An Improved NRW Method for Thin Material Characterization Using Dielectric Filled Waveguide and Numerical Compensation

In this article, permittivity measurements based on the Nicholson–Ross–Weir (NRW) technique are reviewed, and an improved method is proposed based on dielectric-filled waveguides and numerical compensation for the electromagnetic performance measurement of the flexible materials or extremely thin materials. The dielectric-filled waveguide used in this work fixes the sample under test without any deformation during the measurement. To improve the measurement accuracy, a modified algorithm is proposed for the inversion of dielectric material and the compensation of measured results. The proposed method is verified by measuring several commercially available materials in the X-band with high accuracy and then used for the characterization of two paper-based composite electromagnetic parameters.