wavelength of high-frequency signals, reducing signal reflection, and effectively avoiding the appearance of high standing wave ratio peaks in the cable length direction.

[0047] Secondly, the inventors of this application realized that after introducing a continuously gradually changed corrugation pitch, when the radio frequency coaxial cable is produced in a large length, an unforeseen periodic change may be formed again in the length direction, resulting in a new standing wave problem; in this case, considering that each cable has its corresponding attenuation value for the corresponding frequency point, when the attenuation value reaches a certain level, both the system signal or the intensity of the periodic interference signal will be weakened (that is, the standing wave will no longer be superimposed or increased). In view of the above theoretical support, in this application, the corrugation pitch of the outer conductor is specifically designed in a segmented variation control form, so that even if periodic standing wave ratio peaks are generated along the cable length direction, they cannot be superimposed due to the passive attenuation of the signal, correspondingly further improving the effect of reducing the voltage standing wave ratio.

[0048] Finally, since the size of the corrugation pitch will directly affect the bending performance of the cable, correspondingly, in this application, through the above-mentioned zoned continuous gradual change design and the relevant change model, it is also convenient to adopt a phased pitch change according to actual needs during the production process to meet the differentiation of the bending performance at different positions of the same section of the cable, thereby better meeting the comprehensive requirements of the radio frequency coaxial cable for both low standing wave and special bending performance.

[0049] In a preferred embodiment of this application, referring to Figure 1 , the outer conductor includes 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:

[0050] The first functional formula: P i = g + t × func

[0051] The second functional formula: P j = g - t × func

[0052] The third functional formula: P r = g + t × sinα

[0053] Wherein, P i represents the pitch of the wrinkles when the i-th change occurs in the first section, with the unit of mm; P j represents the pitch of the wrinkles when the j-th change occurs in the second section, with the unit of mm; P r represents the pitch of the wrinkles when the r-th change occurs in the third section, with the unit of mm; g represents the preset reference value of the pitch of the wrinkles, with the unit of mm; t represents the preset tolerance value of the pitch of the wrinkles, with the unit of mm; func represents a preset random function for randomly outputting a value between (0, 1) each time; α represents the pitch change period in the third section, and its value range is (0, π).

[0054] Through the above design, a large number of actual tests show that the pitch change model of the above optimized design can still successfully avoid the peak value of the voltage standing wave ratio of the cable even in the high-frequency signal transmission application scenario; 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 voltage 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.

[0055] 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 repeated at least twice or more.

[0056] 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 set as an interval area.

[0057] In another preferred embodiment of the present application, the length L of the intermediate section is designed according to the following relational formula:

[0058] L < A ÷ A min

[0059] Wherein, L is defined as the total length of all the pitches of the wrinkles in the intermediate section divided by 1000, with the unit of m; A represents the cable system loss value within the corresponding length when the actual voltage standing wave V1 of a current coaxial cable is reduced to the target voltage standing wave V2 during testing, with the unit of dB; A minIt 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.

[0060] The design principle of the length L of the above-mentioned third section will be explained below in conjunction with an example.

[0061] On the basis of the above design of the corrugation pitch according to the present application, assuming that the standing wave requirement of the common cable is VSWR ≤ 1.20, which is converted to a return loss of 21 dB, and the standing wave system threshold of the common cable is 1.50, which is converted to a return loss of 14 dB. In this case, in order to reduce the voltage standing wave ratio of 1.50 to 1.20, at least 21 - 14 = 7 dB of loss (attenuation) is required, that is, when the cable reaches the specific length deduced by the above relationship, its attenuation (loss) can exactly reach 7 dB. At this time, even if there are periodic peaks along the cable length direction, they cannot be superimposed due to signal attenuation and will not have an adverse impact on the standing wave.

[0062] 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; among them, when using copper-clad aluminum wire or smooth copper tube, it is necessary to process parameters such as its average diameter, average outer diameter, average wall thickness, roundness, etc. with reference to the technical standard of YD / T 1092.

[0063] In the case of using a spiral corrugated copper tube, the corrugation pitch of the inner conductor is also processed to be continuously gradually changed in a segmented distribution along the cable length direction as a whole, and adjacent segments each have different gradual change 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 times to 0.8 times of the latter.

[0064] The present application also provides a corresponding manufacturing method for a low standing wave radio frequency coaxial cable, including the following steps:

[0065] (1) Processing the inner conductor 1;

[0066] (2) Preparing an insulating layer 2 on the surface of the inner conductor 1;

[0067] (3) Coating an outer conductor 3 outside the insulating layer 2;

[0068] (4) Preparing a protective sleeve 4 on the surface of the outer conductor 3.

