Computing the far-field transient response of a two-dimensional geometry requires a convolution of near-field currents with a two-dimensional far-field impulse response. In this work, a purely time domain implementation is derived and its accuracy is demonstrated. This method is applicable to EMI, radiation, and scattering problems.

The discontinuous Galerkin finite-element time-domain method is presented. The method is based on a high-order finite element discretization of Maxwellpsilas time-dependent curl equations. The mesh is decomposed into contiguous sub-domains of finite-elements with independent function expansions. The fields are coupled across the sub-domain boundaries by enforcing the tangential field continuity. This leads to a locally implicit, globally explicit difference operator that provides an efficient high-order accurate time-dependent solution. An efficient implementation of the perfectly matched layer media boundary truncation is also presented that allows general tetrahedral meshing through the PML region.

This paper examines the benefits of grating thickness in regards to enhancing EMI attenuation. Analysis is performed using the FDTD technique using periodic boundary conditions along with new formulations of the CPML absorbing boundary. Furthermore, it is demonstrated that a simple waveguide below cutoff approximation provides accurate results for the normal incident plane wave case.

This paper documents the analysis and design of a patch antenna array system. The primary analysis technique is the FDTD technique in conjunction with the CPML absorbing boundary condition. A thorough set of measurements were also achieved for the array with good agreement demonstrated. These data and results demonstrate the value of simulation technologies in modem array design.

This paper examines the EMC effect of reference plane splits in modern-day printed circuit board (PCBs). Initially, the EMC impact of the reference plane split is quantified by measuring the gap voltage which exists under a high-speed signal line which crosses a reference plane split. This is accomplished through a variety of full-wave analyses. The effect on the digital signal integrity of the transmission line is also shown. Subsequently, a novel new circuit based treatment is introduced which significantly reduces the ill effects of the discontinuity. It is also demonstrated that circuit based tools, as opposed to full-wave tools, can provide accurate analyses of these effects if the recommended discontinuity treatment is employed.

Recently an unconditionally stable ADI method was successfully applied to the solution of Maxwell's equations using a variation of the FDTD method. The ADI method is most useful for solving problems where the lattice is grossly over discretized spatially (< 10/sup -2//spl lambda//sub min/). For this scheme to be applicable to analyzing practical electromagnetic interaction problems, an efficient absorbing boundary condition that maintains unconditional stability must be derived. In this paper, an absorbing boundary condition using a perfectly matched layer (PML) is introduced. Specifically, the convolutional PML (CPML) method is used with complex frequency shifted scaling coefficients. It is shown that this method maintains unconditional stability. Further, it is demonstrated that the method provides a significant improvement in the reflection error as compared to the originally proposed split-field PML ADI scheme.

A perfectly matched layer (PML) medium with complex frequency shifted constitutive parameters is introduced for the three-dimensional alternating direction implicit (ADI) formulation of the finite-difference time-domain (FDTD) method. The absorbing boundary is implemented using the convolutional PML (CPML) approach. It is demonstrated that the resulting ADI-CPML scheme is unconditionally stable. The effectiveness of the absorbing medium as a function of the time step is also demonstrated. The proposed method has the advantage that it allows the application of the ADI method to low-frequency analysis.

In this paper, a sufficient test for the numerical stability of generalized grid finite-difference time-domain (FDTD) schemes is presented. It is shown that the projection operators of such schemes must be symmetric positive definite. Without this property, such schemes can exhibit late-time instabilities. The origin and the characteristics of these late-time instabilities are also uncovered. Based on this study, nonorthogonal grid FDTD schemes (NFDTD) and the generalized Yee (GY) methods are proposed that are numerically stable in the late time for quadrilateral prism elements, allowing these methods to be extended to problems requiring very long-time simulations. The study of numerical stability that is presented is very general and can be applied to most solutions of Maxwell's equations based on explicit time-domain schemes.

A novel implementation of perfectly matched layer (PML) media is presented for the termination of FDTD lattices. The implementation is based on the stretched coordinate form of the PML, a recursive convolution, and the use of complex frequency, shifted (CFS) PML parameters. The method, referred to here as the convolutional PML (CPML), offers a number of advantages over the traditional implementations of the PML. Specifically, the application of the CPML is completely independent of the host medium. Thus, no modifications are necessary when applying it to inhomogeneous, lossy, anisotropic, dispersive, or nonlinear media. Secondly, it is shown that the CFS–PML is highly absorptive of evanescent modes and can provide significant memory savings when computing the wave interaction of elongated structures, sharp corners, or low-frequency excitations. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 334–339, 2000.

