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Jiao D. Mingyu Lu Michielssen E. Jian-Ming Jin 《Antennas and Propagation, IEEE Transactions on》2001,49(10):1453-1461
A time-domain, finite element-boundary integral (FE-BI) method is presented for analyzing electromagnetic (EM) scattering from two-dimensional (2-D) inhomogeneous objects. The scheme's finite-element component expands transverse fields in terms of a pair of orthogonal vector basis functions and is coupled to its boundary integral component in such a way that the resultant finite element mass matrix is diagonal, and more importantly, the method delivers solutions that are free of spurious modes. The boundary integrals are computed using the multilevel plane-wave time-domain algorithm to enable the simulation of large-scale scattering phenomena. Numerical results demonstrate the capabilities and accuracy of the proposed hybrid scheme 相似文献
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The multiresolution time-domain (MRTD) algorithm is applied to the problem of general two-dimensional electromagnetic scattering. A Haar wavelet expansion is utilized. A parallel between Haar MRTD and the classic Yee finite-difference time-domain (FDTD) algorithm is discussed, and results of simulations on canonical targets are shown for comparison. We focus on the incident-field implementation, which, in our case, consists of a pulsed plane wave. Also, we consider scattering in a half-space environment, with application to subsurface sensing. The results illustrate the advantage of the Haar MRTD method as compared with the classic FDTD, which consists of reduced memory and execution time requirements, without sacrificing accuracy 相似文献
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本文提出利用模拟得到的时域散射信息对埋于半无限大空间中的无耗二维电磁目标进行微波成像的新方法时域变分迭代法(time-domain variational iterative method,TVIM)。这是一种基于电磁体等效原理、变分原理和傅立叶变换的迭代方法,每次迭代各计算正问题和逆问题一次,正问题采用时域有限差分(finite-difference time-domain)方法处理。列举了一些典型的数值反演实例,并与有关文献结果作了比较,考察了TVIM的收敛性能、反演复杂目标能力、抗随机噪声等反演性能,并从理论上简要分析了形成TVIM良好反演性能的原因。 相似文献
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《Antennas and Propagation, IEEE Transactions on》2009,57(8):2397-2408
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本文提出了一种能够加速收敛的助推法,把助推法应用于时域非线性优化方法求解二维有耗介质体的逆散射问题,获得了很好的结果。 相似文献
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Bharadwaj P.K. Runkle P.R. Carin L. 《Antennas and Propagation, IEEE Transactions on》1999,47(10):1543-1554
The method of matched pursuits is an algorithm by which a waveform is parsed into its fundamental constituents here, in the context of short-pulse electromagnetic scattering, wavefronts, and resonances (constituting what we have called wave-based matched pursuits). The wave-based matched-pursuits algorithm is used to develop a codebook of features that are representative of time-domain scattering from a target of interest, accounting for the variability of such as a function of target-sensor orientation. This codebook is subsequently used in the context of a hidden Markov model (HMM) in which the probability of measuring a particular codebook element is quantified as a function of target-sensor orientation. We review the wave-based matched-pursuits algorithm and its use in the context of an HMM (for target identification). Finally, this new wave-based signal processing algorithm is demonstrated with simulated scattering data, with additive noise 相似文献
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We present a time domain algorithm for computation of the maximum likelihood estimate of the location of a known scattering object from wide-band scattering data acquired in a suite of scattering experiments. The algorithm consists of a three-step procedure: (1) data filtering, (2) time-domain backpropagation, and (3) coherent summation and is implemented via a number of forward and inverse Radon transforms integrated into a tomographic scheme. A computer simulation is included for illustration purposes. 相似文献
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The analysis of tapered, coupled microstrip transmission lines is presented. These lines, used as interconnects between integrated circuit devices, are modeled using an iteration-perturbation approach applied in the spatial domain. From this model, a frequency-dependent scattering parameter characterization is determined. A time-domain simulation of pulse propagation through the tapered, coupled microstrip lines is performed. The frequency-domain scattering parameters are inverse Fourier transformed to obtain the time-domain Green's function. The input pulse is convolved with the Green's function, and a Newton-Raphson algorithm is applied to account for nonlinear loads. Some experimental results are shown, and a simulation approximation is proposed 相似文献
