A gradual impedance transformer and a method of processing the same

Abstract

This invention relates to the field of graded impedance converter technology, and more particularly to a graded impedance converter and its processing method. The graded impedance converter includes: a graded section consisting of a beveled outer conductor and a core wire passing through the interior of the beveled outer conductor, and an assembly section disposed at one end of the graded section. The processing method includes: mixing and curing polytetrafluoroethylene (PTFE) dispersion powder with an extrusion aid to form a blank; extruding the blank through an annular gap while simultaneously coating the inner conductor to form a wet blank insulation layer; during the extrusion process, adjusting the extrusion speed according to the temperature anomaly region, adjusting the preheating temperature according to the interface distance between the rigidity anomaly region and the inner conductor, and compensating the extrusion pressure of the annular gap according to the vibration intensity and the area of ​​the rigidity anomaly region; subsequently, drying, sintering, copper tube drawing and beveling, and assembly are performed to obtain the graded impedance converter. This invention achieves continuous impedance transformation of the graded impedance converter.

Description

Technical Field

[0001] This invention relates to the field of gradient impedance transformer technology, and more particularly to a gradient impedance transformer and its fabrication method. Background Technology

[0002] In microwave and radio frequency systems, impedance transformers are key passive components for achieving high-efficiency transmission between transmission lines with different characteristic impedances. Traditional impedance transformation methods mainly include: Firstly, the stepped impedance transformer consists of multiple fixed line segments with different impedances. Its disadvantages are a relatively narrow bandwidth and the generation of parasitic discontinuities at discrete impedance transitions, resulting in degraded performance at high frequencies (especially in the millimeter-wave band).

[0003] Secondly, microstrip line gradient converters: These are formed by etching a substrate to create microstrip lines with gradually varying linewidths. Although they offer a wider bandwidth, their power capacity is limited by substrate and conductor losses, their heat dissipation is generally poor, and their electrical performance is significantly affected by the uniformity of the substrate's dielectric constant and processing errors. Furthermore, their phase stability is highly sensitive to ambient temperature.

[0004] Third, conventional coaxial converters: These use multiple segments of coaxial conductors with different inner and outer diameters spliced ​​together. Although they have a high power capacity, they have multiple connection interfaces, introducing additional voltage standing wave ratio (VSWR) risks and intermodulation distortion. Assembly is complex, and consistency is difficult to guarantee.

[0005] Semi-rigid coaxial cables, with their structure of a copper tube outer conductor, a solid wire inner conductor, and a solid dielectric, offer advantages such as good shielding, low loss, phase stability, and high mechanical strength, making them widely used for interconnecting high-performance microwave devices. However, current impedance transformers based on semi-rigid coaxial cables often employ fixed-diameter splicing structures, failing to fully utilize the material's advantages and leaving a technological gap in achieving continuously variable impedance. Traditional segmented splicing methods create impedance discontinuities at the joints, leading to increased reflection coefficients. Furthermore, machining the copper tube outer conductor to gradually change its diameter presents challenges such as deformation during precision machining of thin-walled copper tubes, difficulty in controlling surface roughness, and challenges in ensuring concentricity between the inner and outer conductors. In addition, the fluidity of solid dielectric materials under heat and the work hardening characteristics of metallic materials make it difficult to achieve the impedance control accuracy and electrical consistency required for millimeter-wave applications in the variable impedance section. Therefore, there is an urgent need for a novel structure and reliable processing method that can fully utilize the superior performance of semi-rigid coaxial cables to achieve truly continuous gradually variable impedance transformation. Summary of the Invention

[0006] To address this, the present invention provides a gradient impedance converter and its processing method, which overcomes the problems of discontinuous impedance transformation and low processing accuracy caused by changes in the fluidity of solid dielectric material under heating during the preparation of the insulating layer in the prior art.

[0007] To achieve the above objectives, in one aspect, the present invention provides a gradually varying impedance transformer, comprising: The transition section includes a beveled outer conductor and a core wire passing through the interior of the beveled outer conductor; The cross-sectional dimensions of the obliquely cut outer conductor vary continuously in the axial direction, and the core wire includes a first inner conductor segment and a first insulating layer covering the inner conductor. The assembly section, which is located at one end of the transition section, includes a second inner conductor section with the same inner diameter as the semi-rigid coaxial cable and connected to the first inner conductor section, an original outer conductor connected to the obliquely cut outer conductor, and a second insulation layer covering the second inner conductor section. The ratio of the inner diameter of the obliquely cut semiconductor to the outer diameter of the inner conductor is positively correlated with the target impedance that varies along the axial direction.

