A. Gascon Bravo

An impedance model, based on transmission line (TL) theory, is introduced for common mode ferrite chokes. The proposed model takes into account the geometrical properties of the choke, the distribution of electromagnetic fields within the core material and the impact of the measurement setup. The validity of the model was tested through numerical simulations. As a practical application, the model was applied to estimate the complex permeability of MnZn and NiZn cores from impedance measurements, resulting in a range of values compatible with those reported in other works.

This article introduces a comprehensive methodology for analyzing common-mode (CM) ferrite chokes in time-domain (TD) methods, employing lumped dispersive loads, and validates it through a typical test setup for cable crosstalk assessment. The analysis begins with the experimental characterization of CM choke material properties using a coaxial line fixture to obtain its constitutive parameters. Subsequently, a simplified lumped dispersive convolutional model is obtained, representing the impedance of the ferrite when placed on a location on the cable. The first approach adopts a multiconductor transmission line (MTL) model for the cables, solving them by a finite-difference (FDTD) space-time scheme. The second approach utilizes the classical full-wave Yee-FDTD method in conjunction with the thin-wire Holland model for cables. The accuracy of the proposed methods is evaluated by comparing simulations performed with MTL-FDTD and Holland-Yee FDTD, to experimental measurements, and results obtained with the the frequency-domain finite element method using a 3-D model of the ferrite with its constitutive parameters. Finally, the validity and performance of the methodologies are critically discussed.

This article introduces a process to design, simulate, and measure a novel multi-band patch antenna with different operation modes, i.e., band centers and bandwidths. Switching between operation modes is possible using a pair of PIN diodes to connect different parts of the antenna with the main antenna patch. Such a reconfigurable design allows for individual control of each frequency range. The main operation mode of the resulting antenna has an impedance bandwidth with two bands, one from 2.4 GHz to 2.73 GHz and another from 3.4 GHz to 5.73 GHz, with a maximum gain of 4.85 dBi and stable radiation patterns. The resulting antenna is suitable for applications using both ultra-wideband technologies and wireless local-area network (WLAN) technologies.

This article studies and improves the stability of a finite-difference time-domain (FDTD) subgridding method based on the orthogonalized-integral-based methodology. First, we identify the electric and magnetic field components of the FDTD lattices used at the interface between different mesh regions playing a critical role in its stability. Then, we use them to find a closed criterion for the Courant–Friedrichs–Lewy number (CFLN). Next, we analyze the stability by the classical spectral method and validate it with numerical heuristic simulations, proving the methodology used in the analytical approach. This information is used to devise a locally enlarged cell technique (LECT) to modify locally the scheme used to update the field components identified as most critical for stability so that an increased time step can be used. Finally, we analyze the effect of these modifications on the accuracy of the method for typical transmission and scattering problems.

Efficiently modeling thin features using the finite-difference time-domain (FDTD) method involves a considerable reduction in the spatial mesh size. However, in real-world scenarios, such reductions can lead to unaffordable memory and CPU requirements. In this manuscript, we present two stable and efficient techniques in FDTD to handle narrow apertures on conductive thin panels. One technique employs conformal methods, while the other utilizes subgridding methods. We validate their performance compared to the classical Gilbert-Holland model and present experimental results in reverberation environments to shed light on these models’ actual confidence margins in real electromagnetic compatibility (EMC) scenarios.