FDTD analysis of photoconducting antennas for millimeter‐wave generation

In this paper, a hybrid numerical technique is presented for modeling a photoconducting antenna structure designed for optoelectronic generation of millimeter waves. The technique interfaces the solid‐state device model with the three‐dimensional (3D) finite‐difference time‐domain (FDTD) method to achieve the active antenna modeling effectiveness and efficiency. The FDTD algorithm is applied to simulate the passive part of the antenna structure, whereas the numerical device simulation is employed to model the photoconductor that is illuminated by lasers. Physical performance of the photoconductor and response of the antenna are analyzed. Numerical results show good correlation with the experimental result and consequently demonstrate the feasibility of the full‐wave modeling. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 213–220, 2000.     

A one‐step leapfrog HIE‐FDTD method for rotationally symmetric structures

In this work, they propose a one‐step leapfrog hybrid implicit‐explicit finite‐difference time‐domain (HIE‐FDTD) method for body‐of‐revolution (BOR). Meanwhile, its Convolutional Perfect Matched Layer (CPML) absorbing boundary condition is implemented. In this method, the implicit difference is applied in the angular direction. All the resultant updating equations are still explicit. However, the stability condition of the proposed method is relaxed. The analytical analysis shows that its time step is only determined by the smaller one of spatial increments Δρ and Δz. A scattering example is provided to demonstrate the new algorithm. At the same time, the relative of reflection error of the CPML is given with comparisons of Mur.     

Implementation and optimization of GPU‐based parallel one‐step leapfrog ADI‐FDTD for far‐field scattering problems

The one‐step leapfrog alternative‐direction‐implicit finite‐difference time‐domain (ADI‐FDTD), free from the Courant‐Friedrichs‐Lewy (CFL) stability condition and sub‐step computations, is efficient when dealing with fine grid problems. However, solution of the numerous tridiagonal systems still imposes a great computational burden and makes the method hard to execute in parallel. In this paper, we proposed an efficient graphic processing unit (GPU)‐based parallel implementation of the one‐step leapfrog ADI‐FDTD for the far‐field EM scattering simulation of objects, in which we present and analyze the manners of calculation area division and thread allocation and a data layout transformation of z components is proposed to achieve better memory access mode, which is a key factor affecting GPU execution efficiency. The simulation experiment is carried out to verify the accuracy and efficiency of the GPU‐based implementation. The simulation results show that there is a good agreement between the proposed one‐step leapfrog ADI‐FDTD method and Yee's FDTD in solving the far‐field scattering problem and huge benefits in performance were encountered when the method was accelerated using GPU technology.     

A new FDTD scheme analysis for the characteristics of the magnetic‐anisotropic EBG structure

In this article, the new grid finite‐difference time‐domain (NG‐FDTD) method is applied to calculate the dispersion curves of electromagnetic band‐gap structures, and the dispersion characteristics of three magnetic‐anisotropic medium EBG structure are obtained using the NG‐FDTD method. According to these results, we can conclude that the EBG structure of a magnetic‐anisotropic medium, in which the permeability of nondiagonal elements is real, has a much larger band‐stop than that of isotropic EBG. Other magnetic‐anisotropic EBG structures can also increase the first band‐stop. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

FDTD modeling of matched impedance terminating a microstrip line

An efficient matched‐impedance scheme for the finite‐difference time‐domain (FDTD) analysis of microstrip circuits is presented. In conventional extended FDTD schemes, the resistive load is introduced as a thin‐line model or is uniformly assigned into a number of cells. The assigning scheme does not agree with the electromagnetic distribution in the microstrip line, and thus causes some reflection errors. The proposed scheme uses the effective impedance of the microstrip line as the value of matched resistive load and assigns it into the resistive‐load mesh region in a proper proportion in order to reduce the reflection errors. The results of the numerical examples show that the reflections can be significantly reduced by this novel scheme. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Applications of anisotropic one‐step leapfrog HIE‐FDTD method in microwave circuit and antenna

To verify the effect of artificial anisotropy parameters in one‐step leapfrog hybrid implicit‐explicit finite‐difference time‐domain (FDTD) method, we calculated several microwave components with different characteristics. Introduced auxiliary field variable can reduce the program difficulty and improve the computational efficiency without additional computational time and memory cost. Analyses of the numerical results are proved that the calculation time is reduced to about one‐sixth compared to the traditional FDTD method for the same example simulated. The memory cost and relative error are remained at a good level. The numerical experiments for microwave circuit and antenna have been well demonstrated the method available.     