[0008] Furthermore, the formula for calculating the target impedance that varies along the axial direction is: ; Where εr is the relative permittivity of the cable medium, Z(z) is the preset target impedance that varies along the axial direction, D(z) is the inner diameter of the outer conductor, and d(z) is the outer diameter of the inner conductor.

[0009] On the other hand, the present invention provides a processing method for the said tapered impedance transformer, comprising: Polytetrafluoroethylene dispersion powder is mixed with liquid extrusion aid and allowed to stand for curing to obtain a cured mixture. The curing mixture is placed into the screw cavity of a plunger-type barrel, and under high pressure, the curing mixture is extruded through the annular gap between the die sleeve and the die core to form a preform. The preform is then extruded onto the inner conductor, which has reached the preheated temperature. The temperature anomaly area on the outer wall of the plunger-type barrel is obtained, the rigidity anomaly area in the billet is determined based on the temperature anomaly area, and the extrusion speed of the annular gap between the die sleeve and the die core is adjusted based on the area of ​​the rigidity anomaly area. Obtain the distance between the interface between the rigid abnormal region and the inner conductor, and adjust the preheating temperature of the inner conductor according to the distance; The transmission distance of vibration on the extrusion die is determined based on the vibration intensity during the extrusion process. The actual decrease in the bonding capacity of the billet-metal interface is determined based on the transmission range area corresponding to the transmission distance and the area of ​​the abnormal rigidity region. The extrusion pressure of the annular gap is increased based on the decrease in the bonding capacity. The plunger-type barrel is controlled according to the extrusion speed, the preheating temperature and the extrusion pressure to continue extruding the matured mixture to form a wet blank insulation layer; The wet blank insulation layer is placed in a drying oven to form a wire with the insulating agent removed; The wire is fed into a high-temperature sintering furnace for sintering to obtain a core wire; The copper tube is drawn to a preset size using a drawing die. After calculating the impedance change curve using the Chebyshev function, the copper tube is beveled. The core wire is then inserted into the beveled copper tube to output the gradual impedance converter.

[0010] Furthermore, the extrusion speed of the annular gap between the die sleeve and the die core is adjusted according to the area of ​​the abnormally rigid region, including: The area of ​​the rigid abnormal region is compared with a preset area threshold. If the area is greater than or equal to the preset area threshold, it indicates that the area of ​​abnormal rigidity of the billet caused by the mechanical heating of the barrel is large, and the billet shows obvious uneven flow. The extrusion speed is reduced according to the difference between the area and the preset area threshold.

[0011] Furthermore, the reduction in the extrusion speed is directly related to the difference between the area and the preset area threshold.

[0012] Furthermore, adjusting the preheating temperature of the inner conductor based on the distance between the rigidity anomaly region and the interface of the inner conductor includes: The distance between the interface between the rigid abnormal region and the inner conductor is compared with a preset distance threshold. If the distance is less than or equal to a preset distance threshold, it is determined that the change in the rigidity of the blank has a significant impact on the bonding ability between the blank and the inner conductor, and the preheating temperature of the inner conductor is increased according to the difference between the preset distance threshold and the distance.

[0013] Furthermore, the increase in the preheating temperature is positively correlated with the difference between the preset distance threshold and the distance.

[0014] Furthermore, the decrease in binding capacity is the sum of the first attenuation and the second attenuation; The first attenuation is the product of the vibration intensity of the plunger-type barrel within the area of ​​the common action region and the attenuation coefficient of the first bonding force. The second attenuation is the product of the area ratio of the rigid abnormal region within the area of ​​the common action region and the second bonding force attenuation coefficient; The area of ​​common action is the overlapping area between the transmission range corresponding to the transmission distance and the rigidity abnormal area. The transmission range corresponding to the transmission distance is all areas where the vibration intensity is greater than or equal to a preset intensity threshold when the vibration is transmitted from the extruder to the extrusion die.

