Improved Permittivity Measurement for the Material With Arbitrary Thickness Based on NRW and Adaptivity of Propagation Constant

An improved Nicolson-Ross-Weir (NRW) transmission/reflection method with the algorithm of adapting propagation constant is proposed in this paper for the permittivity measurement of that material with arbitrary thickness. The basic principle of the NRW method is reviewed and verified first, and the proposed improved method and adaptive algorithm are introduced and simulated for verification using the coaxial line measurement system. Both 2.92 and 7.0 mm measurement systems are fabricated to verify our method by measuring four different materials. By comparing the measured results in existing art and those using the proposed method, as well as the uncertainty and error analyses, one can see that our proposed method has the capability of measuring the permittivity of those materials with arbitrary thickness with high accuracy and efficiency.