Openings

PhD Position

5G at millimeter waves: Near-field exposure assessment in emerging scenarios

  • Research Fields

Microwave modeling, numerical dosimetry, millimeter-wave antennas, tissue modeling, bioelectromagnetics

  •  Research environment

The PhD student will join Electromagnetic Waves in Complex Media Team (WAVES, www.ietr.fr/WAVES.html) of the IETR. Our research activities in biomedical electromagnetics cover a wide spectrum of fundamental and applied research spreading from multi-physics and multi-scale modeling to advanced technologies for body-centric wireless communications. The team was at the origin of pioneering innovations in biomedical electromagnetics, including the first mm-wave tissue-equivalent phantoms, novel reflectivity based surface phantom concept, new broadband multi-physics characterization technique for Debye-type materials, innovative mm-wave textile antennas for smart clothing, ultra-robust miniature implantable UHF antennas, first mm-wave reverberation chamber.

  • Scientific project

Context

Continuous development of mobile terminals, such as smart phones, tablets, body-worn devices, has increased the wireless data traffic, which will keep growing due to video streaming applications and cloud computing. The increasing need in high-performance mobile communications leads to a fast development of next-generation heterogeneous 5G cellular mobile networks. The upper limit of the spectrum used for 5G has shifted towards the millimeter-wave (MMW) band. In coming years, MMW mobile broadband systems will be integrated in 5G networks, in particular for the user access and backhaul / fronthaul applications. In particular, the 60–GHz transceivers (i.e. 57–66 GHz in Europe) are expected to be integrated in the user terminals; this allows for a larger channel bandwidth, higher data rates (beyond several Gb/s), high level of security for short-range communications, and low interference with adjacent cells.

The new usages and services will involve interaction of radiating devices with the human body, both in terms of body impact on wireless device performance as well as in terms of user exposure. This includes near-field exposure by wearable and mobile devices operating in vicinity of the human body. Radiated powers of the user terminals may result in locally very high exposure levels under near-field exposure conditions due to localized absorption at MMW. Proposing solutions for accurate dosimetry in the near-field 60 GHz scenarios is of uppermost importance to anticipate the forthcoming deployment of 5G networks.

Objectives

This PhD project will address open challenges related to numerical and experimental near-field dosimetry around 60 GHz, both for adults and children, contributing to environmental safety of emerging 5G systems.

Work description

The PhD research project will mainly deal with:

1.        Modelling the electromagnetic field and power dissipation induced inside the human body by near-field MMW exposure. A numerical dosimetry study will be performed using tissue models of increasing complexity and generic 60-GHz antenna modules in representative 5G scenarios. Parametric studies will be performed to assess the exposure levels depending on the positioning of the antennas modules in respect to the human body.

2.        Assessment of exposure taking into account morphological differences and age-dependent electromagnetic properties of biological tissues. The age-dependent body models will be developed for the first time in the MMW range to assess the exposure in terms of the specific absorption rate (SAR) and incident power density (IPD). The results will clarify whether the exposure levels in children can exceed those in adults, in particular due to the changing with age electromagnetic properties.

3.        Analysis of resulting heating induced by local exposure to MMW. Due to the increasing power transmission at skin / air interface at MMW compared to lower microwave frequencies and local power absorption in the near-surface body regions, significant local heating may appear even for relatively low IPD. We will numerically analyze induced local temperature rise depending on the size of exposed area, power density, exposure duration, etc.

References

A. Guraliuc, M. Zhadobov, R. Sauleau, L. Marnat, L. Dussopt. Near-field user exposure in forthcoming 5G scenarios in the 60-GHz band. IEEE Transactions on Antennas and Propagation, 65(12), pp. 6606-6615, Dec. 2017.

C. Leduc and M. Zhadobov. Impact of antenna topology and feeding technique on coupling with human body: Application to 60-GHz antenna arrays. IEEE Transactions on Antennas and Propagation, 65(12), pp. 6779-6787, Dec. 2017.

