Radio frequency microwave test cable and preparation method thereof

Abstract

The invention discloses a radio frequency microwave test cable and a preparation method thereof, and relates to the technical field of cables. The method comprises the following steps: firstly, performing drawing, annealing and electrolytic polishing on an oxygen-free copper rod to obtain an inner conductor; then preparing silane modified nano silicon dioxide, and carrying out chemical imidization reaction to obtain modified PI composite resin; and adding the amino-functionalized reduced graphene oxide into the modified PI composite resin, and carrying out crosslinking and curing to obtain the modified PI insulating material. And finally, extruding an insulating material and coating the insulating material on the inner conductor, cooling and shaping, weaving a copper wire shielding layer, and finally coating a polyurethane sheath to obtain the test cable. The radio frequency microwave test cable prepared by the invention has excellent dielectric properties.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to an RF microwave test cable and its manufacturing method. Background Technology

[0002] Radio frequency (RF) microwave test cables, as an indispensable core transmission component in high-frequency signal testing systems, play an irreplaceable role in many key fields such as communications, radar, and electronic measurement. Whether it's the RF performance testing of 5G / 6G base stations, the signal transceiver links of military radar, or the connection between electronic measuring instruments (such as oscilloscopes and spectrum analyzers) and the device under test, they directly determine the reliability of high-frequency signal transmission and the accuracy of test data. The high-frequency signals transmitted by these cables typically cover the range of 1GHz to 40GHz, and in some scenarios even extend to higher frequency bands. These frequency bands have extremely short wavelengths, weak anti-interference capabilities, and are highly sensitive to the performance of the transmission medium. Therefore, the core requirement is not only to simply ensure the physical path for signal transmission, but also to maximize the integrity of high-frequency signal transmission and minimize signal attenuation and distortion during transmission. Any slight signal loss or waveform distortion can lead to deviations in test results, increased bit error rates in communication links, or even malfunctions in core equipment.

[0003] As one of the core functional layers of RF microwave test cables, the insulation layer bears a dual critical responsibility: on the one hand, it must achieve reliable electrical isolation between the inner conductor and the outer shielding layer to avoid the risk of short circuits or leakage; on the other hand, it must provide a stable and uniform dielectric environment for high-frequency signal transmission. The stability of its dielectric properties (especially the dielectric constant and dielectric loss tangent) directly determines the impedance consistency and signal transmission loss of the cable. From a physical perspective, the characteristic impedance of the cable is inversely proportional to the square root of the dielectric constant of the insulation layer. Even small fluctuations in the dielectric constant can directly cause impedance shifts, and impedance mismatch can lead to signal reflection during transmission, thereby exacerbating signal attenuation. At the same time, the higher the dielectric constant, the slower the signal transmission speed in the insulation layer, and the more signal energy is converted into heat energy due to dielectric polarization loss, resulting in increased dielectric loss. This effect is particularly significant in the ultra-high frequency band, directly limiting the effective transmission distance and signal fidelity of the cable.

[0004] In existing technologies, the insulation layer of most radio frequency microwave test cables is made of polyimide (PI) material. This is due to a series of outstanding advantages of PI material: excellent high-temperature resistance, making it suitable for extreme working environments such as aerospace and industrial high-temperature testing; outstanding mechanical strength, with tensile strength and elongation at break meeting the mechanical stress requirements during cable laying and bending, making it less prone to cracking or damage; and good chemical stability, resisting the corrosion of common chemical media and extending the cable's service life. However, the intrinsic properties of PI material have significant shortcomings. Its intrinsic dielectric constant is still too high for the low-loss requirements of ultra-high frequency signal transmission, making it difficult to meet the stringent requirements of modern radio frequency microwave test systems for cable impedance consistency, signal transmission rate, and low loss. This has become a core bottleneck restricting further improvements in cable performance. Summary of the Invention

[0005] The purpose of this invention is to provide an RF microwave test cable and its preparation method, thereby solving the technical problems mentioned in the background section. The PI material prepared by this invention has a low dielectric constant.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for manufacturing an RF microwave test cable includes the following steps: S1. Using oxygen-free copper rod, after continuous drawing, it undergoes annealing treatment and then electrolytic polishing to obtain the inner conductor; S2. Disperse nano-silica in anhydrous ethanol, add γ-glycidoxypropyltrimethoxysilane, and reflux under acidic conditions. After the reaction, centrifuge, wash and dry to obtain silane-modified nano-silica. Silane-modified nano-silica was added to DMAc solvent and dispersed. Then, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added, followed by the addition of pyromellitic dianhydride. The reaction was carried out under nitrogen protection to generate a PAA hybrid solution. Acetic anhydride and isoquinoline were added to the PAA hybrid solution to carry out a chemical imidization reaction. After precipitation with deionized water, washing and drying, the modified PI composite resin was obtained. S3. Graphene oxide is dispersed in deionized water, and hydrazine hydrate is added for reflux reduction to obtain reduced graphene oxide. It is then redispersed in anhydrous ethanol, and 3-aminopropyltriethoxysilane is added for reaction. After reaction, it is centrifuged, washed and dried to obtain amino-functionalized reduced graphene oxide. After the modified PI composite resin is melted, amino-functionalized reduced graphene oxide is added and stirred to disperse it. Then, the crosslinking agent pyromellitic dianhydride is added and stirred again. Subsequently, it is kept warm and cured to obtain the modified PI insulating material. S4. The modified PI insulating material is extruded and coated onto the surface of the inner conductor, and then cooled and shaped to obtain an inner conductor-insulation layer composite. Using oxygen-free copper wire, a shielding layer is wrapped onto the surface of the inner conductor-insulation layer composite using a braiding machine to obtain a core wire-shielding layer composite. Polyurethane material is extruded and coated onto the surface of the core wire-shielding layer composite, and then cooled and shaped to obtain an RF microwave test cable.

