子阵模块不同排列对相控阵天线辐射特性的影响分析

辐射单元矩形栅格排列是相控阵天线中最简单的排列方式,也是最常用的一种排列方式。它是把整个阵面划分成许多矩形栅格,每个辐射元占据一个自然格或栅格的交点。而本文对子阵模块间采用三角形栅格而子阵模块内采用矩形栅格的排列方式进行了分析,通过理论分析验证这种排列方式比普通矩形栅格排列有较大优势。     

Solving Schrodinger Equation with Non-Uniform Grids by Scale Transformation Method

Quantum Mechanical Effects(QMEs) in MOSstructures are well-known in the deep-submicron ULSI device characterization[1— 3] .Rigorous study of QMEs in the MOSinversion and accumulation layer requires self-consistent solution to Schrodi...     

用于双反射面天线分析的网格合并方法

提出一种新的反射面网格构造方法——网格合并方法，它在保证精度的同时，很大程度上缩短了物理光学方法的计算时间。通过与等角网格、方形网格、匹配点网格的对比，说明了网格合并方法的优点，最后给出了一个用网格合并方法分析卡塞格仑双反射面天线的实例。     

同轴馈电耦合微带贴片天线的时域有限差分法分析

提出一种融合曲线坐标和直角坐标的区域网格划分方法。在同轴线区域采用曲线坐标网格,用以代替传统的阶梯剖分,在其它区域及边界上采用直角坐标网格,从而极大地提高了计算效率。同时,在时域有限差分法中还采用了非均匀网格划分,PML吸收边界和Prony外推法等技术,对同轴馈电的耦合微带贴片天线进行了分析。     

基于网格剖分的协方差交集融合新算法

针对协方差交集的最优融合问题,提出了一种基于网格剖分的协方差交集融合新算法。该算法首先利用几何法对位置空间进行网格剖分,求出局部航迹协方差椭圆所包含的网格集合;其次,对所有的网格集合进行与运算,求出局部航迹协方差椭圆所包含的公共网格集合;最后,利用公共网格集合逼近协方差椭圆的交集,求出融合估计值。蒙特卡罗仿真试验证明,该方法能有效提高相关误差航迹的融合精度。     

基于对称复镜象法接地网接地电阻的算法

对称复镜象法是一种适用于非均匀土壤中任意结构接地网接地参数精确计算的新方法。但是在应用对称复镜象法计算接地网接地电阻时,需要假定总的泄漏电流,由此得出每个单元的泄漏电流和地网电位升,进而得到地网接地电阻。本文基于此提出了一种新的优化算法,将对称复镜象法与直接矩阵法结合,在考虑了地网电阻系数矩阵的对称性的基础上通过矩阵变换直接求出接地电阻,不必假设总的泄漏电流,从而节省了计算时间,并提高了计算精度。     

Validity and Accuracy of Equivalent Circuit Models of Passive Inductive Meshes. Definition of a Novel Model for 2D Grids

Accuracy of equivalent circuit models of periodic grids is investigated in amplitude and phase in the visible region. The grids studied here are one-dimensional (1D) and two-dimensional (2D) inductive thin metal meshes. They are located in free space and are illuminated by a plane wave under normal incidence. The range of validity and the accuracy of conventional circuit models are defined by comparison with rigorous results obtained with the Finite-Difference Time-Domain (FDTD) method. In particular, it is shown that electrical models of 1D grids are accurate, whereas equivalent circuits of 2D grids should be used very cautiously. Then, a new formulation is proposed to overcome this major drawback. In the non-diffraction region, the agreement between our model and the FDTD results is within 2% for the power reflectivity and 1° for the phase over a very wide range of strip widths.     

