الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Digital beamforming approach attracts a lot of interest these days because it has the ability to greatly expand the capacity of mobile communication networks. It’s a type of signal processing that optimizes the radiation pattern based on a set of criteria, such as main beam steering, pattern nulling, minimizing mean square error (MSE), and optimizing the signal to interference and noise ratio (SINR). This thesis introduces new beamforming algorithms for linear antenna array (LAA), planar antenna array (PAA), and elliptical cylindrical antenna array (ECAA). At first, new distributed beamforming techniques based on an optimized elliptical arc geometry (EAG) are referred to as single ellipse-EAG (SE-EAG), double ellipses-EAGs (DE-EAG), and double ellipses-EAG with optimized energies (DE-EAG-WOE) are introduced. The proposed beamforming algorithms permit the radiated field from the array elements to add constructively towards the main beam direction and destructively towards the opposite direction, which minimizes the back lobe level without affecting the half power beam width (HPBW) of the main beam. The back lobe mitigation enhances array gain while reducing high back lobe interference levels. As a result, the signal to interference ratio (SIR) of the desired wireless communication system is significantly improved. The back lobes are reduced in the SE-EAG and DE-EAG techniques by applying the particle swarm optimization (PSO) methodology to optimize the elliptical arcs’ minor axes and the elements’ angular distributions. The transmission energies of the elements are maintained the same as that of the original LAA. While the DE-EAG-WOE beamforming approach is developed for further back lobe reduction, where the elements’ locations are optimized using PSO and the II elements’ transmission energies are estimated using the least square mean (LSM). Secondly, a new optimized quadrant pyramid antenna array (O-QPAA) structure is proposed for the back lobe minimization of planar antenna arrays (PAAs). The QPAA is observed as a combination between LAA and uniform squared antenna arrays (SAA) or rectangular antenna arrays (RAA), as it’s supposed to be made up of many concentric co-planar SAAs or RAAs in the XY plane. These concentric SAAs or RAAs are placed vertically along the Z-axis with identical vertical spacing to construct a QPAA. For back lobe cancelation, the O-QPAA structure is presented, which minimizes the back lobe while maintaining control over QPAA pattern properties, including side lobe level (SLL) and half power beamwidth (HPBW). In this O-QPAA structure, the particle swarm optimization (PSO) technique is used to find the optimal values for the three primary QPAA parameters: vertical spacing, inter-element spacing inside each SAA or RAA, and the LAA excitations to construct the whole OQPAA radiation pattern. Thirdly, for elliptical cylindrical antenna arrays (ECAA), new virtual antenna array (VAA) based synthesis approaches are introduced for side lobe level (SLL) reduction, beam thinning, and the number of elements minimization. The proposed approach separates a single transmit/receive ECAA into a transmit linear antenna array (LAA) and a receive elliptical antenna array (EAA). Then, the PSO is used to optimize the number of antenna elements, element spacing, and excitations of the produced LAA and EAA to obtain superior beamformed patterns. Finally, the optimized virtual ECAA (V-ECAA) pattern is formed by applying the Kronker product of the optimized LAA and EAA patterns. In addition, the hyper beamforming is used to achieve further beam thinning and SLL reduction of the proposed V-ECAA. III