【作者】 余平；

【导师】 杨士中；

【作者基本信息】 重庆大学 ， 电路与系统， 2003， 博士

【摘要】 陆地移动卫星通信系统在民用和军用通信领域都具有良好的应用前景。特种小卫星通信系统更以其高度的灵活性和低成本优势在远程情报采集、指令传递、人员调度等方面具有其它通信系统无法替代的作用。由于信道环境复杂，小卫星移动通信信号在本质上是多径传播，所以需要采用各种信号增强技术，以提高系统接收性能。前端采用自适应阵列天线的小卫星通信接收机，可通过一定的信号处理，从空间上区分信号和干扰，并且多个阵元还可获得分集增益，从而改善通信质量。基于自适应阵列天线的空分多址（SDMA）技术，是传统的时分多址（TDMA）、频分多址（FDMA）和码分多址（CDMA）的一种多址倍增技术，可进一步提高频谱的有效利用率，增大系统容量。在给定各阵元的取样数据后，自适应阵列天线信号处理的问题一般可以归结到三个方面：信号源数目的确定、波达方向（Direction of Arrival）的多用户检测和数字波束形成（Digital Beamforming，DBF）。这几个方面不是相互独立的，而是相互关联的。本人在查阅大量国内外相关科技文献资料的基础上，针对特种小卫星通信接收机中自适应阵列天线技术的有关技术问题做了以下几个方面的研究：（1）首先全面分析了信道中由于路径损耗和阴影效应而产生的大尺度衰落和由于多径效应而产生的小尺度衰落，并采用了一种适合特种小卫星移动通信系统的信道模型—全阴影模型；（2）在相关和非相关信号等条件下，对基于子空间的 MUSIC 方法的 DOA 估计性能进行了分析和仿真研究，并将其与传统的 DOA 估计方法进行了对比研究；（3）分析了 MUSIC 空间谱的谱峰的数值特征，采用了二次符号梯度算法来提取谱峰特征，并推导了谱峰特征提取的矩阵模型；在分析包含方位和俯仰信息的二维 MUSIC 空间谱的谱峰特征遍历搜索过程的基础上，采用了递归的格形搜索算法，确保了对二维 MUSIC 空间谱进行可靠而快速的谱峰搜索；（4）分析了数字波束形成的最佳权向量及其自适应调整的算法，并以数字波束形成（DBF）的理论为指导，针对小卫星多星测控问题，提出了对目标方位和俯仰二维方向进行自动跟踪的软天线系统的硬件实现结构。其中，考虑到工程可实现性，在充分利用了关于目标星空间位置的先验信息的情况下，采用了简便易行的梯度算法，保证了阵列输出权向量的自适应调整；（5）研究了一维 Rake 接收机的结构和性能，并将其与自适应阵列天线相结合，采用了一种二维 Rake 接收机结构。针对多用户多径情况下的 DOA 估计问题，采用了一种空时平滑算法。该算法能有效识别出各来波的 DOA，并将其与各用户 I<WP=6>自动分拣。与 FBSS 相比，该算法分辨力高，计算量小。更多还原

【Abstract】 The land mobile Satellite communication systems have a favorable commercial andmilitary application perception. The special type small satellite(STSS) communicationsystems with high flexibility and low cost can be used for remote information collecting,holding, and transferring, remote commands delivering, and remote personnel managing.The special role the STSS communication systems act as can’t be displaced by anyother communication systems. Because of the complex channel environment, thepropagation of the wave of the STSS communication system is essentially a kind ofpropagation via multi-path, so the signal enhancement techniques are necessary. Thereceiver with AAA (adaptive Array Antenna) can differentiate signals from each otherby their different spatial signature. Besides, the receiver can get diversity gain frommore than one element, so as to be helpful to improve the quality of communications.The SDMA (Spatial Divided Multi-Area) based on AAA can enhance the conventionalmulti-area techniques, e.g., TDMA, FDMA & CDMA, so the spectrum efficiency canbe improved and the capacitance of the communications system can be increased. Given the sampled data of each element, the signal processing of AAA consists ofthree parts: the determination of source number, the DOA (Direction of Arrival)multi-user detection and DBF (Digital Beamforming). They are not independent, butassociated with one another. Having read a lot of transactions in the area of interest, the author aims at thetechnologies on AAA based on STSS and makes efforts to study the problems below: (1) The author fully analyzed the large-scale fading, which is resulted by the pathlosses and the shadowing effects, and the small-scale fading because of the multi-patheffects. And the full-shadowing model, which is suitable for the channel of STSS, isadopted. (2) The author studies the DOA estimation performance of MUSIC algorithm in thescenario of correlated signals and uncorrelated signals, compares the performances ofMUSIC and that of the conventional methods, and gives the simulation results. (3) The author analyzes the characteristic of the peaks of MUSIC spectrum in thesense of numerical value, uses the signed gradient algorithm two times to extract thepeaks, and gives the matrix model of the process of peak searching. Based on theanalysis of the searching process of the peaks of the two dimensional MUSIC spectrum III<WP=8>which contains the information of azimuth and elevation of the signal of interest, theRecursive Grid Searching Algorithm is adopted to ensure the peaks being searchedfast ,effectively and reliably. (4) In order to solve the problem of simultaneous TT&C of multi-target, the authormakes use of the prior information of the spatial position of the small satellite of interestand designs the hardware structure of the tracking system with soften antenna based onthe theory of DBF, in which the gradient tracking algorithm is adopted for theengineering purpose; (5)The author studies the structure and performance of the Rake receiver. And thestructure of two dimensional Rake receiver, which combines the advantages of both theRake receiver and the AAA, is adopted. So the spatial-temporal smoothing algorithmcan be used to distinguish each DOA of different path of different user effectively, andthe DOA can be automatically grouped with the corresponding user. Compared with theFBSS method, the spatial-temporal smoothing method can achieve higher resolution.更多还原