Amélioration de la sensibilité de détection et de la qualité du radargramme d’un radar pénétrant GPR par une modulation micro-onde

The primary effect of the field continuously capted by aGpr is the production of a class which limits the contrast of the reflections on the targets. The target response becomes illegible sight the influence of certain disturbances which are due to the reflections caused by certain parasitic elements which are randomly distributed in the soil and the dispersion phenomenon. We present in this paper an approach based on a μ-wave modulation which allowed stage this problem. The technique suggested makes it possible to do a classification of capted signals. It will be shown that the frequency of modulation f_m must be higher than a cut-off frequency f_c which depends on the electric parameters of the ground. In a second part of this paper, we show how to improve quality of the radargram of a systemGpr by a simple convolution between the collected signal and a wavelet with a defined parameters.     

Modélisation semi-empirique de la couche limite nocturne. Application au calcul du profil d’indice de réfraction

Electromagnetic propagation depends on the refraction index profile, which is itself a function of pressure, temperature and water vapor pressure. The authors propose here a method to calculate the evolution of the refraction index profile during the night in order to predict when and how the multipath propagation will occur. The data collected during the 1982 « pacem 1 »campaign are used in the calculations. The present semi-empirical model of the nocturnal boundary layer requires short computer calculations.     

L’apprentissage des modes de vie: une base indispensable au développement d’un habitat «intelligent»

The advent of new technologies in the field of data processing, electronics and wireless communications currently support the integration of essential functions for the provision of services tailored to the user needs at home. These services are destined to address two key societal demands, i.e., keeping health costs and energy costs under control. With this objective in mind, a number of research works involving various approaches have been conducted as those carried out atlaas for the purpose of integrating the habits and practices of home automation users. The principles under investigation rely on learning habits. Two examples of application using these concepts are presented through use of two home automation systems for a personalized behavioral monitoring of the elderly with a view to providing home care, and for the automatic management of thermal comfort. Promising results have been obtained and pave the way for efficient and cost effective systems that could be associated with other functions to contribute to the development of a truly «smart home».     

Étude de la génération d’impulsions brèves d’un laser DFB à trois contrôles de phases (3QWS-DFB)

The purpose of this paper is to study the generation of short pulses of the three quarter wave shift distributed feedback (3Qws-dfb) laser by using switching gain technique. We have used the temporal domain model (Tdm) which is a multimode spatio-temporal model that considers simultaneously all the modes of the overall intra-cavity field as well as the two following nonlinear effects, the spectral hole burning (Shb) and the gain saturation. Obtained results showed that a 3Qws-dfb laser can generate short pulses in accordance with Fourier criteria. These results show that 3Qws-dfb lasers are potential candidates as monomode optical sources for long distance high bit rate telecommunications.     

Présentation d’une technique 3D d’accélération de la recherche de rayons application aux télécommunications microcellulaires

Development of telecommunications using mobile phones requires the installation of many base stations (BTS) in order to cover the large number of cells which make up the network. Existing systems (GSM, DSC) use carrier frequencies within the microwave range. Ideally, operators should have simulation software to determine the position of BTS. This software would be used initially to determine the geometric configuration of the cells. The next step would be to optimise the radiation pattern of each BTS antenna. In this article we present a method for determining radioelectric coverage based on image theory adapted to the problem, which is more accurate and less time-consuming than conventional methods.     

Conception et réalisation d’un simulateur de canal hertzien

The paper presents the design and implementation of a line-of-sight (Los)microwave channel simulator. The basic principle is to reproduce channel transfer functions given by their amplitude and group delay characteristics by driving a linear transversal filter with precomputed data. The transfer functions can be either collected from measurements in the field or derived from any analytical modelling of the Los microwave channel. It is shown that a thirteen tap filter with a 70 MHz period leads to accurate realtime simulations of selective fading in a 50 MHz bandwidth. The control interface, microprocessorbased, allows an efficient and smooth use of the simulator. Finally,hardware problems and technological solutions related to the implementation are presented.     

Utilisation de la corrélation pondérée dans un processus de détection d’intrusions

Generally, an intruder must perform several actions, organized in an intrusion scenario, to achieve his or her malicious objectives. Actions are modeled by their pre and post conditions, which are a set of logical predicates or negations of predicates. Pre conditions of an action correspond to conditions the system’s state must satisfy to perform the action. Post conditions correspond to the effects of executing the action on the system’s state. When an intruder begins his intrusion, we can deduce, from the alerts generated byidss (Intrusion Detection Systems), several possible scenarios, by correlating attacks, that lead to multiple intrusion objectives. However, with no further analysis, we are not able to decide which are the most plausible ones among the possible scenarios. We propose in this paper to define an order over the possible scenarios by weighting the correlation relations between successive attacks composing the scenarios. These weights reflect to what level executing some actions are necessary to execute some action B. We will see that to be satisfactory, the comparison operator between two scenarios must satisfy some properties.     

Étude du couplage d’une onde électromagnétique externe et d’une ligne de transmission aérienne non uniforme

In this paper, a flexible and efficient method for analyzing the electromagnetic field to nonuniform multiwire aerial lines coupling is proposed. This analysis in based upon the finite- difference time- domain (fdtd) algorithm. The transient responses of nonuniform lines excited by different waves obtained by this method are compared with those of Spice and literature. The good agreement between all the simulation results validates the proposed approach.     

Sur une expression des puissances d’une matrice et son application aux réseaux itérés

Annals of Telecommunications - Après une brève introduction, dans unepremière partie, l’auteur donne (I), de lapuissance d’une matrice d’ordre 2, une expression...