A new FDTD stencil for reduced numerical anisotropy in the computer modeling of wave phenomena

An isotropic finite difference scheme is utilized for the development of a new stencil for the finite‐difference time‐domain (FDTD) modeling of electromagnetic wave propagation. The key attribute of the new stencil is the improved isotropy of the numerical phase velocity at fairly moderate spatial sampling of the fields. More specifically, for a given phase velocity anisotropy error, the new stencil requires a much coarser grid than the one required by the standard, second‐order accurate FDTD stencil. This, in turn, amounts to gains in computational resources when transient electromagnetic interactions in electrically‐large domains are being modeled. The numerical attributes of the proposed stencil, namely, its dispersion, anisotropy and stability, are presented in the context of its application to the numerical simulation of two‐dimensional transient electromagnetic wave propagation. Through a series of numerical studies, the enhanced isotropy provided by the proposed scheme is demonstrated and contrasted in a quantitative manner to that of the standard FDTD stencil. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

A novel numerical dispersion formulation of the 2D ADI‐FDTD method

A novel dispersion formulation of the 2D alternating‐direction implicit (ADI) finite‐difference time‐domain (FDTD) method is presented. The formulation is based on an increasing process analysis of the monochromatic wave in free space. A numerical experiment scheme is designed to verify the accuracy of the proposed formulation. The results obtained from the proposed formulation are in a good agreement with those from the numerical experiments, and the proposed formulation is more accurate than those reported in the literature. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Design of hexa‐band planar inverted‐F antenna using hybrid BSO‐NM algorithm for mobile phone communications

This article presents a new design of multiband planar inverted‐F antenna with slotted ground plane and S‐etched slot on the radiation patch. The proposed antenna is optimized using an efficient global hybrid optimization method combining bacterial swarm optimization and Nelder‐Mead (BSO‐NM) algorithm to cover a very important six service bands including GSM900, GPS1575, DCS1800, PCS1900, ISM2450, and 4G5000 MHz with enhanced bandwidths. The BSO‐NM algorithm in Matlab code is linked to the CST Microwave studio software to simulate the antenna. To validate the results, the antenna is analyzed using the finite difference time domain (FDTD) method. A good agreement is achieved between the results of EM simulation and that produced from the FDTD method. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

基于FDTD二维光子晶体器件设计软件的开发

介绍了一个基于时域有限差分法（FDTD）的二维光子晶体器件设计软件PCCAD,所用的核心算法是时域有限差分法。与同类FDTD商业软件相比,特点在于其具有多种光子晶体结构编辑模板,多种点源、线源,先进的边界吸收技术及多种参数优化扫描等功能。快速傅里叶变换及Pade算法在软件设计中的应用使模拟更加精确、快速。软件适用于各种平面光子晶体的仿真设计,探索新的器件结构。最后,利用此软件设计了直波导、T型波导等二维平面光子晶体器件。     

Implementation of convolutional perfectly matched layer for three‐dimensional hybrid implicit‐explicit finite‐difference time‐domain method