M. Zhadobov, C. Leduc, A. Guraliuc, N. Chahat, R. Sauleau. Antenna / human body interactions in the 60 GHz band: state of knowledge and recent advances. State-of-the-Art in Body-Centric Wireless Communications and Associated Applications, IET, pp. 97 – 142, Jun. 2016.

  • Candidate

Education: MS or equivalent.

Background: excellent skills in electromagnetics, numerical modeling, microwave theory and measurements. Knowledge in biophysics / thermal modeling is welcome but not mandatory.

  • Timeline

Duration: 36 months

Starting date: October 01, 2019

  • How to apply

To apply please send your CV, transcripts, motivation letter, and reference letters (optional) to maxim.zhadobov@univ-rennes1.fr

pdf version


PhD Position

5G at millimeter waves: Novel approach for accurate and realistic experimental near-field dosimetry in the 60-GHz band

  • Research Fields

Millimeter waves, microwave modeling and systems, electromagnetic dosimetry, antennas and probes, tissue-equivalent models

  •  Research environment

The PhD student will join Electromagnetic Waves in Complex Media Team (WAVES, www.ietr.fr/WAVES.html) of the IETR. Our research activities in biomedical electromagnetics cover a wide spectrum of fundamental and applied research spreading from multi-physics and multi-scale modeling to advanced technologies for body-centric wireless communications. The team was at the origin of pioneering innovations in biomedical electromagnetics, including the first mm-wave tissue-equivalent phantoms, novel reflectivity based surface phantom concept, new broadband multi-physics characterization technique for Debye-type materials, innovative mm-wave textile antennas for smart clothing, ultra-robust miniature implantable UHF antennas, first mm-wave reverberation chamber.

  • Scientific project

Context

Continuous development of mobile terminals, such as smart phones, tablets, body-worn devices, has increased the wireless data traffic, which will keep growing due to video streaming applications and cloud computing. The increasing need in high-performance mobile communications leads to a fast development of next-generation heterogeneous 5G cellular mobile networks. The upper limit of the spectrum used for 5G has shifted towards the millimeter-wave (MMW) band. In coming years, MMW mobile broadband systems will be integrated in 5G networks, in particular for the user access and backhaul / fronthaul links. In particular, transceivers operating in the 60–GHz band are expected to be integrated in user terminals; this allows for a larger channel bandwidth, higher data rates (beyond several Gb/s), high level of security for short-range communications, and low interference with adjacent cells.

The new usages and services will involve interaction of radiating devices with the human body, both in terms of body impact on wireless device performance as well as in terms of user exposure to electromagnetic fields. This includes near-field exposure by wearable and mobile devices operating in vicinity of the human body. Radiated powers of the user terminals may result in locally very high exposure levels under near-field exposure conditions due to localized absorption at MMW. Proposing solutions for accurate dosimetry in the near-field 60 GHz scenarios is of uppermost importance to anticipate the forthcoming deployment of 5G networks.

Objectives

This PhD project will deal with the design, optimization and experimental characterization of a MMW dosimetry system and associated methodology for near-field exposure assessment accounting for a potential increase of exposure levels due to presence of the human body.

Work description

Existing experimental MMW dosimetry techniques are limited to electromagnetic field measurements using free-space probes in vicinity of wireless devices. These solutions do not account for a potential increase of exposure levels due to the presence of human body and may result in an underestimation of exposure levels. To overcome these limitations, we propose a fundamentally new approach. It is based on a solid skin-equivalent model recently introduced by our research team in the 60-GHz band. This model consists of a lossy 1.3 mm-thick dielectric layer (PDMS saturated with the carbon powder) and a metallic ground plane. The properties of the lossy dielectric (thickness, composition) are optimized to reproduce the reflection coefficient from human skin. This solid tissue-equivalent model will be used as a starting point to design a MMW dosimetry system for measurements of incident power density (IPD) accounting for perturbation of the field radiated by a MMW wireless device due to presence of the human body. The proposed system will integrate two key functionalities: (1) it will accurately reproduce the reflection coefficient of human skin and (2) it will enable retrieval of the IPD distribution based on the field measurements inside the lossy dielectric. To this end, an array of sensors will be integrated into the phantom and coupled to transmission lines printed on a low loss MMW dielectric substrate through coupling slots etched in the ground plane. The main parameters of the system architecture will be optimized (lattice type and size of the antenna array) to maximize the field measurement accuracy and spatial resolution, while minimizing the complexity of the system.

