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 paper 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 employ 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.

An impedance model, based on transmission line 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 manganese zinc (MnZn) and nickel zinc (NiZn) cores from impedance measurements, resulting in a range of values compatible with those reported in other works.

This article presents the hybridization of a multiconductor transmission line (MTL) solver, implemented using the finite-difference time-domain method, with the circuit solver ngspice to treat the terminations and interconnections of transmission lines. Transient analysis and crosstalk in MTLs have been widely studied, but the line terminations and the connections between lines are mostly restricted to lumped resistors, inductors and capacitors (RLC) components. However, realistic systems, such as power distribution or communication systems, typically involve more complex and a priori unknown connections. By integrating the MTL solver with a circuit solver, the proposed approach enables the inclusion of any component for which a circuit model can be written or already exists, i.e., dispersive elements, such as ferrites, and electronic components, such as diodes, amplifiers, or transistors. This capability makes it possible to simulate the MTL networks with complex, including nonlinear, terminations and interconnections modeled by circuits. The proposed method is validated through comparison with experimental laboratory measurements.

This paper introduces an extended Stochastic Finite-Difference Time-Domain (S-FDTD) method tailored to analyze thin panel structures. It aims to predict the standard deviation and probability density function (PDF) of electromagnetic magnitudes (fields and currents), assuming their uncertainties in geometrical and material parameters are both known. The method to account for the sub-cell nature of the thin panel method used is based on the broadly tested subgridding boundary condition (SGBC) approach. This method employs an implicit-explicit hybrid (HIE) scheme in an unconditional Crank-Nicolson (CN) formulation (CN-SGBC), ensuring that it does not introduce any extra limitations to the standard stability criterion of the FDTD method. In the article, classical models of explicit formulations of S-FDTD are extended to the CN-SGBC HIE formulation.