基于小波的多重网格方法

本文将小波的多分辨率分析和多重网格方法结合起来，提出了一种基于小波的多重网格方法，它将小波的尺度空间作为多重网格法的粗网格局，以小波变换作为粗细层间的信息转换，解决了多重网格法中构造粗网格层和选择合适的层间转换算子的困难，因为小波理论自身具有一套完整的体系，粗网格层和转换算子的生成都是自动的，所以这种方法在很多情况下可以作为一种黑匣子算法。     

基于面元模型的FDTD网格及涂敷层网格生成技术

提出了一种基于面元模型的FDTD网格剖分技术和涂敷层网格的生成技术。这种网格剖分技术可以方便地剖分封闭的面元模型和实体模型。针对均匀涂敷复杂模型难以直接产生的问题,提出在FDTD网格模型基础上,生成涂敷网格模型的方法。这种方法很容易得到任意复杂FDTD网格模型的涂敷层网格模型,克服了复杂表面模型和实体模型直接产生涂敷模型的困难。     

Phase unwrapping by means of multigrid techniques forinterferometric SAR

Weighted least squares phase unwrapping is a robust approach to phase unwrapping that unwraps around (rather than through) regions of corrupted phase. Currently, the only practical method for solving the weighted least squares equations is a preconditioned conjugate gradient (PCG) technique. In this paper the authors present a new method for weighted least squares phase unwrapping. Their method is a multigrid technique that solves the equations on smaller, coarser grids by means of Gauss-Seidel relaxation schemes and transfers the intermediate results to the finer grids. A key idea of their approach is to maintain the partial derivatives of the given phase data in separate arrays and to correct these derivatives at the boundaries of the coarser grids. This correction maintains the boundary conditions necessary for convergence to the correct solution. Another key idea of their approach is to transfer the weighting values to the coarser grids in a carefully defined manner. They also present methods for defining the initial phase weights in an automated fashion. The resulting multigrid algorithm converges in only one or two multigrid cycles and is generally 15-25 times faster than the PCG technique     

一种制作W波段自立式线栅极化器的新方法

设计并制作了一个W波段的极化器,设计参数为金属丝直径100 μm,间距300 μm.实测结果表明,金属丝直径和间距的均值分别为100.3 μm,300.2 μm;标准差为5.2 μm,8.3 μm,表明极化器具有较高的加工精度和良好的均匀性;同时其表面平整度优于30 μm.另外,测试了极化器的透射系数以及极化器作为可变衰减器时的透射系数,测试结果与理论计算结果具有良好的一致性,具有良好的极化性能.     

一种基于自适应网格剖分的协方差交集融合新算法

针对分布式航迹融合问题,提出了一种基于自适应网格剖分的协方差交集融合新算法。首先,自适应计算网格剖分误差上限;其次,利用网格剖分法求出局部航迹协方差椭圆的交集;最后,利用交集中心求出融合航迹估计值。通过仿真试验,该算法能自适应估计网格剖分步长上限,提高融合精度。     

高速集成传输线不连续性的全波分析

本文通过多项式近似导出了一种可变网格的时域有限差分算法,其空间网格的大小能沿任意轴向变化,而且具有高阶离散精度,从而节省了机时,提高了计算精度。并首次应用于高速集成传输线变角度拐角的全波分析。本方法简化了以往方法的分析过程,其结果与有关文献相一致,从而验证了算法的可靠性和有效性。     

飞机尾流RCS计算中的网格剖分技术

飞机尾流雷达散射截面(RCS)通常可通过求解尾流的被动保守量和介电常数分布,对尾流区域的电场积分得到。实现尾流区域离散化处理,现有方法一般采用满足被动保守量求解精度要求的非均匀网格剖分技术。由于该剖分存在大量尺度与电磁波长相当甚至更大的网格,因此,不能直接用于计算尾流RCS。针对该问题,提出了一种线性插值处理方法,把被动保守量从被动保守量计算的非均匀网格上映射到满足RCS计算要求的均匀细网格上。该方法在保证较高的电磁计算精度的情况下,避免了使用电磁计算细网格求解被动保守量导致的计算量急剧增加。通过数值实验验证了本处理方法的高效性。     

FDTD local grid with material traverse

Often, a finite-difference time-domain (FDTD) calculation requires a relatively higher mesh resolution in only small subvolumes of the total mesh space. By locally applying finer grids (local grids) to these volumes, the necessary resolution can be obtained. Computation time and memory requirements may be far less than for an FDTD space with the smaller mesh resolution throughout. In many situations, it is important that these local-grids function when materials traverse the main-grid-local-grid (MG-LG) boundary surfaces, since the volumes that require local grids may not be isolated in a homogeneous medium. A local-grid method, which allows dielectric and/or conducting materials to traverse the boundaries, is developed. Three different FDTD problems that utilize the local-grid method are used as validation tests. Results are compared with uniform mesh FDTD solutions     

