Comparison of Metal-Backed Free-Space and Open-Ended Coaxial Probe Techniques for the Dielectric Characterization of Aeronautical Composites

Abstract

The trend in the last few decades is that current unmanned aerial vehicles are completely made of composite materials rather than metallic, such as carbon-fiber or fiberglass composites. From the electromagnetic point of view, this fact forces engineers and scientists to assess how these materials may affect their radar response or their electronics in terms of electromagnetic compatibility. In order to evaluate this, electromagnetic characterization of different composite materials has become a need. Several techniques exist to perform this characterization, all of them based on the utilization of different sensors for measuring different parameters. In this paper, an implementation of the metal-backed free-space technique, based on the employment of antenna probes, is utilized for the characterization of composite materials that belong to an actual drone. Their extracted properties are compared with those given by a commercial solution, an open-ended coaxial probe (OECP). The discrepancies found between both techniques along with a further evaluation of the methodologies, including measurements with a split-cavity resonator, conclude that the implemented free-space technique provides more reliable results for this kind of composites than the OECP technique.

A Synthetic Aperture Radar (SAR)-Based Technique for Microwave Imaging and Material Characterization

“…This contribution extends the SAR-based imaging techniques presented in [21][22][23] to provide a better recovery of geometry and constitutive parameters, making a more efficient use of the imaging information. More precisely, the proposed methodology takes advantage of the reflections at the interfaces between different media to obtain an estimate of the permittivity and the conductivity, avoiding the need of a reference target or a background medium.…”

“…The theoretical fundament is the different velocity of the electromagnetic waves when passing through different media, so that the reflectivity of the imaged targets is displaced backwards with respect to their expected position. In order to detect this shifting, a reference background is needed (the human body surface in the case of [21], a reference metallic plate in [22,23]).…”

Flexible UHF RFID Tag for Blood Tubes Monitoring

“…The main techniques to characterize dielectric materials are based on free space, transmission lines, coaxial probe, parallel plate, and resonators [27,28,29,30]. One of the most popular technique to measure the complex dielectric permittivity of solid and liquid materials is the coaxial probe method [31,32]. This electromagnetic characterization technique is non-destructive and allows to carry out fast broadband measurements of biological substances [33,34].…”

Dual Coaxial Probes in Transmission Inserted by Dielectric With Two Different Thicknesses to Extract the Material Complex Relative Permittivity: Discontinuity Impacts

“…During the method process development, it appears that the discontinuities' admittances and the transfer impedance can be removed. The transfer impedance gives crucial information on the insulator's state, as presented in the literature [11,[19][20][21]. The principle of concentrated elements, applied with two different thicknesses of identical material, is a new approach to characterize materials.…”