Postdoc position on "G/T factor of merit modeling of programmable metasurface-based electronic beamforming antennas "

ESPCI Paris – PSL (École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris) is a generalist engineering school that has been training, since 1882, disruptive, adaptable and creative engineers, with a solid theoretical and experimental background, aware of the challenges facing society. 

It is part of an internationally recognized research center in physics, chemistry and biology (500 publications per year). It is known for its ability to transform knowledge from fundamental research into disruptive innovations (2 patents per month, 3 start-ups per year). 

Distinguished by 6 Nobel Prizes, it welcomes 400 engineering students, 530 researchers (including 250 doctoral students and 100 post-doctoral students) in 10 joint research units and about 100 research and teaching support staff. 

Since its creation, ESPCI has continued to mobilize its strengths and skills in the service of major societal issues and to defend the importance of science in the service of society. The environment, solidarity, health, access to and openness to knowledge are issues that ESPCI is committed to taking into account in its daily life while contributing to advancing them. ESPCI defends equal opportunities and promotes social diversity. It encourages and values the commitment, particularly in associations, of its students. 

Our institution is part of the University of Paris Sciences & Lettres. Number 1 in the world ranking of young universities published by the Times Higher Education, PSL is also in the top 50 of the world's best universities (Shanghai, Times Higher Education, QS, CWUR). 

ESPCI is engaged in a vast renovation project of its Paris campus which will make it one of the most modern scientific sites in Paris. 

The post-doc will take place at the Langevin Institute, which is a joint ESPCI-Paris and CNRS research unit that was created in 2009 by Mr. Fink in order to bring together researchers from various backgrounds on the same site, driven by the same passion: the study of all possible types of waves. The spectrum of the waves concerned is very broad: mechanical waves (acoustic, elastic and seismic waves, waves), electromagnetic waves (radio frequencies, microwaves, Terahertz) and optical waves (infrared and visible). The Institute's researchers aim to understand the propagation mechanisms of these different types of waves in the most complex environments and to take advantage of this better understanding to design original instruments for the manipulation of these waves and the imaging of these environments. 

The fields of application of this research are very varied, ranging from medicine and biology to geophysics, telecommunications and non-destructive testing of materials. 

The Institute's research activities are structured around four major themes that are continuously nourished. The post-doc will integrate the theme, Waves, complexity and information.  

He will benefit from the entire laboratory environment and the theme to carry out his research. The post-doc is part of the COMSO-Ku project whose scientific director for the Langevin Institute is Julien de Rosny (Research Director & Deputy Director). It will also be able to benefit from the experience of Abdelwaheb Ourir, a CNRS research engineer, who is also fully involved in this project.  

This post-doc is part of the COMSO-Ku project which aims to develop electronic beamforming antennas (ESA) based on programmable metasurfaces (RIS).

Compact, lightweight, non-mechanically servo-free electronic beamforming antennas are increasingly used for SATCOM applications, especially in the context of mega-constellations of satellites. However, these antennas are all based on the same concept of phased array antenna, more commonly known as "phased array", which consists of adjusting the phase of a large number of sources in order to be able to point in one direction. This technology can be passive, in the sense that a common RF source is used with a phase shifter array, or active, in the sense that each small transmitter generates a signal and has its own RF source. Current so-called passive technologies are quite simple to manufacture, but are not very efficient.  

Greenerwave's technology, initially developed at the Langevin Institute, is based on a radically different approach. It uses reconfigurable leakage cavity antennas to achieve beamforming  inspired by reconfigurable surfaces[1,2]. Here the reconfigurable surface is included in a reverberant cavity with an access port. To obtain the desired radiation pattern, i.e. to point one or more beams in the desired directions, the cavity is adjusted in real time thanks to a reconfigurable intelligent surface (metasurface) [3]. The metasurface controls the reflections of waves in the cavity via optimized algorithms that allow software control of the antenna's behavior (one beam, two beams, beam direction, polarization, etc.). This technology also supports multi-bands and allows several beams to be emitted simultaneously at different frequencies and with different polarizations. 

For satellite applications, it is essential to simultaneously model the antenna gain provided by the antenna as well as its effective temperature. To this end, the two-year post-doc will consist of various major steps. The first will be to model gain, as well as radiative and non-radiative losses. One approach to model RIS elements is to consider them as charged electromagnetic dipoles of variable impedance, as we have recently studied [4]. However, this modeling is limited to radiating elements corresponding to dipoles. This is why we wish to generalize it from an approach in terms of scattering matrix on the spherical harmonics of each element, as we have done recently [5]. This approach makes it possible to explicitly distinguish the antenna factor from the structure factor, a key parameter, especially in the case of elementary cells made up of patches. 

This modeling will make it possible to take into account the elements in a detailed way by distinguishing between radiation losses and Joule losses, which play a major role in the temperature of the antenna and the gain associated with the reconfigurable surface. This modeling will be validated using numerical simulations carried out with CST Studio. In a second step, the link with the generation of thermal noise will be established. Finally, this approach will make it possible to propose solutions to increase the G/T ratio. A study will also be carried out on the effect of heating of the switching components on the equivalent temperature. 

In collaboration with another post-doctoral fellow in charge of the experimental realization, this model will be validated from measurements made in a calibrated anechoic chamber and in a reverberation chamber. 

References

[1] Marco Di Renzo, Alessio Zappone, Merouane Debbah, Mohamed-Slim Alouini, Chau Yuen, Julien De Rosny, Sergei Tretyakov, Smart radio environments empowered by reconfigurable intelligent surfaces: How it works, state of research, and the road ahead, EEE journal on selected areas in communications, vol 38, p. 2450-2525, 2020 

[2] R Fara, P Ratajczak, DT Phan-Huy, A Ourir, M Di Renzo, J De Rosny, ‘A prototype of reconfigurable intelligent surface with continuous control of the reflection phase’ IEEE Wireless Communications 29 (1), 70-77, 2022. 

[3] J-B. Gros, P. del Hougne, and G. Lerosey ‘Tuning a regular cavity to wave chaos with metasurface-reconfigurable walls’, Phys. Rev. A 101, 061801(R), 2020. 

[4] An Electromagnetic-Compliant Scattering Model for Reconfigurable Intelligent Surfaces, Hussein Ezzeddine, A. Ourir, J. de Rosny, Published in European Conference on… 17 March 2024, Engineering, Physics 

[5] Julien de Rosny and François Sarrazin, Derivation of Antenna $Q$-factor based on Antenna Scattering-Matrix Theory, ArXiv, https://arxiv.org/abs/2403.09894v1, 2024 

• Maxwell's theory applied to microwaves 
• Modeling MIMO Antenna Arrays 
• Multiport Theory of Electrokinetics 
• Intelligent Reconfigurable Surface Modeling 
• Use of full-wave commercial software 
• Calculations, simulation, processing under Python or Matlab software 
• Excellent proficiency in English, both in speaking and writing
• Strong oral communication and scientific writing skills