[0007] In this invention, the dielectric constant of the polyimide (PI) insulation layer in radio frequency microwave test cables is reduced synergistically from multiple aspects. Firstly, fluorinated groups possess extremely low polarizability; introducing them into the PI molecular chain significantly reduces the dielectric contribution of the molecular chain itself, thus mitigating the increase in dielectric constant caused by polarization at the structural level. Secondly, the silane-modified nanoparticles themselves have a low dielectric constant and significantly improved compatibility with the PI matrix. They can be uniformly dispersed in the matrix and construct continuous nanoscale low-dielectric regions, further diluting the overall dielectric strength through optimized spatial distribution. These two mechanisms work together to effectively reduce the dielectric constant of the composite resin without compromising the basic properties of the PI matrix, while simultaneously ensuring the film-forming properties and mechanical strength of the material. On the other hand, amino-functionalized reduced graphene oxide has an ultra-high specific surface area and layered structure. When uniformly dispersed in the PI matrix, it can form a labyrinthine barrier network, which can effectively suppress charge migration and polarization relaxation processes, reduce dielectric loss and dielectric constant increase caused by charge directional movement. At the same time, the construction of cross-linked networks can fix the PI molecular chain structure, restrict the free movement of molecular chains, avoid dielectric property fluctuations caused by molecular chain vibration and orientation changes, and further stabilize and reduce the dielectric constant.

[0008] Preferably, in step S1, the annealing temperature is 320–350°C and the annealing time is 1–2 hours.

[0009] Preferably, in step S2, the mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane is 10:(0.2-0.8).

[0010] Preferably, in step S3, the mass ratio of graphene oxide to hydrazine hydrate is 5:(0.5-1.0).

[0011] Preferably, in step S3, the amount of amino-functionalized reduced graphene oxide added is (2-5) wt% of the modified PI composite resin.

[0012] Preferably, in step S3, perfluorohexylethylaminotriethoxysilane is added after the modified PI composite resin is melted.

[0013] In the technical solution of this invention, further in-depth research revealed that the steric hindrance effect of the fluorinated groups in the modified PI composite resin and the rigidity of the PI molecular chain hinder the full spread of amino-functionalized reduced graphene oxide sheets in the molten PI matrix, making it difficult to form a continuous labyrinthine barrier network and directly weakening the dielectric optimization effect of amino-functionalized reduced graphene oxide on cable insulation. To further solve this technical problem, this invention adds perfluorohexylethylaminotriethoxysilane after the modified PI composite resin is melted. Its molecular chain length is moderate, which can fill the spatial gaps between the fluorinated groups and the amino-functionalized reduced graphene oxide, weakening the steric hindrance of the fluorinated groups and guiding the amino-functionalized reduced graphene oxide sheets to fully spread in the PI matrix, forming a continuous two-dimensional barrier network, thereby further improving the dielectric performance of the cable.

[0014] Preferably, the amount of perfluorohexylethylaminotriethoxysilane added is (1-2) wt% of the modified PI composite resin.

[0015] A radio frequency microwave test cable is prepared by the method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. By grafting low-polarity fluorine-containing groups onto the polyimide (PI) molecular chain and uniformly dispersing silane-modified nano-silica to form a low-dielectric region, the dielectric constant of the insulating material is significantly reduced through synergistic effects at both the molecular structure and material composite levels, thereby improving the high-frequency signal transmission performance of the cable.

[0017] 2. Aminofunctionalized reduced graphene oxide has an ultra-high specific surface area and layered structure. When uniformly dispersed in the PI matrix, it can form a labyrinthine barrier network, which can effectively suppress charge migration and polarization relaxation processes, and reduce dielectric loss and dielectric constant increase caused by directional charge movement.

