Modified Nicolson-Ross-Weir (NRW) method to retrieve the constitutive parameters of low-loss materials

The constitutive parameters of a Teflon sample of arbitrary thickness are retrieved from scattering parameters experimentally measured with a vector network analyzer and a waveguide system into which the test sample is inserted by filling the transverse section of the X-band waveguide. Based on the Nicolson-Ross-Weir (NRW) method and modified to eliminate the phase ambiguity inherent to the NRW procedure, the algorithm used is able to correctly retrieve over the frequency range considered (8.20 to 12.40 GHz) the permittivity and permeability without any divergence at half-wavelength resonant frequencies for either dielectric or magnetic materials.