Research On Design Of Satellite Smart Antenna

With increasing demands for high level communication quality, researchers are attracted by extraordinary advantages of smart antenna. By studying the smart antenna technique for decades, it has become one of the most popular communication approaches nowadays. An adaptive beam forming technique is a core to implement smart antenna system where a single beam is shaped by weighting and summing the antenna outputs. In another words, the smart antenna term is based on the system in which a system using an antenna array together with a processor that can adjust the radiation pattern to the desired user and at the same time place nulls towards interference sources. This thesis is aimed at designing a spaceborne smart antenna system to overcome complex satellites communication environment.The the first section of the thesis is to introduce the research background, study processes and demands for satellite smart antenna. In addition, the research contents of the thesis are arranged in this part.In the second section, the research processes and the theory of satellite phased array antenna are presented. According to a mathematic model of uniform linear array, radiation patterns in different parameters are obtained. And using Monte Carlo method, amplitude errors and phase errors of the linear array are analyzed and estimated.In the third section, basic concept, classification, operational principle and fundamental structure of smart antenna system are discussed. The popular criteria of the adaptive beam-forming, such as MMSE, MAX-SIR, MV and LS, are described. The performance function and optimal weights of the criteria are compared. On the basis of criteria, LMS and RLS algorithms are illustrated and they are simulated by Matlab program. The results of simulation indicate that beam former using LMS is capable to output the desired signal and the convergence rate of LMS is slower than RLS.For most adaptive beam-forming algorithms, the Direction of Arrival(DOA) is prerequisite information, which is important for smart antenna system. In this section, the classical DOA algorithms, such as Bartlett estimation method, Capon estimation method, MUSIC algorithm etc., are introduced. According to those estimation methods, spatial pseudo-spectrums are calculated using Matlab. For searching the peak level of these pseudo-spectrums, direction of arrival can be obtained. The spatial pseudo-spectrum produced by MUSIC show that the MUSIC algorithm is capable to place nulls towards interference so that noise interference between satellite communication can be attenuated and restrained.