Circular waveguide transmission line for millimeter waves and method of manufacturing the same

Abstract

The application discloses a circular waveguide transmission line for millimeter waves and a manufacturing method thereof, which comprises a plastic rod, an outer conductor, a metal ridge line and a sheath layer; the plastic rod comprises a core layer and an outer skin layer from inside to outside in sequence, and the outer skin layer is wrapped on the core layer; the outer conductor is wrapped on the plastic rod; the metal ridge line is connected with the outer conductor, and the metal ridge line is overlapped on the plastic rod; and the sheath layer is wrapped on the outer conductor. According to the technical scheme of the application, the metal ridge line is introduced into the waveguide structure, the polarization deflection problem of the circular waveguide can be effectively improved, the practicability of long-distance transmission is improved, and the circular waveguide transmission line for millimeter waves with the plastic rod as the inner lining layer has more elasticity and recoverability compared with the traditional full-metal copper (aluminum) air tube leaky waveguide, and damage in the transportation or construction laying process can be avoided.

Description

Technical Field

[0001] This invention relates to the field of communication transmission technology, and more specifically to circular waveguide transmission lines for millimeter waves. Background Technology

[0002] With the continuous development of modern communication technology, spectrum resources are becoming increasingly scarce. The millimeter-wave band, however, possesses enormous potential for spectrum resource development. Therefore, how to develop and utilize millimeter-wave spectrum resources, originally used in satellite and radar military systems, has become a key focus of fifth-generation mobile communication technology. Among these challenges, the transmission of millimeter-wave signals between devices faces the issue of improvement and replacement due to the dramatic increase in attenuation of traditional coaxial cables in the millimeter-wave band.

[0003] A circular waveguide is a cylindrical waveguide with a circular cross-section. Circular waveguides possess characteristics of low loss and dual polarization, making them commonly used in antenna feed lines. They can also be used as transmission lines over long distances and are widely used in microwave resonant cavities. As a communication transmission line, a circular waveguide offers many advantages for transmitting millimeter-wave electromagnetic signals: higher transmission power for the same cross-sectional perimeter (due to the largest cross-sectional area of ​​a circle), and lower transmission attenuation. Furthermore, compared to rectangular waveguides, they can be transported in trays and are relatively easier to install and deploy. However, achieving millimeter-wave signal transmission with a circular waveguide requires stringent requirements for manufacturing precision and product consistency. Therefore, improvements to the structure and manufacturing process of circular waveguides are needed to enable their wider application. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a circular waveguide transmission line with stable waveguide structure and electrical performance and a method for manufacturing the same.

[0005] To solve the above-mentioned technical problems, the present invention first provides the following technical solution: a circular waveguide transmission line for millimeter waves, comprising:

[0006] A plastic rod, comprising a core layer and an outer skin layer from the inside out, wherein the outer skin layer covers the core layer;

[0007] An outer conductor, which is wrapped around the plastic rod;

[0008] A metal ridge wire is connected to the outer conductor, and the metal ridge wire overlaps the plastic rod, and the metal ridge wire is continuously arranged along the length direction of the plastic rod;

[0009] A sheath layer that covers the outer conductor.

[0010] By adopting the above technical solution and introducing a metal ridge wire into the waveguide structure, the polarization deflection problem can be effectively improved, enhancing the practicality of long-distance transmission. Simultaneously, using a plastic rod as the inner lining layer of the millimeter-wave circular waveguide transmission line can prevent external moisture from intruding into the transmission line and affecting its electrical performance. Furthermore, compared to traditional all-metal copper (aluminum) hollow tube leaky cable waveguides, millimeter-wave circular waveguide transmission lines with a plastic rod as the inner lining are more flexible and recoverable, avoiding damage during transportation or construction deployment.

[0011] In one embodiment of the present invention, the outer conductor is a single-layer copper-plastic composite film, which includes a copper layer and a plastic layer, wherein the copper layer and the plastic layer are connected.

[0012] In one embodiment of the present invention, the thickness of the copper layer ranges from 0.1 mm to 0.2 mm, and the thickness of the plastic layer ranges from 0.08 mm to 0.2 mm.

[0013] By adopting the above technical solution, using the copper-plastic composite film as the outer conductor of the circular waveguide can improve the performance of the waveguide. At the same time, the size selection of the copper layer and the plastic layer can better meet the communication requirements without affecting other performance of the circular waveguide transmission line.

