一种分析探针加载微带天线的局部共形FDTD法

提出一种局部共形时域有限差分法(LCFDTD),对短路探针加载的小型微带贴片天线进行了精确的数值分析.该方法对任意尺寸和位置的同轴探针和短路探针都可精确模拟,并且可用来模拟多探针加载情况.计算结果和实验结果相一致,证明了本文方法的有效性.     

Conformal finite-different time-domain (FDTD) with overlappinggrids

It is shown how to use many overlapping conformal grids in the neighborhood of the scatterer while using a rectangular grid away from the scatterer for solving Maxwell's equations. The locally conformal grids allow better approximation of the boundary condition on the scattering object while the rectangular grid preserves the simplicity and accuracy of the regular finite-difference time-domain (FDTD) algorithm. These grids overlap typically about three zones. It is shown how to connect together the calculations done in different overlapping grids     

Efficient Algorithm for the Unconditionally Stable 3-D ADI–FDTD Method

This letter presents a new efficient algorithm for the unconditionally stable three-dimensional alternating direction implicit finite-difference time-domain (3-D ADI-FDTD) method. The algorithm involves updating equations whose right-hand sides are much simpler and more concise than those in the conventional implementation. This leads to substantial reduction in the number of arithmetic operations required for their computations. To take full advantage of the efficiency gain, efforts are made as well to maintain or reduce other computation costs in for-looping and solving tridiagonal systems. Certain field array reuse is also exploited which reduces the memory space and the memory indexing overhead     

时域有限差分法的三维曲面共形技术及其应用于卡塞格伦天线系统

本文研究一种时域有限差分法的三维曲面共形技术，将其用于抛物面及卡塞格伦天线的建模，所得近场分布与实验值等吻合较好。     

Unconditionally Stable LOD–FDTD Method for 3-D Maxwell's Equations

This letter presents an unconditionally stable locally 1-D finite-difference time-domain (LOD-FDTD) method for 3-D Maxwell's equations. The method does not exhibit the second-order noncommutativity error and its second-order temporal accuracy is ascertained via numerical justification. The method also involves simpler updating procedures and facilitates exploitation of parallel and/or reduced output processing. This leads to its higher computation efficiency than the alternating direction implicit and split-step FDTD methods     

A New Conformal FDTD(2,4) Scheme for Modeling Three-Dimensional Curved Perfectly Conducting Objects

A new high-order conformal FDTD(2,4) scheme is proposed to solve the electromagnetic scattering from 3-D curved perfectly conducting objects. For electric field components, the update equations do not need to be modified. For magnetic field components, the inner loop is treated with the locally conformal technique, and the outer loop is unmodified. Numerical results demonstrate that the high-order conformal scheme can obtain better numerical precision under coarse grid condition compared with the low-order conformal method and the high-order staircasing approach, which in turn saves CPU time and memory.     

Effectiveness of 2-D and 2.5-D FDTD Ground-Penetrating Radar Modeling for Bridge-Deck Deterioration Evaluated by 3-D FDTD

Computational modeling effectively analyzes the wave propagation and associated interaction within heterogeneous reinforced concrete bridge decks, providing valuable information for sensor selection and placement. It provides a good basis for the implementation of the inverse problem in defect detection and the reconstruction of subsurface properties, which is beneficial for defect diagnosis. The objective of this study is to evaluate the effectiveness of lower order models in the evaluation of bridge-deck subsurfaces modeled as layered media. The two lower order models considered are a 2-D model and a 2.5-D model that uses the 2-D geometry with a compressed coordinate system to capture wave behavior outside the cross-sectional plane. Both the 2- and 2.5-D models are compared to the results obtained from a full 3-D model. A filter that maps the 3-D excitation signal appropriately for 2- and 2.5-D simulations is presented. The 2.5-D model differs from the 2-D model in that it is capable of capturing 3-D wave behavior interacting with a 2-D geometry. The 2.5-D matches results from the corresponding 3-D model when there is no variation in the third dimension. Computational models for air-launched ground-penetrating radar with 1-GHz central frequency and bandwidth for the detection of bridge-deck delamination are implemented in 2-, 2.5-, and 3-D using FDTD simulations. In all cases, the defect is identifiable in the results. Thus, it is found that in layered media (such as bridge decks) 2- and 2.5-D models are good approximations for modeling bridge-deck deterioration, each with an order of magnitude reduction in computational time.      

