Complex Permittivity Characterization of Low-Loss SlabsUsing Time-Gating Technique

This letter presents an innovative method for assessing the complex dielectric constants of low-loss dielectric slabs at sub-terahertz (THz) frequencies. Differing from conventional free-space techniques, the proposed approach removes the need for precise thickness knowledge of the material under test (MUT) and reference plane calibration. Even when the MUT thickness varies in a single sample, the proposed method effectively reduces the relevant estimate uncertainty. When applying it to estimate the permittivity of thick plexiglass and nylon plates across the 140–210-GHz frequency range, it demonstrates good agreement with published articles and lower uncertainty of the estimates. The proposed method is well-suited for permittivity characterizations at THz frequencies, particularly in scenarios where precise rulers are lacking or MUT thickness varies in a single sample.