同轴线缆 PTFE 编织绝缘层介电常数测量与验证

Measurement and verification of dielectric constant of PTFE braided insulation layer in coaxial cables

摘要

采用孔隙率等效原则建立一种聚四氟乙烯(PTFE)编织绝缘层介电常数测量方法,以优化柔性同轴线缆的结构设计。 试验先采用 12 锭的 PTFE 编织绝缘层作为研究对象,测得其孔隙率为5.593%;随后制备孔隙率相近(5. 307%)的 PTFE 平纹织物,通过高品质因子(Q)谐振腔法测试 PTFE 平纹织物的介电性能,获得介电常数为1.438、介电损耗角正切为9.612×10^-3等关键参数;最后,基于这些参数,设计 5 种不同内导体根数的50 Ω特性阻抗同轴线缆,并采用矢量网络分析仪进行阻抗特性测试。结果显示,5 种线缆阻抗实测值与依托等效介电参数求解的理论值,均满足(50±2)Ω的设计要求。 研究表明,基于孔隙率等效方法测得的介电常数可用于编织绝缘同轴线缆特性阻抗理论值的计算,以及同轴线缆的结构设计与优化。

Abstract

A measurement method for the dielectric constant of polytetrafluoroethylene ( PTFE) braided insulation was established based on the porosity equivalence principle to optimize the structural design of flexible coaxial cables. Firstly, a 12-spindle PTFE braided insulation layer was selected as the research object, and its porosity was measured to be 5.593%. Subsequently, a PTFE plain woven fabric with a similar porosity (5.307%) was prepared. The dielectric properties of PTFE plain woven fabrics were tested using the high quality factor (Q) resonant cavity method, and key parameters including a dielectric constant of 1.438 and a dielectric loss tangent of 9.612×10^-3, were obtained. Finally, five types of 50 Ω characteristic impedance coaxial cables with different numbers of inner conductor strands were designed based on these parameters, and their impedance characteristics were tested using a vector network analyzer. The results indicated that all the measured impedance values of the five cables and the theoretical values calculated using the equivalent dielectric parameters satisfied the design requirement of (50±2) Ω. It is demonstrated that the dielectric constant measured based on the porosity equivalence method can be utilized for the calculation of the theoretical characteristic impedance of braided insulation coaxial cables and for the structural design and optimization of coaxial cables.

关键词

射频编织同轴线缆 / 介电常数 / 平纹织物 / 编织物 / 特性阻抗

Key words

radio frequency braided coaxial cable / dielectric constant / plain weave fabric / braided fabric / characteristic impedance

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基金资助

上海市自然科学基金(22ZR1400800)

安徽省制造业重点领域技术攻关项目(JB22053)