[0069] Among them, during the forming process of the inner conductor and / or the outer conductor, in the case of having a corrugated copper tube, its corrugation pitch is designed to be continuously gradually changed in a segmented distribution along the cable length direction as a whole, and adjacent segments each have different gradual change characteristics.

[0070] In another preferred embodiment of the present application, the outer and inner conductors are processed to achieve the corrugation pitch in the following manner:

[0071] The smooth copper strip is longitudinally wrapped through a forming table, and then a corrugated copper tube is formed by welding at the seam of the smooth copper strip using argon arc welding or laser welding;

[0072] 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.

[0073] In still another preferred embodiment of the present application, during the above processing, the following formula is used to achieve automatic control:

[0074] P=(V×K×1000) / R

[0075] Wherein, P represents each corrugation pitch during on-line production, with the unit of mm; V represents the instantaneous forward speed of grooving traction, with the unit of m / min; K represents the compression coefficient that the smooth copper strip has during the processing; R represents the instantaneous rotational speed of the grooving machine during grooving processing, with the unit of r / min.

[0076] Through the above design, not only the dynamic processing process of the above corrugation pitch can be achieved with higher precision and more automation, but also the tolerance of each corrugation pitch can be ensured to be controlled within ±0.05 mm, which is more conducive to improving the final performance of the coaxial cable product to a certain extent.

[0077] More specifically, compared with the traditional 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 a preset input variation function; the grooving processing module is used to adjust the motor speed according to a preset input variation function, and then groove the conductor to output a set pitch.

[0078] The following gives a specific example for better explaining the present application.

[0079] Specific Example 1

[0080] In this specific example, the provided radio frequency coaxial cable is applied to the HHTAY-50-42 radio frequency coaxial cable (cable specification is -42) in the YD / T1092 standard, and its specific processing steps are as follows:

[0081] After the smooth copper strip is formed, it is formed into a copper tube through argon arc welding, and then grooved on the surface of the copper tube to form a corrugated copper tube inner conductor with a diameter of 17.6 mm;

[0082] Extrude a layer of foamed polyolefin on the surface of the inner conductor to form an insulating semi-finished product with a diameter of 42.7 mm;

[0083] After the smooth copper strip is formed, it becomes a copper tube through argon arc welding. Insert the insulating semi-finished product into the copper tube, and advance forward under the clamping of the main traction according to the above control method and enter the corrugating box for high-speed corrugating to form a corrugated copper tube outer conductor semi-finished product with a diameter of 46.5 mm;

[0084] Extrude a layer of polyethylene sheath material on the surface of the outer conductor to form a finished sheath product with a diameter of 49.3 mm.

[0085] The design and verification process of the relevant comparative examples are as follows:

[0086] During the normal production process of the HHTAY-50-42 cable, stop the machine and replace the main traction gearbox of the welding process with a gearbox that had shown wear before. The worn main traction gearbox has periodic defects in speed during traction forward, and the voltage standing wave ratio (i.e., VSWR) of the produced HHTAY-50-42 cable shows multiple-frequency peaks, and the peak positions are near 861 MHz, 1722 MHz, and 2583 MHz respectively. Use the worn main traction to produce 100 meters of cable by normal production technology for shutdown testing (comparative example), and then restart the machine and use the above control method of this application for the main traction drive so that the pitch of the outer conductor undergoes continuous random gradual change, and produce 100 meters of cable for shutdown testing.

[0087] Repeat the above steps alternately 10 times to produce 10 groups of 100-meter cable control groups respectively. Test the voltage standing wave ratio of the 10 groups of control group cables, and the results are shown in Table 1 below.

[0088] Table 1

[0089]

[0090] From the test results in Table 1 above, it can be seen that the VSWR test results of the HHTAY-50-42 cable produced by this application are significantly better than those of the conventional cable produced by using equipment with periodic defects. The effective optimization (reduction) range of its VSWR test value is between 0.17 and 0.29, and its VSWR test results meet the standard requirements.

[0091] In summary, compared with the prior art, this application can not only reduce the voltage standing wave ratio of the radio frequency coaxial cable in a more accurate and convenient way of operation, but also achieve more significant effects compared with the prior art. At the same time, it helps to synchronously improve the cable bending stress and reduce high-frequency signal attenuation, etc.; the designed product structure and processing technology can be fully compatible with the YD / T1092 standard production process, suitable for large-scale mass production, and thus has good practical value and application prospects.

[0092] Those skilled in the art can easily understand 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 replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope 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 a different gradient corrugation pitch; 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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