Array Pattern Synthesis And Adaptive Beamforming

The applications of antenna arrays can be found in many areas such as radar, sonar and wireless communications. Pattern synthesis and adaptive beam-forming are the key technologies in array antennas systems, and have been widely used in interference suppression and parameter estimation.In the literature for adaptive antennas so far, little attention has been paid to circular array topologies despite their ability to offer numerous advantages. An obvious advantage results from the symmetry of the UCA structure. Due to the fact that a UCA does not have edge elements, directional patterns synthesized with a UCA can be electronically rotated in the plane of the array without significant change of the beam shape.Most pattern synthesis and adaptive beam-forming algorithms are developed with the assumption that the elements are omni-directional, but it is not the fact, and it results fail of a lot of algorithms as the elements are directional. Meanwhile, the directional elements can be used to increase the frequency bandwidth performance in some arrays such as circular array, but it is not all.Supported by National Science Foundation of P. R. China and Southwest China Research Institute of Electronic Equipment, the thesis discussed the performance of several popular pattern synthesis and adaptive beamforming algorithms under variety arrays. According to the characteristic of the directional element, the article analyzed the influence of directional elements on DOA estimation performance and some valuable conclusions have been obtained. Proposed a directional element based pattern synthesis algorithm using DFT approach. Besides, the effect of directional elements on array pattern synthesis and adaptive beamforming was deeply studied.The thesis can be divided into several parts as follows:In the first part, we firstly introduce the prepare knowledge of array pattern synthesis, and then have an overview of traditional pattern synthesis and adaptive pattern synthesis, compare the advantages and disadvantage of various algorithms. Specially, we analyze a simple and efficient pattern synthesis method using a discrete Fourier transform (DFT) approach.In the second part, the article analyzed the influence of directional elements on DOA estimation performance. The simulation suggests that the estimation performance is related to the direction of arrival, when direction deviation of arraynormal |a#| < 30", we still might obtain accurate DOA estimation, even if exist angle-dependent error, the phenomenon is useful from the practical application point of view. Besides, we studied the array pattern synthesis with directional elements, proposed a pattern synthesis algorithm based on directional elements using DFT approach, theoretical analysis and computer simulations were given. The results indicate that the method can improve the frequency bandwidth performance effectively. Furthermore, it is very simple and computationally efficient, as it is suitable for implementing FFT algorithms, especially when the number of elements is large. Thus, the algorithm is strongly practical valuable.In the third part, we firstly introduced the principle and criterions of adaptive beamforming, compared the advantages and disadvantage of various algorithms. In this part, the effect of directional elements on array pattern synthesis and adaptive beamforming was deeply studied. It is showed that the introduce of directional elements has effectively improved the beam-pattern of the circular array, reduced the sidelobe level, deepened the adaptive null depths and enhanced the receipt and anti-jamming ability of the antenna systems. However, the improvement is traded by the relative increase of sidelobe level and reduction of array gain.