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Title: Using Efficient Model-Based Parameter Estimation for Pole-Free Solutions of Modal Propagation Constants, as Applied to Shielded Planar Structures
Abstract: A fast and efficient adaptive sampling algorithm is applied to model-based parameter estimation of a Method-of-Lines implementation of two- and three-layer shielded planar structures, creating a pole-free function for the calculation of the propagation constants. The technique minimizes the number of characteristic equation evaluations, and hence reduces the computation time by orders of magnitude when compared to methods using the characteristic equation directly. Examples of a shielded microstrip line and a finline structure are shown below. Between 3 and 15 evaluations of the characterisic function are typically required per determination of an imaginary or real zero.
Author(s): Robert Lehmensiek, Petrie Meyer
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 910 KB

Title: Fast Implementation of Heat Radiation in a Self-Consistent FDTD Analysis Tool for Microwave and Hybrid Ovens
Abstract: This paper presents an efficient simulation tool for conventional, microwave and combined heating. Two heat transfer mechanisms are included: conductive and radiant heat transfer. The conductive heat transfer is modeled by a finite difference algorithm. A modeling technique for radiant heat transfer in non-uniform grids has been developed and is here presented for the first time. A finite difference scheme is not applicable for the radiant heat transfer, as radiation from a material surface is not bounded to the immediate vicinity as is conductive heat transfer. Therefore ray optical methods are used. Rays connecting mutually visible surfaces are obtained by a new fast method. Necessary but acceptable simplifications allow fast computations. The algorithms are conveniently integrated together with an electromagnetic FDTD program into one simulation tool. Representative simulations are presented for an oven heated conventionally, by microwaves, and by a combination of both.
Author(s): J. Haala, J. v. Hagen, W. Wiesbeck
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 923 KB

Title: A General Method for the Ray-Tracing on Convex Bodies.
Abstract: A method to compute the ray tracing over complex bodies composed by smooth convex surfaces of arbitrary shape is presented. The bodies are assumed to be electrically large and perfectly conducting. Free-form parametric surfaces are used to describe the structures. The technique is simple and efficient, so it is suitable for complex bodies. Some results obtained with FASANT code, which implements this technique, are presented to prove the efficiency of the method.
Author(s): F. Saez de Adana, E. Gonzalez, O. Gutierrez, J. Perez, M. F. Catedra
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 540 KB

Title: On the Implementaion of the Equivalence Theorem in the Hybrid FDTD-MoMTD Technique
Abstract: The hybrid FDTD-MoMTD technique is a powerful tool for analysing the transient excitation of inhomogeneous permeable bodies by arbitrary thin-wire antennas. The technique is based upon the calculation of the equivalent electric and magnetic currents on a Huygen's surface that encloses the antenna. The paper studies, by means of several numerical experiments, the effects on the accuracy of the results of the size of the Huygen's box, the size of the spatial increment in the FDTD algorithm and the distance from the Huygen's surface to the observation point.
Author(s): M. A. Hernandez-Lopez, A. Ruibo Bretones, M. Quintillan, R. Gomez Martin
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 409 KB

Title: A Three-Dimensional Finite-Difference Time-Domain Algorithm Based on the Recursive Convolution Approach for Propagation of Electromagnetic Waves in Nonlinear Dispersive Media
Abstract: We present for the first time a successful formulation of a three-dimensional finite-difference time-domain algorithm that is based on the recursive convolution approach and is used to evaluate the propagation of electromagnetic waves in nonlinear dispersive media. We treat in particular the case where the nonlinear polarization term depends only on the product of the square of the electric field and the third-order electric susceptibility function. We find that, in contrast to the usual formulation for linear dispersive materials which uses a simple linear relationship between the next-time-step electric field and the previous-time-step electric field, the formulation for nonlinear dispersive materials with a third-order susceptibility function results in coupled nonlinear cubic equations, which relate the next-time-step electric field vector to the previous-time-step electric field vector. Consequently, the coupled nonlinear cubic equations must be solved at each time step to advance the electric field vector.
Author(s): S. J. Yakura, J. T. MacGillivray, D. Dietz
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 1349 KB

