NEY , Michel

Many practical problems are of multiscale nature. This issue appears when relatively small regions inside the computational domain have a large impact on the overall behavior of the structure. This requires using small mesh size in these regions of interest for adequately representing their geometrical details. Using uniform fine grid...

Volumic time-domain computational methods such as FDTD or Transmission-Line Matrix method (TLM) are widely used for full-wave simulation of structures with arbitrary geometry. While FDTD is a direct discretization of curl Maxwell's equation using finite-difference operators, TLM is seen as a discretized version of Huygens' principle of wave...

Many problems in nature and engineering are multiscale. Thus, for adequately representing structure geometrical details, one has to use small cell sizes which impose small time-step values. In addition, if the mesh is irregular but structured it might lead to exhaustive computer expenditure and higher dispersion. The alternate approach is to...

To find a stable Time-Domain (TD) numerical scheme, that adopts a local time-step in unstructured meshing, is a real challenge in numerical methods. This article presents a theoretical investigation on the origins of such instabilities. New finding shows that using multiple time-steps in one computational domain with TD methods produces a...

With the advancement of technology, modern equipment involves new functionalities that require complex media (e.g., anisotropic dispersive media such as ferrite, lossy dielectrics, or graphene) for a variety of applications. This imposes the necessity to extend simulation techniques capable of solving Maxwell's equations in such media. However,...

National audience

National audience

National audience

National audience

National audience

National audience

Ultra wideband (UWB) antennas are used extensively in the area of biomedical communication devices. The main reasons behind that are their robust performance for indoor environments, high data rates, inherently encrypted data…etc. UWB antennas propagate EM-signals of up to few GHz in bandwidth. However, the dispersive nature of human tissues...

A new 3-D TLM-TW (Transmission Line Matrix - Twin Wire) numerical scheme is proposed for modeling thin wires buried in a general inhomogeneous, dispersive, conductive medium. To solve the time convolution product introduced by the dispersive medium, a recursive algorithm obtained by bilinear Z-transform approach is used. This technique is...

This article presents a time-domain numerical scheme for simulating EM-computational problems that include complex media and fine geometrical details in critical regions. These problems are common in engineering and applied physics. To name a few, microwave and optical devices that contain complex media, antennas characterization in presence of...

Un modèle de fil mince arbitrairement orienté pour le maillage cartésien 3D TLM est présenté. Il permet de tenir compte des jonctions ainsi que du couplage de proximité entre plusieurs fils. Les comparaisons entre les simulations et les mesures d'antennes filaires typiques valident le modèle.

This article presents an optimal connection topology to model the voltage-exchange at the interface between different sub-grids in nonstructured TLM meshes. As a first step, the derivation—using Kirchhoff's circuit laws—of these voltage-exchange equations between two subdomains with an arbitrary meshing ratio and a specific connection topology...

The purpose of this paper is to develop a modeling tool for VLF/LF antennas taking into account surrounding components such as insulators. Numerical results of the field distribution along an insulator using the transmission line method (TLM) are pesented. These results are compared with commercial software data and show a good agreement. A...

This article presents a study of the impact of finite-radius wire antennas in the High Frequency (HF) and the Very HighFrequency (VHF) bands on human operators located in the near-field zone. Modeling a finite-radius wire antenna can be a verytricky task, since the antenna parameters, such as the input impedance and the...

La modélisation et la caractérisation d'antennes basses fréquences dans des environnements réels sont considérées comme l'un des problèmes de calcul les plus difficiles. Cette complexité provient principalement de la nature multi-échelle des scénarios basse fréquence. Dans cet article, nous présentons une technique de maillage par blocs...

Modeling and characterizing low frequency antennas in realistic environments is considered as one of the most difficult computational problems. This complexity arises mainly from the multiscale nature of low-frequency scenarios. In this article, we present a block meshing technique with TLM to accurately represent the geometry of thin-wire...

The insatiable demand to optimize and engineer new functionalities in electromagnetic devices has risen their geometrical complexity to unprecedented levels. This usually results in computationally multiscale problems with some tiny components of great importance to the overall behavior of these devices. Block meshing is a powerful...

This article revisits the ideal transformer model used at the interface between different sub-grids in non-structured TLM meshes. The derivation of the voltage-exchanges equations between two subdomains with an arbitrary meshing ratio and connection topology is presented. The voltage-exchanges process is then generalized as a scattering-matrix...

Numerical dosimetry is a mandatory step in the designing process of any new EM device that operates in presence of living beings. One of its objectives is to ensure that a maximum Specific Absorption Rate (SAR) never exceeds the recommended values. In addition, including human models in simulations is necessary to evaluate the impact of human...

To design any new EM-device, it is of great importance to have a good estimation of the specific absorption rate (SAR) distribution or the Power Density (PD) it induces in users or people in its proximity. Respecting the recommended SAR limits is mandatory for any new technology to go public. Moreover, the good knowledge of SAR/PD is critical...

La conception de nouveaux dispositifs micro-ondes et optiques nécessite de traiter des problèmes de calcul avec des complexités géométriques croissantes et de développer des schémas numériques plus rapides et plus efficaces. Le maillage par blocs est une technique puissante de réduction de ressources informatiques en termes de temps processeur...