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We consider plane wave time-domain scattering from a fixed target in the presence of a rough (random) surface with application to ground penetrating radar. The time-domain scattering data are computed via a two-dimensional (2-D) finite-difference time-domain (FDTD) algorithm. In addition to examining the statistics of the time-domain fields scattered from such a surface, we investigate subsurface target detection by employing a (commonly used) matched-filter detector. The results of such a detector are characterized by their receiver operating characteristic (ROC), which quantifies the probability of detection and probability of false alarm. Such ROC studies allow us to investigate fundamental assumptions in the matched-filter detector: that the target response is deterministic and the clutter signal stochastic, with the two signals treated as additive and independent 相似文献
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The Floquet theorem is combined with the finite-difference time-domain (FDTD) method to obtain sufficiently accurate results for the scattering parameters of a metal strip grating. This accuracy can be achieved by using a suitable absorbing boundary condition. The algorithm described allows any periodically repeated complex irregular shape to be studied.<> 相似文献
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Time-domain finite-element simulation of three-dimensional scattering and radiation problems using perfectly matched layers 总被引:2,自引:0,他引:2
Jiao D. Jian-Ming Jin Michielssen E. Riley D.J. 《Antennas and Propagation, IEEE Transactions on》2003,51(2):296-305
An effective algorithm to construct perfectly matched layers (PMLs) for truncating time-domain finite-element meshes used in the simulation of three-dimensional (3-D) open-region electromagnetic scattering and radiation problems is presented. Both total- and scattered-field formulations are described. The proposed algorithm is based on the time-domain finite-element solution of the vector wave equation in an anisotropic and dispersive medium. The algorithm allows for the variation of the PML parameters within each element, which facilitates the efficient use of higher order vector basis functions. The stability of the resultant numerical procedure is analyzed, and it is shown that unconditionally stable schemes can be obtained. Numerical simulations of radiation and scattering problems based on both the zeroth- and higher order vector bases are presented to validate the proposed PML scheme. 相似文献
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本文首先研究了多区域时域伪谱(MPSTD)算法应用于波导问题分析时的时域激励源设置方法。然后在此基础上,将MPSTD算法应用于矩形波导宽壁复合缝隙耦合器的分析。针对X波段半高波导,得出了耦合缝隙在不同高度、不同偏置和不同倾斜角度下的谐振长度和散射参量特性。仿真结果表明,将MPSTD算法应用于波导缝隙耦合器的分析,具有较高的计算效率和计算精度。同时该问题的MPSTD分析也拓展了MPSTD算法的应用领域,为准确、快速分析复杂波导问题的宽频时域特性提供了一种思路。 相似文献
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A fast higher-order time-domain finite element-boundary integral method for 3-D electromagnetic scattering analysis 总被引:1,自引:0,他引:1
Jiao D. Ergin A.A. Shanker B. Michielssen E. Jian-Ming Jin 《Antennas and Propagation, IEEE Transactions on》2002,50(9):1192-1202
A novel hybrid time-domain finite element-boundary integral method for analyzing three-dimensional (3-D) electromagnetic scattering phenomena is presented. The method couples finite element and boundary integral field representations in a way that results in a sparse system matrix and solutions that are devoid of spurious modes. To accurately represent the unknown fields, the scheme employs higher-order vector basis functions defined on curvilinear tetrahedral elements. To handle problems involving electrically large objects, the multilevel plane-wave time-domain algorithm is used to accelerate the evaluation of the boundary integrals. Numerical results demonstrate the accuracy and versatility of the proposed scheme. 相似文献
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德鲁(Drude)经验模型常用于描述等离子体、金属等媒质的电色散特性.利用宽带的时域测量数据直接反演电参数,相比单频(频域)技术而言,具有信息量大、成像分辨率高的优势.时域直接反演色散媒质电参数的主要困难在于它们是频率相关的.为了克服该困难,本文提出了一种时域电磁(EM)逆散射新技术:转而同时反演德鲁模型的4类频率无关的模型参数.该技术的主要环节为:(1)描述为含正则化项的约束最小化问题;(2)转化为无约束最小化问题;(3)解析导出梯度;(4)分别利用时域有限差分(FDTD)法、共轭梯度(CG)法迭代求解正演、反演子问题.在一维(1-D)、二维(2-D)两个数值算例中,所需的测量数据也由FDTD仿真值代替,并加入了加性高斯白噪声(AWGN).反演结果初步证实了该技术的性能. 相似文献
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Electromagnetic scattering analyses for radar cross-section (RCS) prediction present very large computational demands. Processing on parallel machines will contribute to increasing the size of problem tractable. We present a parallel implementation of the time-domain integral equation method. The issues and options in its parallelization are identified, and domain decomposition strategies to suit these are implemented. Good parallelization is exhibited, with the most costly parts of the algorithm displaying essentially linear speedup. Demonstrations using the Cray T3D are given with, for example, results on the ~12 wavelength NASA almond obtained in ~30 min per illumination angle, using 256 processors 相似文献
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辛时域有限差分(symplectic finite-difference time-domain,SFDTD)算法作为一种高精度、高稳定、高保真度的时域数值算法,在多个学科领域得到了广泛的应用,并已发展成为一种较为成熟的数值计算方法.本文主要对SFDTD算法的构建、数值优化以及相关关键技术处理进行了介绍.重点总结了基于时间和空间上的差分近似优化处理方法,处理不连续边界及金属曲面时的局部修正方法,以及时域电磁仿真中不可或缺的三大关键技术:总场/散射场技术、完全匹配层(perfect matched layer,PML)、近远场变换技术.最后,介绍了SFDTD算法在电磁仿真、量子力学求解、多物理问题建模与分析中的具体应用. 相似文献