Openings

Research Fields: millimeter waves, microwave modeling and systems, electromagnetic dosimetry, antennas and probes, tissue-equivalent models

Research Laboratory: IETR / CNRS, Rennes, France.

Duration: 36 months, expected starting date is Oct. 2022.

Research 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/6G cellular mobile networks. The upper limit of the spectrum used for 5G has shifted towards the millimeter-wave (mmWave) band. In coming years, mmWave mobile broadband systems will be integrated in 5G/6G 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 mmWaves. Proposing solutions for accurate dosimetry in the near-field 60 GHz scenarios is of uppermost importance to anticipate the deployment of 5G/6G networks.

Project overview

This PhD project will deal with the design, optimization and experimental validation of a mmWave 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.

Existing experimental mmWave 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 [1]. To overcome these limitations, we propose a fundamentally new approach. It is based on a solid skin-equivalent model introduced by our research group in the 60-GHz band [2]. 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 mmWave dosimetry system for measurements of the absorbed power density (APD) accounting for perturbation of the field radiated by a mmWave 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 accurate retrieval of the APD distribution. Various technical solutions will be explored. For example, an array of sensors can be integrated into the phantom and coupled to transmission lines printed on a low loss mmWave 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. The experimental part of the PhD project will rely on the advanced numerical methods and state-of-the-art equipment and measurement facilities available at the IETR (anechoic chamber up to 500 GHz, near-field characterization, high-resolution 3D printing, multi-physics dosimetry, etc.).

 

[1]    M. Ziane, R. Sauleau, M. Zhadobov. Antenna / body coupling in the near-field at 60 GHz: impact on the absorbed power density. Applied Sciences, 10(12), 7392(16pp), Oct. 2020

[2]    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.

[3]    M. Ziane, M. Zhadobov, R. Sauleau. High-resolution power density measurement technique in the near-field accounting for antenna/body coupling at millimeter-waves. IEEE Antennas and Wireless Propagation Letters, 20(11), pp. 2151-2155, Nov. 2021.

[4]    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.

[5]    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.

 

Research environment

The PhD student will join Electromagnetic Waves in Complex Media Team (eWAVES, https://www.ietr.fr/ewaves) 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.

Candidate

Education: MS or equivalent.

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

How to apply

To apply please send your CV, transcripts, motivation letter, and reference letters (optional) to:

• Maxim ZHADOBOV, CNRS (maxim.zhadobov@univ-rennes1.fr)
• Ronan SAULEAU, University of Rennes 1 (ronan.sauleau@univ-rennes1.fr)

Funding:              Full-time scholarship provided by the University of Rennes 1.

Research Fields: microwaves, numerical modeling, electromagnetic dosimetry, exposure assessment, microscale characterization, electromagnetic cell and tissue models.

Research Laboratory: IETR / CNRS, Rennes, France.

Duration: 36 months, expected starting date is Oct. 2022.

Research project

Context

Wireless technologies operating in the upper part of the microwave spectrum are increasingly used for various applications. In particular, they have been used for high data rate communications [> 5 Gb/s], and 26-GHz / 60-GHz technologies are expected to be integrated in the near future in the next generation mobile systems (5G/ 6G, IoT, smart homes, human-centered communications). Besides, microwaves have a strong potential for numerous biomedical applications, including remote monitoring of wounds, non-invasive detection of glucose level, microwave imaging, thermal ablation, to list just a few. From the exposure assessment and control viewpoint, characterization of frequency-dependent electromagnetic power deposition at the sub-cellular level constitutes a new research challenge in the field of fundamental biomedical electromagnetics, with a potentially strong impact on the environmental safety and future biomedical applications.

Project overview

The main purpose of this PhD research project is to analyze micro-scale electromagnetic field and power distributions at sub-cellular level in order to gain an insight into local micro- and submm-scale phenomena occurring during exposure of the human body. Stochastic approach will be applied to account for the natural variability of physical parameters of biological cells.

The main research axes of this PhD project are threefold:

1. Micro-scale numerical electromagnetic and transient thermal analysis will be performed on cellular models of progressively increasing complexity. To this end, we will consider simplified geometric models of a single cell with sub-cellular organelles and will increase the complexity to realistic stochastic single- and multi-cell models. Electromagnetic (complex permittivity and conductivity) and thermal (heat capacity and conduction) properties will be assigned to these models accounting for the stochastic variability. This will involve characterization of effective electromagnetic and thermal properties of cells and cellular sub-structures (membrane components, cytoplasm, cellular organelles, etc.).
2. The electromagnetic field and absorbed power distributions will be computed using designed cellular models and appropriate numerical solvers (e.g. COMSOL, CST, SIM4LIFE). Stochastic multi-parametric analysis will be performed to assess the variability of the electromagnetic field and power distributions as a function of the geometry, complex permittivity, conductivity and micro-cellular environment. The data on micro-scale electromagnetic field and power deposition will be used as an input to thermal co-simulations.
3. Finally, numerical results will be validated experimentally on cells using ad hoc metrological facilities and instrumentation of bioelectromagnetic platform of IETR (i.e. high-resolution dosimetry system based on infrared microscopy), with assistance from experts in cellular and molecular biology.

