Electromagnetic characterization of layered materials via direct and de-embed methods

Electromagnetic-material characterization is the process of determining the permittivity and permeability of matter. One of the predominant schemes utilized for computing these constitutive parameters is the Nicolson-Ross-Weir (NRW) algorithm. In this particular technique, the sample under measurement is assumed to be linear, homogeneous, isotropic (i.e., simple medium), and is comprised of a single-layer planar material. However, samples are frequently attached to known substrate materials in order to facilitate measurement; thus, the standard NRW technique cannot be directly employed. This paper presents two schemes, the direct and de-embed methods, for accommodating multilayered-material-characterization measurements. Accuracy is discussed using an uncertainty analysis. In addition, it is shown that the direct method has a distinct advantage over the de-embed method if sample homogeneity is to be monitored.