In this thesis, a Neural Network (NN) based beamforming algorithm is proposed for real time target tracking problem. The algorithm is performed for two applications, linear and cylindrical arrays. The linear array application is implemented with equispaced omnidirectional sources. The influence of the number of antenna elements and the angular seperation between the incoming signals on the performance of the beamformer in the linear array beamformer is studied, and it is observed that the algorithm improves its performance by increasing both two parameters in linear array beamformer. The cylindrical array application is implemented with twelve microstrip patch antenna (MPA) elements. The angular range of interest is divided into twelve sectors. Since three MPA elements are used to form the beam in each sector, the input size of the neural network (NN) is reduced in cylindrical array. According to the reduced size of NN, the training time of the beamformer is decreased. The reduced size of the NN has no degradation in forming the beams to the desired directions. The angular separation between the targets is an important parameter in cylindrical array beamformer.

For a linear array, the excitation coefficients of each element and its geometry play an important role, because they will determine the radiation pattern of the given array. Side Lobe Level (SLL) is one of the key parameters to evaluate the radiation pattern of the array. Generally speaking, we desire SLL to be as low as possible. For the linear array with uniform spacing, there are some classic methods to calculate the excitation coefficients to make the radiation pattern satisfy the given requirements. For the linear array with non-uniform spacing, linear programming and particle swarm optimization are proposed to calculate the excitation coefficients to make the array get minimum SLL in this thesis. They are demonstrated for symmetric and asymmetric array in the first part of this thesis. In the second part of this thesis, a simple method is proposed for correcting excitation coefficients of a linear phased array. This proposed method corrects the coefficients through using the Normalized Least Means Squares(NLMS) algorithm, dither signal and a near-field sensor being used for sensing the field emitted by the array. The advantage of this proposed method is that it avoids the problem of estimating the largest eigenvalue of the coefficient matrix to get optimal step size. Its robustness in different environments is demonstrated as well as the effect of noise with various Signal-to-Noise Ratio (SNR), and mutual coupling. In addition, the effect of using discrete dither signal to the array is considered, because the continuous dither signal cannot be generated in practice.

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Series-fed printed slot antenna arrays excited by microstrip lines are low profile, easy to manufacture, low cost structures that found use in applications that doesn&rsquo / t require high power levels with having advantage of easy integration with microwave front-end circuitry. In this thesis, design and analysis of microstrip line fed slot antenna arrays are investigated. First an equivalent circuit model that ignores mutual coupling effects between slots is studied. A 6-element array is designed by using this equivalent circuit model. From the measurement and electromagnetic simulation results of this array, it is concluded that mutual coupling effects should be considered in order to achieve a successful design that meets the design specifications related to the main beam direction and sidelobe levels of the antenna. Next, an improved equivalent circuit model proposed for stripline fed slot antenna arrays is studied. It is observed that, the mutual coupling effects are incorporated into the equivalent model through the utilization of active impedance concept. Finally, the design equations proposed in the improved equivalent circuit model are derived for the microstrip line fed slot antenna array structure. To demonstrate the validity and the accuracy of the derived design equations, results obtained by the proposed analysis method are compared with simulation and measurement results. It is concluded that the proposed method successfully predicts the radiation pattern of the array by including the mutual coupling effects.

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Milieu où les ultrasons se propagent environ 10% plus rapidement qu’au sein des tissus environnants, le cristallin est connu pour être la source majeure d’aberrations de phase du milieu oculaire. De fait, l’échographie ophtalmique trans cornéenne est affectée par ses effets qui se manifestent sur les B-scans par une dégradation marquée de la résolution spatiale et du contraste, accompagnée de plus, d’importantes distorsions, particulièrement notables au niveau du fond de l’œil. Face à ce problème et en vue de l’arrivée prochaine de barrettes US HF dans la pratique ophtalmologique, un beamforming adapté a été développé au cours de cette thèse. Basé sur un lancer de rayon à 2 points fixes, il permet le calcul de délais de focalisation qui compensent les aberrations induites par le cristallin, en prenant en compte les effets réfractifs à son interface avec les humeurs. Les résultats obtenus in vitro et ex vivo avec une barrette 20MHz et un échographe de recherche (ECODERM) sont rapportés. / In ophthalmic ultrasonography the crystalline lens is known to be the main source of phase aberration, as ultrasounds (US) propagate about 10% faster than in the surrounding intra-ocular medium. Hence, it impairs significantly both spatial and contrast resolution of axial B-scans, and in addition causes important distortion, especially on the ocular fundus. To deal with this issue and in view of the next coming of US arrays in ophthalmologic practice, we developed in this thesis an adapted beamforming (BF) free from crystalline lens aberrations. It lies on a two point ray tracing approach to compute focusing delays that take into account crystalline lens aberrations including refraction at the interface. Initially developed considering a uniform US velocity in the lens, the adapted BF has been extended to consider the velocity gradient that exists in the real lens. In vitro and ex vivo results obtained with a 20 MHz linear array driven by a US research scanner (the ECODERM) are reported.

The aim of the master thesis is to sum up theoretical information about beamforming methods of microphone arrays and to verify their functionality. At the beginning of this work there are simulated different varietes of linear uniform and nonuniform microphone arrays and circular arrays. The results are verificated by a practical measurement in ideal conditions. Then I will focuse on implementation of the DAS(Delay And Sum), SAB(Sub Array Beamforming), CDB(Constant Directivity Beamforming), CDB-CA(CDB-Circular Arrays) beamformer including theoretical and practical verification of the functionality in ideal conditions. At the end of this thesis are all beamforming methods compared with each other at SNR(signal to Noise Ratio) and directivity parameters.