References

A. R. Guraliuc, M. Zhadobov, O. De Sagazan, R. Sauleau. Solid phantom for body-centric propagation measurements at 60 GHz. IEEE Transactions on Microwave Theory and Techniques, 62(6), pp. 1373–1380, Mai 2014.

A. Guraliuc, M. Zhadobov, R. Sauleau, L. Marnat, L. Dussopt. Near-field user exposure in forthcoming 5G scenarios in the 60-GHz band. IEEE Transactions on Antennas and Propagation, 65(12), pp. 6606–6615, Dec. 2017.

M. Zhadobov, C. Leduc, A. Guraliuc, N. Chahat, R. Sauleau. Antenna / human body interactions in the 60 GHz band: state of knowledge and recent advances. State-of-the-Art in Body-Centric Wireless Communications and Associated Applications, IET, pp. 97–142, Jun. 2016.

  • Candidate

Education: MS or equivalent.

Background: excellent skills in electromagnetics, microwave design / measurements, numerical modeling. Knowledge in electronics is welcome but not mandatory.

  • Timeline

Duration: 36 months

Starting date: October 01, 2019

  • How to apply

To apply please send your CV, transcripts, motivation letter, and reference letters (optional) to maxim.zhadobov@univ-rennes1.fr

pdf version


MS project

Computational electromagnetics applied to hybrid modeling of personalized brain stimulation in the kHz range

Context

Brain stimulation is a technique consisting in inducing changes in brain activity, mainly using electric or magnetic fields delivered invasively (intracranial) or non-invasively (scalp electrodes). The main applications of brain stimulation are diagnostic and therapeutic. In the case of epilepsy, a disease with a prevalence of approx. 60 millions of patients worldwide, a third of patients are drug-refractory (> 150 000 in France), and are therefore left of therapeutic options. For those patients, brain stimulation could represent an alternative. However, the brain stimulation protocols that have been investigated so far are mostly empirical, with little guidance from neurophysiological and biophysical consideration, and lack of mechanistic understanding, which is a major roadblock to provide novel therapeutic solutions to epileptic drug-refractory patients. Here, we propose a hybrid approach combining an accurate control of the electromagnetic fields associated with brain stimulation and realistic dynamics of the neuronal networks close to the electrode.

Objective

To analyse numerically the electromagnetic field distribution in brain thus contributing to development of a new tool for realistic modeling of neuronal activity during brain stimulation in the kHz range.

Work program

The research project proposes a hybrid approach consisting in (1) detailed electromagnetic dosimetry using numerical anatomical models of brain, coupled with (2) biologically grounded computational models of neurons generating epileptiform activity on the other hand. This hybrid approach will offer individualized stimulation parameters optimizing the electric field and current induced in brain tissue, in terms of spatial extent, magnitude and dynamics. Electromagnetic field inside brain induced by electrodes used for brain stimulation will be modeled using numerical solvers (CST and / or SEMCAD & SIM4LIFE). To this end, numerical electromagnetic models of the human body of increasing complexity will be employed to accurately simulate the electric field distribution in brain.

Candidate

We are looking for a candidate with a background in electromagnetics and numerical modeling at the Master level or last year of Engineering School. Experience in biomedical engineering is welcome but not mandatory. The intern will join a multidisciplinary team consisting of research scientists in electromagnetics, signal processing, and electrophysiology. The student will be hosted by IETR www.ietr.fr and will work in collaboration with LTSI www.ltsi.univ-rennes1.fr.

Contact

To apply please send your CV, motivation letter, and transcripts to

Maxim Zhabodov (CNRS Researcher, IETR)   maxim.zhadobov@univ-rennes1.fr

Practical information: application deadline Feb. 15, 2019; starting date March 1, 2019; around 570 €/month.