[0015] Further, the step of increasing the extrusion pressure of the annular gap according to the decrease in bonding strength includes, The decrease in binding capacity is compared with a preset threshold for decrease in binding capacity; If the decrease in bonding ability is less than the preset threshold for decrease in bonding ability, it is determined that the bonding ability between the blank and the inner conductor meets the process requirements, and the extrusion pressure of the current annular gap is maintained. If the decrease in bonding ability is greater than or equal to a preset threshold for decrease in bonding ability, it is determined that the bonding ability between the preform and the inner conductor does not meet the process requirements, and the extrusion pressure of the annular gap is increased according to the difference between the decrease in bonding ability and the preset threshold for decrease in bonding ability.

[0016] Furthermore, the increase in the extrusion pressure of the annular gap is positively correlated with the difference between the decrease in bonding capacity and the preset threshold for decrease in bonding capacity.

[0017] Compared with existing technologies, the advantages of this invention are as follows: This invention achieves a continuous monotonic change in characteristic impedance along the axial direction through the coordinated design of a gradient-wrapped outer conductor and a single-diameter inner conductor, fundamentally eliminating impedance discontinuities in traditional stepped impedance converters and significantly reducing voltage standing wave ratio (VSWR) and reflection loss. The use of semi-rigid coaxial cable as the basic structure fully utilizes its excellent shielding performance, low loss, and high phase stability. Simultaneously, the impedance gradient curve is optimized using a Chebyshev function, enabling the converter to maintain a flat transmission response over a wide frequency range.

[0018] Furthermore, in terms of the insulation layer preparation process, this invention determines the rigidity abnormal region in the preform based on the temperature abnormal region, and determines whether the temperature rise due to mechanical operation will cause uneven flowability of the preform based on the area of ​​the rigidity abnormal region. When uneven flowability of the preform is caused, the extrusion speed of the annular gap between the die sleeve and the die core is adjusted. This can effectively suppress the problem of increased local rigidity of the preform caused by mechanical heating of the barrel, and ensure that the preform of polytetrafluoroethylene dispersion powder mixed with extrusion aid maintains uniform rheological properties during extrusion, thereby improving the consistency accuracy of the axial dimensions of the insulation layer.

[0019] Furthermore, by monitoring the distance between the rigidity abnormal region and the interface of the inner conductor in real time, this invention determines the potential impact of changes in the rigidity of the blank on the coating bonding ability of the inner conductor, and adjusts the preheating temperature of the inner conductor accordingly, optimizes the thermal melting state at the interface between the solid medium and the metal, improves the bonding strength between the insulation layer and the inner conductor, and avoids delamination or peeling defects in subsequent sintering processes.

[0020] Furthermore, this invention introduces the area of ​​the combined effect of the vibration transmission distance and the area of ​​the rigidity abnormal region. By quantitatively calculating the decrease in bonding capacity under the combined effect of vibration attenuation and rigidity abnormality, and increasing the extrusion pressure of the annular gap by the decrease in bonding capacity, this control strategy not only compensates for the disturbance of extrusion stability caused by equipment vibration, but also provides pressure compensation for the local reinforcement needs of the rigidity abnormal region, so that the wet blank insulation layer can maintain uniform density and concentricity.

[0021] Furthermore, in the overall assembly of the impedance transformer, this invention employs a copper tube outer conductor fabrication process that combines drawing and beveling. The impedance gradient law is calculated using Chebyshev functions to guide the design of the beveling angle, resulting in a conical covering structure with continuously varying cross-sectional dimensions after the copper tube is inserted into the core wire. This processing method avoids the mechanical damage and deformation risks associated with traditional turning processes on thin-walled copper tubes, while utilizing the work hardening effect generated by drawing to enhance the mechanical strength and dimensional stability of the outer conductor. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the tapered impedance converter according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the core wire structure of the tapered impedance transformer according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the fabrication method of the tapered impedance transformer according to an embodiment of the present invention. Figure 4 This is a flowchart illustrating the process of adjusting the extrusion speed of the annular gap in an embodiment of the present invention. In the diagram: 1. Inner conductor; 2. Insulating layer; 3. Outer conductor. Detailed Implementation

