Pattern Nulling of Linear Antenna Arrays Using Backtracking Search Optimization Algorithm

An evolutionary method based on backtracking search optimization algorithm (BSA) is proposed for linear antenna array pattern synthesis with prescribed nulls at interference directions. Pattern nulling is obtained by controlling only the amplitude, position, and phase of the antenna array elements. BSA is an innovative metaheuristic technique based on an iterative process. Various numerical examples of linear array patterns with the prescribed single, multiple, and wide nulls are given to illustrate the performance and flexibility of BSA. The results obtained by BSA are compared with the results of the following seventeen algorithms: particle swarm optimization (PSO), genetic algorithm (GA), modified touring ant colony algorithm (MTACO), quadratic programming method (QPM), bacterial foraging algorithm (BFA), bees algorithm (BA), clonal selection algorithm (CLONALG), plant growth simulation algorithm (PGSA), tabu search algorithm (TSA), memetic algorithm (MA), nondominated sorting GA-2 (NSGA-2), multiobjective differential evolution (MODE), decomposition with differential evolution (MOEA/D-DE), comprehensive learning PSO (CLPSO), harmony search algorithm (HSA), seeker optimization algorithm (SOA), and mean variance mapping optimization (MVMO). The simulation results show that the linear antenna array synthesis using BSA provides low side-lobe levels and deep null levels

Development of an antenna system for a relay-based wireless network. Simulation and measurement of antenna systems for relay-based wireless network, covering the backhaul and access links and applying beam forming technology.

The proliferation of modern wireless networks increases demand for high capacity and throughput in order to provide faster, more robust, efficient and broadband services to end users. Mobile WiMAX and LTE are examples of such networks in which for some cases they have exposed limited connectivity due to harsh environment. Relay stations are preferred to overcome problems of weak or no access for such network devices, that are placed in specific positions to maintain high quality of data transfer at low cost and provide the required connectivity anywhere anytime. These stations should be equipped with an antenna system capable of establishing communication between base station (backhaul link) and end users (access link). This thesis focuses on the design and development of a new antenna system that is suitable for a relay-based wireless network. Planar geometries of microstrip patch antennas are utilized. The antenna system comprises two antenna modules: a new design of a single antenna for access link and a new design of an antenna array for backhaul link realization. Both antenna specifications are compatible with the IEEE802.16j protocol standard. Hence, relay station should be capable of pointing its radiation pattern to the base station antenna, thus to achieve the desired radiation pattern of the relay station, a new beam-forming module is proposed, designed and developed to generate the proper radiation pattern. The beam-forming module incorporating digital phase shifters and attenuator chips is fabricated and tested. The optimization process using the Least Mean Square (LMS) algorithm is considered in this study to assign the proper phase and amplitude that is necessary to each radiation element excitation current, to produce the desired steered radiation pattern. A comprehensive study on the coupling effects for several relative positions between two new backhaul and access link antenna elements is performed. Two new antenna configurations for coupling reduction are tested and the simulated and measured results in terms of antenna radiation performances were compared and commented

Technique de reconfiguration d'antennes par décomposition des diagrammes de rayonnement

RÉSUMÉ L'expansion des télécommunications entraîne une demande de plus en plus forte en débit et en qualité de service. Ceci implique une constante évolution des systèmes sans-fil utilisés. Le déploiement des systèmes à multiples antennes (MIMO) est une solution très intéressante pouvant augmenter la fiabilité du canal et la quantité d'information transmise. Cependant, de nouveaux problèmes tels que la corrélation des canaux apparaissent. Parallèlement à cette technologie, les antennes reconfigurables sont utilisées depuis bien longtemps dans divers domaines comme celui des radars. Leur capacité à s'adapter à leur environnent n'a pas échappé aux chercheurs. En combinant ce type d'antennes dans des systèmes MIMO, diverses études indiquent une possible diminution de la corrélation des canaux par modification du diagramme de rayonnement de l'antenne par exemple. Tout ceci est très intéressant, encore faut-il une méthode de reconfiguration capable de s'exécuter rapidement. Une technique assurant la meilleure configuration consiste à estimer le canal de transmission pour toutes les configurations possibles de l'antenne. Cependant, toutes ces estimations font perdre un temps précieux et affectent la capacité du canal. Une manière plus élaborée de configurer une antenne est de déterminer la position des sources par des méthodes comme MUSIC ou ESPRIT. Malheureusement, le nombre de sources pouvant être trouvées est limité et la complexité est assez importante. On se propose ici de mettre au point une technique dont le but principal est de reconfigurer une antenne en diminuant le plus possible le nombre d'estimations du canal. Les canaux non-estimés vont devoir être reconstruits par un certain calcul détaillé dans notre étude. Brièvement, ce calcul se base sur une décomposition mathématique du diagramme de rayonnement de l'antenne en fonction de coefficients dépendants uniquement de la configuration de l'antenne et de diagrammes de rayonnement particuliers de l'antenne (configurations fixées). Cette technique doit bien entendu être utilisable dans un système MIMO. Les antennes étudiées sont des réseaux d'antennes linéaires uniformes (ULA) et des antennes à perte formées à partir de méta-matériaux (CRLH).Cette étude va nous mener à observer le comportement de notre technique face à des erreurs d'estimation des canaux mesurés et des erreurs sur la reconstruction des canaux non-mesurés. Chacune de ces erreurs a ses propres caractéristiques mais au final elles dépendent toutes deux des configurations des canaux mesurés. On explique qu'un moyen simple pour parer à ces deux erreurs consiste à mesurer beaucoup de canaux ce qui va à l'encontre du but fixé par notre technique. ----------ABSTRACT The demand for faster data rates and better quality of services constantly increases with the expansion of wireless telecommunications. Employing Multiple Input Multiple Output (MIMO) systems is a very interesting solution to improve reliability of channel and enhance data transmission. Unfortunately, new problems such as channel correlation appear. Next to these systems, reconfigurable antennas have been used for a long time in different fields like radars. Their capability to adapt to their environment has generated significant interest in adding new degrees of freedom. By combining this kind of antenna with a MIMO system, different studies show some enhancements in adapting dynamically their radiation pattern for example. To dynamically adapt antenna, a fast and reliable reconfigurable method has to be used. In order to find the optimal antenna configuration we can proceed to a complete scanning of available configurations, which is time consuming and decreases the achievable data rate. We can also use direction of arrival estimation using the MUSIC algorithm. However, in a rich multipath environment, the direction of arrival is hard to estimate accurately with the MUSIC algorithm. Other algorithms, such as ESPRIT, could be used to estimate the channel parameters. However, they are computationally intensive, especially in a MIMO environment. Furthermore the number of direction of arrival which can be found is limited by the number of receiver. To save time we describe here a technique using estimations of the channel for a low number of configurations of the antenna