Vol. 59 n°9-10, sept.-oct. 2004
Open Topics
FDTD simulations and measurements for cell phone with planar antennas
Claudio R. FERNÁNDEZ*, Mateus BONADIMAN**, Alvaro. A. A. DE SALLES*
* Electrical Engineering Department, Optoelectronic Communications Laboratory, Federal University of Rio Grande do Sul (UFRGS), Av. Osvaldo Arahna, 103, Porto Alegre, RS 90035-190, Brasil
** was with the E.E.Dept. UFRGS. He is now with the Electrical Engineering Department, Aeronautical Technologic Institute (ITA), São José dos Campos, SP, Brasil
Abstract: The Finite-Difference Time-Domain (FDTD) method is used to calculate the cellular phone far and near field and the specific absorption rate (SAR) in the user's head. The conventional l/4 monopole and a simple planar antenna are simulated and measured. The simulated results are in good agreement with those measured for the VSWR and for the radiation patterns on the horizontal and vertical planes. These results show that significant improvements in the antenna radiation efficiency and in the reduction of the SAR in the head are obtained when planar antennas are used. 1
Key words : Electromagnetic field, Finite difference method, Time domain method, Portable telephone set, Mobile service radiocommunication, Monopole antenna, Absorbed radiation dose, Radiation effect, Radiation pattern, Wave absorption.
Analysis of the spectral stability of the three phase shift DFB laser (3PS-DFB)
Abdelkarim ZATNI*, Driss KHATIB***, Mohamed BOUR*, Jean LE BIHAN**, Mohamed ELHAZITI*
* Laboratoire optronique, Ecole Supérieure de Technologie d'Agadir, B. P. 33/S, 80000 Agadir, Maroc
** Laboratoire RESO, Ecole Nationale d'Ingénieurs de Brest, Technopôle Iroise - B.P. 30815, 29608 Brest Cedex, France.
*** Laboratoire de Physique de solide, Université Ibn Zohr, Faculté des Sciences, B. P. 8106 Dakhla, 80000 Agadir, Maroc.
Abstract: The aim of this article is to analyze the spectral stability of the three phase shift distributed feedback (3PS-DFB) laser by using Time domain model (TDM). We have developed a software that simulates static and dynamic properties of distributed feedback (DFB) multi-sections laser at large signal. The best single-mode stability operation up to 18 mW of the 3PS-DFB is achieved for three phase shifts at (p, p, p) whatever the phase position. These results showed that the 3PS-DFB laser was a much more suitable structure to realize stable single-mode high-power operation for a coherent optical communication system.
Key words: Distributed feedback laser, Frequency stability, Time domain method, Large signal behavior, Static conditions, Dynamic conditions, Optical source, Telecommunication application.
On the fly pattern matching for intrusion detection with Snort
Tarek ABBES*, Adel BOUHOULA**, Michael RUSINOWITCH*
* LORIA-INRIA Lorraine, 615, rue du Jardin Botanique B.P. 101, 54602 Villers-Les-Nancy cedex, France
** École Supérieure des Communications de Tunis, 2083 Ariana, Tunisie
Abstract: Intrusion Detection Systems are becoming necessary tools for system administrators to protect their network. However they find more and more difficulties with high speed networks. To enhance their capacity and deal with evasion techniques, frequently used by hackers, we have introduced a new method to filter the network traffic. The detection method, while being stateful, processes each packet as soon as it is received. We have employed this strategy after a new classification of detection rules. Then, we have used efficient multisearch methods and suitable datastructure for signatures. The method has been successfully implemented as an extension of the Intrusion Detection System "Snort".
Key words: Computer security, Local Area Network, Intruder detector, Filtering, Protection, Packet transmission.