[0018] 3. By adding perfluorohexylethylaminotriethoxysilane as an interface modifier, the steric hindrance caused by fluorine-containing groups is effectively alleviated, and the full spread of amino-functionalized reduced graphene oxide sheets in the PI matrix and the establishment of a continuous network are promoted, thereby further improving the dielectric performance of the cable. Attached Figure Description

[0019] Figure 1 This is a SEM image of the surface of the cable insulation layer prepared in Example 4 of the present invention.

[0020] Figure 2 This is the XPS image of the cable insulation layer prepared in Example 4 of the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for manufacturing an RF microwave test cable includes the following steps: Step 1: Take oxygen-free copper rods with a copper content ≥99.99%, process them to a diameter of 0.5mm using a continuous drawing process, place the drawn copper conductors into an annealing furnace, and hold them at 330℃ for 1.5h to complete the annealing treatment. Subsequently, the surface is treated with an electrolytic polishing process, controlling the electrolytic polishing voltage at 12V and the current density at 2A / dm². 2 Polishing time was 15 minutes to obtain the inner conductor.

[0023] Step 2: Disperse 30nm nano-silica in anhydrous ethanol and ultrasonically disperse it at 350W for 35min to obtain a 5% (w / w) dispersion. Add γ-glycidoxypropyltrimethoxysilane to the dispersion, with a mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane of 10:0.7. Adjust the pH of the system to 5.0 with 0.1mol / L hydrochloric acid solution. Place the mixture in a reflux apparatus and reflux at 80℃ for 2.5h. After the reaction, centrifuge at 10000r / min for 15min, collect the precipitate, wash it 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 108℃ for 5h to obtain silane-modified nano-silica.

[0024] Silane-modified nano-silica was added to DMAc solvent at a mass-to-volume ratio of 6 g / 500 mL. After ultrasonic dispersion for 45 min, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio 7:3) were added sequentially, with a mass ratio of 4,4'-diaminodiphenyl ether to silane-modified nano-silica of 5:1. The system was cooled to 5 °C, and pyromellitic dianhydride was added in batches (pyromellitic dianhydride and... 4,4'-Diaminodiphenyl ether (molar ratio 1:0.7) was reacted under nitrogen protection for 6 h to generate a PAA hybrid solution. Finally, a dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (where the mass ratio of acetic anhydride to pyromellitic dianhydride is approximately 2.1:1), and were added dropwise to the system. The temperature was raised to 80℃ and held for 3 h to complete chemical imidization. The resulting solution was precipitated with deionized water, washed, and vacuum dried at 180℃ to obtain the modified PI composite resin.

[0025] Step 3: Disperse graphene oxide in deionized water and ultrasonically disperse for 18 min at 450 W to obtain a uniform GO dispersion with a mass fraction of 0.5%. Add hydrazine hydrate to the dispersion, with a mass ratio of graphene oxide to hydrazine hydrate of 5:0.9. Reduct at 98 °C under constant reflux for 2.5 h. After the reaction, filter and collect the precipitate. Wash with deionized water until the filtrate is neutral to obtain reduced graphene oxide (rGO). Redisperse rGO in anhydrous ethanol at a mass-volume ratio of 1 g / 100 mL. Add 3-aminopropyltriethoxysilane, with a mass ratio of rGO to 3-aminopropyltriethoxysilane of 5:0.4. Reduct at 85 °C under stirring and reflux at 50 r / min for 2.2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Then dry under vacuum at 102 °C for 3.5 h to obtain amino-functionalized rGO.

[0026] Modified PI composite resin was added to a reactor and the temperature was set to 350℃. After the resin was completely melted, 4% (by weight of resin) of amino-functionalized rGO and 1.8 wt% (by weight of resin) of perfluorohexylethylaminotriethoxysilane were added through the side feed port. The mixture was stirred and dispersed at a speed of 300 r / min for 35 min. Then, 4% (by weight of resin) of the crosslinking agent pyromellitic dianhydride was added and stirred at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290℃ for 1.2 h to obtain the modified PI insulating material.

[0027] Step 4: Add the modified PI insulating material to a single-screw extruder. Set the barrel temperature in stages: 280℃ at the inlet, 300℃ in the middle section, 310℃ at the rear section, and 320℃ at the die head. Introduce the pretreated inner conductor as the core wire into the die head, controlling the traction speed at 2.5 m / min to ensure the insulating material is evenly extruded onto the surface of the inner conductor. Then, cool and shape it using a 25℃ water-cooling device to obtain the inner conductor-insulation layer composite. Select oxygen-free copper wire with a diameter of 0.09 mm and use a braiding machine to coat the above inner conductor-insulation layer composite with a shielding layer. Control the braiding density at 96%, maintain the tension at 6 N during the coating process, and keep the braiding speed consistent with the traction speed during the insulation layer forming stage (2.5 m / min), finally forming the core wire-shielding layer composite. Polyurethane material was selected as the raw material for the outer sheath. It was fed into a single-screw extruder, and the barrel temperature was set in sections: 140℃ at the inlet, 160℃ in the middle section, 170℃ in the rear section, and 180℃ at the die head. The core wire-shielding layer composite was introduced into the die head, and the traction speed was controlled at 2.5m / min to make the PU material evenly extruded onto the surface of the shielding layer. Then, it was cooled and shaped by an air-cooling device to obtain an RF microwave test cable covered with an outer sheath.