Statistical extraction and modeling of inductance considering spatial correlation

In this paper, we present a novel method for statistical inductance extraction and modeling for interconnects considering process variations. The new method, called statHenry, is based on the collocation-based spectral stochastic method where orthogonal polynomials are used to represent the statistical processes. The coefficients of the partial inductance orthogonal polynomial are computed via the collocation method where a fast multi-dimensional Gaussian quadrature method is applied with sparse grids. To further improve the efficiency of the proposed method, a random variable reduction scheme is used. Given the interconnect wire variation parameters, the resulting method can derive the parameterized closed form of the inductance value. We show that both partial and loop inductance variations can be significant given the width and height variations. This new approach can work with any existing inductance extraction tool to extract the variational partial and loop inductance or impedance. Experimental results show that our method is orders of magnitude faster than the Monte Carlo method for several practical interconnect structures.     

Constructing the phase converters consisting of arbitrary number oftranslucent surfaces

An effective analytical method of synthesis of an artificial anisotropic structure has been developed. At a design frequency, it ensures perfect match and a phase shift given. The structure may be formed by arbitrary number of inductive and capacitive grids. The method has been applied to constructing circular polarizers and twist polarizers. The geometrical parameters of the polarizers were found in the explicit form. Analytical criteria for an estimate of the bandwidth of the devices have been derived. Performance of the polarizers over a frequency band was studied. A circular polarizer has been proposed which consists of both a cascade of two inductive grids and a cascade of two capacitive grids. The polarizer can be used when very high axial ratio is needed. It ensures more than 10% bandwidth for 0.99 axial ratio. Measurements have been presented that prove adequacy of the mathematical model for real inductive and capacitive screens     

基于修正交错网格方案的RFG-FFT算法

本文提出了修正的交错网格方案结合基于快速傅里叶变换（FFT）的算法,用于减少快速算法中近场修正矩阵的计算负担.该方案首先使用两套交错的网格分别用于场点和源点的投影,其后为了进一步提高拟合精度,对部分网格间的格林函数值进行了修改.实验表明将提出的方案与实系数拟合格林函数FFT方法结合,提高了近场拟合元素的精度,因此减少了近场修正矩阵中元素的个数.从而,新的方案降低了总的内存需求和计算时间.     

球铁点阵分布激光表面强化的微硬度分布

采用经过二元光学变换后呈3×3和7×7 二维点阵分布的脉冲激光束对球铁试样作了表面强化处理。针对点阵分布脉冲激光表面强化球铁材料提出了微硬度分布合理表征的统计方法。即在整个月牙形强化区横截面上按30μm×30μm或30μm×50μm划分网格,沿层深方向按列(行)对网格的交叉点进行硬度测试。然后,利用数学方法对硬度分布进行统计处理并绘制等高线轮廓图。应用表明,对于强化区具有多相交错分布特征的球铁材料,与传统方法相比,采用统计方法能够比较准确地评价强化层深度和微硬度分布特征。同时,在一定程度上揭示了激光强化工艺与强化效果之间的关系。     

Modeling and Analysis of Composite Antenna Superstrates Consisting on Grids of Loaded Wires

We study the characteristics and radiation mechanism of antenna superstrates based on closely located periodical grids of loaded wires. An explicit analytical method based on the local field approach is used to study the reflection and transmission properties of such superstrates. It is shown that as a result of proper impedance loading there exists a rather wide frequency band over which currents induced to the grids cancel each other, leading to a wide transmission maximum. In this regime radiation is produced by the magnetic dipole moments created by circulating out-of-phase currents flowing in the grids. An impedance matrix representation is derived for the superstrates, and the analytical results are validated using full-wave simulations. As a practical application example we study numerically the radiation characteristics of dipole antennas illuminating finite-size superstrates.