Electromagnetic wave diffraction using a finite volume method

The authors describe a finite volume time domain (FVTD) method for the resolution of electromagnetic diffraction by `complex' structures. Results obtained for an aircraft by this technique which allow a conformal meshing are compared with results from a classical FDTD code     

Hybrid technique combining finite element, finite difference andintegral equation methods in time domain

A new hybrid time domain method is presented which combines three well-known numerical techniques. i.e. the finite difference time domain (FDTD) method, finite element (FE) method and method of moments (MoM). The hybrid scheme has been designed to handle complex geometries comprising arbitrary thin-wire structures and inhomogeneous dielectric regions the shape of which can also be arbitrary. Numerical results are presented which illustrate the accuracy of the method     

采用FDTD/FVTD混合算法分析蝶形微带天线

用FDTD和FVTD混合算法分析了蝶形微带天线的反射损失.在适于矩形网格的区域采用常规的非均匀FDTD算法,在微带贴片天线的斜边或PEC弯曲表面处采用FVTD算法,重叠区域的场通过邻近场的线性插值得到.程序仿真和实际测量结果的比较表明在较宽的频带内,该算法在不损失精度,不显著增加CPU时间和内存的情况下,极大地降低了常规FDTD所要求的网格密度.     

Frequency dispersive materials for 3-D hybrid solvers in time domain

The recursive convolution method to treat linear dispersive materials in the finite difference time domain (FDTD) is here generalized to an explicit finite volume solver and an implicit finite element solver. Both solvers are interfaced to FDTD resulting in two hybrid solvers. The stability of the solvers is analyzed and the accuracy is demonstrated in several scattering cases, where a plane wave illuminates a sphere with complex permittivity. Excellent agreement with the analytical Mie series solution is obtained for materials of Debye and Lorentz type as well as for a material consisting of two Lorentz poles.     

Cylindrical-Cartesian FDTD model of a 17-element conformal antennaarray

A novel hybrid cylindrical-Cartesian finite difference time domain (FDTD) method is presented, which permits a dramatic increase in the flexibility of the basic FDTD algorithm. It is shown to be particularly well-suited to the analysis of faceted conformal antenna arrays and its accuracy is demonstrated by comparison with experimental measurements of couplings within a 17-element array     

Finite difference time domain analysis of cylindrical coplanar waveguide circuits

There is a growing interest in using cylindrical transmission line structures in microwave applications. In this paper, the finite difference time domain (FDTD) method is used to characterize several three-dimensional cylindrical coplanar waveguide (CCPW) geometries. Specifically, a CCPW series stub and a three-section CCPW filter are studied both theoretically and experimentally. Moreover, CCPW gap is characterized and the FDTD results are compared to those obtained using conformal mapping techniques. Effective absorbing boundary conditions are employed to truncate the FDTD mesh at the end walls and the outer radial boundary.     

A hybrid time-domain technique that combines the finite element, finite difference and method of moment techniques to solve complex electromagnetic problems

This paper describes a hybrid technique directly operating in time domain that combines the finite element time domain (FETD), the finite-difference time-domain (FDTD) and the integral-equation-based method of moments in the time domain (MoMTD) techniques to analyze complex electromagnetic problems involving thin-wire antennas radiating in the presence of inhomogeneous dielectric bodies whose shape can be arbitrary. The method brings together the ability of the FDTD scheme to deal with arbitrary material properties, the versatility of the FETD to accurately model curved geometries, and that of the MoM to analyze thin-wire structures. Working in the time domain provides wide-band information from a single execution of the marching-on-in-time procedure and simplifies the interfacing of the FE and MoM methods with the FDTD, an approach specifically designed for time domain analysis. Numerical results that validate the hybrid method and show its capabilities are presented in the paper.     

Hybrid finite-difference/finite-volume time-domain analysis formicrowave integrated circuits with curved PEC surfaces using anonuniform rectangular grid

In this paper, we present a hybrid algorithm that combines the finite-difference time-domain (FDTD) and finite-volume time-domain (FVTD) methods to analyze microwave integrated-circuit structures that may contain curved perfect electric conductor (PEC) surfaces. We employ the conventional nonuniform FDTD in regions where the objects are describable with a rectangular mesh, while applying the FVTD method elsewhere where we need to deal with curved PEC configurations. Both the FDTD and FVTD quantities are defined in the mutually overlapping regions, and these fields from the respective regions are interpolated by using their nearest neighbors. We validate this algorithm by analyzing the scattering parameters of a stripline with one or more adjacent cylindrical vias, whose geometries are frequently encountered in printed-circuit-board designs. It is found that the hybrid FDTD-FVTD approach requires little increase in central processing unit time and memory in comparison to the conventional FDTD, while its computational accuracy is significantly improved over a wide range of frequencies. Specifically, this accuracy is found to be comparable to that achieved by doubling the mesh density of the staircased FDTD     

Cross-shaped dielectric resonator antenna analysis using conformalfinite difference time domain method

A cross-shaped dielectric resonator antenna, designed for circular polarisation, is analysed via the conformal finite difference time domain technique. The conformal technique, which can handle canted surfaces that do not conform to the Cartesian system of co-ordinates, is used to generate accurate results with a relatively coarse mesh, e.g. it is shown that the conformal FDTD offers a 2:1 advantage over staircasing, without compromising accuracy     

3D crank-nicolson finite difference time domain method for dispersive media

The unconditionally stable Crank-Nicolson finite difference time domain (CN-FDTD) method is extended to incorporate frequency-dependent media in three dimensions. A Gaussian-elimination-based direct sparse solver is used to deal with the large sparse matrix system arising from the formulation. Numerical results validate and confirm that the scheme is unconditionally stable for time steps over the Courant-Friedrich-Lewy limit of classical FDTD.     