The hybrid implicit‐explicit (HIE) finite‐difference time‐domain (FDTD) method with the convolutional perfectly matched layer (CPML) is extended to a full three‐dimensional scheme in this article. To demonstrate the application of the CPML better, the entire derivation process is presented, in which the fine scale structure is changed from y‐direction to z‐direction of the propagation innovatively. The numerical examples are adopted to verify the efficiency and accuracy of the proposed method. Numerical results show that the HIE‐FDTD with CPML truncation has the similar relative reflection error with the FDTD with CPML method, but it is much better than the methods with Mur absorbing boundary. Although Courant‐Friedrich‐Levy number climbs to 8, the maximum relative error of the proposed HIE‐CPML remains more below than ?71 dB, and CPU time is nearly 72.1% less than the FDTD‐CPML. As an example, a low‐pass filter is simulated by using the FDTD‐CPML and HIE‐CPML methods. The curves obtained are highly fitted between two methods; the maximum errors are lower than ?79 dB. Furthermore, the CPU time saved much more, accounting for only 26.8% of the FDTD‐CPML method while the same example simulated.     

An improved method of designing optimum microstrip Rotman lens based on 2D‐FDTD

In this article we propose an efficient method for analysis of microstrip Rotman lens using two‐dimensional finite difference time domain (2D‐FDTD). Both the dielectric and conductor losses are modeled in this method in order to achieve results which are in good agreement with 3D simulation. Using 2D analysis, the required simulation time is reduced considerably, which in turn, enables us to use the proposed analysis method in an optimization procedure. Based on this optimization procedure, we present an improved design of a microstrip Rotman lens in which both the efficiency and also the gain of isotropic antenna array are increased. In this design, the Rotman lens has 5 beam ports and 16 array ports and operates in Ku frequency band.     

FDTD方法吸收边界条件的研究及应用

用时域有限差分法(FDTD)求解电磁散射问题中,吸收边界条件的设置起着关键性作用.通过时间和空间上的递推算法对时域有限差分法中的两种吸收边界条件:Mur吸收边界条件和完全匹配层(PML)的吸收效果进行了比较和分析.同时,引入参数对PML的差分方程进行了优化,避免了将电磁场分裂为两个分量进行计算,进而降低了计算内存开销.实验结果证明PML具有更优越的吸收性能.最后,在FDTD算法中应用PML吸收层对一圆柱形导体的雷达散射截面积(RCS)进行数值仿真,验证了FDTD算法在计算雷达散射截面积(RCS)上的有效性.     

基于异构计算的三维FDTD并行算法及其在电磁仿真中的应用

时域有限差分(FDTD)法是求解电磁学中麦克斯韦方程组的重要方法之一,一直以来获得了广泛的使用,但是应用于电大尺寸目标仿真时存在巨大的耗时问题。为解决这一问题,利用图形处理器(GPU)的并行处理特性,结合计算统一设备架构(CUDA),以低通滤波器为算例,实现了时域卷积理想匹配层(CPML)吸收边界的三维FDTD高性能加速计算,目标网格数达5百万。实验在Fermi架构的Quadro 4000和Tesla M2050两款GPU上实测,误差均在10~(-4)范围内,相对于同时期的CPU分别可获得36和55倍以上的加速,结果表明该方法具有精度高、效率高、通用性和实用性强等特点。     

A study of microwave imaging for a metallic cylinder

This article presents the studies of time‐domain inverse scattering for a metallic cylinder which based on the finite‐difference time‐domain (FDTD) method and the dynamic differential evolution (DDE). For this study, the FDTD is used for the analysis of the forward scattering part, while for the DDE is applied for the reconstruction of the two‐dimensional metallic cylinder. For the forward scattering, the FDTD method is used to calculate the scattered E fields. Based on the scattering fields, these inverse scattering problems are transformed into optimization problem. By comparing the simulated scattered fields and the calculated scattered fields, the shape and location of the metallic cylinder are reconstructed. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In addition, the effects of Gaussian noise on the reconstruction results are investigated. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2012.     

