Extraction of tensor parameters of general biaxial anisotropic materials

This paper proposes a novel S-parameter retrieval method to extract the arbitrary permittivity and permeability tensors of general biaxial anisotropic materials. The proposed method uses three measurements of the reflection and transmission coefficients of a simple normal-incident circularly polarized plane wave. The circular polarization is employed to overcome the ambiguity attributed to the discontinuities in the extracted possible positive and negative values of the permittivity and permeability tensors for natural or synthesized anisotropic materials. The mathematical procedure of the proposed method directly relates the combined parameters deduced from the circularly polarized wave components to the tensor permittivity and permeability linear components while avoiding the need for heavy computations or optimization schemes. This simple procedure successfully overcomes the limitations to the usable frequency band and the material losses observed in previously published retrieval techniques for lossless and lossy anisotropic materials at low- and high-frequency regions. The retrieved tensor elements are validated by comparison to analytical data obtained from solving the original electromagnetic problem using the Berreman 4 × 4 matrix method after extending it to the case of circularly polarized fields.