Low-loss, miniaturized millimeter wave transmission line and method of manufacture and use thereof

Abstract

The application relates to the technical field of communication transmission, in particular to a low-loss and miniaturized millimeter wave transmission line and a preparation method and application thereof. The millimeter wave transmission line is prepared from a composite material, the composite material comprises a polymer matrix and high-dielectric fillers dispersed in the polymer matrix, the dielectric constant of the high-dielectric fillers is greater than that of the polymer matrix; the high-dielectric fillers are selected from one-dimensional / two-dimensional inorganic fillers or one-dimensional / two-dimensional functionalized fillers, and the functionalized fillers are formed after modification of the inorganic fillers; in the transmission line, the high-dielectric fillers are distributed in the polymer matrix in an orientation direction, and the orientation direction of the high-dielectric fillers is perpendicular to the electric field oscillation direction. The low-loss and miniaturized millimeter wave transmission line can meet the requirements of high dielectric constant and low transmission loss under the millimeter wave frequency.

Description

Technical Field

[0001] This invention relates to the field of communication transmission technology, specifically to a low-loss, miniaturized millimeter-wave transmission line, its fabrication method, and its application. Background Technology

[0002] Millimeter-wave transmission lines are increasingly being used in high-definition video transmission, autonomous driving data interconnection, and industrial internet intelligent sensing due to their advantages of high carrier frequency, fast transmission rate, and low cost.

[0003] Currently, millimeter-wave transmission lines mainly include hollow metal waveguides, ridge waveguides, and dielectric waveguides. The high rigidity of metal and ridge waveguides makes it difficult to achieve flexibility and bendability when used as millimeter-wave transmission lines, limiting their further application in obstacle avoidance communication. Dielectric waveguides made of polymer materials, with their high flexibility, show great promise for millimeter-wave transmission lines. However, the low dielectric constant of non-polar polymers results in insufficient millimeter-wave signal confinement, leading to larger cross-sectional dimensions. This reduces port density and flexibility, and fails to meet miniaturization requirements.

[0004] Existing technologies improve the dielectric constant of polymer materials by adding inorganic fillers with high dielectric constants, thereby enhancing their ability to confine millimeter-wave signals and achieving miniaturization. However, in practice, using inorganic fillers with high dielectric constants leads to interfacial impedance mismatch due to the large difference in dielectric constant between the filler and the polymer matrix. This results in severe interfacial electric field coupling concentration between the fillers, causing a large loss tangent and making it difficult to ensure stable signal transmission. While using inorganic fillers with lower dielectric constants can achieve impedance matching and reduce electric field coupling while maintaining low loss, these fillers cannot effectively improve the dielectric constant of the composite material, resulting in high filler doping levels and low efficiency.

[0005] To achieve the preparation of polymer-based composite materials with high dielectric constant and low dielectric loss, existing technologies have been extensively studied. These studies mostly focus on surface modification of fillers to improve the interfacial compatibility between the filler and the matrix, thereby reducing losses caused by interfacial defects. For example, Chinese patent CN103408775A discloses a method for preparing flexible composite dielectric materials with high dielectric constant and low dielectric loss. This method uses large aspect ratio BaTiO3 or MgTiO3 inorganic nanofibers to improve the dielectric constant of the composite material. Chemical modification is performed on the fiber surface to introduce carbon-fluorine bonds. On the one hand, the introduction of carbon-fluorine bonds significantly improves the compatibility between the nanofibers and the polymer matrix and reduces interfacial defects; on the other hand, the polarization loss of carbon-fluorine bonds is small. These two effects effectively reduce the dielectric loss of the composite material. Some studies have focused on coating high dielectric constant fillers with low dielectric constant inorganic materials (such as silicon dioxide or titanium dioxide) to reduce the dielectric constant difference at the contact interface. For example, Chinese patent CN116355331A discloses a core-shell structured barium titanate-doped PVDF-based composite film, its preparation method and application. It discloses a composite film made of core-shell structured BaTiO3@Al2O3 nanofibers loaded in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), wherein the shell is alumina and the core is barium titanate. The introduction of alumina in the shell alleviates the dielectric difference between barium titanate and the polymer matrix, which can effectively reduce the electric field distortion at the interface and thus reduce losses.

[0006] However, while the aforementioned existing technologies can reduce the losses of filler-doped polymer composite materials to some extent, they still fail to meet the requirements of low loss and miniaturization for transmission lines at millimeter-wave frequencies. Therefore, developing a transmission line that meets the requirements of low loss and miniaturization at millimeter-wave frequencies remains a key technical problem that urgently needs to be solved in the field of millimeter-wave communication. Summary of the Invention

[0007] The primary objective of this invention is to provide a low-loss, miniaturized millimeter-wave transmission line that meets the requirements of high dielectric constant and low dielectric loss at millimeter-wave frequencies.

[0008] Another object of the present invention is to provide a method for fabricating the above-mentioned low-loss, miniaturized millimeter-wave transmission line.

[0009] A third objective of this invention is to provide applications of the aforementioned low-loss, miniaturized millimeter-wave transmission line.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] In a first aspect, the present invention provides a low-loss, miniaturized millimeter-wave transmission line prepared from a composite material, the composite material comprising a polymer matrix and a high-dielectric filler dispersed in the polymer matrix, wherein the dielectric constant of the high-dielectric filler is greater than that of the polymer matrix; the high-dielectric filler is selected from one-dimensional / two-dimensional inorganic fillers or one-dimensional / two-dimensional functionalized fillers, wherein the functionalized filler is formed by modifying the inorganic filler; in the transmission line, the high-dielectric filler is oriented and distributed in the polymer matrix, and the orientation direction of the high-dielectric filler is perpendicular to the direction of electric field oscillation.

[0012] This invention involves adding one-dimensional or two-dimensional high-dielectric fillers to a polymer matrix. The high-dielectric fillers are oriented and distributed within the polymer matrix in the transmission line, with their orientation perpendicular to the direction of the electric field oscillation during signal transmission. This significantly reduces the local coupling effect between fillers caused by the polarized electric field during signal transmission, effectively suppressing localized accumulation in high-field regions and minimizing dielectric breakdown and energy loss caused by electric field concentration. Consequently, it maintains extremely low transmission loss while increasing the dielectric constant.

