Relative Permittivity Measurements With SIW Resonant Cavities at mm- Wave Frequencies

In this paper an effective though simple method to accurately characterize dielectric substrate materials at mm-wave frequencies is presented. The method is based on the use of a resonant cavity in SIW technology realized in a substrate made out of the material to characterize. Based on the measured resonant frequency, it is then possible to extract the electrical properties of the material exclusively from the geometry of the cavity. The SIW cavity is fed by two grounded coplanar waveguides to reduce the loading effect of the transmission lines and to avoid errors in the estimations of relative permittivity. The proposed cavity provides a solution for material characterization for emerging 5G-and-beyond applications operating at high frequencies. Measurements have been performed in the frequency range from 10 GHz to 30 GHz, but the design is scalable to lower or higher frequency ranges, if within the possibilities of the manufacturing process of the cavity.