Feasible Extraction Method for Permittivity Determination of Reflection-Asymmetric Structures

A feasible, yet accurate, extraction method is proposed for permittivity determination of a low-loss material positioned on a substrate material using reference-plane-invariant (RPI) transmission/reflection measurements. The method, in addition to its RPI property, does not necessitate the thickness information of the sample and substrate material. Its working principle is based on isolation of first reflected peaks of forward and backward reflection scattering parameters through a proper time-gating procedure. Permittivity measurements have been performed for acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PET-G), and the polylactic acid sample for validation of our method. The effects of number of frequency points and the value of bandwidth (BW) on permittivity measurements are examined.