A Finite Volumes-Based 3-D Low Dispersion FDTD Algorithm

An algorithm extension to three dimensions is developed and presented for the highly phase-coherent modified second-order in time, fourth-order in space (or M24) finite-difference time-domain (FDTD) algorithm. A finite-volumes approach in conjunction with Yee's standard FDTD lattice is used for algorithm development. The corresponding dispersion relation is also developed, analyzed and compared to both the standard second-order and fourth-order FDTD algorithms as well as to two closely related high-order phase-coherent algorithms. Wideband algorithm attributes are also presented as well as sets of ready to use optimized algorithm coefficients.     

用3D-FDTD法分析用于近场光存储的光纤探针电磁波传输特性

提高近场光存储的存储信息密度的关键主要在于掌握近场存储光纤探针的透光率、近场光斑直径尺寸以及场梯度等近场物理量。采用三维时域有限差分 (3D FDTD)法分析了可用于近场光存储的光纤探针尖的光学性质 ,对不同类型光纤的近场光场分布进行了数值计算 ,给出结果并进行比较 ,从光学性质的角度对其在近场光存储中的应用加以讨论。完全镀膜光纤尖在极近场处的光斑可获得 10nm的尺寸 ,远小于传统光纤光学聚焦的光斑尺寸大小。     

A 3-D Spectral Integral Method (SIM) for Surface Integral Equations

An efficient 3-D spectral integral method (SIM) has been proposed to speed up the method of moments (MOM) calculation of induced currents on a cuboid. This method utilizes the Toeplitz structure in the impedance matrix and the fast Fourier transform to accelerate the MOM solution. It reduces the memory and CPU time per iteration from $O(N^2)$ in the MOM to $O(N^{1.5})$ and $O(N^{1.5}log N)$, respectively. Thus, the SIM can be also used as an efficient radiation boundary condition for the finite element method. Numerical results confirm the effectiveness of this method.      

Domain-overriding and digital filtering for 3-D FDTD subgridded simulations

We report on an extension of finite-difference time-domain (FDTD) subgridding (SG) algorithms incorporating digital filters and domain-overriding to three-dimensional (3-D) simulations and to problems involving materials traversing the SG interfaces. We show that significant improvements in accuracy can be obtained for these cases as well.     

三维TEM喇叭天线瞬态辐射的FDTD模拟

本文应用FDTD方法分析放置于无限大理想导体地面上并由同轴线馈电的TEM喇叭天线瞬态辐射问题。对FDTD计算区域中的细导线结构采用网格共形技术进行了特殊处理,同时引入一维传输线模型模拟同轴线馈电以大大减少FDTD的计算空间,并实现了天线与同轴线相互耦合的FDTD方法。数值结果表明本文方法处理瞬态天线辐射问题的有效性。     

三维多物体散射问题的区域分解时域有限差分方法

提出一种用于计算三维多物体散射问题的区域分解时域有限差分算法(DD-FDTD)。各散射体之间用三维时域Green函数传递信息，取代经典FDTD算法通过网格迭代运算传递信息的方式。每个物体处理为一个子域，当各物体相距一定距离时，省去了各物体间大量网格，减小了存储量。将各物体间的互偶处理为等效球面波照射，采用惠更斯原理，等效球面波激励信号可处理为球面波入射场阵列(SWIFA)，大幅度提高了计算速度；同时采用近远场变换的方法来获得等效球面波，进一步提高了计算速度。通过几个实例的分析，验证了该算法的正确性。     

