【作者】 周劼；

【导师】 李广军；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2013， 博士

【摘要】 多目标遥测系统是一个典型的无线多址通信系统，它采用直接序列扩频体制和基于阵列天线的数字波束形成技术组合的架构，可以综合利用码分多址和空分多址技术，实现多目标遥测系统的多址通信需求，而且直扩体制在时域频域的抗干扰能力与智能天线的空域滤波性能使得遥测系统具有更加优异的抗干扰性能。但是，与日常的蜂窝移动通信系统不同的是，遥测系统的功能架构往往要求更为简洁，加之为了充分挖掘遥测链路的潜力，系统必须在作用距离远、低信噪比的情况下完成信号的检测和捕获。在低信噪比输入的条件下，天线指向增益与伪码同步解扩增益的形成互为前提，本文就是围绕直扩体制与数字波束形成组合的多址通信技术架构，针对信号的空时二维联合捕获问题展开研究，重点对基于相关检测的空时联合捕获算法、空时二维搜索捕获算法和自适应空时二维捕获算法在多径入射和干扰条件下的性能进行了深入研究，取得了一系列创新性研究成果，论文的主要工作和创新点包括：1.重点围绕抗干扰性能，理论上分析和证明了自适应空时二维捕获算法自适应迭代求解的多值性，仿真验证了在低信干噪比时自适应算法迭代求解的发散特性，据此提出了两种改进算法，第一种是构建二维滤波器模型及代价函数，理论推导证明了该算法求解与原算法的期望解相同，且具有唯一性；第二种是在原算法中增加优化约束条件来剔除非期望的平凡解。两种算法均能在低信干噪比的条件下实现自适应迭代求解，正确收敛得到期望解。2.分析并仿真验证了基于相干检测空时联合捕获算法中归一化最小均方算法在低信干噪比条件难以正确收敛，针对此问题，提出并理论分析了一种改进算法，通过权值约束，实现解的唯一性，其对角加载特性保证了迭代解算具有更好的稳定性，仿真实验验证该改进算法对干扰有明显的抑制。3.提出了一种基于最大信干噪比准则的相干检测空时二维联合维捕获算法，在理论分析的基础上，进行了仿真实验，该算法在伪码相关检测的过程中就实现了空域滤波，能更好地抑制干扰，从而提高了信号捕获性能。4.针对空时二维搜索捕获算法，分析了基于协方差矩阵差分方法的信号波达方向估计方法，该方法降低了噪声影响，可以实现多径相干接收和空域非平稳噪声环境中的信号捕获。研究了将基于相关检测的方法用作估计波达方向，该方法能够适应更低的信干噪比，并分析了角度扩展条件对检测性能的影响，结合仿真实验结果，为角度扩展模型下的应用技术方案选择提供支撑。5.围绕空时二维搜索捕获算法的实现与试验，设计并实现一个八通道中频数字接收机，构建了一个双目标试验系统，开展了静态和直升机挂飞动态试验，试验结果表明算法的可行性与正确性，能够实现目标的有效捕获，为工程应用奠定了基础。更多还原

【Abstract】 Multi-target telemetry system is a typical wireless multi-access communicationsystem, which combines direct sequence spread spectrum with digital beamformingtechnology. It fulfills multi-access communication by using code division multi accessand space division multi access. Furthermore, the abilities of interference reduction ofspread spectrum communication and the advantages of spatial filtering of smart antennacan both be taken to enhance the interference resistance in the combined application.But being different from the cell phone communication systems, the telemetry systemalways has a simpler architecture for the same function as mobile communicationsystem, especially when the power of amplifier must be fully used to extend thedistance to the ultimate edge. Thus, the redundancy of the link is limited, the lowersignal-to-noise rate caused by the long distance and high spread spectrum gain must beconsidered for the detection and acquisition in signal processing. In such applications,the code acquisition and antenna beamforming can not be achieved without each other,so the spatial beamforming and tempotal code acquisition should be consideredsimultaneously, instead of being done separately. Thus, the two-dimention acquisition isthe focus of the thesis. Three kinds of algorithms are further researched, includingcorrelator-based joint acquisition, spatial and temporal serial search acquisition andadaptive spatial and temporal acquisition, several novel method and conclusion areachieved.The main achievement and innovations include:1. Aiming at interference suppression, the adaptive spatial and temporal acquisitionalgorithm is proved theoretically and by simulation to have more than one solution withpresence of interference. Thus, the iteration diverges instead of converging. To avoid theproblem, two novel algorithms are proposed, of which, one is based on a twodimentiaonal adaptive wiener filter model and subsequently a new suggested costfunction, which has only one solution being same as the original algorithm. The other isbased on one more constraint on the original cost function to avoid the undesired trivialsolution. The two novel algorithms have better iteration convergence and only one solution in low signal to interference and noise rate scenarios.2. Of joint acquisition algorithm based on correlators, the normalized least meansquare algorithm has more than one solution and probably diverges during iterration inlow signal to interference and noise rate scenarios, which is proved in simulation. Anovel algorithm is proposed and theoretically analysed to eliminate these defects, whichis based on the additional constraints on the weight vector. Simulations are presented toprove it has better performance of interference resistance.3. A novel joint acquisition algorithm based on correlators is proposed, whichadheres to maximum signal-to-interference-plus-noise rate criterion. Theoreticalanalysis and simulation results prove that the better performances of acquisition andinterference suppression can be achieved.4. In the serial search method, a direction of arrival estimation algorithm usingdifferential covariance matrix is studied. By forward/backward smoothing of covariancematrix, the noise is reduced and the direction estimation performance is improved,which is presented with theoretical analysis and simulaton. Angular spread is consideredfor code acquisition with antenna array. Analysis and simulation lead to the conclutionthat with diversity effects, the presence of angular can improve the code acquisition.5. A intermedium frequency digital receiver with eight channels is designed andfabricated. In addition, an experimental system with two targets is constructed,including a static model in which the source terminal is placed on a fixed spot and adynamic model in which the source terminal is palced on a flying helicopter. Theexperiment results verify the algorithm and the signal acquisition are effectivelyachieved.更多还原