ElectroMagnetic properties as a function of temperature – GEMT

The ANR/ASTRID Maturation project entitled GEMT, for ElectroMagnetic Properties as a function of Temperature, is based on the research results of the DGA/AMU (Aix Marseille University) co-funded thesis by Thibaut LETERTRE. This project aims to make the experimental concepts demonstrated in the thesis more reliable and to prepare them for industrialization in the near future. GEMT targets defense and civil applications.
The main objective of the thesis was exploring potential solutions in order to electromagnetically characterize different materials by developing one or several measurement cells and adequate temperature setting solutions. The spectral range was between 10 MHz and 18 GHz with a coaxial measurement cell, for temperatures ranging from ambient to 250°C. The joint explorations of these two domains have never existed before the thesis. At the end of the thesis, a demonstrator was set up and a validation measurement was performed. The results are reported in the thesis manuscript.
The challenge of this ASTRID Maturation 2020 GEMT project is to make the TRL level of these experimental techniques evolve from 4 to 7 in order to be able to propose industrial solutions for the electromagnetic characterization of materials depending on frequency AND temperature. There is currently no solution of that kind existing in the world.
GEMT is structured into three scientific parts and one non-scientific part. The first part is focused on the new coaxial connection system implemented during Mr. Letertre's thesis called “smart connectors”. The system allows to thermally isolate all the measurement systems in order to secure the connection elements and thus avoid degradation and problems related to thermal expansion phenomena. The phases of the measurement signals are extremely sensitive to these thermal expansion phenomena. The second part is focused on the evolution and reliability of the measuring cell and the calculation of the electromagnetic properties of material with an increased attention on the temperature regulation part, from 25° to 400°C. The third part concerns the set of measurements used to demonstrate the Defense and Civil applications envisaged in this project. The fourth part refers to the management of the project and the exploitation of the results.
Within the framework of the project, we have already identified applications in both civil and military fields. There are three civil applications. The first one is the biomedical field, in which it is now essential to be able to determine as precisely as possible permittivity and dielectric loss values of different biological tissues. The second application involves geology, especially volcanology. The third application relates to electronics industry and more specifically the study of materials used in the manufacture of printed, organic and/or soft support components. The defense application developed corresponds to that of the thesis. The thesis works have allowed to understand the electromagnetic behavior of materials depending on temperature in order to model the impact of heating generated by air friction on an aircraft during a high-speed flight. This theme is fundamental, especially for electromagnetic stealth level maintenance, which is obtained thanks to materials with highly specific properties. The electromagnetic characteristics modification of the materials, linked with temperature rising, could deteriorate the electromagnetic stealth level of the aircraft or modify the radiation properties of the antennas present on the aircraft. Being able to predict physical behaviour over the widest possible frequency bands then becomes necessary.