[0028] Example 2 A method for manufacturing an RF microwave test cable includes the following steps: Step 1: Take oxygen-free copper rods with a copper content ≥99.99%, process them to a diameter of 0.5mm using a continuous drawing process, place the drawn copper conductors into an annealing furnace, and hold them at 330℃ for 1.5h to complete the annealing treatment. Subsequently, the surface is treated with an electrolytic polishing process, controlling the electrolytic polishing voltage at 12V and the current density at 2A / dm². 2 Polishing time was 15 minutes to obtain the inner conductor.

[0029] Step 2: Disperse 30nm nano-silica in anhydrous ethanol and ultrasonically disperse it at 350W for 35min to obtain a 5% (w / w) dispersion. Add γ-glycidoxypropyltrimethoxysilane to the dispersion, with a mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane of 10:0.3. Adjust the pH of the system to 5.0 with 0.1mol / L hydrochloric acid solution. Place the mixture in a reflux apparatus and reflux at 80℃ for 2.5h. After the reaction, centrifuge at 10000r / min for 15min, collect the precipitate, wash it 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 108℃ for 5h to obtain silane-modified nano-silica.

[0030] Silane-modified nano-silica was added to DMAc solvent at a mass-to-volume ratio of 6 g / 500 mL. After ultrasonic dispersion for 45 min, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio 7:3) were added sequentially, with a mass ratio of 4,4'-diaminodiphenyl ether to silane-modified nano-silica of 5:1. The system was cooled to 5 °C, and pyromellitic dianhydride was added in batches (pyromellitic dianhydride and... 4,4'-Diaminodiphenyl ether (molar ratio 1:0.7) was reacted under nitrogen protection for 6 h to generate a PAA hybrid solution. Finally, a dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (where the mass ratio of acetic anhydride to pyromellitic dianhydride is approximately 2.1:1), and were added dropwise to the system. The temperature was raised to 80℃ and held for 3 h to complete chemical imidization. The resulting solution was precipitated with deionized water, washed, and vacuum dried at 180℃ to obtain the modified PI composite resin.

[0031] Step 3: Disperse graphene oxide in deionized water and ultrasonically disperse for 18 min at 450 W to obtain a uniform GO dispersion with a mass fraction of 0.5%. Add hydrazine hydrate to the dispersion, with a mass ratio of graphene oxide to hydrazine hydrate of 5:0.6. Reduce the GO by reflux at 98 °C for 2.5 h. After the reaction, filter and collect the precipitate. Wash the precipitate with deionized water until the filtrate is neutral to obtain reduced graphene oxide (rGO). Redisperse rGO in anhydrous ethanol at a mass-volume ratio of 1 g / 100 mL. Add 3-aminopropyltriethoxysilane, with a mass ratio of rGO to 3-aminopropyltriethoxysilane of 5:0.4. Stir the reaction at 85 °C and 50 r / min for 2.2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Then dry the mixture under vacuum at 102 °C for 3.5 h to obtain amino-functionalized rGO.

[0032] Modified PI composite resin was added to a reactor and the temperature was set to 350℃. After the resin was completely melted, 3% (by weight of resin) of amino-functionalized rGO and 1.2 wt% (by weight of resin) of perfluorohexylethylaminotriethoxysilane were added through the side feed port. The mixture was stirred and dispersed at a speed of 300 r / min for 35 min. Then, 4% (by weight of resin) of the crosslinking agent pyromellitic dianhydride was added and stirred at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290℃ for 1.2 h to obtain the modified PI insulating material.

[0033] Step 4: Add the modified PI insulating material to a single-screw extruder. Set the barrel temperature in stages: 280℃ at the inlet, 300℃ in the middle section, 310℃ at the rear section, and 320℃ at the die head. Introduce the pretreated inner conductor as the core wire into the die head, controlling the traction speed at 2.5 m / min to ensure the insulating material is evenly extruded onto the surface of the inner conductor. Then, cool and shape it using a 25℃ water-cooling device to obtain the inner conductor-insulation layer composite. Select oxygen-free copper wire with a diameter of 0.09 mm and use a braiding machine to coat the above inner conductor-insulation layer composite with a shielding layer. Control the braiding density at 96%, maintain the tension at 6 N during the coating process, and keep the braiding speed consistent with the traction speed during the insulation layer forming stage (2.5 m / min), finally forming the core wire-shielding layer composite. Polyurethane material was selected as the raw material for the outer sheath. It was fed into a single-screw extruder, and the barrel temperature was set in sections: 140℃ at the inlet, 160℃ in the middle section, 170℃ in the rear section, and 180℃ at the die head. The core wire-shielding layer composite was introduced into the die head, and the traction speed was controlled at 2.5m / min to make the PU material evenly extruded onto the surface of the shielding layer. Then, it was cooled and shaped by an air-cooling device to obtain an RF microwave test cable covered with an outer sheath.

