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International audience; This paper presents a new concept of Land Mobile Propagation Satellite model. The main idea is to predict the propagation channel based on the analysis of 360° images. To do so, concurrent RF / optic measurements have been done in the past and this paper will present the correlation study between the images and RF signal. Finally, a coupling model RF / images is proposed here, which allows a LMS channel prediction between 1 to 30 GHz.

International audience; This paper presents a comparison between Rec. ITU-R P.833-9 ("slant path" section), versus measurements acquired by CNES and NICT at 20 and 18 GHz. Although several comparisons to measurements have been done between 1 and 3 GHz in previous works, we show here also a good agreement between Rec. ITU-R P.833-9 and the measurements at Ka band for satellite propagation channel, without excessive model tuning. The demonstration is done on isolated trees and long wooden road with an innovating fitting process.

This manuscript is presenting various research works on the modeling of the propagation of electromagnetic waves (EMW) in complex environments. The work includes numerical and analytical modelling of EMW interactions in the maritime environment, in the troposphere and then the ionosphere, natural environments whose effects on EMW propagation are sensitive to microwave frequencies. In this work, numerical modeling of the propagation by resolution of the Parabolic Wave Equation (PWE) is central. It will be applied to different propagation environments, for different types of applications (radar, telecommunication or positioning by GNSS radio navigation). The effects of refraction and atmospheric scintillation (tropospheric, ionospheric), interactions with ground or sea surface will then be illustrated.The presentation will be complemented by examples of application to active remote sensing of the atmosphere (retrieval of vertical refraction index profiles by inversion of radar echoes or GNSS signals in Radio-Occultation geometry, characterization of tropospheric turbulence by GNSS). The prospects for work envisaged are centered on the problems of EMW propagation in the ionosphere, with the main objectives of characterizing the turbulent fluctuations in the electron density of the ionospheric plasma, their occurrence, modelling and prediction of ionospheric scintillations.

International audience; This paper presents an optimized Land Mobile Satellite (LMS) propagation channel model for Ku/Ka band. Here, a physical-statistical hybrid approach is proposed in order to simplify as much as possible the synthetic environment and the electromagnetic model, while keeping a good representation of the satellite propagation channel. This approach is complementary of full statistical approach [1] as a specific environment can now be tackled instead of a mixture of different propagation conditions. An original validation of the model is presented here, with an innovative method based on 360° panoramic images analysis in order to rebuild a simple synthetic environment.

International audience; The statistical characterization of the propagation channel is of paramount importance in the design of future mobile satellite communication systems. At Ka band, the propagation channel can be strongly impacted by tropospheric events but also by the receiver local environment. Buildings, poles or trees can lead to partial or even total shadowing effects. In this paper, we present an extensive characterization of the local propagation effects in various environments such as urban, rural, highway or railway environments. The statistical analysis of measurements made in Ka band confirms and extends observations that have been made previously in comparable or lower frequency bands.

The assessment of the availability and the optimization of the control loop require the use of space–time-correlated attenuation time series over the various sites. The performance assessment of those disposals should be made considering space–time-correlated link budgets at the scale of satellite coverage to optimize the areas in which the additional power should be focused. To perform the space–time link budgets, space–time-correlated propagation data are needed. As there are no data that can be used directly to simulate space–time-correlated link budgets, the use of space–time tropospheric propagation model is required. Different techniques have been used to generate space–time-correlated inputs: the transformation of a stationary Gaussian random field, the simulation of fractal fields, or the use of a spatially correlated time series. The use of space–time-correlated propagation impairment fields is of prime importance for the optimization of radio frequency systems using an adaptive fade countermeasure to cope with atmospheric attenuation.

This paper presents the design of a novel Ground-Penetrating Radar (GPR) test site that has been integrated into the mini-city demonstrator Sense-City located at University Paris-Est (France). This test site provides several sources of measurement interest expressed by the presence of a multilayered soil with significant dielectric contrasts, and various dielectric pipes and blades buried at various depths in trenches filled with a backfill soil different from the natural soil. This paper presents experimental Bscans associated with the pipe zone acquired by three different GPR systems at frequencies ranging from 300 MHz to 1.5 GHz. The interpretation and comparison of the raw Bscans have allowed to characterize the dielectric properties of the soil layers, and to detect the hyperbola signatures of the buried pipes. The results of this study will help to guide future developments on polarization, operating frequency and signal processing to extract parameters (orientation, dielectric characteristics, position and size) associated with pipes.

