Time-Frequency Decomposition of an Ultrashort Pulse: Wavelet Decomposition

An efficient numerical algorithm is presented for the numerical modeling of the propagation of ultrashort pulses with arbitrary temporal and frequency characteristics through linear homogeneous dielectrics. The consequences of proper sampling of the spectral phase in pulse propagation and its influence on the efficiency of computation are discussed in detail. The numerical simulation presented here is capable of analyzing the pulse in the temporal-frequency domain. As an example, pulse propagation effects such as temporal and spectral shifts, pulse broadening effects, asymmetry and chirping in dispersive media are demonstrated for wavelet decomposition

Neural Networks for Synthesis and Optimization of Antenna Arrays

This paper describes a usual application of back-propagation neural networks for synthesis and optimization of antenna array. The neural network is able to model and to optimize the antennas arrays, by acting on radioelectric or geometric parameters and by taking into account predetermined general criteria. The neural network allows not only establishing important analytical equations for the optimization step, but also a great flexibility between the system parameters in input and output. This step of optimization becomes then possible due to the explicit relation given by the neural network. According to different formulations of the synthesis problem such as acting on the feed law (amplitude and/or phase) and/or space position of the radiating sources, results on antennas arrays synthesis and optimization by neural networks are presented and discussed. However ANN is able to generate very fast the results of synthesis comparing to other approaches

Microstrip antennas array Design Using Genetic algorithms and Simulated Annealing

This publication presents two new approaches of design microstrip antennas array. First is based on the technique of the genetic algorithms inspired from the processes of the evolution of the species and the natural genetics and the second based on the analogy between the resolution of the combinative problems of optimization and the annealing of the solids. These two approaches permits to seek simultaneous the law of optimal feed and the space distribution of the radiant elements so that the radiation pattern is as close as possible to an optimal desired diagram specified from a function or a pattern shape.Cette publication présente deux nouvelles approches de conception de réseaux d'antennes imprimées. La première est basée sur la technique des algorithmes génétiques inspirée des processus de l'évolution des espèces et de la génétique naturelle et la deuxième sur l'analogie entre la résolution des problèmes d'optimisation combinatoire et le recuit des solides. Ces deux approches permettent de rechercher simultanément la loi d'alimentation optimale et la répartition spatiale des éléments rayonnants pour que le diagramme de directivité du réseau soit aussi proche que possible d'un diagramme désiré optimal spécifié à partir d'une fonction ou d'un gabarit

MULTILAYERED BOW-TIE ANTENNAS DESIGN FOR RFID AND RADAR APPLICATIONS USING A SIMPLE EQUIVALENT TRANSMISSION LINE MODEL

ABSTRAC

Corporate-Feed Multilayer Bow-Tie Antenna Array Design Using a Simple Transmission Line Model

A transmission line model is used to design corporate-fed multilayered bow-tie antennas arrays; the simulated antennas arrays are designed to resonate at the frequencies 2.4 GHz, 5 GHz, and 8 GHz corresponding to RFID, WIFI, and radars applications. The contribution of this paper consists of modeling multilayer bow-tie antenna array fed through an aperture using transmission line model. The transmission line model is simple and precise and allows taking into account the whole geometrical, electrical, and technological characteristics of the antennas arrays. The proposed transmission line model showed its interest in the design of different multilayered bow-tie antennas and predicted the correct resonance frequency for different applications in telecommunications. To validate the proposed transmission line model, the simulation results obtained are compared with those obtained by the method of moments. The results of simulations are presented and discussed. Using this transmission line approach, the resonant frequency, input impedance, and return loss can be determined simultaneously. The paper reports several simulation results that confirm the validity of the developed model. The obtained results are then presented and discussed

HEIDELBERGER AKADEMIE

3 The Workshop is dedicated to Professor Tofik Ismail-Zadeh (1930-2004), a prominent Azerbaijan geophysicist, honoured scientist of Azerbaijan, and fellow of the Russian Academy of Natural Sciences. The dedication is in recognition of his pioneering works in paleomagnetism, seismology, and seismic hazard and of his leading role in cooperation of academic and industrial research. 4 Workshop Summary The human faces devastating geological and geophysical disasters on different scales in time and space: Earthquakes, landslides and erosions, mud volcanoes, rock falls, sediment pollutions, subsidences and collapses, floods and other water and weather related hazards. The geohazards affect not only the human life and health, but have also dramatic impact on the sustainable development, e.g. land value, deterioration of the environment, partial or total loss of infrastructure, and other social and economic processes on which life depends

Controlled Random Search Optimization for Linear Antenna Arrays

An optimization problem for designing nonuniformly spaced, linear antenna's arrays is formulated and solved by means of a controlled random search algorithm. The proposed iterative method aims at a linear array and the optimization of element positions and excitations coefficients by minimizing the side-lobes level and respecting a beam pattern shape. Selected examples are included, which demonstrate the effectiveness and the design flexibility of the proposed method in the framework of the electromagnetic synthesis of linear antenna arrays