[0034] Example 3 A method for manufacturing an RF microwave test cable includes the following steps: Step 1: Take oxygen-free copper rods with a copper content ≥99.99%, process them to a diameter of 0.5mm using a continuous drawing process, place the drawn copper conductors into an annealing furnace, and hold them at 330℃ for 1.5h to complete the annealing treatment. Subsequently, the surface is treated with an electrolytic polishing process, controlling the electrolytic polishing voltage at 12V and the current density at 2A / dm². 2 Polishing time was 15 minutes to obtain the inner conductor.

[0035] Step 2: Disperse 30nm nano-silica in anhydrous ethanol and ultrasonically disperse it at 350W for 35min to obtain a 5% (w / w) dispersion. Add γ-glycidoxypropyltrimethoxysilane to the dispersion, with a mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane of 10:0.5. Adjust the pH of the system to 5.0 with 0.1mol / L hydrochloric acid solution. Place the mixture in a reflux apparatus and reflux at 80℃ for 2.5h. After the reaction, centrifuge at 10000r / min for 15min, collect the precipitate, wash it 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 108℃ for 5h to obtain silane-modified nano-silica.

[0036] Silane-modified nano-silica was added to DMAc solvent at a mass-to-volume ratio of 6 g / 500 mL. After ultrasonic dispersion for 45 min, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio 7:3) were added sequentially, with a mass ratio of 4,4'-diaminodiphenyl ether to silane-modified nano-silica of 5:1. The system was cooled to 5 °C, and pyromellitic dianhydride was added in batches (pyromellitic dianhydride and... 4,4'-Diaminodiphenyl ether (molar ratio 1:0.7) was reacted under nitrogen protection for 6 h to generate a PAA hybrid solution. Finally, a dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (where the mass ratio of acetic anhydride to pyromellitic dianhydride is approximately 2.1:1), and were added dropwise to the system. The temperature was raised to 80℃ and held for 3 h to complete chemical imidization. The resulting solution was precipitated with deionized water, washed, and vacuum dried at 180℃ to obtain the modified PI composite resin.

[0037] Step 3: Disperse graphene oxide in deionized water and ultrasonically disperse for 18 min at 450 W to obtain a uniform GO dispersion with a mass fraction of 0.5%. Add hydrazine hydrate to the dispersion, with a mass ratio of graphene oxide to hydrazine hydrate of 5:0.7. Reduce the GO by reflux at 98 °C for 2.5 h. After the reaction, filter and collect the precipitate. Wash the precipitate with deionized water until the filtrate is neutral to obtain reduced graphene oxide (rGO). Redisperse rGO in anhydrous ethanol at a mass-volume ratio of 1 g / 100 mL. Add 3-aminopropyltriethoxysilane, with a mass ratio of rGO to 3-aminopropyltriethoxysilane of 5:0.4. Stir the reaction at 85 °C and 50 r / min for 2.2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Then dry the mixture under vacuum at 102 °C for 3.5 h to obtain amino-functionalized rGO.

[0038] Modified PI composite resin was added to a reactor and the temperature was set to 350℃. After the resin was completely melted, 3.5% (by weight of resin) of amino-functionalized rGO and 1.5 wt% (by weight of resin) of perfluorohexylethylaminotriethoxysilane were added through the side feed port. The mixture was stirred and dispersed at a speed of 300 r / min for 35 min. Then, 4% (by weight of resin) of the crosslinking agent pyromellitic dianhydride was added and stirred at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290℃ for 1.2 h to obtain the modified PI insulating material.

[0039] Step 4: Add the modified PI insulating material to a single-screw extruder. Set the barrel temperature in stages: 280℃ at the inlet, 300℃ in the middle section, 310℃ at the rear section, and 320℃ at the die head. Introduce the pretreated inner conductor as the core wire into the die head, controlling the traction speed at 2.5 m / min to ensure the insulating material is evenly extruded onto the surface of the inner conductor. Then, cool and shape it using a 25℃ water-cooling device to obtain the inner conductor-insulation layer composite. Select oxygen-free copper wire with a diameter of 0.09 mm and use a braiding machine to coat the above inner conductor-insulation layer composite with a shielding layer. Control the braiding density at 96%, maintain the tension at 6 N during the coating process, and keep the braiding speed consistent with the traction speed during the insulation layer forming stage (2.5 m / min), finally forming the core wire-shielding layer composite. Polyurethane material was selected as the raw material for the outer sheath. It was fed into a single-screw extruder, and the barrel temperature was set in sections: 140℃ at the inlet, 160℃ in the middle section, 170℃ in the rear section, and 180℃ at the die head. The core wire-shielding layer composite was introduced into the die head, and the traction speed was controlled at 2.5m / min to make the PU material evenly extruded onto the surface of the shielding layer. Then, it was cooled and shaped by an air-cooling device to obtain an RF microwave test cable covered with an outer sheath.