[0014] In one embodiment of the present invention, the width of the metal ridge is 0.5 mm to 3 mm.

[0015] By adopting the above technical solution, the polarization problem generated by the circular waveguide during application can be better improved without affecting other performance characteristics of the circular waveguide.

[0016] In one embodiment of the present invention, the core layer is a foamed polyolefin material.

[0017] In one embodiment of the present invention, the outer skin layer is an unfoamed polyolefin material.

[0018] In one embodiment of the present invention, the dielectric constant of the materials used for the core layer and the outer skin layer is less than 2.25 F / m.

[0019] By adopting the above technical solution, on the one hand, it can prevent external moisture from invading the transmission line during long-term operation, thereby affecting the transmission performance of the circular waveguide transmission line used for millimeter waves; on the other hand, the core layer and the outer skin layer are made of materials with relatively low permittivity, which can reduce the impact of the filler on high-frequency signal transmission.

[0020] In one embodiment of the present invention, the ellipticity of the plastic rod is 0.001, and the straightness of the plastic rod is no more than 3 mm per meter.

[0021] By adopting the above technical solution, the signal transmission performance of the circular waveguide transmission line can be improved.

[0022] In one embodiment of the present invention, the sheath layer is made of polyolefin, flame-retardant polyolefin or polyvinyl chloride.

[0023] By adopting the above technical solution, the circular waveguide can be protected from mechanical damage, and flame-retardant properties can be provided when required.

[0024] To address the aforementioned technical problems, the present invention also provides a method for manufacturing a circular waveguide transmission line for millimeter waves, comprising the following steps:

[0025] S1: A plastic rod is extruded using a double-layer extruder. The resulting plastic rod includes a core layer and an outer skin layer. The core layer is physically foamed during the extrusion process by injecting nitrogen or carbon dioxide gas. The outer skin layer is not foamed and uniformly wraps around the core layer.

[0026] S2: A chemical agent is coated on the outside of the plastic rod, and the outer conductor is attached to the outer surface of the plastic rod in a longitudinal wrapping manner using the chemical agent. During the adhesion process, the two edges of the outer conductor overlap and connect to the plastic rod to form a metal ridge.

[0027] S3: Through a negative pressure suction process, the molten sheath material is passed through an extruder and can be tightly wrapped around the outer conductor to tighten and fix the outer conductor to the plastic rod.

[0028] By adopting the above technical solution, the present invention forms a metal ridge by overlapping the two edges of the outer conductor on the plastic rod, which not only improves the polarization deflection problem of circular waveguide transmission lines in practical applications, but also greatly improves the feasibility of process production, enabling continuous, large-scale industrial production, and improving product consistency and stability.

[0029] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A schematic diagram of the structure of a circular waveguide transmission line for millimeter waves provided by the present invention;

[0032] Figure 2 A schematic cross-sectional view of a circular waveguide transmission line for millimeter waves provided by the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the single-layer copper-plastic composite film provided by the present invention;

[0034] Figure 4 A flowchart illustrating the manufacturing method of a circular waveguide transmission line for millimeter waves provided by the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] like Figures 1 to 3As shown, this invention provides a circular waveguide transmission line for millimeter waves, which comprises, from the inside out, a plastic rod 1, an outer conductor 2, a metal ridge wire 3, and a sheath layer 4. The plastic rod 1 includes, from the inside out, a core layer 11 and an outer sheath layer 12, with the outer sheath layer 12 covering the core layer 11. The outer conductor 2 covers the plastic rod 1, that is, the outer conductor 2 covers the outer sheath layer. The metal ridge wire 3 is connected to the outer conductor 2 and overlaps the plastic rod 1, and the metal ridge wire 3 is continuously arranged along the length of the plastic rod 1. The sheath layer 4 covers the outer conductor 2. In this embodiment, the outer conductor 2 is integrated longitudinally wrapped around the plastic rod 1. In this embodiment, the outer conductor 2 is a single-layer copper-plastic composite film, comprising a copper layer 21 and a plastic layer 22. The copper layer 21 is a copper strip, such as TU2 type oxygen-free copper, with a thickness ranging from 0.1 mm to 0.2 mm. The plastic layer 22 can be made of ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer, with a thickness ranging from 0.08 mm to 0.2 mm. The selection of the copper-plastic composite film thickness needs to meet communication requirements without affecting the performance of the circular waveguide transmission line used for millimeter waves. Furthermore, according to the skin depth calculation formula for high-frequency electromagnetic field transmission in a metallic conductor: Where: δ is the skin depth, ω is the angular frequency, M is the permeability, and ρ is the resistivity. These can be calculated as follows:

[0038]

[0039] Therefore, the thickness of the copper layer 21 in the copper-plastic composite film can meet the communication requirements at high frequencies, and can be used as the outer conductor 2 of a millimeter-wave circular waveguide transmission line without affecting its high-frequency electrical performance. Introducing the metal ridge 3 into the waveguide structure, with the ridge 3 continuously arranged along the length of the plastic rod 1, can effectively improve polarization deflection and enhance the practicality of long-distance transmission. Simultaneously, using the plastic rod as the inner lining layer of the millimeter-wave circular waveguide transmission line can prevent external moisture from intruding into the transmission line and affecting its electrical performance. Furthermore, compared to traditional all-metal copper (aluminum) hollow tube leaky cable waveguides, the millimeter-wave circular waveguide transmission line with the plastic rod as the inner lining layer is more flexible and recoverable, avoiding damage during transportation or installation.

[0040] like Figures 1 to 3As shown, in this embodiment, the plastic rod 1 has a double-layer structure, consisting of a core layer 11 and an outer skin layer 12 from the inside out. The core layer 11 is a low-density polyolefin material after physical foaming, or other materials with excellent dielectric constant properties. The outer skin layer 12 is an unfoamed low-density polyolefin material, or other materials with the same or similar dielectric constant properties as the core layer material. The dielectric constants of the materials used in the core layer 11 and the outer skin layer 12 are less than 2.25 F / m. In this embodiment, using the plastic rod as the waveguide liner can improve the structural stability and electrical performance stability of the circular waveguide transmission line used for millimeter waves. Simultaneously, on the one hand, it can prevent moisture from the surrounding environment from gradually intruding during long-term operation, thereby affecting the electrical performance of the circular waveguide; on the other hand, the plastic material is more elastic and recoverable, preventing damage during transportation or construction deployment, further improving the stability of the product structure. In this embodiment, the outer diameter of the plastic rod 1 is linearly related to the cutoff wavelength of the transmitted signal. The outer diameter of the plastic rod 1 can be selected according to the communication operating frequency and the cutoff frequency of the circular waveguide, using a formula. For example, high-frequency signal transmission in a circular waveguide is limited by the cutoff wavelength, that is, when the dominant mode transmitted in the circular waveguide is TE... 11 Time and TM 01 When the corresponding cutoff wavelength is reached, the diameter of the circular waveguide can be derived using the following formulas: λc = 3.412 * D / 2, λc = 2.61 * D / 2, where λc is the cutoff wavelength; D is the diameter of the circular waveguide, which is the outer diameter of the plastic rod 1 in this embodiment. The outer diameter of the plastic rod 1 should be controlled within a deviation of less than ±0.05mm, an ellipticity of 0.001, and a straightness of no more than 3mm per meter. Of course, in practical applications, for the transmission of waveguide signals, it is also necessary to distinguish the equivalent dielectric constant ε of the circular waveguide. g The two cases are greater than or equal to 1 and less than 1, while ε g The outer diameter of the circular waveguide is determined by parameters such as the dielectric constant of the core layer 11, the waveguide operating frequency, and the waveguide cutoff wavelength. Therefore, determining the outer diameter of the circular waveguide requires considering the equivalent dielectric constant of the core layer 11 within the plastic rod, the waveguide's operating radiation mode, operating frequency, waveguide cutoff wavelength, the size and period of the slots used for signal transmission, and so on. In this embodiment, the sheath layer 4 is made of polyolefin, but it is not limited to this; it can also be made of flame-retardant polyolefin, polyvinylidene fluoride, or other materials, as long as it can protect the cable from mechanical damage and provide flame-retardant functionality when needed.

