Two-Port Frequency-Domain Measurement of Material Parameters Using Network Analysis Method

The two-port transmission line method has been described and used to determine the complex (relative) permeability μ and permittivity ε of materials under test in the frequency range from 10 MHz to 6.5 GHz by means of a vector network analyser. The μ and ε were extracted from the measured scattering parameters or corresponding reflection and transmission coefficients using Nicolson-Ross-Weir algorithm. For high-frequency measurements, a segment of coaxial transmission line with 50 Ω of characteristic impedance was made and verified. Measurement results of a (representative) soft magnetic material are presented, and some phenomena (or effects) such as phase displacement fault and half-wave divergence are also discussed.