[0040] Example 4 A method for manufacturing an RF microwave test cable includes the following steps: Step 1: Take oxygen-free copper rods with a copper content ≥99.99%, process them to a diameter of 0.5mm using a continuous drawing process, place the drawn copper conductors into an annealing furnace, and hold them at 320℃ for 2 hours to complete the annealing treatment. Subsequently, use an electrolytic polishing process to treat the surface, controlling the electrolytic polishing voltage at 12V and the current density at 2A / dm². 2 Polishing time was 15 minutes to obtain the inner conductor.

[0041] Step 2: Disperse 30nm nano-silica in anhydrous ethanol and ultrasonically disperse it at 350W for 35min to obtain a 5% (w / w) dispersion. Add γ-glycidoxypropyltrimethoxysilane to the dispersion, with a mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane of 10:0.8. Adjust the pH of the system to 5.0 with 0.1mol / L hydrochloric acid solution. Place the mixture in a reflux apparatus and reflux at 80℃ for 2.5h. After the reaction, centrifuge at 10000r / min for 15min, collect the precipitate, wash it 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 108℃ for 5h to obtain silane-modified nano-silica.

[0042] Silane-modified nano-silica was added to DMAc solvent at a mass-to-volume ratio of 6 g / 500 mL. After ultrasonic dispersion for 45 min, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio 7:3) were added sequentially, with a mass ratio of 4,4'-diaminodiphenyl ether to silane-modified nano-silica of 5:1. The system was cooled to 5 °C, and pyromellitic dianhydride was added in batches (pyromellitic dianhydride and... 4,4'-Diaminodiphenyl ether (molar ratio 1:0.7) was reacted under nitrogen protection for 6 h to generate a PAA hybrid solution. Finally, a dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (where the mass ratio of acetic anhydride to pyromellitic dianhydride is approximately 2.1:1), and were added dropwise to the system. The temperature was raised to 80℃ and held for 3 h to complete chemical imidization. The resulting solution was precipitated with deionized water, washed, and vacuum dried at 180℃ to obtain the modified PI composite resin.

[0043] Step 3: Disperse graphene oxide in deionized water and ultrasonically disperse for 18 min at 450 W to obtain a uniform GO dispersion with a mass fraction of 0.5%. Add hydrazine hydrate to the dispersion, with a mass ratio of graphene oxide to hydrazine hydrate of 5:1.0. Reduce the GO by reflux at 98 °C for 2.5 h. After the reaction, filter and collect the precipitate. Wash with deionized water until the filtrate is neutral to obtain reduced graphene oxide (rGO). Redisperse rGO in anhydrous ethanol at a mass-volume ratio of 1 g / 100 mL. Add 3-aminopropyltriethoxysilane, with a mass ratio of rGO to 3-aminopropyltriethoxysilane of 5:0.4. Stir at 85 °C and 50 r / min for 2.2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Then dry under vacuum at 102 °C for 3.5 h to obtain amino-functionalized rGO.

[0044] Modified PI composite resin was added to a reactor and the temperature was set to 350℃. After the resin was completely melted, 5% (by weight of resin) of amino-functionalized rGO and 2 wt% (by weight of resin) of perfluorohexylethylaminotriethoxysilane were added through the side feed port. The mixture was stirred and dispersed at a speed of 300 r / min for 35 min. Then, 4% (by weight of resin) of the crosslinking agent pyromellitic dianhydride was added and stirred at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290℃ for 1.2 h to obtain the modified PI insulating material.

[0045] Step 4: Add the modified PI insulating material to a single-screw extruder. Set the barrel temperature in stages: 280℃ at the inlet, 300℃ in the middle section, 310℃ at the rear section, and 320℃ at the die head. Introduce the pretreated inner conductor as the core wire into the die head, controlling the traction speed at 2.5 m / min to ensure the insulating material is evenly extruded onto the surface of the inner conductor. Then, cool and shape it using a 25℃ water-cooling device to obtain the inner conductor-insulation layer composite. Select oxygen-free copper wire with a diameter of 0.09 mm and use a braiding machine to coat the above inner conductor-insulation layer composite with a shielding layer. Control the braiding density at 96%, maintain the tension at 6 N during the coating process, and keep the braiding speed consistent with the traction speed during the insulation layer forming stage (2.5 m / min), finally forming the core wire-shielding layer composite. Polyurethane material was selected as the raw material for the outer sheath. It was fed into a single-screw extruder, and the barrel temperature was set in sections: 140℃ at the inlet, 160℃ in the middle section, 170℃ in the rear section, and 180℃ at the die head. The core wire-shielding layer composite was introduced into the die head, and the traction speed was controlled at 2.5m / min to make the PU material evenly extruded onto the surface of the shielding layer. Then, it was cooled and shaped by an air-cooling device to obtain an RF microwave test cable covered with an outer sheath.

