A free-space time-domain method is proposed to retrieve dielectric constant (ϵr), conductivity (σe), 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 ϵr and σe. Free-space time-domain measurements have been implemented after transforming frequency-domain measurements into time-domain ones to extract ϵr, σe, and d of polypropylene, polyethylene, and polyoxymethylene samples.

A new de-embedding technique is proposed for relative complex permittivity εr determination of dielectric materials using gated free-space measurements. Its three main features are a) it does not require any formal calibration procedure (calibration-free), b) it is position-insensitive, and c) it extracts ripple-free εr due to gating process. The objective function derived to determine εr by the proposed method is validated by free-space measurements of three dielectric samples (polypropylene, polyethylene, and polyoxymethylene). Besides, the accuracy of our method is compared with the accuracy of other calibration-free and calibration-dependent methods in the literature.

A broadband, stable, and non-iterative free-space method is proposed for dielectric constant ε ^′ _r determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of non-disperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and Polyoxymethylene samples (9–11 GHz) are carried out to examine the accuracy of our method.

A time-domain free-space technique has been proposed to extract relative permittivity (εr) and effective conductivity (σe) of low-loss dielectric samples using their metal- and air-backed calibration-free reflected powers. Numerical computations and 3D electromagnetic simulations were performed to validate the method. A sensitivity analysis was carried out to examine its accuracy. Calibration-free time-domain free-space measurements over 1-12 GHz were conducted by VNA to extract εr and σ e of polyethylene and polypropylene low-loss samples.

Microwave techniques, as an indirect approach, can be applied for analyzing water content in honey by way of permittivity measurements. However, these techniques require proper calibration to accurately perform such indirect evaluation. Improper calibration standards used in this calibration process could naturally result in a reduction in the accuracy and thus the performance of dielectric characterization using microwaves. Self-calibrating microwave techniques can reduce the effects of imprecise standards and thus improve the performance of microwave measurements by bypassing the requirement of calibration standards. In this study, we develop a self-calibrating microwave measurement technique to determine the relative permittivity of honey samples and implement binary mixing models to predict adulteration levels of water-adulterated honey. From this implementation, it is observed that the parallel-capacitance mixing model could efficiently be applied to determine the concentration of water adulteration by examining the differences between absolute values of the real parts of the measured and predicted complex permittivities of adulterated honey.

A new de-embedding line-line method has been proposed for accurate complex relative permittivity (εr) determination of soil samples loaded into a EIA 1-5/8” coaxial transmission line measurement system. The method has three main features. First, it bypasses the requirement of calibration of this system by using only two identical coaxial lines with different lengths. Second, it does not need any numerical technique for εr determination. Third, it does not require knowledge of electromagnetic properties and thickness information of the bead used for supporting soil samples. The method is next validated by simulations performed using a full 3D electromagnetic simulation program (CST Microwave Studio) and by εr measurement of a polyethylene material. Finally, εr values of three air-dry and water-saturated soil samples having 90% or more sand content with different electrical conductivities and gathered from different areas of the city Gaziantep in Turkey, were measured.