R. Aksas

An optimized shaped antenna for multiband applications using Genetic Algorithm

In this paper, a novel shaped microstrip patch antenna fed by microstrip lines is proposed. This antenna optimally designed, is achieved by applying Genetic Algorithm (GA) to find the optimum parameters for shaped configuration. The objective function constitutes a multi-objective optimization problem. The simulation and measured results show good multiband antenna suitable for applications operating at 2.4/3.6/5.5GHz (WLAN communications systems). Also, good antenna performances such as radiation patterns and antenna gains over the operating bands have been observed.

Multiband microstrip antenna array for modern communication systems

This paper presents the design and development of a microstrip G-shape multiband antenna operating at 3.7 GHz, 5.2 GHz and 5.8 GHz. Moreover, in order to increase its gain, identical dual-element patch multiband antenna is also proposed. The array elements are fed by only one feed network, which improves the impedance bandwidth of the two element G-shape microstrip antenna. The choice of the radiating element shape depends on different factors such as: the radiated power, the multiband operation, the polarization type, the gain and the bandwidth. The array elements showed a peak gain of 4 dB at 3.7 GHz, 1 dB at 5.2 GHz and 5.2 dB at 5.8 GHz. The overall patch multiband array antenna has a compact dimension of 7.5×52.5 mm2. The comparison between the simulated and measured results showed a very good understanding, which implies the practical suitability of the proposed multiband antenna array design.

New design method of the single stage distributed amplifier

This article describes a new design method of the single stage distributed amplifier, based on the approximation of the amplifier transducer gain by the Chebyshev polynomial. This method allows making a very significant improvement in bandwidth, compared with the conventional distributed amplifier with a single field effect transistor, and a significant reduction in ripple ratio with a slight broadening of the bandwidth compared with an identical amplifier topology designed with another method that we had developed. These improvements are of 128% in bandwidth compared with the conventional distributed amplifier. In addition, we can, with this method, design an amplifier so that it has the same performance as the conventional distributed amplifier with 4 transistors.

Numerical Determination of Permittivity and Permeability Tensors of a Dielectric Metamaterial Composed of an Infinite Number of Split Ring Resonators

In this paper, the determination of electric permittivity and magnetic permeability of a dielectric metamaterial composed of an infinite number of conductors (split ring resonators) using the quasi-static Lorentz theory is investigated. The induced currents on the conductors are calculated with the method of moments. Negative values of the real parts of the permittivity and permeability are obtained within a given frequency band. Various modifications to the original configuration are made and their effects on the behavior of both permittivity and permeability are discussed. The obtained results are in good satisfactory with the theory predicting the possibility to have negative values of the considered parameters as well as the numerous reported works.

Novel analysis and design approaches of the planar antenna arrays

New approaches for the determination of the radiation characteristics of planar arrays are proposed. Conventionally, the best compromise directivity-side lobes level is achieved using Dolf-Chebyshev amplitude distribution. However, classical distribution forms present disadvantages in calculation time, possibility in analyzing larger arrays and the array factor is only optimum in the two principle planes. To overcome these problems, the excitation amplitudes are written under the modal form. The obtained radiated fields compared with measurement results validate the technique. It is also shown that square arrays provide improved performances from point of view of directivity compared to those of rectangular arrays with comparable size. However, above specific array size, the directivity saturates. For this, another modification of the array factor of Chebyshev square array is proposed. The modification preserves the radiation pattern configuration (same number of null radiation directions and sidelobes) and improves both directivity and side lobe levels. Analytical expressions of the array factor, the directivity, maximum half-power beamwidth, and the maximum spacing between elements have been derived. It has been shown that the use of this new technique results in an improved directivity with respect to the classical Chebyshev for a square arrays identical in size, element spacing, direction of the main lobe and side lobes level.RésuméDe nouvelles approches pour la détermination des caractéristiques de rayonnement d’antennes en réseau rectangulaire planaire sont proposées. Habituellement, un bon compromis directivité-niveau de lobes secondaires est obtenu grâce à la distribution d’amplitudes de type Dolf-Chebyshev. Cependant, les formes classiques de distribution présentent des inconvénients relatifs au temps de calcul, à la possibilité d’analyse de réseaux de grande taille et au facteur du réseau qui est optimal seulement dans les deux plans principaux. Pour palier ces problème s y les amplitudes d’excitation sont écrites sous la forme modale. La comparaison des champs rayonnes obtenus avec les mesures valide cette technique. Aussi, il est montré que, du point de vue directivité, la configuration carrée offre de meilleures performances que celles d’un réseau rectangulaire de taille comparable. Cependant, au-delà de certaines tailles de réseau, la directivité est invariable. Pour cela, une autre modification de facteur de réseau d’une antenne carrée de type Chebyshev est proposée. Le diagramme de rayonnement préserve la même configuration (même nombre de directions de rayonnement nul et de lobes secondaires) avec une réduction sensible à la fois de la largeur du lobe principal et du niveau des lobes secondaires. Des expressions analytiques du facteur de réseau, de la directivité, de la largeur maximale du faisceau à mi-puissance et de l’espacement maximal entre les éléments sont présentées. L’usage de cette technique donne une meilleure directivité que celle obtenue par la méthode de Chebyshev classique pour des réseaux carrés identiques en taille, en espacement, en direction du lobe principal et en niveau des lobes secondaires.

Evaluation of polarization diversity antenna for wireless communication applications

In this paper, polarization diversity antenna is evaluated as a solution to reduce the effect of fading on transmitted signal strength. Two experiments using different types of antennas orthogonally polarized, horns and wired dipoles, are made. The acquisition of the received signals is done by an Arduino board interfaced with Matlab and diversity results are illustrated by real time plots. The measured results obtained by the experiments show that the evaluation of such system, using polarization diversity, gives interesting results and proves its use as a good solution for fading problem.

Spectral‐domain integral‐equation analysis of microstrip antenna working around 24 GHz

The full-wave analysis based on the moment method in the spectral domain is used to perform an analysis of the rectangular patch antenna working around 24 GHz. The resonant frequency is in good agreement with the measured result. The value of the relative permittivity which is taken is at 10 GHz, and the severe tolerances in the substrate thickness cause some discrepancies between the theoretical and experimental input impedances. The copolarization and cross-polarization components of the radiation pattern of this antenna are also drawn in both die E-plane and the H-plane

Full-wave analysis of the broadband circular polarization microstrip patch antenna

A full-wave analysis based on the moment method in the spectral domain is used to perform an analysis of the rectangular (quasisquare) patch antenna. The conventional rectangular patch shape excited by a coaxial cable at a point favoring the resonance of only one patch edge results in a very narrow bandwidth structure that radiates linear polarized waves. In this work, the rectangular shape replaced by a quasisquare patch excited on a point of its diagonal line is analyzed A broadband structure radiating almost circular polarized waves is obtained