On the use of weighted correlation in intrusion detection process
Fabien AUTREL*, Salem BENFERHAT**, Frédéric CUPPENS***
* ONERA-CERT, 2 Av. E. Belin, 31055, Toulouse Cedex, France. email : autrel@cert.fr
** CRIL CNRS Université d'Artois, Rue Jean Souvraz, SP 18, 62307 Lens Cedex, France
*** GET/ENST Bretagne, BP 78 - 2, rue de la Châtaigneraie - 35512 Cesson Sévigné Cedex, France
Abstract: 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 by IDSs (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.
Key words: Computer security, Intruder detector, Correlation, Weighting, Alarm, Modeling.
Optimization of the multichip module performance modeling using neural networks
Mustapha C. E. YAGOUB*
* École d'Ingénierie et de Technologie de l'Information, Université d'Ottawa, 161 Louis Pasteur, Ottawa, ON, Canada, K1N 6N5
Abstract: Widely used in microwave multichip module design, passive device models are subject to intensive researches. This paper introduces the concept of automate generation of neural models for passives and interconnects. Accurate and fast, these models efficiently integrate electromagnetic effects present at microwave frequencies. By optimizing the circuit performance, the proposed approach can automatically predict not only the final geometrical structure of the different passive components and their respective interconnects but also, for the fist time, their optimum location in the circuit. Applications using passive models implemented in circuit simulators are presented.
Key words: Microwave integrated circuit, Hybrid integrated circuit, Passive component, Interconnection, Neural network, Optimization, Automation, Simulator, Multichip module.
Theoretical and experimental simulation for measuring transfer impedance of multi-wire shielded cable using triaxial set up
Saad Dosse BENNANI*, Jamal BELKADID**, Mounir RIFI***
* ENSA de Oujda, Université Mohamed I, BP 696, Oujda - Maroc
** ENSA d'Agadir, Université Ibn Zohr BP 33./S Agadir - Maroc.
*** EST de Casablanca, Université Hassan II Km 7 Route d'El Jadida BP 8012, Casablanca - Maroc.
Abstract: We are interested in the present paper in the measure of the transfer impedance and the near-end crosstalk voltages of multi-wire shielded cable by applying the well-known transmission- line theory. Using the impedance and admittance transfer measurement set up, we show that conductors inside the shield play an important role in the evaluation of the internal voltages. We equally show that when the conduction coupling appear, we can not neglect the reaction of the interior wires with regard to the exterior.
Key words: Shielded cable, Transfer function, Electric impedance, Electric admittance, Electromagnetic disturbance, Theoretical study, Experimental result, Crosstalk, Test facility, Modal analysis, Transmission line, Coupled line, Induced voltage.
Multi-mode analysis of filters using multi-sections iris. Genetic optimization and realization of filters with low dimensions and transmission zeros
Pierre JARRY*, Nicolas BOUTHEILLER*, Jean-Marie PHAM*, Eric KERHERVE*
* Laboratoire IXL UMR CNRS 5818, Université Bordeaux I - 351, Cours de la Libération, 33405 Talence Cedex, France
Abstract: We present the design and the development of a research method for new microwave waveguide filtering structures with low dimensions and tranmission zeros. An electromagne- tic analysis technique is exposed. It permits to characterize all structures composed of rectilinear pieces of rectangular waveguide whose opened areas at the extremities partially overlap. Non shared areas are supposed perfectly conductive and every piece of waveguide is filled with homogeneous isotropic dielectric material. Basic elements are size discontinuities and dielectric discontinuities. We determine the generalized scattering matrix using multimode analysis. Using a lot of modes leads also to reduce dimensions. Coupling of two modes leads to the realization of a zero transmission and improves the selectivity of the filters. Optimization is made using genetic algorithm. In addition to theory, the measured response of a filter is presented and valids the proposed filter concept.
Key words: Microwave filter, Rectangular waveguide, Iris waveguide, Modal analysis, Optimization, Genetic algorithm, Discontinuity, Scattering matrix, Selectivity, Multimode waveguide.