[0023] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0024] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0026] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Please see Figure 1-4 As shown, these are respectively a schematic diagram of the overall structure of the gradient impedance converter according to an embodiment of the present invention, a schematic diagram of the core wire structure of the gradient impedance converter, a flowchart of the processing method of the gradient impedance converter, and a flowchart of the extrusion speed for adjusting the annular gap. On one hand, the present invention provides a gradually varying impedance transformer, comprising: The transition section includes a beveled outer conductor and a core wire passing through the interior of the beveled outer conductor; The cross-sectional dimensions of the obliquely cut outer conductor vary continuously in the axial direction, and the core wire includes a first inner conductor segment and a first insulating layer covering the inner conductor. The assembly section, which is located at one end of the transition section, includes a second inner conductor section with the same inner diameter as the semi-rigid coaxial cable and connected to the first inner conductor section, an original outer conductor connected to the obliquely cut outer conductor, and a second insulation layer covering the second inner conductor section. The ratio of the inner diameter of the obliquely cut semiconductor to the outer diameter of the inner conductor is positively correlated with the target impedance that varies along the axial direction.

[0028] Specifically, the formula for calculating the target impedance that varies along the axial direction is: ; Where εr is the relative permittivity of the cable medium, Z(z) is the preset target impedance that varies along the axial direction, D(z) is the inner diameter of the outer conductor, and d(z) is the outer diameter of the inner conductor.

[0029] Specifically, one end of the converter retains an unprocessed uniform assembly section for soldering to a standard connector.

[0030] On the other hand, the present invention provides a method for fabricating a gradient impedance transformer, comprising: Step S1: Mix polytetrafluoroethylene dispersion powder with liquid extrusion aid and allow it to stand and mature to obtain a matured mixture; Step S2: The curing mixture is placed into the screw cavity of the plunger-type barrel, and the curing mixture is extruded through the annular gap between the die sleeve and the die core under high pressure to form a preform. The preform is then extruded onto the inner conductor that has reached the preheated temperature. Step S3: Obtain the temperature abnormality area on the outer wall of the plunger-type barrel, determine the rigidity abnormality area in the billet based on the temperature abnormality area, and adjust the extrusion speed of the annular gap between the die sleeve and the die core based on the area of ​​the rigidity abnormality area. Step S4: Obtain the distance between the interface between the rigid abnormal region and the inner conductor, and adjust the preheating temperature of the inner conductor according to the distance. Step S5: Determine the transmission distance of vibration on the extrusion die based on the vibration intensity during the extrusion process; determine the actual decrease in bonding capacity of the billet-metal interface based on the transmission range area corresponding to the transmission distance and the area of ​​the rigidity abnormal region; and increase the extrusion pressure of the annular gap based on the decrease in bonding capacity. Step S6: The plunger-type barrel is controlled according to the extrusion speed, the preheating temperature and the extrusion pressure to continue extruding the matured mixture to form a wet blank insulation layer; Step S7: Place the wet blank insulation layer into a drying oven to form a wire with the insulating agent removed; send the wire into a high-temperature sintering furnace for sintering to obtain a core wire; Step S8: The copper tube is drawn to a preset size using a drawing die. After calculating the impedance change curve using the Chebyshev function, the copper tube is beveled. The core wire is then inserted into the beveled copper tube to output the gradual impedance converter.

[0031] In the embodiments, the mixing ratio of the polytetrafluoroethylene dispersion powder to the liquid extrusion aid is between 100:8 and 100:12, with a preferred ratio of 100:10. The liquid extrusion aid is liquid paraffin. The standing curing time is controlled at 8 hours, and the curing environment temperature is maintained at 25°C to ensure that the polytetrafluoroethylene dispersion powder fully absorbs the extrusion aid and forms a uniform plastic material system.

