Numerical Study of the Dielectric Properties of Lung Tissue Measured with Two different Open-Ended Coaxial Probes

The open-ended coaxial probe technique is a widely used technique for microwave characterization of different materials, especially biological tissues. The measurements with this technique can be performed with different types of probes which enable measurements in different frequency ranges. However, the size of the sensing volume of the probe changes with its diameter, and this can become a drawback of the technique when measuring heterogenous media where different inclusions are present. Therefore, it is necessary to characterize the probes themselves, to understand how the presence of inclusions influences the bulk properties perceived by the probe. To this end, in this work two probes, with different diameters, were numerically modelled and the influence of the proximity of inclusions to the probe's aperture was studied. Finally, an explicit expression for bulk properties depending on the distance and properties of the inclusion is obtained.