基于时域抽样法的FDTD近远场变换

提出一种基于时域抽样法的近远场变换算法以改善经典时域近远场变换算法计算量大、计算速度慢的缺点.时域抽样法是基于这样一个事实:在时域近远场变换过程中不需要与时域有限差分计算同样的时间精度.在近远场变换前先对时域近场数据进行采样以减少数据的冗余,然后用改进后的算法进行近远场变换计算从而达到减少数据量、提高计算速度的目的.为验证本算法,以计算七元八木天线远场方向图为例进行算法说明, 并与经典时域法进行比较,结果表明本算法在保证与经典法具有同样精度的前提下,减少了90%数据存储空间,同时提高计算速度80%.应用本算法可以为天线仿真优化设计、雷达散射截面(RCS)计算等提供一种快速的时域计算方法.     

修正共形FDTD技术在声散射中的应用

传统时域有限差分法(UFDTD)将曲面目标边界作为台阶近似来处理,当网格划分不很精细时,计算结果会有很大的误差.共形技术可以解决这一问题,但它要满足一定的共形条件,实现起来比较困难.针对刚性目标的声散射问题,提出一种修正共形技术,它不需要满足任何共形条件就能达到很好的稳定性.文中给出了此共形技术的基本原理和稳定性证明,并针对声散射问题进行数值模拟.仿真结果表明:在同样计算量的情况下,此方法的计算精度明显高于传统方法;在同样计算精度的情况下,此方法的计算量大约比传统方法节省50%.     

GPU‐accelerated finite‐difference time‐domain method for dielectric media based on CUDA

The simulation of electromagnetic (EM) waves propagation in the dielectric media is presented using Compute Unified Device Architecture (CUDA) implementation of finite‐difference time‐domain (FDTD) method on graphic processing unit (GPU). The FDTD formulation in the dielectric media is derived in detail, and GPU‐accelerated FDTD method based on CUDA programming model is described in the flowchart. The accuracy and speedup of the presented CUDA‐implemented FDTD method are validated by the numerical simulation of the EM waves propagating into the lossless and lossy dielectric media from the free space on GPU, by comparison with the original FDTD method on CPU. The comparison of the numerical results of CUDA‐implemented FDTD method on GPU and original FDTD method on CPU demonstrates that the CUDA‐implemented FDTD method on GPU can obtain better application speedup performance with reasonable accuracy. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:512–518, 2016.     

Analysis for scattering of conductive objects covered with anisotropic magnetized plasma by trapezoidal recursive convolution finite‐difference time‐domain method

The finite‐difference time‐domain method (FDTD) is extended to three‐dimensional (3D) anisotropic magnetized plasma based on the trapezoidal recursive convolution (TRC) technology. The TRC technique requires single convolution integral in the formulation as in the recursive convolution (RC) method, while maintaining the accuracy comparable to the piecewise linear recursive convolution (PLRC) method with two convolution integrals. In this article, the numerical results indicate that the TRC‐FDTD method not only improves accuracy over the RC‐FDTD with the same computational efficiency but also spends less computational time than the PLRC‐FDTD based on the same accuracy. The 3D TRC‐FDTD formula is provided and the bistatic radar scattering sections of conductive targets covered with anisotropic magnetized plasma are calculated. The results show that magnetized plasma cover layer can greatly reduce echo energy of radar targets, and the anisotropic magnetized plasma cover has better absorption effect than nonmagnetized. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

A new multilevels Huygens sub‐gridding finite difference time domain based on a tree structure and object oriented programming

In this article, an efficient sub‐gridding finite‐difference time‐domain is developed for the simulation of multiscaled electromagnetic problems. The proposed technique is based on using the Huygens surfaces for interfacing electromagnetic fields between different grids. The use of the Object Oriented Programming for modeling FDTD simulations facilitates the imbrication of multiple sub‐grids. That heightens the spatial ratio without affecting the accuracy and stability of the sub‐gridding technique. Spatiotemporal interpolation is used to evaluate the electromagnetic fields in Huygens surface location among the coarse grid. Results of numerical experiments prove that the use of imbricated sub‐grids and spatiotemporal interpolation in the Huygens sub‐gridding is more efficient than the use of a single sub‐grid with only spatial interpolation.