Biomedical electromagnetics: Exploration of new frequency bands in dosimetry

Initially, the research activities of the IETR in bioelectromagnetics were mainly focused on millimeter waves, anticipating the upcoming use of this band for emerging applications (high-data-rate short range communications and more recently, body-centric wireless communications, 5G). Most of the obtained results are innovative and pioneering at an international level, including the first millimeter-wave tissue-equivalent phantoms, a novel reflectivity-based surface phantom concept, a new multi-physics characterization technique for Debye-type materials, the first millimeter-wave textile antennas for smart clothing, a reverberation chamber above 10 GHz and multi-physics tools for EMC testing. Our ambition for 2017-2021 is to explore frequency bands for which few dosimetry data are available today (in terms of methodology, models, exposure assessment and reduction, etc.). The HF band used for civil and military communications as well as for upcoming wireless power transfer applications is, for example, poorly explored from the viewpoint of interactions with living organisms, in spite of the specificity of bioelectromagnetic interactions at these frequencies. In this context, the development of new dosimetric methodologies and models is of the utmost importance, given the experimental challenges faced at these frequencies (ongoing studies within the framework of ANSES Expo-WPT, SAD Région Bretagne WiBody, and as part of a CIFRE PhD in collaboration with Thales Communications & Security). Most of obtained results are innovative and pioneering at an international level. Attaining such results would help, on the one hand, to assess the real exposure in terms of tolerated thresholds at a normative level, and on the other hand to propose methodologies to precisely control, and, whenever possible, reduce the exposure levels inside the human body.

Biomedical electromagnetics: towards novel biomedical applications

Investigation of bioelectromagnetic interactions goes far beyond research on biological and health effects. Numerous research challenges - related to biomedical, healthcare, wellbeing and sport applications - in the context of developing or applying treatment, could be the source of potential innovations in the field. The ongoing studies are being conducted in two directions:

Electromagnetic compatibility: ultra-wideband reverberation and new applications

In recent years, research activities related to electromagnetic reverberation chambers have significantly grown at international level, and the IETR is recognized as a world leader in this field. The IETR has contributed to in-depth statistical analysis and the development of engineering methods of reverberation chambers for extremely various applications, such as the production of specific propagation channel properties, the measurement of antenna efficiency and of the antenna radiation pattern. As regards EMC applications, optimized measurement protocols have been developed.

The first objective for the 2017-2021 period is to extend the frequency bandwidth of reverberation chambers. The benefit could be considerable as part of radiated immunity testing for equipment at frequencies as low as 80 MHz required by some standards. It may enable characterization of radiating structures in the VHF band. Such an objective may be reached using the universal properties of chaotic cavities. This challenge is addressed in the framework of a partnership with the ESYCOM and LPMC (now INPHINI) research laboratories. Above 10 GHz, there are very few ‘accredited’ studies and standard tests set up to perform EMC measurements. As a consequence, knowledge of electronic components susceptibility at millimeter waves should be developed. It now seems relevant to explore the millimeter-wave band with reverberation chambers, dealing with future communication devices and standards as well as with military applications (high-intensity radiated fields up to 40 GHz and probably beyond in the near future).

Electromagnetic compatibility: statistical approaches for EMC modeling

EMC modeling is useful at the early stages of equipment or system design, when most parameters remain to be determined. Added value for EMC modeling is even optimum when the equipment orf system under investigation does not yet exist. . An ideal simulation tool would provide a way to perform a virtual approval of numerous tests to be passed. There are two hurdles to overcome to design such a tool. These are the freedom of choice of parameters and their uncertainty due to their variability from one piece of equipment or system to another (e.g. cabling networks). It makes the modeling process very tricky. Indeed, it limits the application of fully deterministic modeling approaches and leads rather to the consideration of statistical approaches, such as those used in many fields of engineering sciences (e.g. structural mechanics). As far as EMC is concerned, recently this new trend has emerged in Europe, through research performed by the University of Nottingham, the Politecnico di Torino and Milano, and in France at the Institut Pascal as well as within Orange-labs (dosimetry modeling). The IETR resolutely committed to these approaches in 2012, aiming to demonstrate the specific advantages of statistical mathematic tools for predicting interference levels. The goal is to examine the notion of EMC system/equipment failure from a probabilistic viewpoint. We rely on different sets of methods that aim to not systematically retrieve the entire probability density function of the output of interest, but rather look at the extreme values of a distribution. Without predicting the methods that will exactly meet the needs for 2017-2021, those based on risk analysis and estimation of the failure domain are a possible avenue, which is currently evaluated at the IETR and will be further investigated for different EMC scenarios. Other approaches based on simple surrogate models could also be very relevant for some techniques currently used in EMC modeling. Beyond EMC applications, these techniques will be also applied to antenna applications in collaboration with the CUTE and BEAMS teams of the IETR.