[0013] In addition, the orientationally distributed high-dielectric filler in the transmission line of this invention equalizes the electric field distribution, thereby enhancing the signal confinement capability during transmission and enabling the transmission line to achieve a higher signal-to-noise ratio and communication stability while maintaining low loss. Simultaneously, the uniform orientation of the filler interface optimizes the dielectric properties of the material in the transmission direction, providing a more scalable structural basis for its transmission applications in the millimeter-wave band.

[0014] Preferably, the inorganic filler of the present invention is selected from alumina whiskers, strontium titanate whiskers, barium titanate whiskers, zinc oxide whiskers, alumina flakes, strontium titanate flakes, or barium titanate flakes. These inorganic fillers are relatively easy to prepare into one-dimensional or two-dimensional shapes, and they themselves have high dielectric constants, and are often used as fillers to improve dielectric constants.

[0015] More preferably, when the inorganic filler is a one-dimensional material, the length of the inorganic filler is 8~12μm and the diameter of the inorganic filler is 0.8~1.2μm; when the inorganic filler is a two-dimensional material, the length of the inorganic filler is 8~12μm, the width is 0.8~1.2μm and the thickness is 10~20nm.

[0016] The selection of inorganic filler size requires consideration of two factors. First, it is necessary to avoid excessive agglomeration in the polymer matrix, so the size cannot be too small. Second, it is necessary to avoid excessive porosity defects at the interface between the filler and the polymer matrix, which would increase losses, so the size cannot be too large. In addition, the aspect ratio of inorganic filler cannot be too small so that it can form an oriented distribution in the transmission line, and the aspect ratio cannot be too large to avoid breakage during the mixing process.

[0017] To better reduce losses, the present invention preferably uses functionalized fillers as high dielectric fillers. Specifically, the functionalized fillers include inorganic fillers, a first coating layer covering the surface of the inorganic fillers, and a second coating layer covering the surface of the first coating layer. The dielectric constants of the inorganic fillers, the first coating layer, the second coating layer, and the polymer matrix satisfy the following order: inorganic fillers > first coating layer > second coating layer > polymer matrix.

[0018] Based on the principle of suppressing local electric field accumulation through the orientation distribution of fillers, this invention further suppresses the interfacial polarization effect by constructing a functionalized filler structure consisting of a core layer, a first coating layer, and a second coating layer.

[0019] Specifically, this structure of the functionalized filler utilizes the gradual decrease in dielectric constant between the first and second coating layers to form a multi-layered reflective interface during electric field propagation. This achieves impedance matching at each stage, effectively reflecting and attenuating the local electric field generated by the polarization of the high-dielectric inorganic filler, blocking the electric field coupling channel between fillers, suppressing the interface polarization effect, and significantly reducing the dielectric loss of the composite material. It should be noted that, according to the multi-level reflection theory of this invention, in practice, theoretically, a third or even fourth coating layer could be added on top of the second coating layer to achieve better electric field reflection. This invention chooses two coating layers because a single coating layer has limited reflectivity; the two-level reflection formed by two coating layers can effectively solve the electric field coupling problem between inorganic fillers with extremely high dielectric constants in the polymer matrix. Multi-layer coating not only increases the proportion of low-dielectric-constant components in the functional filler, affecting the overall dielectric performance of the functional filler, but also makes the manufacturing process more complicated and increases manufacturing costs.

[0020] Preferably, the functionalized filler of the present invention further includes surface functional groups. The surface of the inorganic filler after being sequentially coated with a first coating layer and a second coating layer is subjected to silane coupling agent functionalization treatment to obtain the functionalized filler. The silane coupling agent is preferably 3-(2-aminoethylamino)-propyltriethoxysilane (AEAPTMS) or γ-aminopropyltriethoxysilane (APTES).

[0021] This invention modifies the surface of functionalized fillers with silane coupling agents, thereby increasing the hydrophilicity and polarity of the surface of the functionalized fillers, reducing the van der Waals forces between functionalized fillers, thus reducing the agglomeration of functionalized fillers and improving the dispersion stability of functionalized fillers in the matrix.

[0022] Preferably, the material of the first coating layer is selected from silicon dioxide or titanium dioxide; the material of the second coating layer is selected from silicon dioxide, mesoporous silicon dioxide or mesoporous titanium dioxide.

[0023] The above materials were chosen as coating materials not only because their dielectric constants meet the requirements, but more importantly, because the coating films can be prepared by the sol-gel method or the template method. The processes are already mature and facilitate the industrial production of the products.

[0024] It should be noted that the selection of the first and second coating materials should be determined in conjunction with the selection of the inorganic filler in the core layer and the polymer matrix, and should meet the requirement that "the dielectric constant of the material from the core layer to the surface layer decreases step by step and is greater than the dielectric constant of the polymer matrix".

[0025] In actual preparation, the dielectric constant of mesoporous silica and mesoporous titanium dioxide can be adjusted by controlling their porosity, so that they meet the requirement of being less than the dielectric constant of the first coating layer material.

[0026] The preferred material for the second coating layer in this invention is mesoporous silica or mesoporous titanium dioxide. This is because the invention requires silane coupling agent functionalization treatment on the surface of the second coating layer. The presence of mesopores can provide more attachment sites for the silane coupling agent, resulting in better dispersion of the entire functionalized filler in the polymer matrix. This overcomes the problems of interfacial incompatibility between inorganic fillers and polymer matrix, as well as the easy formation of pore defects at the interface between inorganic fillers and polymer matrix, thereby improving the dielectric properties of the overall composite material.

[0027] Preferably, the thickness of the first coating layer is 0.05~0.1μm; the thickness of the second coating layer is 0.1~0.3μm. The design of the thickness of the first and second coating layers needs to ensure that they can play a corresponding role in multilayer electric field reflection, and at the same time, they need to occupy as small a proportion of the entire functionalized filler as possible to avoid weakening the dielectric constant of the overall material.

[0028] Preferably, when the second coating layer is selected from mesoporous silica or mesoporous titanium dioxide, the porosity of both the mesoporous silica and the mesoporous titanium dioxide satisfies the following conditions: porosity of 10%~40% and pore size of 5nm~10nm. The porosity and pore size of the mesoporous coating layer directly affect its reflection effect on the electric field. If the porosity or pore size is too large, the electric field will pass through the pores, weakening the reflection effect of the layer on the electric field. This, in turn, strengthens the electric field coupling between the inorganic fillers, increasing losses.

