Complex Permittivity and Thickness Evaluation of Low-Loss Dielectrics From Uncalibrated Free-Space Time-Domain Measurements

A free-space time-domain method is proposed to retrieve dielectric constant ( $\varepsilon _{r}$ ), conductivity ( $\sigma _{e}$ ), and thickness ( $d$ ) of metal-backed low-loss dielectric samples using calibration-independent reflected power peak measurements. Its algorithm is validated by numerical calculations and simulations (CST Microwave Studio) using a sine-modulated Gaussian window. A sensitivity analysis is followed to examine its performance considering the dependencies of reflected power peaks with respect to $\varepsilon _{r}$ and $\sigma _{e}$ . Free-space time-domain measurements have been implemented after transforming frequency-domain measurements into time-domain ones to extract $\varepsilon _{r}$ , $\sigma _{e}$ , and $d$ of polypropylene, polyethylene, and polyoxymethylene samples.