An improved NRW method to extract electromagnetic parameters of metamaterials

摘要

In this article, an improved Nicolson-Ross-Weir (NRW) method has been developed to accurately retrieve electromagnetic parameters of metamaterials. By solving roots of higher degree for transmission term and applying first-order approximation of Taylor's series to the resultant term, the accuracy of the proposed NRW method can be greatly improved. Combined with Kramers-Kronig (K-K) relationship, the developed method can correctly solve the branch of the refractive index caused by complex exponential function and thus the proposed method is free from the limitation of the electric thickness of the measured materials. Numerical results including a single slab of fishnet structure and three slabs of wires and split-ring resonators are given to show accuracy and efficiency of the proposed method. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:647-652, 2016