[0029] Preferably, the volume ratio of the high dielectric filler to the polymer matrix is ​​1:3 to 1.2:1.

[0030] This invention, through the design of high dielectric filler oriented perpendicular to the electric field direction, can maintain a low loss tangent characteristic while improving the overall dielectric constant, thereby ensuring that its dielectric properties, loss characteristics, and mechanical properties all meet the requirements for use.

[0031] The polymer matrix of the present invention can be any non-polar thermoplastic polymer, such as polypropylene, polyethylene or polytetrafluoroethylene, etc.

[0032] It should be noted that, like conventional transmission lines, the transmission line of this invention also includes a surface metal shielding layer to achieve functions such as electromagnetic interference resistance and physical protection.

[0033] Secondly, the present invention provides a method for fabricating the aforementioned low-loss, miniaturized millimeter-wave transmission line.

[0034] The core of this preparation method is as follows: The composite masterbatch obtained from the composite material preparation is extruded through an extruder to produce transport lines; and by setting a hot-rolling die at the die of the extruder, the molten transport lines, under the action of extrusion pressure, cause the high-dielectric filler to undergo a highly oriented alignment in the polymer matrix, with its orientation direction perpendicular to the electric field oscillation direction. The aforementioned composite masterbatch is obtained by physically blending the high-dielectric filler and the polymer matrix.

[0035] Preferably, the extrusion temperature in the above extrusion process is controlled at 200℃, the extrusion speed at 300 rpm, and the traction speed at 500 rpm to 600 rpm; the hot rolling temperature in the hot rolling process is 180℃, the roller compression ratio is 80%, the roller pressure is 1 MPa, and the roller linear speed is set to 350 rpm to 400 rpm. The orientation degree of the high-dielectric filler is controlled by adjusting the traction speed and the roller linear speed.

[0036] More specifically, the preparation method of composite material masterbatch is as follows: weigh the polymer masterbatch, mechanically blend the components according to the proportion, at a speed of 300 rpm, for 5 minutes each time, in 3 batches; add the mixed raw materials into a twin-screw extruder, with a twin-screw processing temperature of 220℃ and a screw speed of 300 rpm; extrude the blended composite material melt, water-cool and pelletize it, and dry the granulated composite material masterbatch in a vacuum drying oven for 6 hours at a drying temperature of 80℃ to obtain the composite material masterbatch.

[0037] Under normal circumstances, after the transmission line is extruded, its surface layer still needs to be prepared with a metal shielding layer. Specifically, the preparation method of the metal shielding layer is as follows:

[0038] Sample pretreatment: Place the transmission line sample to be plated in 95% ethanol and ultrasonically clean for 5 minutes to remove surface grease and impurities. Then rinse with deionized water and soak in a 1:1 volume ratio of hydrochloric acid (36~38%) and deionized water for 2 minutes to remove surface oxides and residues. Then rinse with deionized water again for later use.

[0039] Sensitization treatment: Weigh 10 g of tin chloride dihydrate (SnCl2·2H2O) and dissolve it in 100 mL of hydrochloric acid to form a sensitization solution. Immerse the sample in this solution for 5 minutes to allow stannous ions to be adsorbed on the surface, and then gently rinse with deionized water.

[0040] Activation treatment: Prepare a silver nitrate solution (1.7g AgNO3 dissolved in 100 mL deionized water), immerse the sensitized sample in the solution for 2 minutes to generate silver nuclei on the surface, which promotes the subsequent deposition of silver layers.

[0041] Chemical silver plating: Prepare the plating solution by dissolving 1.7g of silver nitrate in 100mL of deionized water, adding 25% ammonia dropwise until the white precipitate is completely dissolved, forming an [Ag(NH3)2]⁺ complex. Add 3.6g of glucose as a reducing agent and adjust the pH to 10.5 with sodium hydroxide. Immerse the activated sample in the plating solution and react for 20-30 minutes to form a silver layer approximately 2μm thick. Gently stir during the process to ensure uniform deposition.

[0042] Immediately after the silver plating is completed, the sample is removed, rinsed with deionized water, dehydrated with 95% ethanol, and then dried with nitrogen to obtain the final transmission line with a metal shielding layer.

[0043] Preferably, when selecting functionalized fillers for the high dielectric filler of the present invention, the functionalized filler needs to be prepared first, and then the functionalized filler and the polymer matrix are prepared into composite material masterbatch by the above-mentioned physical blending method.

[0044] The preparation method of the functionalized filler is as follows:

[0045] A first coating layer is coated onto the surface of an inorganic filler to form a first coating. The first coating layer is coated using a sol-gel method. When the first coating layer is silica, the sol is a silica sol, preferably tetraethyl orthosilicate, tetraethoxysilane, or sodium silicate as the silicon source; when the first coating layer is titanium dioxide, the sol is a titanium sol, preferably tetrabutyl titanate or isopropyl titanate as the titanium source.

[0046] A second coating layer is coated onto the surface of the first coating to form a second coating. When the second coating layer is a non-mesoporous material, the sol-gel method is used for coating; when the second coating layer is a mesoporous material, the template method is used for coating, which involves adding a template agent to the sol to initiate the coating reaction. Similarly, when the sol is a silica sol, tetraethyl orthosilicate, tetraethoxysilane, or sodium silicate are preferably used as the silicon source; when the sol is a titanium sol, tetrabutyl titanate or isopropyl titanate are preferably used as the titanium source. The template agent is selected from cetyltrimethylammonium bromide, polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, or polyvinylpyrrolidone.

[0047] In some technical solutions, the functionalized filler also includes surface functional groups. It is necessary to coat the surface of the inorganic filler with a first coating layer and a second coating layer in sequence, and then perform surface silane coupling agent functionalization treatment. At this time, the second coating obtained after coating the second coating layer is dispersed in a solution prepared with silane coupling agent and stirred and soaked, and then dried to obtain the functionalized filler.