Synthetic Aperture Radar (SAR) systems have been used since many years for military applications such as the detection of hidden targets. With improved resolutions of these systems, high level of details can be distinguished in the corresponding images. However, some difficulties are encountered when analyzing the SAR images of urban areas. In particular, in these areas, many physical phenomena and interactions occur that make the detection of a target a challenging task. In this framework, the goal of the thesis is to investigate the feasibility of detecting Non Line Of Sight targets inside a simple and representative scene: the urban canyon. A study of the electromagnetic (EM) phenomenology of propagation inside urban canyons has been performed using indoor data at a reduced scale. These data allowed the validation of an EM commercial tool that studies the EM propagation at a real scale. Based on the results of simulation of this code, an in-house code was developed dedicated to predict the detection of a target inside an urban canyon and to analyze the corresponding EM signature. Moreover, this code contributed to a full interpretation of InSAR data of a real complex urban scene with targets., Les Radar à synthèse d'ouverture (RSO) ont été utilisés depuis de nombreuses années pour des applications militaires telles que la détection de cibles cachées. Avec des résolutions qui s'améliorent toujours plus, un haut niveau de détail peut être obtenu dans ces images. Cependant, certaines difficultés sont rencontrées lors de l'analyse des images SAR des zones urbaines. En particulier, dans ces régions, de nombreuses interactions se produisent qui rendent la détection d'une cible difficile. Dans ce cadre, l'objectif de la thèse est d'étudier la faisabilité de la détection de cibles en visée non directe dans une scène simple mais représentative: le canyon urbain. Une étude de la propagation à l'intérieur de ces canyons urbains a été effectuée en utilisant des mesures en chambre à une échelle réduite. Ces données ont permis la validation d'un outil commercial (FEKO) et qui nous a permis d'étudier la propagation à une échelle plus réaliste. Sur la base de ces résultats, un code a été développé pour prédire la détection d'une cible à l'intérieur d'un canyon urbain et pour en analyser la signature électromagnétique. De plus, ce code a contribué à une interprétation de données InSAR d'une scène réelle urbaine contenant des cibles et présentant un artefact.

National audience; Cet article propose une méthode d'estimation de l'exposition des personnes aux rayonnements électromagnétiques dans un problème variable et fortement multiéchelle. Le champ électromagnétique est estimé grâce à l'association de deux méthodes. On propose ainsi la combinaison d'une méthode rigoureuse de simulation temporelle multiéchelle, la DG-FDTD (Dual Grid FDTD) avec un modèle de substitution basé sur le principe de superposition et l'utilisation de fonctions de transfert.

International audience; Les signaux radioélectriques se propageant sur un trajet Terre-satellite sont parfois perturbés par la scintillation ionosphérique. Ce phénomène se traduit par l’apparition de fluctuations rapides du signal reçu qui sont susceptibles d’affecter les performances du système. C’est en particulier le cas du GPS pour lequel les scintillations sont un sujet de préoccupation pour certaines applications exigeantes en termes de précision, de disponibilité et de fiabilité. Dans le présent article, on rapporte les résultats d’une campagne de mesures de la scintillation en régions équatoriales. Cette campagne, menée dans le cadre de coopérations internationales, a permis de valider des outils spécifiques de surveillance et de prévision de la scintillation.

This thesis addresses the visibility computation between two polygons and its representation. We bring up the potential of this information to solve difficult problems in image synthesis and in electromagnetic waves propagation.We present a new algorithm for the visibility computation in thePlücker space. In comparison to previous méthods, it reduces thetime computation and the memory requirements.In image synthesis, we use the computed information to design a new solution for the analytic computation of soft shadows. This solution is both accurate and fast in comparison with stochastic approaches.In electromagnetic waves propagation, we present the first ray based model optimisation without path lost. This optimisation allows to perform accurate simulations using significative environments.; Cette thèse aborde le problème du calcul et de la représentation de la visibilité mutuelle de polygones. Elle montre tout le potentiel et l'intérêt de cette information pour la résolution de problèmes difficiles en synthèse d'images et en propagation électromagnétique. Nous proposons un nouvel algorithme pour calculer la visibilité dans l'espace de Plücker, afin de minimiser les coûts en temps et mémoire vis-à-vis des précédentes approches.En synthèse d'images, nous utilisons l'information ainsi calculée pourproposer une nouvelle solution au calcul analytique des ombres douces en illumination directe. Cette solution concilie la qualité et la rapidité du rendu.En propagation électromagnétique, nous proposons l'optimisation sans perte d'un modèle basé rayons. Celle-ci permet d'effectuer des simulations dont la précision est optimale tout en s'appliquant à des environnements de tailles significatives.