入射平面波复射线展开精度的分析

从复射线展开表达式出发,通过参数变换,得到了入射平面波复射线展开拟合精度的单变量表达式,利用该式对展开面上及离开展开面后的拟表度进行了系统的讨论,建立了一种系统分析入射平面波复射线展开精度的方法。这一方法有助于建立通用的任意目标散射复射线分析软件。     

用复射线展开法计算目标散射场的误差特性分析

复射线展开法是计算目标散射场的一种简捷的方法,其可靠性有赖于对误差特性的系统研究。本文以平面波谱积分为散射场计算的参考标准,以L2空间中由范数定义的距离作为复射线展开法计算结果的误差,从而得到了复射线展开法在目标散射场计算中的误差特性,找到了减小误差的方法并给出这一方法的适用范围。     

用复射线展开法计算目标散射场的误差特性分析

复射线展开法是计算目标散射场的一种简捷的方法，其可靠性有赖于对误差特性的系统研究，本文以平面波谱积分为散射计算的参考标准，以Ｌ＾２空间中由范数定义的距离作为复射线展开法计算结果的误差，从而得到了复射展开法在目标散射场计算中的误差特性，找到了减误差的方法并给出这一方法的适应范围。     

瞬态矢量平面波的三维复源脉冲波束展开

本文导了了瞬态矢量平面波三维复源脉冲波束平行射线展开的完整公式，并得到了展开截断误差，离散化展开误差与总误差的表达式。这种展开适用于任意脉冲信号。通过选择复源参量，展开间距与展开半径，可使其在从展开面到最大展开距离之间规定的半径范围内，空间各处的合城场处处满足给定误差要求。     

基于复射线方法的导电平板散射问题分析

本文通过建立导电平板反射场分析模型,利用复射线方法特别是角域中的复射线近轴近似方法,有效地实现了导电平板在整个后向范围内散射场的计算,同时计算精度可以由复射线展开参数ξ来加以控制.有关的数值计算结果及其与参考解的比较证实了本文所用方法的正确性和有效性,以及所具有的推广应用价值.     

用复射线展开法分析目标的雷达截面

本文根据复射线分析和场的高斯波束展开,提出了一种计算复杂目标电磁散射特性的简便方法。由于复射线法不受目标形状的限制,因此该方法可用于任意形状的目标。本文以矩形进气道为例,进行了雷达截面分析计算,并将计算值与测试值比较,结果表明这种方法是可行的。     

平面波的复射线束展开

本文在高频渐近意义下，导出了平面波的复射线束展开系数公式，从而为已得到成功应用的平面波复射线束拟合展开提供了理论依据。     

平面波的复射线束展开

本文在高频渐近意义下,导出了平面波的复射线束展开系数公式,从而为已得到成功应用的平面波复射线束拟合展开提供了理论依据。     

复射线理论在电磁散射和雷达截面分析中的应用

复射线理论为高频电磁波在各种复杂环境中的传播和散射提供了一种简便而有效的分析方法。本文讨论了自由空间的复射线场,在单层界面上的反射和折射,通过分层媒质的多次反射和传输,在乎界面上的全反射和临界反射,在结构边缘上的绕射,复射线展开和叠加,以及用复射线法计算目标的雷达截面等。文中还给出了某些数值计算结果。     

复宗量菲涅耳积分的计算及其性质

复宗量菲涅耳（Ｆｒｅｓｎｅｌ）积分的计算，是有耗介质劈电磁散射中遇到的一个难题。本文综合运用了复宗量菲涅耳积分的小宗量级数展开和大宗量渐近展开，并且找到了大宗量展开与小宗量展开的衔接部，圆满地解决了菲涅耳积分在整个复平面内的计算机计算问题。本方法计算速度快，精度高。此外，本文还研究了菲涅耳积分在复平面上的对称性、零点等性质，给出了菲涅耳积分在复平面上的三维立体图和二维等值线图。     

Note on a new computational data smoothing procedure suggested by minimum mean square error estimation

Computational procedures for obtaining minimum mean square error estimates of parameters are developed for the case in which the observation functions, describing the dependence of observed data on the unknown parameters, can be accurately approximated by expansions through quadratic terms in the unknown parameters. Analytical closed-form solutions are obtained for the minimum mean square error estimates of real valued functions of the unknown parameters. It is pointed out that even in cases where the statistical assumptions are not satisfied the resulting computational procedures may be applicable. In such cases adequate, although nonoptimum, estimates may still be obtained and the computational procedure may be more convenient than iterative least-square methods.     

Nonlinear error modified equalization algorithm in high-order modulation of satellite communication

Aiming at the larger computation and the slower speed of nonlinear error compensation of traditional equalization algorithms,the fast nonlinear error equalization algorithm with amplitude and phase separation was constructed.It combined the feedback equalization to reduce the computational complexity respectively.In order to eliminate nonlinear interference and memory interference,the algorithm utilized the Volterra model to modify the error and it was adapted to update the feedback equalization parameters.The theoretical analysis and simulation compared proposed algorithm and existing conventional equalization algorithms from the bit error rate,convergence speed and computational complexity.The results show that the computational complexity is only equivalent to 14.1%～24.9% of other algorithms and proposed method can cancel the nonlinear interference quickly.     