[0032] In this embodiment, the extrusion pressure of the annular gap is set to 50 MPa, and the width of the annular gap between the die sleeve and the die core is set according to the target insulation layer thickness, preferably 2.0 mm. The preheating temperature of the inner conductor is 80°C to 120°C, preferably 100°C, and the preheating time is controlled at 30 min to ensure that the surface temperature of the inner conductor is uniform and reaches a suitable thermal equilibrium state, thereby promoting good bonding between the polytetrafluoroethylene material and the metal surface during subsequent insulation layer extrusion. The extrusion speed of the annular gap between the die sleeve and the die core is set to 0.5 m / min to 1.5 m / min, preferably 1.0 m / min. The setting of this speed range needs to comprehensively consider the balance between the plasticizing characteristics of the polytetrafluoroethylene material, the requirement for uniform insulation layer thickness, and production efficiency. Too low an extrusion speed will cause the material to stay in the die cavity for too long, causing local overheating and degradation, while too high a speed will easily cause defects such as rough insulation layer surface and internal pores.

[0033] Specifically, identifying temperature anomaly areas includes: real-time acquisition of the surface temperature distribution of the barrel using an array of infrared temperature sensors arranged on the outer wall of the barrel; comparison of the acquired temperature values ​​with the set operating temperature of the barrel; and marking areas with a temperature deviation exceeding 8°C as temperature anomaly areas, where the set operating temperature is 55°C. The rigidity anomaly area is the billet area corresponding to the temperature anomaly area.

[0034] Specifically, the wet blank insulation layer is placed in a drying oven, and the extrusion aid is removed by heating. The drying temperature is gradually increased to 200°C at a rate of 15°C per hour, and then maintained at 200°C for 4 hours to allow the liquid paraffin extrusion aid to fully evaporate without damaging the pre-formed structure of polytetrafluoroethylene, ultimately obtaining a dried wire with the extrusion aid removed. During the drying process, the air velocity inside the oven must be controlled at 0.5 m / s to avoid local overheating that could cause the insulation layer to crack or deform.

[0035] The dried wire is fed into a high-temperature sintering furnace for sintering. The sintering process adopts a segmented temperature control strategy: in the first stage, the temperature is increased from room temperature to 327°C at a rate of 50°C / h to allow the polytetrafluoroethylene (PTFE) to complete its crystal transformation; in the second stage, the temperature is increased slowly at a rate of 20°C / h between 327°C and 380°C to achieve densification, with the maximum sintering temperature controlled between 380°C and 400°C, preferably 385°C, and the holding time is 2 hours; in the third stage, the temperature is cooled to room temperature at a rate of 30°C / h to allow the PTFE molecular chains to fully expand and recrystallize, forming a dense and uniform insulating layer structure.

[0036] Specifically, the process of drawing copper tubes to a predetermined size using a drawing die includes: selecting annealed soft copper tubes with a wall thickness of 0.3mm as raw material; reducing the outer diameter of the copper tube through a two-pass drawing process; controlling the deformation per drawing pass between 15% and 25%; after the first drawing pass, the outer diameter of the copper tube is reduced from the initial 3.0mm to 2.6mm; after the second drawing pass, it is further reduced to 2.3mm; the half-cone angle of the drawing die is set to 12°; the drawing speed is controlled at 0.3m / s; and a palm oil-based lubricant is used for cooling and lubrication during the drawing process to reduce the surface friction coefficient of the copper tube and prevent surface scratches. After drawing, the Vickers hardness of the copper tube increases from the initial 85HV to 135HV, and the work hardening effect significantly improves the mechanical strength and deformation resistance of the outer conductor.

[0037] Specifically, the process of obliquely cutting the copper tube after calculating the impedance change using the Chebyshev function includes: designing an impedance gradient curve using the Chebyshev polynomial approximation method based on the initial impedance Z0 and final impedance ZL of the target impedance transformer, so that the reflection coefficient exhibits equiripple characteristics within the passband. The maximum voltage standing wave ratio (VSWR) within the passband is set to 1.2, and the gradient law of the outer conductor's inner diameter is calculated using the Chebyshev synthesis formula, thereby determining the axial variation function of the copper tube wall thickness.

[0038] Specifically, the extrusion speed of the annular gap between the die sleeve and the die core is adjusted according to the area of ​​the abnormally rigid region, including: The area of ​​the rigid abnormal region is compared with a preset area threshold. If the area is less than the preset area threshold, it indicates that the area of ​​the abnormal rigidity of the billet caused by the mechanical heating of the barrel is small, and the flowability of the billet is not affected by the mechanical heating of the barrel. If the area is greater than or equal to the preset area threshold, it indicates that the area of ​​abnormal rigidity of the billet caused by the mechanical heating of the barrel is large, and the billet shows obvious uneven flow. The extrusion speed is reduced according to the difference between the area and the preset area threshold. The decrease in the extrusion speed is directly related to the difference between the area and the preset area threshold.