Research environment

The candidate will join the IETR laboratory of CNRS. 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 millimeter-wave tissue-equivalent models, novel reflectivity based surface phantom concept, new broadband multi-physics characterization technique  for Debye-type materials, innovative millimeter-wave textile antennas for smart clothes, ultra-robust miniature implantable UHF antennas, and the first millimeter-wave reverberation chamber.

Candidate

We seek for highly engaged and motivated candidates with a MS or equivalent degree in electromagnetics, electrical engineering or electronics. The required skills and qualifications are:

• Strong background in electromagnetics, analytical/numerical modeling, and microwave engineering. Knowledge in biomedical engineering / biophysics is welcome but not mandatory.
• Knowledge of numerical modeling and experience with commercial or open-source numerical solvers (e.g. COMSOL, CST, SIM4LIFE), programming skills (e.g. MATLAB).
• Fluency in English: the candidate should be conversant and articulate in English and must have strong writing skills. The successful candidate will be expected to present results of the work in high-profile journals and conferences. Knowledge of French is not required but would be appreciated.

Benefits

The qualified candidate will be part of a dynamic multidisciplinary team in an international, highly collaborative, and stimulating environment. He/she will have access to state-of-the-art laboratories, workshops, high-performance computing facilities, continuous training and receive a competitive salary.

In addition:

• Approximately 7 weeks of annual leave per year + possibility of exceptional leave (moving home, etc.).
• Generous statutory benefits: French national health coverage, unemployment allowances, retirement/pension funds, etc.
• Possibility of subsidized meals, student housing, and partial reimbursement of public transport costs.
• Location in one of the most attractive cities in France for professional and nonprofessional activities [entertainment, culture, sport, gastronomy, etc; 1:25 to Paris by train and 0:47 to a seaside].

 

How to apply

To apply please send your applications to: Maxim Zhadobov (maxim.zhadobov@univ-rennes1.fr).

The application should consist of (in PDF format):

• CV (incl. the contact details of two professional references [mail, address, position])
• Motivation letter (incl. explanation relevance to this PhD research project and why the candidate believes he/she is suitable for the position)
• Copy of PhD diploma
• Reference letters (optional)

Context

This post-doctoral research project focuses on near-field millimeter-wave human exposure assessment applied to 5G networks. Interaction of 5G terminals with the human body not only affects the wireless performance of the system but requires careful consideration of user exposure to electromagnetic fields. This includes millimeter-wave exposure by wearable and mobile devices resulting in local absorption under near-field exposure conditions [1]. The existing dosimetry approaches—originally developed for 3G/4G networks operating in sub-6 GHz range—are not directly scalable to millimeter-waves. This motivates our research towards new solutions for accurate experimental dosimetry, in particular in 24 GHz and 60 GHz bands [2]. This project builds on the unique scientific and technical expertise of the IETR laboratory of CNRS in the fields of bioelectromagnetics and complex radiating systems.

Project overview

Existing experimental millimeter-wave dosimetry techniques are limited to electromagnetic field measurements using free-space probes in vicinity of wireless devices. These solutions do not account for the effects of the close vicinity to human body and therefore introduce significant error into estimated exposure levels. To overcome these limitations, we proposed an alternative approach based on a solid skin-equivalent model in the 60 GHz band [3]. This solid tissue-equivalent model will be used as a starting point to design a millimeter-wave dosimetry system prototype for measurements of the power density accounting for perturbation of the electromagnetic field radiated by a wireless device in presence of the human body. The project will mainly focus on development of an instrumented system that will integrate two key functionalities: (1) it will accurately reproduce the reflection coefficient from the human skin; (2) it will enable retrieval of the power density based on the field measurements inside the tissue-equivalent model.

‍

1) 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.

2) 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. Advances in Body-Centric Wireless Communication: Applications and State-of-the-art, IET, pp. 97 – 142, Jun. 2016.

3) 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, May 2014.

Research environment

The candidate will join the IETR laboratory of CNRS.  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 millimeter-wave tissue-equivalent models, novel reflectivity based surface  phantom concept, new broadband multi-physics characterization technique  for Debye-type materials, innovative millimeter-wave textile antennas for smart  clothes, ultra-robust miniature implantable UHF antennas, and the first millimeter-wave reverberation chamber.

Candidate

We seek for highly engaged and motivated candidates with a PhD degree in electro­magnetics, electrical engineering or electronics. The required skills and qualifications are:

• Strong background in electromagnetics, antenna design and microwave  engineering. Knowledge in electronics and / or bioelectromagnetics is welcome  but not mandatory.
• Knowledge of numerical modeling and experience with commercial or open-source numerical solvers (e.g. CST, Ansys, SIM4LIFE); programming skills (e.g. MATLAB).
• Fluency in English: the candidate should be conversant and articulate in English and must have strong writing skills. Knowledge of French is not required but would be appreciated.

How to apply

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