【作者】 杨美英；

【导师】 王建英；

【作者基本信息】 西南交通大学 ， 信号与信息处理， 2008， 硕士

【摘要】 智能天线技术作为3G、B3G/4G移动通信中的关键技术受到了广泛关注,其借助现代数字信号处理技术,选择合适的自适应算法,动态形成空间定向波束,充分利用移动用户信号来抵消或最大程度地抑制干扰信号。同时,通过引入空分多址,和其他多址方式结合,有效地对抗系统的共信道干扰,大大降低了系统误码率,提高了系统容量和频谱利用率。本文主要研究了智能天线的核心技术——波束形成算法。主要工作包括:1.对智能天线和波束形成技术进行了简单地介绍,分析比较了几种常用的波束形成准则和算法,并分别给出了各算法的仿真及性能分析。2.针对现代通信信号的宽带和非平稳特性,分析了已有的宽带非平稳信号波束形成算法的性能,包括基于时域、频域和一般变换域的方法,总结了它们各自存在的主要问题。在此基础上,建立了该类信号的典型模型——宽带线性调频(LFM)信号,提出了一种基于分数阶Fourier变换的宽带LFM波束形成算法。该算法充分利用LFM信号在分数阶Fourier域具有极高的紧致性,实现在分数阶Fourier域上的波束形成。仿真结果验证了该算法的有效性。3.考虑到智能天线的实际应用,本文将智能天线和正交频分复用(OFDM)技术结合,实现波束形成。首先针对目前应用于OFDM系统的波束形成算法——盲算法和非盲算法,分析了它们存在的问题。在此基础上,提出一种新的应用于OFDM系统的波束形成算法。该算法根据OFDM分组中前导字建立过完备原子库,从而获得期望信号到达角和导向矢量的估计。再通过稳健的波束形成算法,提高存在指向误差时波束形成器的性能。该算法不需要复杂的信道估计技术,也不受较少导频信道的影响。与基于训练序列的非盲算法相比,本文算法有着更低的系统误码率。更多还原

【Abstract】 Smart antenna technology has been concerned widely as a key technology in the 3G and B3G/4G mobile communications, which selects appropriate adaptive algorithms to form space directional beam dynamically by means of modern digital signal processing techniques, taking full advantage of mobile users signal to counteract or suppress the interference to the greatest extent. At the same time, by introducing space division multiple access and combing with other multiple accesses, smart antenna technology not only suppresses the co- channel interference effectively, and decreases bit error rate significantly, but also increases spectral efficiency and system capacity.This thesis mainly focuses on the core technology of smart antenna, the beamforming algorithm. The main work involves:1. The technologies of smart antenna and beamforming are introduced briefly; some common rules and algorithms are analyzed and compared, then the algorithm simulations and performance analysis are given.2. Aimed at the broadband and non-stationary character of modern communication signals, the performance of existing broadband and non-stationary beamforming algorithms are analyzed, using the methods based on time domain, frequency domain and the general transforming domain, and the problems of each method are summarized. On the basic of above, a typical signal mode—broadband Liner Frequency Modulation (LFM) signal model is established, and the beamforming algorithm of broadband LFM signal based on the fractional Fourier transform is proposed. This algorithm makes full use of the highly compact property of LFM on the fractional Fourier transform domain, and achieves beamforming on this domain. The simulation results verified the effectiveness of the algorithm.3. Considering the practical application of smart antenna, this thesis integrates smart antenna with the Orthogonal Frequency Division Multiple (OFDM) to achieve beamfomring. First of all, in the view of the current beamforming algorithm applied in OFDM system—blind algorithm and non-blind algorithm, some existing problems are analyzed. On the basic of those, a new bemforming algorithm for OFDM system is proposed. The algorithm projects the observations onto the over-complete dictionaries, which were built out of the preamble of OFDM frame, thereby obtains the estimation of DOA and steering vector of interested signal. Then through the robust beamforming algorithm, performance of the beamformer which has the directional error is improved. The algorithm does not need the complex channel estimation technology, neither affected by small number of pilot channels. Compared with the blind algorithm based on training symbols, the new algorithm has lower bit error rate.更多还原