Study of planar structures in very high frequencies using a new mom formulation in the spatial domain
Aline LATIRI*,**, Abdelaziz SAMET*, Amar BOUALLEGUE***
* Unité de Recherche Composants et Systèmes électroniques, École Polytechnique de Tunisie - BP 743, 2070 La Marsa - Tunisie.
** Institut Supérieur d'Informatique et des Techniques de Communication - 4000 Hammam Sousse - Tunisie.
*** Laboratoire des Systèmes de Communications, ENIT, BP 37, 1002 Belvédère - Tunis, Tunisie.
Abstract: An efficient analytical integration technique for computation of spatial method of moments (MoM) integrals in conjunction with numerical matched loads is presented. The current distribution on the device is solved by using the well-known Galerkin's MoM procedure applied to mixed potential integral equation in the spatial domain. The scattering parameters are determined by considering infinite lines at each port where only the fundamental mode is assumed to propagate. The contribution of this work is the development of an integration technique for the computation of spatial domain integrals, that is fast and rigorous. This technique is based on a Taylor series expansion of the integrands involving only polynomial functions. The use of polynomial forms in the integrals leads an immediate analytical integration, and the computation time will be considerably reduced.
Key words: Planar technology, Microwave device, Moment method, Space processing, Discontinuity, Microstrip technology, Analytical method, Taylor series, Scattering parameter, Integral equation, Series expansion, Green function.
Parallel multiple access interference cancellation in optical DS-CDMAsystems
Claire GOURSAUD*, Naufal M. SAAD*,Younes ZOUINE*, Anne JULIEN-VERGONJANNE*, Christelle AUPETIT-BERTHELEMOT*, Jean-Pierre CANCES*, Jean-Michel DUMAS*
* Université de Limoges - École Nationale Supérieure d'Ingénieurs de Limoges (ENSIL), Groupe d'Étude des Systèmes de Télécommunications de l'ENSIL (UMOP/GESTE CNRS FRE 2701) - 16, Rue Atlantis - Parc ESTER - BP 6804- 87068 Limoges Cedex, France.
Abstract: This paper investigates the Parallel Interference Cancellation technique in Direct Sequence Optical Code Division Multiple Access (DS-OCDMA) system. In the proposed system, the estimated interference is removed from the received signal. We have developped a new approach to obtain the analytical expression of error probability in chip synchronous case, for Optical Orthogonal Codes (OOC). We have shown that under specific conditions between codes parameters and users'number, the interference can be completely neutralized. Simulation results have validated the theoretical analysis. It is shown that the proposed receiver is effective in reducing significantly the effects of Multiple Access Interference (MAI) compared to other interference cancellation systems.
Key words: Optical telecommunication, Optical fiber transmission, Code division multiple access, Direct sequence spread spectrum, Signal interference, Error probability, Orthogonal sequence, Parallel configuration, Theoretical study, Numerical simulation, Receiver.
Maximum likelihood decoding rules for STBC: Generalized framework for detection and derivation of accurate upperbounds
Gholam Reza MOHAMMAD-KHANI*, Guillaume FERRE*, Jean-Pierre CANCES*, Vahid MEGHDADI*
* Université de Limoges - École Nationale Supérieure d'Ingénieurs de Limoges (ENSIL) Groupe d'Étude des Systèmes de Télécommunications de l'ENSIL (UMOP/GESTE CNRS FRE 2701) - 16, Rue Atlantis - Parc ESTER - BP 6804- 87068 Limoges Cedex, France.
Abstract: In this paper we propose first a generalized framework for the Maximum Likelihood decoding of STBC. Using algebraic tools we then derive a new matrix model particularly well suited to the description of MIMO systems. After giving our particular detection rules we determine a new accurate upperbound for the BER performances of STBC transmitting schemes. Performance results are given which show the accuracy of the derived upperbound.
Key words: Mobile radiocommunication, Decoding, Maximum likelihood, Block code, Space diversity, Space and time signal, Rayleigh fading, Matrix method, Upper bound.
