A Calibration-Free Method for the Dielectric Constant Calculation of Low-Loss Materials

This article presents a new method for the calculation of the dielectric constant of low-loss materials having a thickness of more than half a wavelength in the sample. The proposed method relies solely on the frequency values at which the reflection coefficient $S_{11}$ resonance occurs and does not require precalibration or shifting of the reference measurement plane from the input port to the material under test (MUT) air interface. The method is analyzed and tested for a large set of dielectric materials, where the accurate estimation of their electric permittivity is obtained. It is valid for scenarios where the MUT is inside a waveguide transmission line and can be extended to materials inserted in a transverse-electromagnetic (TEM) transmission line, such as in a coaxial cable. This method can be integrated into different sensors used for permittivity measurements of low-loss dielectrics and to provide the transition between the measured wave reflection coefficient and sample permittivity.