一种用于单脉冲成像的自聚焦算法

本文针对单脉冲成像技术在实际处理中,鉴角曲线误差引起的方位分辨率下降问题,提出了一种用于单脉冲成像的自聚焦算法。算法通过迭代,自动从雷达接收数据中挑选孤立强散射点回波信号精确估计实际鉴角曲线,将其用于单脉冲成像处理中,实现图像方位自聚焦。仿真及实测数据处理结果表明,该方法能够有效降低测角误差对成像效果的影响,且对多数地貌场景数据具备鲁棒性,是一种实际可行的单脉冲成像自聚焦算法。     

ADAPTIVE MESH REFINEMENT METHODS FOR THREE-DIMENSIONAL INVISCID FLOW PROBLEMS

SUMMARY

The local grid refinement technique is incorporated into a finite volume program that solves the three-dimensional compressible Euler equations. The underlying idea is to improve the solution accuracy in domains of dominating physical flow features, thus avoiding a global fine mesh to resolve most of the smooth flow. An unstructured data system is introduced to manage point enrichment on multiple refinement levels for structured meshes of hexahedral cells. Grid adaption is utilized to cluster points automatically in domains of interest. The multi-block formulation permits the application of the refinement method to various external flow configurations.     

Shape Optimization for 3D Turbulent Flows Using Automatic Differentiation

Abstract

We present through this paper some new results with our approach for optimal shape design based on a CAD-free framework for shape and unstructured mesh deformations, automatic differentiation by program for the gradient computation and mesh adaption by metric control. Automatic differentiation allows for an easy, reliable and fast discrete adjoint computation. We managed to get the Jacobian of our Navier-Stokcs solver including a k-e turbulence model and wall-laws. The CAD-free framework is shown to be particularly convenient for optimization when the mesh connectivities and the shape discretization arc variable during optimization. Using these ingredients constrained optimization for turbulent transonic flows has been investigated in both 2 and 3D.     

PID神经网络在飞控解耦中的仿真研究

在进行飞行控制律设计时,为了获得好的控制品质,有必要对各输出量进行解耦,并且使控制器能根据被控对象动力学特性的改变而自适应调整。为此,介绍了两种PID神经网络解耦控制结构和一种神经网络辨识器,并分别给出了PID神经网络解耦控制器和辨识器的前向算法及反向传播算法;最后分别应用两种解耦方法针对飞机横侧向线性模型进行计算仿真,得到了两种解耦结果;证明了PID神经网络解耦控制的有效性,并比较了两种结构的优缺点。     

主/旁瓣干扰对单脉冲测角的影响分析

存在干扰的情况下,采用自适应阵列信号处理可以有效地抑制干扰.在对单脉冲特性曲线的影响因素进行分析的基础上,研究了基于单脉冲比的最大似然法角度估计算法及干扰情况下的单脉冲测角技术,对线性约束最小方差单脉冲算法进行了仿真分析,仿真过程中采用泰勒加权以降低和波束旁瓣.结果表明,将主瓣内的干扰置零,会导致和差波束的畸变.和差波束的畸变导致在单脉冲特性曲线中出现奇异值,奇异值将导致在一个检测单元内的角度估计模糊.     

基于复数经验模式分解的空中颤振目标成像

针对毫米波雷达照射条件下,逆合成孔径雷达成像过程中目标主体颤振引起的微多普勒效应对成像造成的干扰问题,在建立颤振目标成像模型、分析目标颤振对回波造成的微多普勒调制以及对成像的影响的基础上,提出了基于复数经验模式分解的颤振目标成像方法.该方法利用复数经验模式分解的自适应特性,将目标回波信号分解为多个不同频率的分量信号;进而采用复杂度的概念对各分量信号进行区分;并结合各分量信号所占的能量百分比,剔除微动信号分量,有效消除了由于目标颤振所造成的微多普勒调制.采用复杂度与能量百分比相互结合的方法有效地提高了准确度和空中颤振目标的成像质量.     

LTE上行接入技术研究

上行接入为用户设备UE（UserEquipment）接入网络提供上行支撑,是移动通信不可或缺的重要组成部分。优秀、高效的上行接入技术可以大大提高上行链路的频谱效率,增加系统容量,扩大覆盖范围,最大化的减小时延。本文通过对LTE（LongTimeEvolution）标准中上行接入技术的研究,较为全面地对LTE环境下上行接入进行了分析和介绍。     

The Performances of the Antennas in Active/Passive Compounded Guidance Part I: Broad-Band Antennas and Passive Direction-Finding Schemes

Part one of a two-part paper analyses the performances of the ultra broad-band antennas which are the key components in the broadband passive guidance in details. Two kinds of passive direction-finding schemes which have wide fields of vision are raised and analyzed in this part. Because of the uncertainty of the phase-centers of the antennas, the usual amplitude sun-subtraction monopulse technique can not be used to find the direction of a radiative source in a wide frequency range. A beam-operation network which can be used to form two secant beams from single broad-band spiral antenna is able to applied in the amplitude-monopulse system. An algorithm to eliminate the angle-confusion in the amplitude-phase monopulse direction-finding system is also studied.     

单脉冲雷达对目标源的检测研究

对于单脉冲雷达 ,当回波受到多个目标信号 (信号在频域、时域上不可区分 )的干扰时 ,得到的目标角到达方向 (DOA)不是所跟踪目标的真实信息 ,影响了系统对目标的可靠跟踪。本文在一种对回波是来自单目标还是两个不可区分目标的检测方法的基础上将其推广 ,应用到回波可能来自N个不可区分的目标。仿真表明 ,多目标情况下的检测概率不一定大于两个目标时的检测概率 ,处于间距最大上的两目标的信噪比对整个检测概率影响较大。     

平面相控阵天线和差分布馈电网络设计

大型单脉冲相控天线馈电网络的接收波束存在"和差矛盾"问题,传统的解决方案需要相当复杂的馈电网络和硬件成本。因此提出一种馈电网络设计方法,在获得接收和波束、方位差波束以及俯仰差波束低副瓣电平的同时,降低大型单脉冲相控阵天线馈电网络的复杂性。用该方法设计的3 000单元二维相扫平面阵列天线馈电网络,仿真结果为:接收和波束副瓣电平<-28 d B,俯仰差波束副瓣电平<-22 d B,方位差波束副瓣电平<-22 d B,仿真结果验证了该设计方法的有效性。