[0046] Example 5 A method for manufacturing an RF microwave test cable includes the following steps: Step 1: Take oxygen-free copper rods with a copper content ≥99.99%, process them to a diameter of 0.5mm using a continuous drawing process, place the drawn copper conductors into an annealing furnace, and anneal them at 350℃ for 1 hour. Subsequently, treat the surface with an electrolytic polishing process, controlling the electrolytic polishing voltage at 12V and the current density at 2A / dm². 2 Polishing time was 15 minutes to obtain the inner conductor.

[0047] Step 2: Disperse 30nm nano-silica in anhydrous ethanol and ultrasonically disperse it at 350W for 35min to obtain a 5% (w / w) dispersion. Add γ-glycidoxypropyltrimethoxysilane to the dispersion, with a mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane of 10:0.2. Adjust the pH of the system to 5.0 with 0.1mol / L hydrochloric acid solution. Place the mixture in a reflux apparatus and reflux at 80℃ for 2.5h. After the reaction, centrifuge at 10000r / min for 15min, collect the precipitate, wash it 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 108℃ for 5h to obtain silane-modified nano-silica.

[0048] Silane-modified nano-silica was added to DMAc solvent at a mass-to-volume ratio of 6 g / 500 mL. After ultrasonic dispersion for 45 min, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio 7:3) were added sequentially, with a mass ratio of 4,4'-diaminodiphenyl ether to silane-modified nano-silica of 5:1. The system was cooled to 5 °C, and pyromellitic dianhydride was added in batches (pyromellitic dianhydride and... 4,4'-Diaminodiphenyl ether (molar ratio 1:0.7) was reacted under nitrogen protection for 6 h to generate a PAA hybrid solution. Finally, a dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (where the mass ratio of acetic anhydride to pyromellitic dianhydride is approximately 2.1:1), and were added dropwise to the system. The temperature was raised to 80℃ and held for 3 h to complete chemical imidization. The resulting solution was precipitated with deionized water, washed, and vacuum dried at 180℃ to obtain the modified PI composite resin.

[0049] Step 3: Disperse graphene oxide in deionized water and ultrasonically disperse for 18 min at 450 W to obtain a uniform GO dispersion with a mass fraction of 0.5%. Add hydrazine hydrate to the dispersion, with a mass ratio of graphene oxide to hydrazine hydrate of 5:0.5. Reduce the GO by reflux at 98 °C for 2.5 h. After the reaction, filter and collect the precipitate. Wash the precipitate with deionized water until the filtrate is neutral to obtain reduced graphene oxide (rGO). Redisperse rGO in anhydrous ethanol at a mass-volume ratio of 1 g / 100 mL. Add 3-aminopropyltriethoxysilane, with a mass ratio of rGO to 3-aminopropyltriethoxysilane of 5:0.4. Stir the reaction at 85 °C and 50 r / min for 2.2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Then dry the mixture under vacuum at 102 °C for 3.5 h to obtain amino-functionalized rGO.

[0050] Modified PI composite resin was added to a reactor and the temperature was set to 350℃. After the resin was completely melted, 2% (by weight of resin) of amino-functionalized rGO and 1 wt% (by weight of resin) of perfluorohexylethylaminotriethoxysilane were added through the side feed port. The mixture was stirred and dispersed at a speed of 300 r / min for 35 min. Then, 4% (by weight of resin) of the crosslinking agent pyromellitic dianhydride was added and stirred at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290℃ for 1.2 h to obtain the modified PI insulating material.

[0051] Step 4: Add the modified PI insulating material to a single-screw extruder. Set the barrel temperature in stages: 280℃ at the inlet, 300℃ in the middle section, 310℃ at the rear section, and 320℃ at the die head. Introduce the pretreated inner conductor as the core wire into the die head, controlling the traction speed at 2.5 m / min to ensure the insulating material is evenly extruded onto the surface of the inner conductor. Then, cool and shape it using a 25℃ water-cooling device to obtain the inner conductor-insulation layer composite. Select oxygen-free copper wire with a diameter of 0.09 mm and use a braiding machine to coat the above inner conductor-insulation layer composite with a shielding layer. Control the braiding density at 96%, maintain the tension at 6 N during the coating process, and keep the braiding speed consistent with the traction speed during the insulation layer forming stage (2.5 m / min), finally forming the core wire-shielding layer composite. Polyurethane material was selected as the raw material for the outer sheath. It was fed into a single-screw extruder, and the barrel temperature was set in sections: 140℃ at the inlet, 160℃ in the middle section, 170℃ in the rear section, and 180℃ at the die head. The core wire-shielding layer composite was introduced into the die head, and the traction speed was controlled at 2.5m / min to make the PU material evenly extruded onto the surface of the shielding layer. Then, it was cooled and shaped by an air-cooling device to obtain an RF microwave test cable covered with an outer sheath.

