Luc Knockaert

Bio: Luc Knockaert is an academic researcher from Ghent University. The author has contributed to research in topics: Parametric statistics & Interpolation. The author has an hindex of 25, co-authored 181 publications receiving 2157 citations. Previous affiliations of Luc Knockaert include Intec, Inc. & Agilent Technologies.

Skin effect modeling based on a differential surface admittance operator

Abstract: An important issue in high-frequency signal integrity prediction is the modeling of the skin effect of thick conductors. A new differential surface admittance concept is put forward allowing to replace the conductor by equivalent electric surface currents and to replace the material of the conductor by the material of the background medium the conductor is embedded in. This new concept is studied in detail for the two-dimensional TM case starting from the Dirichlet eigenfunctions of the cross section. Detailed expressions are derived for the important practical case of a rectangular cross section. Next, the differential surface admittance operator is exploited to determine the resistance and inductance matrices of a set of multiconductor lines. A first set of numerical results provides the reader with some insight into the behavior of the surface admittance matrix. A second set of results demonstrates the correctness and versatility of the new approach to determine inductance and resistance matrices.

Laguerre-SVD reduced-order modeling

Abstract: A reduced-order modeling method based on a system description in terms of orthonormal Laguerre functions, together with a Krylov subspace decomposition technique is presented. The link with Pade approximation, the block Arnoldi process and singular value decomposition (SVD) leads to a simple and stable implementation of the algorithm. Novel features of the approach include the determination of the Laguerre parameter as a function of bandwidth and testing the accuracy of the results in terms of both amplitude and phase.

Surrogate-based infill optimization applied to electromagnetic problems

Abstract: The increasing use of expensive computer simulations in engineering places a serious computational burden on associated optimization problems. Surrogate-based optimization becomes standard practice in analyzing such expensive black-box problems. This article discusses several approaches that use surrogate models for optimization and highlights one sequential design approach in particular, namely, expected improvement. The expected improvement approach is demonstrated on two electromagnetic problems, namely, a microwave filter and a textile antenna. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.

Variability Analysis of Multiport Systems Via Polynomial-Chaos Expansion

Abstract: We present a novel technique to perform variability analysis of multiport systems The versatility of the proposed technique makes it suitable for the analysis of different types of modern electrical systems (eg, interconnections, filters, connectors) The proposed method, based on the calculation of a set of univariate macromodels and on the use of the polynomial chaos expansion, produces a macromodel of the transfer function of the multiport system including its statistical properties The accuracy and the significant speed up with respect to the classical Monte Carlo analysis are verified by means of two numerical examples

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Discrete-Dipole Approximation For Scattering Calculations

Abstract: The discrete-dipole approximation (DDA) for scattering calculations, including the relationship between the DDA and other methods, is reviewed. Computational considerations, i.e., the use of complex-conjugate gradient algorithms and fast-Fourier-transform methods, are discussed. We test the accuracy of the DDA by using the DDA to compute scattering and absorption by isolated, homogeneous spheres as well as by targets consisting of two contiguous spheres. It is shown that, for dielectric materials (|m| ≲ 2), the DDA permits calculations of scattering and absorption that are accurate to within a few percent.

Prolog to a chronology of interpolation: from ancient astronomy to modern signal and image processing

Abstract: This paper presents a chronological overview of the developments in interpolation theory, from the earliest times to the present date. It brings out the connections between the results obtained in different ages, thereby putting the techniques currently used in signal and image processing into historical perspective. A summary of the insights and recommendations that follow from relatively recent theoretical as well as experimental studies concludes the presentation.