Multifrequency Contrast Source Inversion-Based Permittivity Estimation for Terahertz Multilayer Analysis

In this study, the method of estimating permittivity using inverse scattering is presented for multilayered analysis in the terahertz (THz) frequency band. While many studies have been conducted to determine the relative permittivity estimation of multilayer media, most of the studies are based on the time-of-flight (TOF) analysis, which requires the careful consideration of multiple reflection factors and a sufficiently short pulse, i.e., a wider frequency bandwidth, to discriminate the number of TOF from each layer. Therefore, the contrast source inversion-based permittivity estimator exploiting multiple frequency cost function analysis has been introduced. The efficiency of our proposed approach is shown using THz time-domain spectroscopy measurements on two thin layer objects.