Hybrid finite-volume finite-difference time-domain modelling ofcurved surfaces

A computationally efficient hybrid finite-volume finite-difference time-domain (FV-FDTD) method is proposed to model the scattering from curved objects. The hybrid FV-FDTD method uses a local conforming mesh consisting of only two FVTD cells, one either side of the scatterer's contour, giving a better approximation to the surface. The improved definition of the scatterer using the hybrid FV-FDTD method is shown to improve the solution in comparison to the FDTD method     

预测反射面天线馈源毁伤效应的混合算法

提出了一种预测反射面天线系统在馈源毁伤状态下辐射特性的混合算法.采用时域有限差分法(FDTD)分析了波导开口辐射器馈源穿孔毁伤时的初级辐射特性,利用物理光学法(PO)和物理绕射理论(PTD)分析了反射面天线的次级辐射特性.并采用非场分裂式完全匹配层(UPML)吸收边界条件、共形网格(Conformalmesh)技术提高计算精度和效率,取得了良好的效果,充分验证了混合算法的有效性.     

A new anisotropic perfectly matched layer medium for mesh truncation in finite difference time domain analysis

In this paper an unsplit anisotropic perfectly matched layer (PML) medium, previously utilized in the context of finite element analysis, is implemented in the finite difference time domain (FDTD) algorithm. The FDTD anisotropic PML is easy to implement in the existing FDTD codes, and is well suited for truncating inhomogeneous and layered media without special treatment required in the conventional PML approach. A further advantage of the present approach is improved performance at lower frequencies. The applications of the unsplit anisotropic PML/FDTD method are illustrated by considering the problems of a plane wave propagation and an open microstrip line.     

High spatial order finite element method to solve Maxwell's equations in time domain

This paper presents a finite element method with high spatial order for solving the Maxwell equations in the time domain. In the first part, we provide the mathematical background of the method. Then, we discuss the advantages of the new scheme compared to a classical finite-difference time-domain (FDTD) method. Several examples show the advantages of using the new method for different kinds of problems. Comparisons in terms of accuracy and CPU time between this method, the FDTD and the finite-volume time-domain methods are given as well.     

Analysis of electromagnetic radiation from shaped-end radiatorsusing the finite difference time domain method

The finite difference time domain (FDTD) technique is a popular method for analyzing electromagnetic scattering, radiation, and penetration problems. Several authors have recently applied the FDTD method to antenna radiation problems. To date, the antenna structures considered have been wire and conical monopole antennas, rectangular waveguides, pyramidal horn antennas, and microstrip antennas. Results from these analysis have been in the form of normalized field patterns and no results showing absolute gain have been presented. The article demonstrates the first staircased application of the FDTD method to the analysis of radiation from circular waveguides and other shaped-end radiators. Results of absolute gain versus angle are shown for a straight-cut circular waveguide and for two different shaped-end radiators. All FDTD analyses are full three-dimensional computations and are compared in each case with measured data     

求解三维问题的区域分解时域有限差分方法

该文提出一种用于三维复杂问题的区域分解时域有限差分算法(DD-FDTD)。依据待解三维复杂问题的特点,将其分解为几个子区域。每个子域中的问题相对简单,可采用适合于该区域的共形网格进行划分计算,通过插值再修正误差的办法,把各个子区域综合起来,获得原问题的解。这样,应用区域分解的思想,简化了复杂的问题。修正误差的方法,使本算法得以实现并大幅度提高了计算精度。采用本算法对三维口径天线问题进行了分析计算并与实测数据进行了比对,验证了算法的正确性。     

平面波在时域有限差分法中的引入方法研究

基于角点延迟的思想,研究了时域有限差分(FDTD)法中,两种在连接边界上引入平面波的方法--一维平面波推进法和解析法.仿真结果表明:一维平面波推进法与解析法同样有效;一维平面波推进法很大程度上抵消了FDTD法的数值色散误差,溢出波较少,而解析法出现了较多的溢出波;使用一维平面波推进法时,减小网格尺寸能够进一步减小溢出波...     

Analysis of Millimeter Wave Microstrip Circulator with a Magnetized Ferrite Sphere by FDTD Method with Modified Matrix Pencil Method

In this paper, the modified matrix pencil (MMP) method is used in the finite difference time domain (FDTD) method to eliminate the late time instability of time domain responses when analyzing the novel microstrip circulator with a magnetized ferrite sphere. The frequency dependent scattering parameters: reflection, isolation and insertion parameters of the microstrip circulator calculated over a wide band of frequencies with this hybrid method are compared with that obtained by direct FDTD method which agree well with the experimental results.     

Analysis of electromagnetic coupling through a thick aperture inmultilayer planar circuits using the extended spectral domain approachand finite difference time-domain method

Electromagnetic coupling plays a very important role in the design and development of integrated antenna arrays and microwave circuits. With the availability of accurate computer-aided design tools, proper characterization and analysis, this coupling phenomenon could be used to simplify the packaging and fabrication process, to reduce manufacturing cost, and also to add flexibility to the design of multilayer structures in many cases. An accurate and efficient spectral domain approach (SDA) is proposed as a means to study the coupling effect through an arbitrary aperture in a thick common ground plane of multilayer planar circuits. In addition, the finite difference time domain (FDTD) method is present as an alternate approach to this type of problem and also is used as a validation tool for the spectral domain method because of its simplicity, generality, and accuracy. The proposed methods are applied to different aperture coupled structures for illustration