[0048] More specifically, when the first coating layer is silicon dioxide, the second coating layer is mesoporous silicon dioxide, and the surface of the second coating layer is further functionalized with a silane coupling agent, the preparation method is as follows:

[0049] A silica layer is coated onto the surface of the inorganic filler to form the first coating:

[0050] Tetraethyl orthosilicate (TEOS), tetraethoxysilane (TESO), or sodium silicate (Na2SiO3) were dissolved in an appropriate amount of ethanol solvent. An appropriate amount of water and an acidic catalyst (hydrochloric acid, adjusted to pH 4-5) were added, and the mixture was stirred at room temperature for 2 hours to form a silica sol. High dielectric constant inorganic filler particles were added to the sol, and the mixture was stirred for a certain time to allow SiO2 to be uniformly deposited on the particle surface. By adjusting the concentration of the silica sol and the stirring time, a SiO2 layer with a final thickness of approximately 0.05-0.1 μm was formed. The mixture was then calcined in air (600℃, 1 hour) to obtain the first coating.

[0051] A mesoporous silica layer is coated onto the surface of the first coating to form a second coating:

[0052] Tetraethyl orthosilicate (TEOS), tetraethoxysilane (TESO), or sodium silicate (Na2SiO3) are dissolved in an appropriate amount of ethanol solvent. An appropriate amount of water and an acidic catalyst (hydrochloric acid, adjusted to pH 4-5) are added, and the mixture is stirred at room temperature for 2 hours to form a silica sol. A template agent (hexadecyltrimethylammonium bromide, CTAB; or polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, P123; or polyvinylpyrrolidone, PVP) is then added, along with an appropriate amount of deionized water. Adjust the pH to alkaline (9-10) and stir at room temperature to form a mesoporous silica sol. Add the first coating to the mesoporous silica sol and keep stirring. React for a certain time. By adjusting the concentration of the silica sol and the stirring time, the mesoporous SiO2 layer is deposited on the outside of the inner SiO2 layer to form a mesoporous SiO2 layer with a thickness of 0.1~0.3μm. Then calcine in air (550℃, 1h) to remove the template agent and form a second coating with a mesoporous SiO2 layer.

[0053] The surface of the second coating is functionalized to obtain the functionalized filler:

[0054] A silane coupling agent (γ-aminopropyltriethoxysilane (APTES) or 3-(2-aminoethylamino)-propyltriethoxysilane (AEAPTMS)) was dissolved in toluene to form a 5 vol% solution; the second coating material was added to the solution and stirred at room temperature for 3 h to functionalize its surface; then it was dried in a vacuum oven at 100 °C for 6 h to obtain the functionalized filler.

[0055] Thirdly, the present invention also provides applications of the aforementioned low-loss, miniaturized millimeter-wave transmission line as a signal transmission device in the millimeter-wave frequency band.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] (1) The low-loss, miniaturized millimeter-wave transmission line provided by the present invention has the flexibility that metal transmission lines and ridge waveguides do not have. By designing "high dielectric filler is oriented and distributed in the transmission line, and the orientation direction of the high dielectric filler is perpendicular to the electric field oscillation direction of the signal transmission of the transmission line", the local coupling effect between fillers caused by polarization electric field is significantly weakened during signal transmission. This effectively suppresses the local accumulation phenomenon in the high field strength region and reduces the energy loss caused by electric field concentration. It achieves the purpose of high dielectric and low loss, thus integrating low loss, miniaturization and flexibility, and has a good application prospect.

[0058] (2) In the transmission line of the present invention, the high dielectric filler is oriented and distributed in the transmission line, which makes the electric field distribution more uniform and enhances the ability to constrain the signal during transmission. This enables the transmission line to achieve a higher signal-to-noise ratio and communication stability while maintaining low loss. At the same time, the uniformity of the filler interface orientation optimizes the dielectric properties of the material in the transmission direction, providing a more scalable structural basis for its transmission application in the millimeter-wave band.

[0059] (3) The present invention functionalizes one-dimensional or two-dimensional inorganic fillers to form two-layer coated functional fillers, and further disperses them in the transmission line in a direction perpendicular to the electric field oscillation direction. The dielectric constant of the two coating materials satisfies the following: it decreases stepwise from the core inorganic filler to the outer layer. This can further improve the concentration of polarization electric field generated when the tips of the oriented inorganic fillers approach each other. Specifically, the two coating layers form two-level electric field reflection, which can effectively reflect and attenuate the local electric field generated when the tips of the high dielectric inorganic fillers approach each other, block the electric field coupling channel between fillers, suppress the interface polarization effect, and further reduce the loss.

[0060] (4) This invention introduces functional groups on the surface of functional fillers by using silane coupling agents, which enables the functional fillers to be more uniformly and stably dispersed in the polymer matrix, reduces the formation of agglomerate structures in the composite material, effectively avoids the problem of unstable composite material performance caused by uneven filler dispersion, improves the uniformity and stability of the composite material, and is beneficial to the high dielectric and low loss dielectric performance in the millimeter wave band; and the presence of surface functional groups strengthens the interfacial compatibility between the functional filler and the matrix surface, reduces interfacial porosity defects, helps to improve the dielectric properties of the material, and reduces loss.

[0061] (5) In this invention, silica is used as the first coating layer and mesoporous silica is used as the second coating layer. This not only achieves two coating layers with decreasing dielectric constants that are both higher than the dielectric constant of the matrix, but also provides more binding sites for silane coupling agents due to the mesoporous nature of the second coating layer. This allows the functionalized groups to be more stably bound to the surface of the functionalized filler, enabling the functionalized filler to be better dispersed in the polymer matrix and to have better interfacial compatibility with the polymer matrix.

[0062] (6) The high dielectric filler orientation method of the present invention is relatively mature, and the preparation process of the coating layer during the preparation of functional filler is also relatively mature. The preparation of the entire transmission line can be quickly industrialized, which is convenient for large-scale promotion and application. Attached Figure Description

[0063] Figure 1 This is the fabrication process of the low-loss, miniaturized millimeter-wave transmission line in Example 1;

[0064] Figure 2 These are finite element simulation diagrams of the electric field coupling between packing materials in different composite models in Experiment Example 1; among them, Figure 2 (a) is a finite element simulation diagram of the electric field coupling between the packings in composite model 1; Figure 2 (b) is a finite element simulation diagram of the electric field coupling between the packings in composite model 2; Figure 2 (c) is a finite element simulation diagram of the electric field coupling between the packings in composite model 3;

[0065] Figure 3 This is a SEM image of the filler orientation distribution in the millimeter-wave transmission line prepared in Example 1;

[0066] Figure 4 This is a SEM image of the millimeter-wave transmission line prepared in Example 1. Detailed Implementation

[0067] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0068] Example 1

[0069] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The fabrication process can be found in the appendix. Figure 1 Specifically, it includes the following steps:

[0070] S1 Functionalized Filler Preparation

[0071] S11 A first coating layer is coated on the surface of the inorganic filler to form a first coating material.

