Analytical Model For The Contribution Of Small Scatterers to Open-Ended Coaxial Probe Measurements

TL;DR

This paper develops an analytical model to understand how small scatterers affect open-ended coaxial probe measurements in inhomogeneous media, aiding in better interpretation and property extraction.

Contribution

It introduces a novel analytical model for scatterer contribution to probe admittance, enabling accurate property extraction and sensing depth mapping.

Findings

Model verified with full-wave simulations

Allows extraction of scatterer properties from admittance measurements

Defines sensing depth as a function of scatterer properties

Abstract

The open-ended coaxial probe (OECP) technique is one of the most commonly used methods for the characterization of homogeneous media properties, especially in the biomedical sciences. However, when considering inhomogeneous media, the effect of the heterogeneity on the probe terminal admittance is unclear, making the measured admittance hard to interpret and relate to the medium properties. In this paper we present an analytical model for the contribution of an isotropic scatterer embedded in an otherwise homogeneous medium to the probe admittance. We utilize rigorous scattering theory and various approximations to obtain simplified, closed-form expressions. Using the obtained results we present a method to accurately extract the scatterer properties from a measurement of the admittance. In addition, we define the sensing depth, and show how it can be mapped as a function of the expected scatterer properties. Full-wave simulations are used to verify the analytical model, and the proposed method paves a path for further generalization to additional scenarios of open-coaxial probe sensing of an inhomogeneous medium.