Institut Fresnel

Laboratory : Institut Fresnel, UMR-CNRS 7249, CONCEPT team
Title : Non-diffractive Bessel beams for near-field wireless RF link : modelization, synthesis, dynamic control and self-healing
Context : ANR LinkALL project (IETR/IF/Thales)
Period : November 2021- November 2024
PhD supervisors : G. Soriano, C. Amra, M. Zerrad
Emails : gabriel.soriano@fresnel.fr, claude.amra@fresnel.fr, myriam.zerrad@fresnel.fr
Summary : Our society is increasingly connected. A growing number of our daily activities, both professional and personal, are carried out digitally, with a multitude of terminals allowing us to work and interact remotely. Wireless communication technologies, the keystone of our nomadic uses, facilitate access to these terminals.
This nomadic connectivity is coupled with a constant increase in data traffic and data rates. This justifies the expansion of bandwidths through the recurrent upgrade of mobile networks to the millimeter and sub-millimeter domains of the electromagnetic spectrum. However, this increase in frequency is accompanied by an increase in natural free-space path loss (FSPL), which is highly detrimental to applications. Indeed, as soon as the communication distance exceeds a small multiple of the transmitter size, these FSPL become the major cause of signal attenuation. To overcome this difficulty, a current research approach is to develop high gain antennas, but there are alternatives, one of which is the subject of this PhD project.
Rather than compensating these FSPL by increasing the gain, we propose to reduce them by using weakly diffractive waves. True Bessel beams [1], rigorous solutions of the Helmholtz equation, are the idealization of these weakly-diffractive waves, whose transverse intensity profile remains stable over a large propagation distance, at least in the context of radio-frequency near-field applications. This fruitful idea of weakly-diffractive waves has already given rise to numerous applications in optics [2], for laser machining, optical trapping, etc. In the field of radio waves, the ratio between the size of the antenna and the wavelength is much less favorable, which makes these beams even more strategic. These waves are thus an essential element for the development of the next generation of near-field wireless networks. They should allow to drastically reduce propagation losses, and even to extend the distance of use for a millimeter wave wireless link. First realizations have been made in France (IETR), using meta-surface antennas [3].
The thesis project will consist in continuing and extending this work, within the framework of the ANR (French national research agency) LinkALL project (2021 edition), which is a collaboration between the IETR (Institut d’Electronique et des Technologies du NuméRique - UMR 6164), the Institut Fresnel (UMR 7249) and Thales Research and Technology. The doctoral work will be primarily theoretical and numerical in nature, and will take place mainly at the Institut Fresnel. The experimental aspects will be carried out in partnership within the ANR consortium.
The student will first work on the generation, propagation and reception of a Bessel beam. This work will be developed in the framework of electromagnetic optics [4] (Maxwell’s equations). Meta-surfaces will be introduced to proceed to the impedance synthesis allowing the generation of low diffraction beams. A specific coupling system at 60 GHz between a transmitter and receiver placed coaxially will be optimized. The coupling performance will be compared to the FSPL predicted by the Friis transmission equation [5].
The PhD student will also study the near-field self-healing properties of the beams, i.e. their ability to partially reform after an obstacle. For this purpose, the generation/propagation/reception model will be coupled to a surface [6] or volume [7] model of electromagnetic wave scattering. The Fresnel Institute has several of these scattering models, and the expertise required to use them.
Then, we will try to release the constraint on the alignment of the two antennas ; for this we will determine to what extent the Bessel beam can be de-pointed to aim at an off-axis receiver. The influence of such de-pointing on the link budget will examined. We will consider the case of a moving receiver, and the limits in terms of distance and efficiency induced by the motion. This will lead to explore the potential of components whose physical properties vary at high frequency with time (time-varying metasurfaces).
References :
[1] J. Durnin et al., Diffraction-free beams, Phys. Rev. Lett. 58, pp1499-1501 (1987)
[2] D. McGloin et al., Bessel beams : diffraction in a new light, Contemporary Physics 46, pp15-28 (2005)
[3] M. Ettorre et al., Generation of propagating Bessel beams using leaky-wave modes : Experimental validation, IEEE Trans. Antennas Propag. 60, pp2645-2653 (2012)
[4] C. Amra, M. Lequime, and M. Zerrad, Electromagnetic Optics of Thin-Film Coatings : Light
Scattering, Giant Field Enhancement, and Planar Microcavities, Cambridge University Press (2021)
[5] C.A. Balanis, Antenna theory : analysis and design, John Wiley & sons (2015)