[0072] The inorganic filler is selected as strontium titanate whiskers with a length of 8μm and a diameter of 0.8μm; the first coating layer is silicon dioxide with a thickness of 0.05μm.

[0073] Tetraethyl orthosilicate (TEOS 10g) was dissolved in an appropriate amount of ethanol solvent (40mL), and an appropriate amount of water (2g) and an acidic catalyst (hydrochloric acid, adjusted to pH 4-5) were added. The mixture was stirred at room temperature for 2h to form a silica sol. Strontium titanate whiskers with high dielectric constant were added to the sol, and the mixture was stirred and reacted for 0.5h to allow SiO2 to be uniformly deposited on the particle surface, eventually forming a SiO2 layer with a thickness of about 0.05μm. The mixture was then calcined in air (600℃, 1h) to obtain the first coating.

[0074] S12 Apply a second coating layer to the surface of the first coating to form the second coating.

[0075] The second coating layer is mesoporous silica, and the thickness of the second coating layer is 0.15 μm.

[0076] Tetraethyl orthosilicate (TEOS 15g) was dissolved in an appropriate amount of ethanol solvent (50mL), and an appropriate amount of water (3g) and acidic catalyst (hydrochloric acid, adjusted to pH 4-5) were added. The mixture was stirred at room temperature for 2h to form a silica sol. Then, a template agent (hexadecyltrimethylammonium bromide, CTAB, 3g) was added, along with an appropriate amount of deionized water (40mL) and the pH was adjusted to alkaline (9-10). The mixture was stirred at room temperature to form a mesoporous silica sol. The first coating was added to the mesoporous silica sol, and the mixture was stirred for 1h to allow the mesoporous SiO2 layer to deposit on the outside of the inner SiO2 layer, forming a mesoporous SiO2 layer with a thickness of 0.15μm. The mixture was then calcined in air (550℃, 1h) to remove the template agent, forming a second coating with a mesoporous SiO2 layer. The pore size of the mesoporous silica layer was 5nm and the porosity was 20%.

[0077] S13 performs functionalization treatment on the surface of the second coating to obtain functionalized filler.

[0078] The silane coupling agent γ-aminopropyltriethoxysilane (APTES) was dissolved in toluene to form a 5 vol% solution. The second coating material was added to the solution and stirred at room temperature for 3 h to allow the ethoxy groups in the APTES molecules to undergo a condensation reaction with the hydroxyl groups on the surface of mesoporous SiO2, thereby grafting aminopropyl functional groups onto the surface. Subsequently, the surface was dried in a vacuum oven at 100 °C for 6 h to obtain the functionalized filler.

[0079] S2 composite material preparation

[0080] Functionalized fillers are dispersed in a polymer matrix to form a composite material. The polymer matrix is ​​polypropylene.

[0081] Weigh 500 g of polypropylene masterbatch, and weigh the corresponding amount of functional filler according to the volume ratio of functional filler to polypropylene of 1.2:1; mechanically blend the polypropylene masterbatch and functional filler at a speed of 300 rpm for 5 minutes each time, for 3 times; add the mixed raw material to a twin-screw extruder at a processing temperature of 220°C and a screw speed of 300 rpm; extrude the blended composite melt and water-cool it into pellets to form composite masterbatch; dry the composite masterbatch in a vacuum drying oven for 6 hours at a drying temperature of 80°C to obtain the composite masterbatch of this embodiment.

[0082] S3 transmission line preparation

[0083] The obtained composite masterbatch was added to a single-screw extruder at an extrusion temperature of 200℃, an extrusion speed of 300 rpm, and a traction speed of 500 rpm. A hot-rolling die was set at the die, causing the filler to align highly under extrusion pressure in the molten composite transmission line. The hot-rolling temperature was 180℃, the roller compression ratio was 80%, the roller pressure was 1 MPa, and the roller linear speed was set to 400 rpm. After water cooling and setting, a millimeter-wave transmission line product with highly oriented filler was obtained.

[0084] S4 Metal Shielding Layer Fabrication

[0085] S41 Sample Pretreatment: Place the transmission line sample prepared in step S3 to be plated in 95% ethanol and ultrasonically clean it for 5 minutes to remove surface grease and impurities. Then rinse it with deionized water and soak it in a 1:1 volume ratio of hydrochloric acid (36~38%) and deionized water for 2 minutes to remove surface oxides and residues. Then rinse it with deionized water again for later use.

[0086] S42 Sensitization treatment: Weigh 10 g of tin chloride dihydrate (SnCl2·2H2O) and dissolve it in 100 mL of hydrochloric acid to form a sensitization solution. Immerse the sample in this solution for 5 minutes to allow tin ions to be adsorbed on the surface, and then gently rinse with deionized water.

[0087] S43 activation treatment: Prepare silver nitrate solution (1.7g AgNO3 dissolved in 100 mL deionized water), immerse the sensitized sample in it for 2 minutes to generate silver nuclei on the surface to promote subsequent silver layer deposition.

[0088] S44 underwent chemical silver plating: A silver plating solution was prepared by dissolving 1.7 g AgNO3 in 100 mL of deionized water, adding 25% ammonia dropwise until the white precipitate was completely dissolved, forming an [Ag(NH3)2]⁺ complex. 3.6 g glucose was added as a reducing agent, and the pH was adjusted to 10.5 with sodium hydroxide. The activated sample was immersed in this plating solution for 20-30 minutes to form a silver layer approximately 2 μm thick, with gentle stirring during the process to ensure uniform deposition.

[0089] Immediately after silver plating, the sample is removed, rinsed with deionized water, dehydrated with 95% ethanol, and then dried with nitrogen. This yields the low-loss, miniaturized millimeter-wave transmission line of this embodiment.

[0090] Example 2

[0091] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S1, the inorganic filler is selected as alumina whiskers with a length of 8 μm and a diameter of 0.8 μm.

[0092] Example 3

[0093] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S1, barium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm are selected as the inorganic filler.