[0039] Specifically, the preset area threshold is set to 20 mm². This threshold is based on the critical plasticizing characteristics of polytetrafluoroethylene dispersion powder in a liquid paraffin extrusion aid system. When the area of ​​the abnormally rigid region exceeds this range, the molecular chain entanglement density inside the billet increases significantly due to the local temperature rise, and the shear viscosity shows a non-linear upward trend, thereby disrupting the laminar flow stability of the material during extrusion.

[0040] In implementation, when the area is within 5 mm² of the preset area threshold, the extrusion speed is adjusted to 0.9 times. When the area exceeds the preset area threshold by more than 5 mm², the extrusion speed is reduced by 0.05 m / min for every 1 mm² exceeding the threshold. In a specific embodiment, the current area is 27 mm², the current extrusion speed is 1.0 m / min, and the reduced extrusion speed is 1.0 m / min × 0.9 - (2 mm² / 1 mm²) × 0.05 m / min = 0.8 m / min.

[0041] Specifically, adjusting the preheating temperature of the inner conductor based on the distance between the rigidity anomaly region and the interface between the inner conductor includes, The distance between the interface between the rigid abnormal region and the inner conductor is compared with a preset distance threshold. If the distance is less than or equal to a preset distance threshold, it is determined that the change in the rigidity of the blank has a significant impact on the bonding ability between the blank and the inner conductor, and the preheating temperature of the inner conductor is increased according to the difference between the preset distance threshold and the distance.

[0042] Specifically, the preset distance threshold is set to 3.6 mm. This threshold is set based on the thermodynamic characteristics of the interface bonding between PTFE preform and the metal inner conductor. When the distance between the abnormally rigid region and the bonding interface is less than this critical value, the increased rigidity of the molecular chains in this region due to the temperature rise will directly act on the interface transition layer, weakening the entanglement and adsorption between the PTFE molecular chain segments and the active sites on the metal surface, and significantly reducing the interface bonding strength.

[0043] Specifically, the increase in preheating temperature is directly related to the difference between the preset distance threshold and the distance. In implementation, when the distance is less than the preset distance threshold by less than 0.6 mm, the preheating temperature of the inner conductor is adjusted to 1.1 times the current preheating temperature. When the distance is less than the preset distance threshold by more than 0.6 mm, the preheating temperature is increased by 3°C for every 0.2 mm exceeding the threshold. In a specific embodiment, the current distance is 2.8 mm, the current preheating temperature is 100°C, and the increased preheating temperature is 100°C × 1.1 + (0.2 mm / 0.2 mm) × 3°C = 113°C.

[0044] Specifically, the decrease in binding capacity is the sum of the first attenuation and the second attenuation; The first attenuation is the product of the vibration intensity of the extrusion equipment within the area of ​​the common action region and the first bonding force attenuation coefficient; wherein the first bonding force attenuation coefficient is 0.15 N / (mm²·g), which characterizes the degree of loss of interfacial bonding force per unit area under the action of unit vibration intensity; The second attenuation is the product of the area ratio of the rigid abnormal region within the area of ​​the common action region and the second bonding force attenuation coefficient, wherein the second bonding force attenuation coefficient is 0.08 N / mm², which characterizes the basic weakening effect of the degradation of the material properties of the rigid abnormal region on the interfacial bonding force. The area of ​​the common action region is the overlapping area of ​​the transmission range area corresponding to the transmission distance and the area of ​​the rigid abnormal region. The transmission range corresponding to the transmission distance is all areas where the vibration intensity is greater than or equal to a preset intensity threshold when the vibration is transmitted from the extruder to the extrusion die.

