The transmission/reflection frequency-sweep measurement to determine the relative complex permittivity (εr) and permeability (μr) of radio frequency (RF) materials based on coaxial transmission line is studied in this paper. Some ill-behaved characteristics of the nicolson-ross-weir (NRW) method such as half-wavelength divergence, phase jump and multiplicity of roots are discussed and improved solutions are presented. The multiplicity of roots is solved by the aid of frequency-sweep and data processing techniques. Teflon, polypropylene, polyoxymethylene, ferrite cores and some absorbers are tested. The uncertainties of the test system due to air gap, scattering parameters measurement, and sample length uncertainty are discussed. The influence of higher modes on test accuracy is analyzed by measuring the same sample in two setups with different coaxial fixtures (φ16mm/φ7mm and φ7mm/φ3.05mm coaxial lines).%介绍了传输/反射法测量射频介质参数(复介电常数(εr=ε′r-jε″r=ε′r-jσ/ω·ε0)和相对复数磁导率(μr=μ′r-jμ″r))的基本原理;对Nicolson算法中的厚度谐振、多值性和相角跳变等问题进行了深入分析,并提出了改进方案.利用网络分析仪的扫频技术解决了多值性的问题.文章利用矢量网络分析仪和同轴夹具组成的测试系统对聚氯乙烯、聚丙烯、聚甲醛、铁氧体及介电型吸波材料的电磁参数进行了测算,对空气间隙、试样长度和S参数等误差影响因素进行了分析.文章还利用两个系列的同轴夹具(Ф16mm/Ф7mm和Ф7mm/Ф3.05mm).对几种常用电介质材料进行了测算,对同轴传输线高次模对测试频率范围的影响规律进行了探索.本文为研究电工电子功能材料在高频应用场合下的储能特性和损耗特性奠定了基础.
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