Perfectly matched layer (PML) absorbing media has proven to be the most robust and efficient technique for the termination of FDTD lattices. Unfortunately, the PML can still suffer from late time reflections when terminating highly elongated lattices or when simulating fields with very long time signatures. This is partly due to the weakly causal nature of the PML. Alternatively, a strictly causal PML was introduced in Kuzuoglu and Mittra (1996). The resulting tensor is referred to here as the complex frequency shifted (CFS) tensor. The application of this technique within the FDTD has been presented previously. Here, the formulation is postulated for a generalized medium, including lossy, dispersive, anisotropic, or non-linear media. For such a medium, there are no additional memory requirements as compared to the standard FDTD/PML methods. Furthermore, it is demonstrated that it accurately absorbs highly oblique incident waves with long time signatures and is computationally efficient.

In this paper, the FDTD technique is applied to the common mode radiation analysis of a printed circuit board. In the past, the FDTD technique had limitations in its applications to such problems due to poor absorbing boundary condition performance. A highly efficient implementation of an extended PML absorbing boundary condition is formulated and applied to the PCB in this paper. Results are given for some common PCB geometries which demonstrate various common mode current phenomena as well as the accuracy of this technique.

This paper discusses the efficient incorporation of skin-effect losses into the nonorthogonal finite-difference time-domain technique. A survey of previous work is presented and it is shown that the exponential approximations used by previous methods may lead to considerable error when good conductors are modeled using a fine time discretization. Subsequently, an improved exponential approximation is given and applied to various curved conducting waveguide surfaces using the nonorthogonal finite-difference time-domain technique.

In this paper the broadband propagating and radiating properties of a twisted pair transmission line are studied. This is accomplished by defining a coordinate system which conforms to the twisted wire geometry and subsequently solving Maxwell's equations in this general curvilinear coordinate system. Several new techniques were employed in this work. Specifically, the surface impedance boundary condition, the lumped source/load, and the near-field to far-field transformation were each applied in general curvilinear coordinates.

Periodic structures, such as frequency selective surfaces, photonic bandgap structures, and antenna arrays, are being more widely used in electromagnetic systems. To make the numerical modeling of a periodic structure more practical, usually a single unit cell of the structure is modeled and periodic boundary conditions are used to incorporate the periodic nature. Traditionally, frequency-domain techniques are used to numerically model such structures because of the simple way in which the boundary condition can be applied. However, when broadband data is needed, a time-domain approach is desirable. Unfortunately, periodic boundary conditions in the time-domain introduce the need for time-advanced data, obviously a problem for a time-domain approach. To get around this, a field transformation can be applied which simplifies the boundary conditions, but results in a more complex set of equations to be solved. The FDTD algorithm can be applied to the transformed field equations; however, additional variables must be introduced because of stability considerations. One technique that has been developed for discretizing and solving the transformed field equations is the split-field method. This paper extends the method to include general anisotropic dielectric and magnetic media.

A novel implementation of periodic boundary conditions incorporated into the finite-difference time-domain (FDTD) technique in both orthogonal and nonorthogonal grids is presented in this paper, The method applied is a field-splitting approach to the discretization of the Floquet-transformed Maxwell equations, As a result, computational burden is reduced and the stability criterion is relaxed, The results of the two methods are compared to experimental data.

It is demonstrated that the source of late time instabilities in the non-orthogonal FDTD (NFDTD) and discrete integral equation/generalized Yee (DSI/GY) methods is due to the ill-posed nature of the original formulations. Specifically, for general problems the explicit operators are not well posed. This leads to solutions that are unstable in the late time independent of the time step. Secondly, methods by which to repose the problem in a manner that is well posed, accurate and stable are presented.

In this work, a novel implementation of the uniaxial PML absorbing boundary condition in a 3D nonorthogonal space is proposed and studied. To evaluate the PML, the medium is applied to a bifilar helical waveguide structure. The effectiveness of the PML is thoroughly investigated versus the PML depth, profile, and conductivity. Results are presented for both homogeneous and inhomogeneous geometries. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14, 71–75, 1997

An accurate and efficient method of including frequency-dependent conductor losses into the time-domain solution of the multiconductor transmission line equations is presented, It is shown that the usual 1 + B root s representation of these frequency-dependent losses is not valid for some The reason for this is the practical geometries, representation of the internal inductance of the at lower frequencies. A computationally efficient method for improving this representation in the finite-difference time-domain (FDTD) solution method is given and is verified using the conventional time domain to frequency-domain (TDFD) solution technique.

In this paper we demonstrate the accuracy of the FDTD technique in calculating the signal propagation characteristics of a twisted pair transmission line. The PML absorbing boundary condition is applied in non-orthogonal coordinates in order to accurately model the wire contours with minimal error from sidewall reflections. The effects of the wire dielectric coating as well as the wire twist are examined