[0041] like Figures 1 to 3As shown, in this embodiment, a metal ridge 3 is formed by overlapping and connecting the two edges of the outer conductor 2 onto the plastic rod. The shape of the metal ridge 3 can be rectangular, circular, etc., and the maximum size of the metal ridge 3 can vary within a range smaller than the radius of the circular waveguide. In this embodiment, the width of the metal ridge 3 ranges from 0.5 mm to 3 mm. When there is no metal ridge 3 in the circular waveguide, the boundary conditions of the circular waveguide are rotationally symmetric, and TE... 11 The field distribution at any angle of deflection of the waveguide's electric field polarization surface is a solution to Maxwell's equations under the same boundary conditions. The electric field inside the waveguide increases with the width of the metal ridge 3, and more energy is concentrated around the ridge 3 as its width increases. The addition of the metal ridge 3 eliminates the rotational symmetry of the boundary conditions, thus improving the polarization deflection problem of the circular waveguide. However, the width of the metal ridge 3 cannot be too large, as this will affect the field distribution inside the circular waveguide and consequently the signal transmission. Different widths of the metal ridge 3 can affect the distribution of the electromagnetic field inside the circular waveguide, thereby increasing transmission loss. Therefore, in this embodiment, the width of the metal ridge 3 is set between 0.5 mm and 3 mm. This improves the polarization deflection problem of the circular waveguide without significantly affecting signal transmission, and is a reasonable design based on the outer diameter of the circular waveguide and the frequency of the transmitted signal.

[0042] like Figure 4 As shown, the present invention also provides a method for manufacturing a circular waveguide transmission line for millimeter waves, comprising the following steps:

[0043] S1: A plastic rod is extruded using a double-layer extruder. The resulting plastic rod includes a core layer and an outer skin layer. The core layer is physically foamed during the extrusion process by injecting nitrogen or carbon dioxide gas. The outer skin layer is not foamed and uniformly wraps around the core layer.

[0044] S2: A chemical agent is coated on the outside of the plastic rod, and the outer conductor is attached to the outer surface of the plastic rod in a longitudinal wrapping manner using the chemical agent. During the adhesion process, the two edges of the outer conductor overlap and connect to the plastic rod to form a metal ridge.

[0045] S3: Through a negative pressure suction process, the molten sheath material is passed through an extruder and can be tightly wrapped around the outer conductor to tighten and fix the outer conductor to the plastic rod.

[0046] It should be noted that in step S1, the core layer undergoes physical foaming by injecting nitrogen or carbon dioxide gas. To ensure the uniformity and consistency of the foamed cells in the core layer, the degree of foaming (the volume ratio between gas and material in the core layer) needs to reach at least 75%. The core layer uses foamed low-density polyolefin material, while the outer skin layer uses unfoamed low-density polyolefin material. The dielectric constants of both the core layer and the outer skin layer are less than 2.25 F / m and their properties are similar. The foamed structure of the core layer can effectively reduce the dielectric constant of the material and reduce the attenuation of high-frequency electromagnetic signals in the circular waveguide. Nitrogen is a non-polar gas and has little impact on high-frequency electromagnetic signals, while carbon dioxide gas can operate in a supercritical fluid state during injection, increasing the degree of foaming. Ensuring the uniformity and consistency of the foamed cells can improve the stability of electromagnetic wave signal transmission inside the circular waveguide and reduce the impact on the signal voltage standing wave ratio performance. At the same time, it can prevent external moisture from invading the transmission line during long-term operation, thereby affecting the transmission performance of the circular waveguide transmission line used for millimeter waves. In step S2, a single-layer copper-plastic composite film is selected as the outer conductor. The copper layer of the composite film is faced inwards and longitudinally adhered to the outer surface of the plastic rod. During the longitudinal adhesion, the two edges of the composite film need to overlap on the plastic rod, with an overlap width of 0.5mm to 3mm. The introduction of metal ridges can improve the polarization deflection problem of circular waveguides in engineering applications. When the circular waveguide has a circular symmetrical structure, its internal structure has slight inhomogeneities, affecting the dominant mode TE. 11 The polarization surface of the waveguide field structure will rotate, affecting signal transmission. Traditional methods of producing circular waveguides struggle to completely eliminate structural inhomogeneities generated during production, transportation, installation, and use. This method, during the longitudinal wrapping process of the copper-plastic composite film, overlaps the two edges of the composite film to form a metal ridge along the length of the waveguide. This metal ridge disrupts the rotational symmetry of the circular waveguide boundary conditions, ensuring the uniqueness of the polarization direction of the waveguide's internal field structure. This makes the circular waveguide practical for long-distance transmission.

