An Analytical Framework for Modeling Inhomogeneities in Open-Ended Coaxial Probe Measurements

Open-ended coaxial probes (OECP) are commonly used for dielectric characterization, across the RF/Microwave frequency range. A significant challenge in using this measurement technique is to measure properties of inhomogeneous materials, due to the complexity of modeling the fields in the inhomogeneous sample. In this letter we present a theoretical model and an experimental verification for the extraction of the physical parameters of a small scatterer from open-ended coaxial probe reflection measurements. Using an analytical framework, we show that the depth and radius of a conductive scatterer can be extracted from reflection data obtained using two different probes. A 3D printed inhomogeneous sample was produced by embedding a conductive scatterer within a homogeneous dielectric sample. With average relative errors of 13%−20%, the results show that two scatterer parameters (radius and depth) can be accurately estimated relying solely on the approximate, dipolar, analytical model.