Daniël De Zutter

Macromodeling of Multiport Systems Using a Fast Implementation of the Vector Fitting Method

Broadband macromodeling of large multiport systems by vector fitting can be time consuming and resource demanding when all elements of the system matrix share a common set of poles. This letter presents a robust approach which removes the sparsity of the block-structured least-squares equations by a direct application of the QR decomposition. A 60-port printed circuit board example illustrates that considerable savings in terms of computation time and memory requirements are obtained.

Selection of lumped element models for coupled lossy transmission lines

A practical method is developed for selecting the minimal number of lumped elements needed to represent a lossy transmission line if a certain accuracy is desired in a well-defined frequency range. This method, which uses dimensionless transmission line parameters, can be used in a wide range of applications and is also extended to hybrid equivalent circuits, consisting of ideal single lossless lines and resistors. For completeness, a lumped element model for coupled lossy lines is presented which uses the same dimensionless parameters and the same criteria as proposed for single lines. An example of coupled transmission line structure including skin-effect losses illustrates the approach. >

Laguerre-SVD reduced-order modeling

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.

Efficient mode-matching analysis of discontinuities in finite planar substrates using perfectly matched layers

A new method to determine the reflection of substrate modes in finite substrate planar circuits is proposed. The perfectly matched layer (PML) concept is used to transform the open problem into a closed one. The discrete set of substrate, evanescent, and Berenger modes of the resulting anisotropic waveguides are then used in a mode-matching scheme to deduce the scattering coefficients of the substrate modes for oblique incidence on the edge of the substrate. We show results for single- and double-layered substrates and compare with finite-difference time-domain (FDTD) results. The combined perfectly matched layer (PML) mode-matching technique turns out to be very efficient.

Numerical and experimental study of the shielding effectiveness of a metallic enclosure

This paper presents a detailed study of the shielding effectivity properties of metal enclosures. Measurements in anechoic chambers are compared to full-wave electromagnetic simulations. The study is not limited to the frequency range below the first resonance frequency. Different aspects are investigated such as the influence of the size, position and number of apertures, and the effect of the presence of metal plates and of absorbing materials. Where possible, the specific behavior of the shielding effectivity is explained theoretically and existing simple design rules are assessed.

Analysis of cylindrical waveguide discontinuities using vectorial eigenmodes and perfectly matched layers

In this paper, we analyze the scattering at discontinuities in cylindrical waveguides, starting from a vectorial eigenmode expansion and by introducing perfectly matched layer (PML) boundary conditions. The structure under study is enclosed in a metal cylinder to discretize the radiative mode spectrum, while the coating of this cylinder with PML vastly reduces the influence of parasitic reflections at the metal. This allows for a model that is both faster and more accurate than previous models.

Skin effect modeling based on a differential surface admittance operator

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.

Rigorous analysis of the propagation characteristics of general lossless and lossy multiconductor transmission lines in multilayered media

The frequency-dependent propagation characteristics of lossless and lossy open coupled polygonal conductor transmission lines in a multilayered medium are determined based on a rigorous full-wave analysis. A boundary integral equation technique is used in conjunction with the method of moments. Losses in conductors and layers are included in an exact way without making use of a perturbation approach. Dispersion curves for the complex propagation constants and impedances are presented for a number of relevant examples and, where possible, compared with published data. >

Adaptive CAD-model building algorithm for general planar microwave structures

A new adaptive technique is presented for building multidimensional parameterized analytical models for general planar microwave structures with a predefined accuracy and based on full-wave electromagnetic (EM) simulations. The models can be incorporated in a circuit simulator and the time required to calculate the circuit representation of a practical network is reduced by several orders of magnitude compared to full EM simulations. Furthermore, the accuracy of the results is significantly better compared to the circuit models used in state-of-the-art computer-aided design tools.

Measurement of low-permittivity materials based on a spectral-domain analysis for the open-ended coaxial probe

A new coaxial probe was designed to measure materials with a low dielectric constant at frequencies up to 1.5 GHz. Inconsistencies found while measuring samples of different thicknesses were solved by abandoning the model of Levine and Papas for the probe and developing a new model. Using the spectral-domain technique, a closed-form expression is obtained for the admittance of a hanged open-ended coaxial line radiating into a planar-stratified material backed by a metal plate. This new expression can be considered as a correction to the model of Levine and Papas. The model considers the dominant mode as well as the effect of higher order modes. With this new model measurements of low dielectric constant materials were performed together with a perturbation analysis of the influence of air gaps. Theory and measurements were found to be in good agreement. >