Title: FDTD Time Domain Near- to Far-Zone Transformation Above a Lossy Dielectric Half-Space
Abstract: Near- to Far-zone transformations in the Finite-Difference Time-Domain (FDTD) method can be performed in either the time domain or in the freuency domain. For free space conditions, the time domain near- to far-zone transformation is generally much faster and more memory efficient to use, when we require results at a large number of frequency points at a small number of far-zone directions. However when a lossy dielectric half-space is present, representing the ground, the frequency domain transformation has been favored since the Green's functions involved are relatively simple to express the frequency domain compared with the efforts needed to transform the equivalent currents into the frequency domain. This paper describes a combined time and frequency domain near- to far-zone transformation above a lossy dielectric half-space, where it is not necessary to transform the equivalent currents into the frequency domain. This transformation is much faster than the pure frequency domain transformation and comparisons are made between the two different approaches. For validation purposes, scattering of a dihedral above a lossy dielectric half-space is considered.
Author(s): Torleif Martin, Lars Pettersson
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 865 KB

Title: A Fast and Rapidly Convergent Iterative Physical Optics Algorithm for Computing the RCS of Open-Ended Cavities
Abstract: Two major enhancements to the iterative physical optics (IPO) method are described for analyzing the EM scattering from open-ended cavities. First, a Jacobi Minimal Residual (JMRES) iterative algorithm is developed which preserves the physically appealing nature of IPO while establishing robust convergence criteria based on minimizing the residual error. It is shown that the JMRES algorithm usually converges much faster than conjugate gradient based methods for cavities. Second, a form of the fast far field approximation (FaFFA) is implemented to accelerate the computation of the integral operator in IPO. The FaFFA decreases the CPU time by a factor of about 1/5*N[exp(1/3)], where N is the number of surface integration sample points. These improvements allow much larger and more realistically complex cavities to be analyzed with fast IPO.
Author(s): Robert J. Burkholder
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 700 KB

Title: Wave Concept Iterative Process Merges with Modal Fast Fourier Transformation to Analyze Microstrip Filters.
Abstract: A novel iterative method based on the concept of waves is reported for use in the field theory, computer aided design and optimization of high frequency integrated circuits. It consists of a recursive relationship between a given source and reflected waves from the discontinuity plane which is divided into cells. A high computational speed has been achieved by using Modal Fast Fourier Transformation (MFFT). The theory as well as its procedure implementation is described. Numerical results are succussfully compared with published data.
Author(s): A. Gharsallah, R. Garcia, A. Gharbi, H. Baudrand
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 459 KB

Title: A Random-Phase-Assisted Ray-Tracing Code for Wireless Channel Modeling
Abstract: A random-phase-assisted ray-tracing computer code for predicting spatio-temporal wireless channel parameters is presented. A two dimensional-three dimensional (2D-3D) hybrid ray-tracing algorithm is implemented in code for the prediction of channel parameters in outdoor micro- and pico-cellular urban environments. Meanwhile, a Random Phase Approach (RPA) is applied in the ray-tracing algorithm. The application of the RPA is intended for two-fold purposes: 1) to account for the effects of inaccurate antenna positions; 2) to predict the range of short-term fading fluctuation. Several measurements carried out in pico-cell environments confirm that calculation accuracy of the code. It wa found that measured fluctuation of path-loss and delay profiles are almost fully confined within the 90% confidence interval, proving that the approach can account for the effects mentioned above. In addition, the conventional verification of path-loss and delay profiles predicted by ray tracing was extended to include the verification of angle-or-arrival (AOA). The demonstrated calculation accuracy in spatial and temporal domain confirms the applicability of authors' code to analyze system performance in real environments.
Author(s): Houtao Zhu, Jun-ichi Takada, Kiyomichi Araki, Takehiko Kobayashi
File Type: Journal Paper
Issue:Volume: 16      Number: 1      Year: 2001
Download Link:Click here to download PDF     File Size: 840 KB