Multibeam Antennas Array Pattern Synthesis Using a Variational Method

In this paper a new method is described for multibeam antennas synthesis where both the amplitude and phase of each radiating element is a design variable. The developed optimization method made possible to solve the synthesis problem and to answer all the constraints imposed by the radiation pattern. Two approaches for visualizing satellite antenna radiation patterns are presented. Gain-level contours drawn over a geographical map gives clearest qualitative information. A three-dimensional (3D) surface plot displays the qualitative shape of the radiation pattern more naturally. The simulations results have shown power, precision and speed of the variational method with respect to the constraints imposed on radiation pattern of the of multibeam antennas network

Study of the Alamouti-OFDM system using ZP technique and training symbols in multi path selective fading channel

In this paper, we propose a modified Alamouti code matrix and it associated with zero padding orthogonal frequency division multiplexing known as (Alamouti- ZP OFDM). Which zero padding (or zeros samples) are adopted over the OFDM symbols that construct also the encoded symbols of the Alamouti matx. Training symbols are applied for the channel estimation. Furthermore, the ML decoding algorithm  is used to get output bits which the BER can be measured. Using the selective multi path fading as model for wireless channel to evaluate the performance provided by the system proposed. The performance of  the approach proposed is based on BER parameter. For that, the system  is simulated  in two profiles of paths number (3 paths, and 6 paths) have used, which the spread delays of these paths are taken (in millisecond and in microsecond) respectively. Different data stream are simulated and compared. And the BER performance are compared also for ifft lengths 512 and 1024 and the BER results presented for all parameters of (paths number, and spread delays). The simulation  results show that the system  presented performed good even the spread delays of multi path channel are great (microseconds or milliseconds) and even increased  the data simulated from  increasing the parallel of the data streams transmitted in the system study . So, the system could keen their effectiveness against of fading channel and ISI phenomenon.  And finaly, it is shown that increasing IFFT samples in the simulation process the improvements are more enhanced of the approach proposed

Analyse des Antennes Imprimées Alimentées par des Lignes adaptées

L’utilisation des méthodes simples et améliorées pour l’analyse des antennes imprimées permettant d’aboutir à des résultats proches de ceux obtenus par les méthodes rigoureuses est souvent demandé. L’objet de ce travail, consiste en l’analyse des réseaux d’antennes imprimées à l’aide de modèle équivalent basé sur celui des lignes de transmissions. Pour rendre le modèle rigoureux, il a été tenu compte de l’adaptation de l’alimentation à l’élément rayonnant

Parallel Coupled Microstrip Bandpass Filter for G.S.M Band Applications

Design procedure and optimization of a parallelcoupled microstrip bandpass filter for G.S.M band applications is presented in this paper. The filter is designed and optimized at a center frequency of 6.2 GHz. Half wavelength long resonators and admittance inverters are used to design the filter. The filter is simulated using ADS (Advanced Design System) design software and implemented on Roger 4003C substrate

Synthese de reseaux non periodiques d'antennes microruban a loi d'alimentation uniforme ou predeterminee

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Analytical bound for the CCDF of Crest Factor in NC-OFDM Systems

Non-contiguous orthogonal frequency division multiplexing (NC-OFDM) is a promising framework for wireless communication systems due to OFDM characteristics like the spectral bandwidth efficiency, robustness to frequency selective fading channels, etc. However, it has been widely known that multicarrier signals generated by OFDM technique exhibit a large peak to average power ration (PAPR), one of the main impediment that has limited the applicability of OFDM systems. Several approaches are employed in literature to derive the PAPR distribution and thus try to reduce it in OFDM context, as Central limit theorem and modern extreme value theory. In new contexts like NC OFDM systems when flexible access to spectrum is done with non contiguous portions, the PAPR distribution remains generally unknown, and it is necessary to describe it, since this is one of the key design parameters. In this correspondence, we develop the PAPR bound expression in NC-OFDM context