M. Khalladi

Absorbing boundary conditions for the TLM method

The numerical behavior of different absorbing boundary conditions when applied to the transmission-line modeling (TLM) method is presented. These conditions may be classified into three different groups according to the way they are derived. The first group is obtained by discretizing one-way analytical conditions derived for the analytical wave equation. The second group is a set of discrete conditions directly obtained for the discrete wave equation. The last group is based on appropriate reflection coefficients derived purely from transmission-line theory. Because of their different behaviors, the numerical study is explicitly carried out for both two- and three-dimensional free-space scattering problems. >

Dispersion analysis for a TLM mesh of symmetrical condensed nodes with stubs

In this paper, the dispersion characteristics of a TLM mesh formed by interconnected symmetrical condensed nodes with stubs are calculated using two different formulations. The dispersion relation derived is an implicit function of the wave number, frequency, dielectric permittivity, and magnetic permeability. Group and phase velocities are obtained for the three fundamental directions and different values of the relative permittivity. The study demonstrates that an increase in the modeled-medium permittivity leads to a decrease in the cutoff frequency for TLM numerical results. >

Modeling of frequency-dependent magnetized plasma in hybrid symmetrical condensed TLM method

In this paper, magnetized plasma media are modeled using the time-domain TLM method with hybrid symmetrical condensed node (HSCN). The proposed technique consists in adding voltage sources characterizing dispersive media in the HSCN. Numerical results are presented for reflection and transmission coefficients for a magnetized plasma wall, proving the efficiency of the proposed model.

An SCN-TLM model for the analysis of ferrite media

The modeling of ferrite media using the symmetrical condensed node (SCN) of transmission line matrix (TLM) method and current sources is developed. The proposed approach allows one to study the interaction between electromagnetic (EM) waves and gyromagnetic media. The obtained results are in good agreement with the analytical ones.

The far-zone scattering calculation of frequency-dependent materials objects using the TLM method

The transmission-line matrix method is used for the calculation of the far scattered field and radar cross section of frequency dependent materials objects. Three different materials have been considered, namely, Debye, plasma, and Lorentz for which the electric susceptibility is complex. The proposed model is based on the computation of the equivalent currents and on a time domain near-to-far-field transformation technique. To illustrate this study, the far-zone scattering results for different spheres using the three materials indicated above are presented.

Wire-junction matrix model for the TLM method

The additional capacitance and inductance introduced by a conducting wire can be modelled in the transmission line modelling (TLM) method by a special node. A symmetrical transmission-line structure is proposed for the modelling of wire junctions in a coarse mesh. The model is tested by calculating the response of a wire-cross scatterer and the RCS of a perfectly conducting plate simulated by means of a square wire mesh. Although, initially, TLM was not developed for solving wire structures, the results are in good agreement with the theoretical and moment-method solutions traditionally used for this type of structure. >

Two near-to far-zone approaches for scattering problems using the TLM method

The far-scattered field and radar cross section (RCS) are calculated by transforming the results of the transmission-line-matrix (TLM) method with the symmetrical condensed node (from the near-to the far-zone) by means of two different approaches, in the time domain. The first approach is based on the electromagnetic equivalence principle, and the second is based on the Kirchhoff theory of integration. Details and a complete description of the two approaches are given. Examples of far-zone-scattering results for three-dimensional conducting bodies are given to validate and compare the two methods. >

Efficient modeling of isotropic cold plasma media using JE-TLM method

New simulation technique, by the transmission line matrix method(TLM), of electromagnetic waves in dispersive cold plasma media is proposed. This technique exploits the dependence of the current density J and the electric field E, and the derivation of the ordinary differential equations (ODE) by the exponential fitting method. The TLM Model uses the standard symmetrical condensed node(SCN) with 12 principal ports and 3 additional ports in which we incorporate voltage sources to model the dispersive behavior of cold plasma media. To investigate the accuracy of this approach, reflection and transmission coefficients of non-magnetized plasma wall are computed. Also the far-zone scattering results of a cold plasma sphere are presented. All the obtained results, using the new modeling technique named JE-TLM are in good agreement with those of the theoretical ones.

Group and phase velocities in the TLM-symmetrical-condensed node mesh

This paper presents the analytical expressions of group and phase velocities as a function of frequency in the TLM-symmetrical-condensed node mesh for the three fundamental directions. The direction /spl lsqb/1, 1, 1/spl rsqb/ happens to be more dispersive than the directions /spl lsqb/1, 1, 0/spl rsqb/ and /spl lsqb/1, 0, 0/spl rsqb/, giving the TLM-symmetrical-condensed formulation dispersion characteristics similar to those of the FD-TD algorithm with a Courant number of 1//spl radic/3. >

New approach: WCIP and FDTLM hybridization

In this letter, we presents a new diakoptics approach, which combines two numerical methods in the frequency domain : The Frequency Transmission Line Matrix (FDTLM) and the Wave concept Iterative Process (WCIP), to analyse three dimensional (3-D) microwave structures.