Les travaux de cette thèse s’intéressent à un nouveau concept d’antenne reconfigurable offrant un bon compromis entre performances, complexité et coût. Ce concept, qualifié d’hybride, vise à combiner les avantages des réseaux d’antennes lacunaires et des antennes à éléments parasites. Cette hybridation est une alternative à la complexité des réseaux d’antennes conventionnels pour répondre aux exigences d’une architecture modulaire, générique et reconfigurable. L’intérêt majeur de ce concept est de proposer une architecture d’antenne permettant de réduire la complexité du circuit de formation des faisceaux (par la réduction du nombre d’éléments rayonnants à alimenter) tout en adressant les problématiques d’adaptation (TOS actif) des éléments excités. Ceci est permis grâce à la présence d’éléments parasites qui permettent de gérer la diffusion des couplages sur l’antenne. Cette thèse décrit le principe du concept hybride et propose une évaluation de ses potentialités. Par la suite, une définition des éléments à mettre en œuvre pour réaliser une preuve de concept est effectuée, en mettant l’accent sur l’importance de la caractérisation expérimentale. Les performances d’un prototype d’antenne hybride reconfigurable sont ensuite présentées afin de valider les développements et conclure sur cette solution innovante. / The work of this thesis aims to investigate a new concept of reconfigurable antenna allowing a good trade-off between performances, complexity and cost. This concept is called ‘hybrid’ because it is based on the capabilities of thinned arrays and parasitic element antennas. It is an alternative to classical antenna arrays and their complexity. The proposed concept has a modular architecture, and a good versatility for reconfigurable beams. The main advantage of this hybrid antenna is the simplicity of its beam formation network (BFN) which requires only a few number of excited elements. The antenna uses parasitic elements to manage the effects of couplings between the electromagnetic access. The problematic of active VSWR is also solved at the antenna level, avoiding the use of additional components in the BFN. This work details the principle of the reconfigurable hybrid antenna concept. The potentialities are evaluated. The elements required to realize a proof of concept are then defined, using a dedicated experimental setup. A prototype is manufactured and the performances have been checked to validate this innovative concept.

This thesis is concentrated on the Angle / Direction of Arrival (A/DOA) estimation and Beamforming techniques that can be used in the current and future engineering applications such as tracking of targets, wireless mobile communications, radar systems, etc. This thesis firstly investigates different types of AOA and beamforming techniques. A comprehensive comparison between the common AOA algorithms is performed to evaluate the estimation accuracy and illustrate the computational complexity of each algorithm. The effect of mutual coupling between the radiators and the impact of the position-error of the antenna elements on the estimation accuracy is also studied. Then, several new efficient AOA methods for current wireless localisation systems are proposed. The estimation accuracy and computational complexity are compared with well-known AOA methods over a wide range of scenarios. New methodologies for Covariance Matrix (CM) sampling are proposed to enhance and improve operational performance without increasing the computational burden. A new beamforming algorithm is proposed and implemented on a compact mm-Wave linear and planar antenna arrays to enhance the desired signal and suppress the interference sources in wireless communication systems. The issue of asset tracking in dense environments where the performance of the Global Positioning System (GPS) becomes unavailable or unreliable is addressed in the thesis as well. The proposed solution uses a low-profile array of sensors mounted on a finite conducting ground. A compact-size omnidirectional spiral sensor array of six electrically small dual-band antenna elements was designed to operate in the 402 and 837 MHz spectrum bands. For the lower band, a three-element superposition method is applied to support the estimated AOA whereas six sensors are considered for the higher band. An efficient and low complexity Projection Vector (PV) AOA method is proposed. An Orthogonal Frequency Division Multiplexing (OFDM) modulation is integrated with the PV technique to enhance the estimation resolution. The system was found to be suitable for installation on top of vehicles to localise the position of assets. The proposed system was tested to track non-stationary objectives, and then two scenarios were investigated: outdoor to outdoor and outdoor to indoor environments using Wireless In-Site Software. The results confirm that the proposed tracking system works efficiently with a single snapshot. / Higher Commission for Education Development (HCED) in Iraq Basra Oil Company Ministry of Oil