Postdoc postion on "Characterization of electronic beamforming antennas based on programmable metasurfaces in mode stirring chambers"

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.  

Electronic beamforming antennas, compact, lightweight, without mechanical servo, 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 any application, it is crucial to accurately characterize the electromagnetic properties of the metasurface. For satellite communications, a key parameter is the G/T merit factor. First, to calculate the equivalent temperature of the reconfigurable metasurface, it will be necessary to use a mode mixing chamber [4] in order to evaluate the ohmic losses or in other words the efficiency of the surface as a function of the diode state. To this end, experiments in the microwave field will be undertaken, and then once the approach has been validated, experiments with millimeter waves will be conducted. On this occasion, a reverberation chamber adapted to this frequency range must be designated. The gain will be evaluated by a conventional anechoic chamber method, and the technique will be validated by reference measurements performed in a calibrated anechoic chamber. 

The second part of the post-doc will consist of developing methods for rapid characterization of cells from measurements in reverberation chambers. For this purpose, an element of RIS will be equated with an antenna connected to a port of variable impedance. We will rely on work carried out in part at the Langevin Institute [5], where a detailed modelling of the interaction of a variable load antenna has been undertaken. Thus, it will be a question of experimentally validating the proposed model in order to extract the structural factors, the efficiency as well as the load impedances of the element. In a second step, in conjunction with a second post-doc in charge of the modeling aspects, it will be a question of generalizing this approach but this time to a set of resonators, taking into account the recent work of characterization of the scattering matrix between several antennas and the elements of a reconfigurable surface [6]. 

Références

[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] Christopher L. Holloway et al., Reverberation Chamber Techniques for Determining the Radiation and Total Efficiency of Antennas, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 4, APRIL 2012 

[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 

[6] Philipp del Hougne, Minimal-Ambiguity Scattering Matrix Estimation with Load-Tunable Ports, arXiv:2403.08074v1, 2024 

• Expertise in the practice and theory of stirring Chambers of Modes
• Proficiency in the theory and practice of electromagnetic antenna characterization
• Knowledge in signal processing basics, with an emphasis on statistical processing
• Advanced experience with RF instrumentation, particularly vector analyzers
• Knowledge of intelligent reconfigurable surfaces and their applications
• Excellent proficiency in English, both in speaking and writing
• Strong oral communication and scientific writing skills