[0045] Specifically, increasing the extrusion pressure of the annular gap according to the decrease in bonding strength includes, The decrease in binding capacity is compared with a preset threshold for decrease in binding capacity; If the decrease in bonding ability is less than the preset threshold for decrease in bonding ability, it is determined that the bonding ability between the blank and the inner conductor meets the process requirements, and the extrusion pressure of the current annular gap is maintained. If the decrease in bonding ability is greater than or equal to a preset threshold for decrease in bonding ability, it is determined that the bonding ability between the preform and the inner conductor does not meet the process requirements, and the extrusion pressure of the annular gap is increased according to the difference between the decrease in bonding ability and the preset threshold for decrease in bonding ability.

[0046] Specifically, the preset bonding strength reduction threshold is set to 0.45 N / mm². This threshold is determined based on the lower limit requirement of the process for the peel strength of the interface between the PTFE insulation layer and the copper inner conductor. When the bonding strength reduction exceeds this critical value, the effective bonding force at the interface will be lower than the minimum safety margin required to ensure the cable maintains structural integrity under bending, torsion, and thermal cycling conditions, which may lead to micro-gap or delamination defects between the insulation layer and the inner conductor.

[0047] Specifically, the increase in the extrusion pressure of the annular gap is directly related to the difference between the decrease in bonding capacity and the preset threshold for decrease in bonding capacity. In implementation, when the decrease in bonding capacity is greater than the preset threshold for decrease in bonding capacity but within 0.1 N / mm², the extrusion pressure of the annular gap is adjusted to 1.05 times the current pressure; when the decrease in bonding capacity exceeds the preset threshold for decrease in bonding capacity by more than 0.1 N / mm², the extrusion pressure of the annular gap is increased by 2 MPa for every 0.02 N / mm² exceeding the threshold. In a specific embodiment, the current decrease in bonding capacity is 0.58 N / mm², the current extrusion pressure of the annular gap is 50 MPa, and the increased extrusion pressure of the annular gap is 50 MPa × 1.05 + (0.08 N / mm² / 0.02 N / mm²) × 2 MPa = 52.5 MPa + 8 MPa = 60.5 MPa. The increase in extrusion pressure of the annular gap is adjusted by the hydraulic device of the plunger extruder. The hydraulic device uses an internal pressure sensor to provide real-time feedback of the extrusion pressure value and controls the hydraulic output pressure to ensure that the pressure adjustment accuracy is controlled within ±1MPa, thus meeting the precise requirements of process adjustment.

[0048] Specifically, obtaining the vibration intensity during the extrusion process includes: arranging a triaxial accelerometer on the outer wall of the barrel, setting the sampling frequency to 2kHz, and the acquisition time window to 10s. The effective vibration intensity is calculated using the root mean square value, with the unit being g.

[0049] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A gradually varying impedance transformer, characterized in that, include: The transition section includes a beveled outer conductor and a core wire passing through the interior of the beveled outer conductor; The cross-sectional dimensions of the obliquely cut outer conductor vary continuously in the axial direction, and the core wire includes a first inner conductor segment and a first insulating layer covering the inner conductor. The assembly section, which is located at one end of the transition section, includes a second inner conductor section with the same inner diameter as the semi-rigid coaxial cable and connected to the first inner conductor section, an original outer conductor connected to the obliquely cut outer conductor, and a second insulation layer covering the second inner conductor section. The ratio of the inner diameter of the obliquely cut semiconductor to the outer diameter of the inner conductor is positively correlated with the target impedance that varies along the axial direction.

2. The gradually changing impedance transformer according to claim 1, characterized in that, The formula for calculating the target impedance that varies along the axial direction is: ； Where εr is the relative permittivity of the cable medium, Z(z) is the preset target impedance that varies along the axial direction, D(z) is the inner diameter of the outer conductor, and d(z) is the outer diameter of the inner conductor.

