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.