Characterization of Anisotropic Materials using Scattered Field Measurements

This research uses monostatic far-zone scattered field measurements to estimate the permittivity of biaxial materials at X-Band. Utilizing Radar Cross Section (RCS) measurement techniques, this effort examines the efficacy of whole-sample TEM illumination in the estimation of anisotropic permittivity, in contrast with traditional subsample illumination methods. The research examines the impact that dielectric supports have on measurement error and uncertainty in permittivity estimates. Following an incremental approach, the research first demonstrates successful estimation of permittivity for isotropic spheres followed by a Teflon isotropic cube. Finally, the method is applied to uniaxial and biaxial cubes whose anisotropic permittivity is validated through comparisons with published data. The method showed success for a material with high contrast between tensor axes but had increased uncertainty when the contrast between those axes was small. The research also indicated that the method displayed excessive uncertainty in loss tangent estimates due to mutual coupling between the dielectric support structure and the material under test. Finally, the method demonstrated that estimates of biaxial dielectric constants are possible in a free space far-field context without the use of costly measurement facilities or complex hardware