[0052] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 2 is omitted in the cable preparation process, and the modified PI composite resin in step 3 is replaced with an equal mass of polyimide resin.

[0053] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in the cable preparation process, the amino-functionalized rGO in step 3 is replaced with an equal mass of graphene oxide.

[0054] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that perfluorohexylethylaminotriethoxysilane is not added in step 3 during the cable preparation process.

[0055] Performance testing: 1. Insulation layer dielectric constant and dielectric loss tangent test: The parallel plate capacitance method was used. A circular sample with a thickness of 0.2 mm and a diameter of 20 mm was peeled from the cable insulation layer. The dielectric constant (εr) and dielectric loss tangent (tanδ) were measured using a precision dielectric constant tester at 25℃ and 1MHz. Each sample was tested 3 times, and the average value was taken. The test results are shown in Table 1.

[0056] 2.40GHz Signal transmission loss test: The insertion loss method was used, and a network analyzer was used to measure the signal transmission loss of a 10m long cable at a frequency of 40GHz. The unit is dB / m. The test environment temperature was 25℃ and the relative humidity was 50%. Each sample was tested 3 times, and the average value was taken. The test results are shown in Table 1.

[0057] 3. Cut dumbbell-shaped Type I specimens (gauge length 25 mm, width 4 mm) from the insulation layer. Use a universal testing machine to test the tensile strength and elongation at break at a tensile speed of 5 mm / min. Test each specimen 5 times and take the average value. The test results are shown in Table 1.

[0058] 4. Temperature stability test of dielectric properties: The insulation sample was placed in a high and low temperature test chamber and kept at -55℃, -35℃, -15℃, 5℃, 25℃, 45℃, 65℃, 85℃, 105℃, 125℃, and 150℃ for 30 minutes respectively. εr was then measured according to the dielectric constant test method described above. The maximum fluctuation value of the dielectric constant was calculated over the entire temperature range. The fluctuation value = (maximum value - minimum value) / average value × 100%. The test results are shown in Table 1.

[0059] Table 1: Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an RF microwave test cable, characterized in that, Includes the following steps: S1. Using oxygen-free copper rod, after continuous drawing, it undergoes annealing treatment and then electrolytic polishing to obtain the inner conductor; S2. Disperse nano-silica in anhydrous ethanol, add γ-glycidoxypropyltrimethoxysilane, and reflux under acidic conditions. After the reaction, centrifuge, wash and dry to obtain silane-modified nano-silica. Silane-modified nano-silica was added to DMAc solvent and dispersed. Then, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added, followed by the addition of pyromellitic dianhydride. The reaction was carried out under nitrogen protection to generate a PAA hybrid solution. Acetic anhydride and isoquinoline were added to the PAA hybrid solution to carry out a chemical imidization reaction. After precipitation with deionized water, washing and drying, the modified PI composite resin was obtained. S3. Graphene oxide is dispersed in deionized water, and hydrazine hydrate is added for reflux reduction to obtain reduced graphene oxide. It was redispersed in anhydrous ethanol, and 3-aminopropyltriethoxysilane was added to carry out the reaction. After the reaction, it was centrifuged, washed and dried to obtain amino-functionalized reduced graphene oxide. After the modified PI composite resin is melted, amino-functionalized reduced graphene oxide is added and stirred to disperse it. Then, the crosslinking agent pyromellitic dianhydride is added and stirred again. Subsequently, it is kept warm and cured to obtain the modified PI insulating material. S4. The modified PI insulating material is extruded and coated onto the surface of the inner conductor, and then cooled and shaped to obtain an inner conductor-insulating layer composite. Using oxygen-free copper wire, a shielding layer is wrapped around the surface of the inner conductor-insulation layer composite using a braiding machine to obtain a core wire-shielding layer composite. Polyurethane material is then extruded and wrapped around the surface of the core wire-shielding layer composite. After cooling and shaping, an RF microwave test cable is obtained.

2. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S1, the annealing temperature is 320–350°C and the annealing time is 1–2 hours.

3. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S2, the mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane is 10:(0.2-0.8).

4. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, the mass ratio of graphene oxide to hydrazine hydrate is 5:(0.5-1.0).

5. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, the amount of amino-functionalized reduced graphene oxide added is (2-5) wt% of the modified PI composite resin.

6. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, perfluorohexylethylaminotriethoxysilane is added after the modified PI composite resin is melted.

7. The method for preparing an RF microwave test cable according to claim 6, characterized in that, The amount of perfluorohexylethylaminotriethoxysilane added is (1-2) wt% of the modified PI composite resin.

8. A radio frequency microwave test cable, characterized in that, It is prepared by the method described in any one of claims 1-7.

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