Mixture Model- and Least Squares-Based Packet Video Error Concealment

A Gaussian mixture model (GMM)-based spatio-temporal error concealment approach has recently been proposed for packet video. The method improves peak signal-to-noise ratio (PSNR) compared to several famous error concealment methods, and it is asymptotically optimal when the number of mixture components goes to infinity. There are also drawbacks, however. The estimator has high online computational complexity, which implies that fewer surrounding pixels to the lost area than desired are used for error concealment. Moreover, GMM parameters are estimated without considering maximization of the error concealment PSNR. In this paper, we propose a mixture-based estimator and a least squares approach for solving the spatio-temporal error concealment problem. Compared to the GMM scheme, the new method may base error concealment on more surrounding pixels to the loss, while maintaining low computational complexity, and model parameters are found by an algorithm that increases PSNR in each iteration. The proposed method outperforms the GMM-based scheme in terms of computation-performance tradeoff.     

Symmetrized Split-Step Fourier Scheme to Control Global Simulation Accuracy in Fiber-Optic Communication Systems

Analytical expressions involving both system parameters and step-size are proposed to represent the local simulation error for the symmetrized split-step Fourier (SSSF) simulation method. This analytical expression can be used for a step-size selection rule to achieve comparable local simulation accuracy for SSSF simulations. This can lead to computational savings since there is no waste of computation in each simulation step. Furthermore, based on the local error expression, scaling rules are derived to achieve comparable global simulation accuracy for wide ranges of key system parameter values. This is significant in enhancing the computational efficiency in optical fiber communication system design and optimization. Extensive validation tests were performed to explore the application range of the proposed step-size selection and scaling rules. The desired global accuracy can be achieved with the use of our local error expression and scaling rules by only a couple of test trial simulation runs for a variety of practical applications.     

PCM遥测帧同步技术性能分析

在分析假同步和漏同步现象的基础上,介绍了脉冲编码调制(PCM)遥测帧同步工作的三态逻辑转换过程,通过进一步简化搜索态重叠区假同步概率计算公式,重新对搜索态和校核态的帧同步工作性能指标进行理论建模和仿真,根据仿真结果对影响帧同步性能的相关因素和参数进行讨论,为帧同步参数设计提供参考。     

一种甚低速率语音编码的抗误码算法

为满足在高误码率的窄带信道上进行语音通信的需求，本文研究了一种适用于甚低速率语音通信的抗误码参数估值算法。在一定的解码状态下，声码器通过计算最小均方误差（MMSE）估计的方法估计最优参数，充分降低信道误码对重建语音质量的影响。对于解码状态参数，通过计算最大后验转移概率的方法作最佳估计，并给出了一种简化的计算方法。这种抗误码算法复杂度低。计算机仿真结果表明，在不同误码率下该算法恢复出的语音的平均谱失真（ASD）低于帧删除方法的谱失真最大可达0.4dB。     

A constraint-length based modified Viterbi algorithm with adaptiveeffort

A modified Viterbi (1971) algorithm for convolutional codes is described that provides for signal-to-noise ratio (SNR) adaptive computational effort. The algorithm has three levels of prioritized effort. Movement from one level to the next is controlled by parameters that can be selected according to desired output bit error rate performance. For 3-bit soft decision detected signals, a coding gain within 0.06 dB of Viterbi at a 3-dB SNR is achieved for the same constraint-length code with modest parameter values and computational effort. At values of SNR above 6 dB, the algorithm decodes with very low computational effort. Effort levels are controlled by spanning the decoding trellis in steps that are one constraint-length long     

径向点插值法局部形参的改进校准方法

径向点插值法（Radial Point Interpolation Method,RPIM）中基函数形参、支持域大小和平均节点间距等因素直接影响算法的精度与计算效率,而过小形参会引起插值不稳定现象.针对此问题,提出一种基于局部形参校准法（Local Shape Factor Calibration Method,LSFCM）改进的形参优化算法,研究RPIM应用于电磁场问题中插值精度的影响因素,在不同形参、支持域大小和节点距离时的全局均方根插值误差曲线上,根据插值精度和计算效率灵活选择全局形参,简化形参设置与节点插值计算过程,提高计算效率.数值试验结果验证了所提方法的有效性.     

测量光伏探测器PN结品质因子与反向饱和电流的方法

由于制造工艺和生产条件的不同,光伏探测器的特征参量结品质因子和反向饱和电流有很大差别。提出一种PN结特征参量的间接测量方法,并对该测量方法所用的数值计算方法的收敛性进行数学证明。提出了两个使用开路电压和短路电流计算光电池PN结品质因子和反向饱和电流的简化解析计算公式。与迭代法的计算结果相比,使用简化解析计算公式得到的结品质因子和反向饱和电流的相对误差分别为0.03%和0.25%;与实验结果相比,使用迭代法计算结果的开路电压值的相对误差不小于0.3%。