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175-RF propagation through turbulent media: multiscale modelling investigation

175-RF propagation through turbulent media: multiscale modelling investigation

  • Contract :Ph.D.
  • Duration :36 months
  • Working time :Full-time
  • Experience :Entry Level
  • Education level :Master’s Degree, MA/MS/MSc

Your mission at CNES :

Atmospheric turbulence has an important impact on RF and optical signal propagation, on both their phase and amplitude. Amongst many examples, let us cite three of them. At L-band, ionospheric scintillation affects GNSS signals, causing receivers loss of lock . Due to the need of a long acquisition time, geosynchronous SAR imaging is impaired by tropospheric turbulence. Optical wireless communications are also impacted by turbulence phenomena. A proper modelling of the turbulence and its impact on propagation is a key for accurate sizing and/or failure
prediction of propagation systems.
Propagation tools have been already developed to estimate the phase and amplitude of electromagnetic signals through a turbulent atmospheric layer. They mainly use a spectral Kolmogorov representation to model the turbulence, both for the troposphere and the ionosphere, considered using phase screens. The main advantage of this representation is that phase and amplitude variances are computed very fast. However, turbulent structures exhibit multiscale anisotropy features that are not correctly modeled by the Kolmogorov spectrum. Moreover, the error
made using Kolmogorov’s representation in propagation tools has not been assessed yet.
The main objective of this thesis work is to propose a multiscale model for the atmospheric turbulence (ionosphere and troposphere), based on multi-fractal developments, scattering moments and hydro-dynamic models [8] of the atmosphere, in order to better fit the physical characteritics of traversed media. First efforts have been proposed for optical propagation, based on a wavelet decomposition of the medium statistics. For this purpose, three main steps are then followed:
• to assess the error of Kolmogorov representation vs multiscale developments;
• to model an accurate and fast atmospheric model based on a multiscale representation (wavelets and scattering moments);
• to implement multi-scale schemes in the propagation tools using SSW formalism, without increasing the computation time;
• to retrieve medium physical parameters from real data.
This thesis project will follow the following steps:
• state-of-the-art on multi-scale solutions and SSW propagation formalism;
• state-of-the-art on tropospheric and ionospheric turbulence and scintillation;
• assessment of the error between physic-based models, multi-scale modelling and Kolmogorov spectrum for the estimation of propagation parameters (amplitude and phase);

• data processing to characterize tropospheric and ionospheric medium physics using the parameters of the multiscale representation.

For more information, contact  remi.douvenot@enac.fr from ENAC

Candidate profile searched:

Education: Master level M2 in electromagnetism or signal processing, either from a University or an Engineering School
Skills: physics, electromagnetics, mathematics, computer programming (Matlab/Python)


We suggest you to contact first the PhD supervisor about the topics and the co-financial partner (found by the lab !). Then, prepare a resumé, a recent transcript and a reference letter from you M2 supervisor/ engineering school director and you will be ready to apply online !

CNES will inform about the status of your application in mid-June.

More details on CNES website : https://cnes.fr/en/web/CNES-en/10685-st-doctoral-grants.php

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