[0094] Example 4

[0095] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S1, the inorganic filler is selected as strontium titanate whiskers with a length of 12 μm and a diameter of 1.2 μm.

[0096] Example 5

[0097] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S11, the first coating layer is titanium dioxide, and in step S12, the second coating layer is mesoporous titanium dioxide; the thickness of the first coating layer and the thickness of the second coating layer are the same as in Embodiment 1. Specifically, in the fabrication process, tetraethyl orthosilicate (TEOS) in step S11 is replaced with tetrabutyl titanate (TBOT); and in step S12, tetraethyl orthosilicate (TEOS) is replaced with tetrabutyl titanate (TBOT).

[0098] Example 6

[0099] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S12, by controlling the content of the template agent and the calcination heating process, the porosity of the second coating layer mesoporous silica is made to be 10%.

[0100] Example 7

[0101] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S12, by controlling the content of the template agent and the calcination heating process, the porosity of the second coating layer mesoporous silica is made to be 40%.

[0102] Example 8

[0103] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S12, by controlling the content of the template agent and the calcination heating process, the pore size of the second coating layer mesoporous silica is 8 nm.

[0104] Example 9

[0105] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S12, by controlling the content of the template agent and the calcination heating process, the pore size of the second coating layer mesoporous silica is 10 nm.

[0106] Example 10

[0107] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S2, the amount of functionalized filler added satisfies the following condition: the volume ratio of functionalized filler to polypropylene is 1:1.

[0108] Example 11

[0109] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The only difference from Embodiment 1 is that in step S2, the amount of functionalized filler added satisfies the following condition: the volume ratio of functionalized filler to polypropylene is 2:3.

[0110] Example 12

[0111] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S3, the traction speed is increased to 600 rpm and the hot rolling roller speed is reduced to 350 rpm in order to improve the orientation of the filler in the transmission line.

[0112] Example 13

[0113] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that step S1 is not required, i.e., no functionalization treatment is performed on the inorganic filler. Strontium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm are directly used as inorganic fillers and mechanically blended with a polypropylene matrix in step S2 to prepare a composite material. In this embodiment, the volume ratio of inorganic filler to polypropylene is 1:3.

[0114] Example 14

[0115] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S1, the functionalized filler is only coated with a first layer of silica and a second layer of mesoporous silica, without the silane coupling agent surface functionalization treatment in step S13. The volume ratio of the functionalized filler to polypropylene is the same as in Embodiment 1, which is 1.2:1.

[0116] Example 15

[0117] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S1, the functionalized filler only undergoes a first silica layer coating and surface functionalization treatment with a silane coupling agent; that is, step S12 is skipped, and the first coating obtained in step S11 is directly added to the silane coupling agent solution for step S13. Furthermore, in this embodiment, the volume ratio of the functionalized filler to polypropylene is 1:2.

[0118] Example 16

[0119] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S1, the functionalized filler only undergoes coating with a second layer of mesoporous silica and surface functionalization treatment with a silane coupling agent; that is, step S11 is skipped, and the strontium titanate whiskers are directly coated in step S12 followed by the subsequent step S13. Furthermore, in this embodiment, the volume ratio of the functionalized filler to polypropylene is 1:2.

[0120] Example 17

[0121] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S1, the inorganic filler is first coated with a mesoporous silica layer, then coated with a silica layer; that is, the positions of the first and second coating layers are interchanged. Step S12 is performed before step S11. The mesoporous silica layer has a thickness of 0.05 μm, a porosity of 20%, a pore size of 10 nm, and a silica layer thickness of 0.15 μm. In this embodiment, the volume ratio of functionalized filler to polypropylene is the same as in Embodiment 1, which is 1.2:1.

[0122] Example 18

[0123] This embodiment provides a method for fabricating a low-loss, miniaturized millimeter-wave transmission line. The difference from Embodiment 1 is that in step S1, the functionalized filler is only coated with a first layer of silica and a second layer of mesoporous silica, without surface functionalization treatment with a silane coupling agent, i.e., step S13 is not performed. Furthermore, in this embodiment, the volume ratio of the functionalized filler to polypropylene is 1:3.

[0124] Comparative Example 1

[0125] This comparative example provides a method for preparing a transmission line, which differs from Example 1 in that: this comparative example does not perform functionalization treatment on the inorganic filler and does not perform orientation control on the inorganic filler.

[0126] In this comparative example, step S1 is unnecessary; that is, no functionalization treatment is performed on the inorganic filler. Strontium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm are directly used as the inorganic filler and mechanically blended with a polypropylene matrix in step S2 to prepare the composite material. Furthermore, the volume ratio of the functionalized filler to polypropylene in this comparative example is 1:3.

[0127] Meanwhile, the specific operation of the transmission line preparation in step S3 of this comparative example is as follows:

[0128] The obtained composite material masterbatch was added to a single screw extruder at an extrusion temperature of 200℃, an extrusion speed of 300rpm, and a traction speed of 500rpm. After water cooling and shaping, the transmission line product of this comparative example was obtained.

[0129] Comparative Example 2

[0130] This comparative example provides a method for preparing a transmission line, which differs from Example 1 in that: this comparative example does not perform orientation treatment on the functionalized filler, that is, the specific operation of preparing the transmission line in step S3 is as follows:

[0131] The obtained composite material masterbatch was added to a single screw extruder at an extrusion temperature of 200℃, an extrusion speed of 300rpm, and a traction speed of 500rpm. After water cooling and shaping, the transmission line product of this comparative example was obtained.

[0132] The volume ratio of the functionalized filler to polypropylene in this comparative example is the same as that in Example 1, which is 1.2:1.

[0133] Experiment Example 1: Simulation Experiment

[0134] Different composite models were constructed using numerical simulation software, and incident and received signal ports were set. The electric field coupling between fillers during millimeter-wave signal transmission was simulated using the finite element method.

[0135] Composite Model 1 is a composite model in which untreated inorganic filler (strontium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm) is dispersed in a polypropylene matrix without any orientation treatment; Composite Model 2 is a composite model in which untreated inorganic filler (strontium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm) is oriented and dispersed in a polymer matrix, with the orientation direction perpendicular to the electric field oscillation direction; Composite Model 3 is a composite model in which the functionalized filler of Example 1 is oriented and dispersed in a polymer matrix, with the orientation direction perpendicular to the electric field oscillation direction, wherein the functionalized filler is formed by sequentially coating the surface of the inorganic filler (strontium titanate whiskers with a length of 8 μm and a diameter of 0.8 μm) with a silica layer and a mesoporous silica layer, and the surface of the mesoporous silica layer is functionalized with a silane coupling agent (as in Example 1).