3. A method for fabricating a tapered impedance converter according to any one of claims 1-2, characterized in that, include: Polytetrafluoroethylene dispersion powder is mixed with liquid extrusion aid and allowed to stand for curing to obtain a cured mixture. The curing mixture is placed into the screw cavity of a plunger-type barrel, and under high pressure, the curing mixture is extruded through the annular gap between the die sleeve and the die core to form a preform. The preform is then extruded onto the inner conductor, which has reached the preheated temperature. The temperature anomaly area on the outer wall of the plunger-type barrel is obtained, the rigidity anomaly area in the billet is determined based on the temperature anomaly area, and the extrusion speed of the annular gap between the die sleeve and the die core is adjusted based on the area of ​​the rigidity anomaly area. Obtain the distance between the interface between the rigid abnormal region and the inner conductor, and adjust the preheating temperature of the inner conductor according to the distance; The transmission distance of vibration on the extrusion die is determined based on the vibration intensity during the extrusion process. The actual decrease in the bonding capacity of the billet-metal interface is determined based on the transmission range area corresponding to the transmission distance and the area of ​​the abnormal rigidity region. The extrusion pressure of the annular gap is increased based on the decrease in the bonding capacity. The plunger-type barrel is controlled according to the extrusion speed, the preheating temperature and the extrusion pressure to continue extruding the matured mixture to form a wet blank insulation layer; The wet blank insulation layer is placed in a drying oven to form a wire with the insulating agent removed; The wire is fed into a high-temperature sintering furnace for sintering to obtain a core wire; The copper tube is drawn to a preset size using a drawing die. After calculating the impedance change curve using the Chebyshev function, the copper tube is beveled. The core wire is then inserted into the beveled copper tube to output the gradual impedance converter.

4. The fabrication method of the gradually varying impedance transformer according to claim 3, characterized in that, Adjusting the extrusion speed of the annular gap between the die sleeve and the die core according to the area of ​​the abnormal rigidity region includes: The area of ​​the rigid abnormal region is compared with a preset area threshold. If the area is greater than or equal to the preset area threshold, it indicates that the area of ​​abnormal rigidity of the billet caused by the mechanical heating of the barrel is large, and the billet shows obvious uneven flow. The extrusion speed is reduced according to the difference between the area and the preset area threshold.

5. The fabrication method of the gradually varying impedance transformer according to claim 4, characterized in that, The decrease in the extrusion speed is directly related to the difference between the area and the preset area threshold.

6. The fabrication method of the tapered impedance transformer according to claim 5, characterized in that, Adjusting the preheating temperature of the inner conductor based on the distance between the rigidity anomaly region and the interface of the inner conductor includes, The distance between the interface between the rigid abnormal region and the inner conductor is compared with a preset distance threshold. If the distance is less than or equal to a preset distance threshold, it is determined that the change in the rigidity of the blank has a significant impact on the bonding ability between the blank and the inner conductor, and the preheating temperature of the inner conductor is increased according to the difference between the preset distance threshold and the distance.

7. The fabrication method of the tapered impedance transformer according to claim 6, characterized in that, The increase in the preheating temperature is positively correlated with the difference between the preset distance threshold and the distance.

8. The fabrication method of the tapered impedance transformer according to claim 7, characterized in that, The decrease in binding capacity is the sum of the first attenuation and the second attenuation; The first attenuation is the product of the vibration intensity of the plunger-type barrel within the area of ​​the common action region and the attenuation coefficient of the first bonding force. The second attenuation is the product of the area ratio of the rigid abnormal region within the area of ​​the common action region and the second bonding force attenuation coefficient; The area of ​​common action is the overlapping area between the transmission range corresponding to the transmission distance and the rigidity abnormal area. The transmission range corresponding to the transmission distance is all areas where the vibration intensity is greater than or equal to a preset intensity threshold when the vibration is transmitted from the extruder to the extrusion die.

9. The fabrication method of the tapered impedance transformer according to claim 8, characterized in that, The step of increasing the extrusion pressure of the annular gap according to the decrease in bonding ability includes, The decrease in binding capacity is compared with a preset threshold for decrease in binding capacity; If the decrease in bonding ability is less than the preset threshold for decrease in bonding ability, it is determined that the bonding ability between the blank and the inner conductor meets the process requirements, and the extrusion pressure of the current annular gap is maintained. If the decrease in bonding ability is greater than or equal to a preset threshold for decrease in bonding ability, it is determined that the bonding ability between the preform and the inner conductor does not meet the process requirements, and the extrusion pressure of the annular gap is increased according to the difference between the decrease in bonding ability and the preset threshold for decrease in bonding ability.

10. The fabrication method of the tapered impedance transformer according to claim 9, characterized in that, The increase in the extrusion pressure of the annular gap is positively correlated with the difference between the decrease in bonding capacity and the preset threshold for decrease in bonding capacity.

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