利用三维FDTD法分析非对称横电磁波室内场的分布

本文利用三维ＦＤＴＤ法分析了ＡＴＥＭ Ｃｅｌｌ内场的分布,着重介绍计算方法和不同频率ＡＴＥＭ Ｃｅｌｌ内场分布的特点,以及实际测量结果。     

PDP 显示单元三维网格产生

网格发生是计算机数值模拟PDP放电的重要准备。本文使用Visual C 语言开发的网格发生软件,可以产生各种PDP结构的三维网格。该网络发生器不仅能处理常见的对向放电式结构和表面放电式结构,还能对文中所介绍的新型PDP结构做较好的处理,具有较强的通用性。对各种结构,可以不断改变障壁的形状、厚度,电极的电压、宽度,以及介质层的厚度、介电常数等等,研究网格的产生情况,利用网格信息及流体力学近似模型对显示单元的放电情况进行模拟,对显示单元的结构不断进行优化。该网格发生器不仅记录了后续计算中需要用到的各种有用的数据信息,还对网格产生情况进行了可视化输出。     

Transient Analysis of Creeping Wave Modes Using 3-D FDTD Simulation and SVD Method

Creeping wave modes on smooth structures are of importance in the control of scattering properties, such as radar cross section of such structures. We have shown a novel procedure to examine the excitation of creeping wave modes by plane wave illumination of a perfectly electrically conducting (PEC) cylinder. Detailed information about transients of creeping wave modes and their spatial structure, have been obtained for the first time using Singular Value decomposition (SVD) analysis of 3D Finite Difference Time Domain (FDTD) data. The transient analysis shows how the amplitudes of different modes vary in time, and how the dominant modes eventually stabilize to the time-harmonic solution given by analytical methods. Although the method is computationally expensive, this technique will be particularly useful for purely transient signals, complex geometries and situations involving spatially-varying material properties such as a plasma shielded object.     

A Monte-Carlo FDTD Technique for Rough Surface Scattering

A Monte-Carlo finite-difference time-domain (FDTD) technique is developed for wave scattering from randomly rough, one-dimensional surfaces satisfying the Dirichlet boundary condition. Both single-scale Gaussian and multiscale Pierson-Moskowitz surface roughness spectra are considered. Bistatic radar cross sections are calculated as a function of scattering angle for incident angles of 0, 45, 70, and 80 degrees measured from the vertical. The contour path FDTD method is shown to improve accuracy for incident angles greater than 45 degrees. Results compare well with those obtained using a Monte-Carlo integral equation technique     

A 3-D Miniaturization Method for Low-Impedance Designs

Microstrip interconnects with a V conductor are designed, fabricated, and measured to provide a compact solution for designs requiring low characteristic impedance lines. S-parameter curves are shown up to 35 GHz for 0.5-cm-long lines. The 308-mum-deep V structure produces a 33.8-Omega line with strong standing waves and reflections under 5 dB. To further reduce the impedance, a partial shield is added that results in 6.7 times reduction of signal line width, near elimination of open-end effect, and excellent correlation with a standard 15-Omega microstrip up to 25 GHz. A filter demonstration shows near ideal behavior in the 3 dB response and low return loss when compared to a similar conventional design.     

Enlarged cells for the conformal FDTD method to avoid the time step reduction

Recently, the conformal finite-difference time-domain (CFDTD) method has emerged as an efficient FDTD method with a higher order accuracy than the conventional FDTD methods that are degraded by staircasing errors. The only obvious point to further improve on the CFDTD method is its requirement for a smaller time step increment due to the existence of small irregular cells near the boundary. In this letter, an enlarged cell technique is introduced to ensure the stability of the CFDTD method without the time step reduction. The introduction of the enlarged cells therefore makes the CFDTD method much more efficient and suffers from a smaller dispersion error, as shown in several two-dimensional examples.     

二维时域有限差分法对接地板宽度有限的共面波导的特性参数分析

本文利用二维时域有限差分（FDTD）法分析接地板宽度有限的共面波导（FGCPW）在高达1THZ频段内的频变特性。将计算结果与三维FDTD法分析结果相比较发现，其一致性较好，且大大提高了仿真的效率，通过比较拉地板宽度对FGCPW的色散和衰减特性的影响，说明设计共面波导的关键在于对几何尺寸参数的正确选择。文中还引出各参数间的一般约束关系。