[0136] The simulation results of the three composite models are shown in the appendix. Figure 2 As shown in (a), (b), and (c) of the diagram. Where:

[0137] Appendix Figure 2 (a) shows the finite element simulation diagram of the electric field coupling between the packings in composite model 1; (See attached diagram) Figure 2 (a) It can be seen that the inorganic filler without any treatment is randomly distributed in the matrix without orientation. The random distribution of filler doping can easily cause electric field coupling concentration effect at the filler tip, which in turn leads to leakage current and significantly increases the transmission loss of millimeter wave transmission lines.

[0138] Appendix Figure 2 (b) shows the finite element simulation diagram of the electric field coupling between the packings in composite model 2; (See attached diagram) Figure 2 (b) It can be seen that the inorganic filler without any treatment is distributed perpendicular to the direction of electric field oscillation after orientation control. During the transmission of millimeter wave signals, the electric field oscillates along the direction perpendicular to the whisker filler, thereby weakening the electric field coupling at the tip and significantly reducing the loss.

[0139] Appendix Figure 2 (c) shows the finite element simulation diagram of the electric field coupling between the packings in composite model 3; (See attached diagram) Figure 2 (c) It can be seen that after the inorganic filler undergoes the functionalization treatment in step S1 of Example 1 of this invention, and then the orientation is controlled so that the orientation direction of the filler is perpendicular to the direction of electric field oscillation, the concentration of electric field between the fillers can be further reduced based on the orientation control alone in composite model 2. This shows that after the functionalized filler of this invention is doped, a multi-level interface reflection of the electric field is formed through gradient coating and step-by-step impedance matching. This can effectively reflect and attenuate the local electric field generated when the tips of the high-dielectric inorganic fillers approach each other, block the electric field coupling channel between the fillers, suppress the interface polarization effect, and further reduce the loss.

[0140] Experiment Example 2: Dielectric Constant and Transmission Loss Test

[0141] The transmission lines prepared in Examples 1-18 and Comparative Examples 1-2 were tested for dielectric and transmission performance at 40 GHz, 60 GHz, 100 GHz, and 150 GHz using a vector network analyzer. Their dielectric constant (Dk) and transmission loss (dB / m) were measured. The test results are shown in Table 1 below.

[0142] Table 1. Dielectric constants and transport properties of samples from each embodiment and comparative example.

[0143]

[0144] Analyzing the data in Table 1, we can see that:

[0145] (1) Comparison of data from Examples 1-18 and Comparative Examples 1-2: Examples 1-18 all underwent orientation distribution of high dielectric filler, and the orientation distribution direction was perpendicular to the electric field oscillation direction of the transmission line; Comparative Examples 1-2 did not underwent orientation distribution of high dielectric filler.

[0146] As can be seen from the data in Table 1, Examples 1-18 all achieved low transmission loss of the transmission line under the condition of high dielectric constant, which can realize the miniaturization and low loss of the transmission line. Comparative Examples 1-2, on the other hand, have significantly higher losses at the same dielectric constant level.

[0147] Furthermore, comparing the data of Example 1 and Comparative Example 2, the high-dielectric fillers added in Example 1 and Comparative Example 2 are the same, both being functionalized fillers that have undergone two-layer coating and surface silane coupling agent functionalization treatment. Specifically, the functionalized filler in Example 1 underwent orientation treatment, while the functionalized filler in Comparative Example 2 did not. Comparative data shows that at 100 GHz, with similar dielectric constants between Example 1 and Comparative Example 2 (Dk ~ 8.58 for Example 1, Dk ~ 8.54 for Comparative Example 2), the transmission loss of Example 1 is significantly lower than that of Comparative Example 2 (Loss ~ 10.2 dB / m for Example 1, Loss ~ 22.1 dB / m for Comparative Example 2).

[0148] Similarly, comparing the data of Example 13 and Comparative Example 1, the high-dielectric fillers added in Example 13 and Comparative Example 1 are the same, both being untreated one-dimensional strontium titanate whiskers. However, the high-dielectric filler in Example 13 underwent orientation treatment, while the high-dielectric filler in Comparative Example 1 did not. Comparative data shows that at 100 GHz, with similar dielectric constants between Example 13 and Comparative Example 1 (Dk ~ 6.98 for Example 13, Dk ~ 6.90 for Comparative Example 1), the transmission loss of Example 13 is approximately 72.1% of the transmission loss of Comparative Example 1.

[0149] Analysis reveals that by orienting one-dimensional fillers in the transmission line and ensuring that the orientation of the fillers is perpendicular to the oscillation direction of the electric field, the local coupling effect between fillers caused by the polarization electric field can be significantly reduced during signal transmission. This effectively suppresses the local accumulation phenomenon in the high field strength region, reduces energy loss caused by electric field concentration, and achieves the goal of high dielectric constant and low loss.

[0150] (2) Comparison of data from Examples 13 and 14: The high-dielectric filler in Example 14 is a functionalized filler that has undergone two-layer coating treatment, namely, a first coating layer and a second coating layer are applied to the strontium titanate whiskers. The dielectric constant of the two coating layers decreases from the core layer to the surface layer. The high-dielectric filler in Example 13 is an untreated strontium titanate whisker. Although both were oriented, a comparison of the data from Examples 14 and 13 shows that Example 14, with a higher dielectric constant than Example 13 (Dk~8.51 for Example 14 and Dk~6.98 for Example 13 at 100GHz), can achieve a significantly lower loss than Example 13 (Loss~16.5 dB / m for Example 14 and Loss~23.6 dB / m for Example 13 at 100GHz).

[0151] Analysis reveals that applying a two-layer surface coating to one-dimensional inorganic fillers can further improve the concentration of the polarization electric field generated when the tips of the oriented inorganic fillers approach each other. The two coating layers form a two-stage electric field reflection, which can effectively reflect and attenuate the local electric field generated when the tips of the high-dielectric inorganic fillers approach each other, block the electric field coupling channel between fillers, suppress the interface polarization effect, and further reduce losses.

