BEAM STEERING IN SMART ANTENNAS BY USING LOW COMPLEX ADAPTIVE ALGORITHMS

Array antenna systems are often used to enhance the received signal to interference and noise ratio when the signal operates in heavily jammed environment. Proper modeling of the received data at different antenna elements is important when evaluating the performance of this system, especially when both the signal and interference have wide frequency bands.. The antenna output is the linear combination of data from all the antenna elements. In conventional narrowband beam forming, time sequences at different antenna elements are related by some fixed phase shift. The phase shift is determined by the wave forms direction of arrival (DOA). In this paper, an efficient method for the pattern synthesis of the linear antenna arrays with the prescribed nulling and steering lobe is presented. The proposed method is based on Least Mean Square (LMS) algorithm provide a comprehensive and detailed treatment of the signal model used for beam forming, as well as, describing adaptive algorithms to adjust the weights of an array. In order to improve the convergence rate of LMS algorithm in smart antenna system, in this paper we proposes a new normalized LMS (NLMS) algorithm, This new algorithm can be treated as a block based simplification of NLMS algorithm which gives satisfactory performance in certain applications in comparison with conventional NLMS recursion, i.e., BBNLMS algorithm. By taking advantage of spatial filtering, the proposed scheme promises to reduce the bandwidth required for transmitting data by improving convergence rate. The performance of the BBNLMS algorithm in the presence of Multi-path effects and multiple users is analyzed using MATLA