[0047] In summary, this invention provides a circular waveguide transmission line for millimeter waves and its manufacturing method. By using a copper-plastic composite film as the outer conductor of the circular waveguide, it replaces the traditional process of continuously drawing and segmenting all-metal copper (aluminum) tubes. This allows for continuous and long-length production of circular waveguides while significantly reducing material consumption and lowering production costs.

[0048] This invention improves the polarization deflection problem in the engineering application of circular waveguides by overlapping the two edges of the outer conductor to form a metal ridge. When a circular waveguide has a circular symmetrical structure, slight inhomogeneities in its internal structure can affect signal transmission. Traditional manufacturing processes often fail to completely eliminate these structural inhomogeneities generated during production, transportation, installation, and use. The metal ridge disrupts the rotational symmetry of the circular waveguide's boundary conditions, ensuring the uniqueness of the polarization direction of the electromagnetic field structure within the waveguide. This maintains the unchanged polarization direction of the electromagnetic field structure, making circular waveguides practical for long-distance transmission.

[0049] This invention uses a plastic rod as the inner lining layer of a circular waveguide, which can prevent external moisture from entering the waveguide and improve the waveguide's electrical performance. At the same time, compared with traditional all-metal copper (aluminum) hollow tube leaky cable waveguides, the plastic rod is more elastic and recoverable, which can prevent damage during transportation or construction and deployment.

[0050] The plastic rod of this invention is made of low-density polyolefin material after physical foaming, which can reduce the impact on the transmission performance of the circular waveguide at high frequencies of communication, and the outer skin layer can further prevent moisture from entering the circular waveguide.

[0051] The circular waveguide transmission line provided by this invention has better bending performance than traditional all-metal copper (or aluminum) hollow tube leaky cable waveguides, and has advantages such as reducing material usage, reducing transmission line weight, reducing cost, and facilitating installation.

[0052] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A circular waveguide transmission line for millimeter waves, characterized in that, include: The plastic rod (1) comprises, from the inside out, a core layer (11) and an outer skin layer (12), wherein the outer skin layer (12) covers the core layer (11); the core layer (11) is a foamed polyolefin material, and the outer skin layer (12) is an unfoamed polyolefin material; the dielectric constant of the materials used for the core layer (11) and the outer skin layer (12) is less than 2.25 F / m. An outer conductor (2) is wrapped around the plastic rod (1); A metal ridge (3) is connected to the outer conductor (2), and the metal ridge (3) overlaps the plastic rod (1), and the metal ridge (3) is continuously arranged along the length direction of the plastic rod (1); the width of the metal ridge (3) is 0.5 mm to 3 mm, and the metal ridge (3) is used to make the polarization direction of the waveguide inner field structure unique; Sheath layer (4), which covers the outer conductor (2).

2. The circular waveguide transmission line for millimeter waves according to claim 1, characterized in that, The outer conductor (2) is a single-layer copper-plastic composite film, which includes a copper layer (21) and a plastic layer (22), wherein the copper layer (21) and the plastic layer (22) are connected.

3. The circular waveguide transmission line for millimeter waves according to claim 2, characterized in that, The thickness of the copper layer (21) ranges from 0.1 mm to 0.2 mm, and the thickness of the plastic layer (22) ranges from 0.08 mm to 0.2 mm.

4. The circular waveguide transmission line for millimeter waves according to claim 1, characterized in that, The ellipticity of the plastic rod (1) is 0.001, and the straightness of the plastic rod (1) is no more than 3 mm per meter.

5. The circular waveguide transmission line for millimeter waves according to claim 1, characterized in that, The sheath layer (4) is made of polyolefin, flame-retardant polyolefin or polyvinyl chloride.

6. A method for manufacturing a circular waveguide transmission line for millimeter waves according to any one of claims 1-5, characterized in that, Includes the following steps: S1: A plastic rod is extruded using a double-layer extruder. The resulting plastic rod includes a core layer and an outer skin layer. The core layer is physically foamed during the extrusion process by injecting nitrogen or carbon dioxide gas. The outer skin layer is not foamed and uniformly wraps around the core layer. S2: A chemical agent is coated on the outside of the plastic rod, and the outer conductor is attached to the outer surface of the plastic rod in a longitudinal wrapping manner using the chemical agent. During the adhesion process, the two edges of the outer conductor overlap and connect to the plastic rod to form a metal ridge. S3: Through a negative pressure suction process, the molten sheath material is passed through an extruder and can be tightly wrapped around the outer conductor to tighten and fix the outer conductor to the plastic rod.

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