[0152] Further comparison of the data from Examples 1 and 14-17 reveals that when the functionalized filler has only one layer of coating or when the dielectric constant of the two coating layers does not decrease from the core layer to the surface layer, its loss is higher than that of the two-layer gradient coating design with decreasing dielectric constant. This is because a single coating layer cannot create a multi-level reflection effect of the electric field, thus having limited ability to weaken the local electric field at the tip of the inorganic filler; while two coating layers with non-decreasing dielectric constants cause the electric field that should be reflected at the interface of the first coating layer to be attracted by the second coating layer with a higher dielectric constant than the first coating layer, thus failing to achieve the effect of multi-level reflection of the electric field.

[0153] (3) Comparison of data from Example 1 and Example 14: The functionalized filler of Example 1 was further modified by introducing a silane coupling agent onto the surface of the functionalized filler of Example 14. With a dielectric constant that is not much different from that of Example 14, the transmission loss of Example 1 is lower than that of Example 14. At 100 GHz, the transmission loss of Example 1 is 61.8% of that of Example 14.

[0154] Analysis reveals that introducing functional groups onto the surface of functionalized fillers using silane coupling agents allows for more uniform and stable dispersion of the fillers within the polymer matrix. This reduces the formation of agglomerates in the composite material, effectively preventing performance instability caused by uneven filler dispersion. It also improves the uniformity and stability of the composite material, contributing to high dielectric and low-loss dielectric performance in the millimeter-wave band. Furthermore, the presence of surface functionalized groups enhances the interfacial compatibility between the functionalized filler and the matrix surface, reducing interfacial porosity defects and further improving the dielectric properties and reducing losses.

[0155] Experiment Example 3: Scanning Electron Microscopy Experiment

[0156] The millimeter-wave transmission line prepared in Example 1 was subjected to SEM testing, and its SEM images at 200x, 10000x, and 35000x magnification were observed. The results are shown in the appendix. Figure 3 and attached Figure 4 As shown, the attached Figure 3 Here is a SEM image of the millimeter-wave transmission line cross-section in Example 1 at 10,000x magnification; (Attached) Figure 4 The images show SEM images of the millimeter-wave transmission line cross-section in Example 1 at 200x magnification, and SEM images of the range shown in the figures at 35,000x magnification.

[0157] From the appendix Figure 3 It can be seen that in the millimeter-wave transmission line prepared in Example 1, the filler is regularly oriented and the orientation distribution direction is along the signal transmission direction of the transmission line, that is, the orientation direction is perpendicular to the electric field oscillation direction.

[0158] From the appendix Figure 4 It can be seen that the uniform silver coating on the outer layer of the transmission line can ensure that the signal is well isolated from the external environment during transmission, thus providing shielding protection and giving the transmission line good resistance to environmental interference.

[0159] In summary, the low-loss, miniaturized transmission line prepared by the method of this invention can significantly reduce transmission loss while improving the dielectric constant, providing a good foundation for its application in millimeter-wave communication. Furthermore, the preparation method of this invention is simple, easy to industrialize, and has a promising prospect for widespread application.

Claims

1. A low-loss, miniaturized millimeter-wave transmission line, characterized by, The composite material is prepared from a composite material including a polymer matrix and a high dielectric filler dispersed in the polymer matrix, the high dielectric filler having a dielectric constant greater than that of the polymer matrix; The high dielectric filler is a one-dimensional / two-dimensional functional filler, the functional filler including an inorganic filler, a first coating layer coated on the surface of the inorganic filler, and a second coating layer coated on the surface of the first coating layer; the dielectric constants of the inorganic filler, the first coating layer, the second coating layer and the polymer matrix satisfy: the inorganic filler > the first coating layer > the second coating layer > the polymer matrix; the inorganic filler is selected from one or more of alumina whiskers, strontium titanate whiskers, barium titanate whiskers, zinc oxide whiskers, alumina platelets, strontium titanate platelets, and barium titanate platelets; In the transmission line, the high dielectric filler is oriented and distributed in the polymer matrix, and the orientation direction of the high dielectric filler is perpendicular to the oscillation direction of the electric field.

2. The low-loss, miniaturized millimeter-wave transmission line of claim 1, wherein, When the inorganic filler is a one-dimensional material, the length of the inorganic filler is 8-12 μm, and the diameter of the inorganic filler is 0.8-1.2 μm.

3. The low-loss, miniaturized millimeter-wave transmission line of claim 2, wherein, The functional filler further includes a surface functional group, and the surface of the inorganic filler after being coated with the first coating layer and the second coating layer is subjected to silane coupling agent functionalization treatment to obtain the functional filler.

4. The low-loss, miniaturized millimeter-wave transmission line of claim 3, wherein, The material of the first coating layer is selected from silicon dioxide or titanium dioxide; and the material of the second coating layer is selected from silicon dioxide, mesoporous silicon dioxide or mesoporous titanium dioxide.

5. The low-loss, miniaturized millimeter-wave transmission line of claim 1, wherein, The volume ratio of the high dielectric filler to the polymer matrix satisfies 1:3-1.2:

1.

6. Use of a low-loss, miniaturized millimeter wave transmission line according to any one of claims 1 to 5, characterized in that, The transmission line is used as a signal transmission device at a millimeter wave frequency band.

7. A method of manufacturing a low-loss, miniaturized millimeter wave transmission line according to any one of claims 1 to 5, characterized by, The composite material master batch prepared from the composite material is extruded by an extruder to prepare the transmission line, and a hot rolling module is arranged at the die of the extruder.

8. The preparation method of the low-loss and miniaturized millimeter wave transmission line according to claim 7, characterized in that, When the high dielectric filler is selected from a functional filler, the following steps are included: Preparation of a functional filler: sequentially coating a first coating layer and a second coating layer on the surface of an inorganic filler to form a functional filler; Preparation of a transmission line: mixing the functional filler with a polymer matrix by mechanical blending to form a composite material master batch; extruding the composite material master batch by an extruder to prepare the transmission line; and arranging a hot rolling module at the die of the extruder; When the high dielectric filler is selected from an inorganic filler, the following steps are included: Preparation of a transmission line: mixing the inorganic filler with a polymer matrix by mechanical blending to form a composite material master batch; extruding the composite material master batch by an extruder to prepare the transmission line; and arranging a hot rolling module at the die of the extruder.

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