Frequency-domain Transmission Line Matrix Research Articles

A Hybrid Formulation of a Frequency-Domain TLM and Integral Equations Field Method

In many applications, heterogeneous structures are separated by some distance in a homogeneous medium. This homogenous space must be entirely meshed when volumic methods are used. This letter presents a hybrid formulation between the frequency-domain transmission line matrix (FDTLM) method and a field integral equation formulation that avoids the meshing of the homogeneous background in which complex objects are located. In addition, it prevents the use of absorbing boundary conditions. To simplify the theoretical development for the 3-D case, the problem of a rectangular waveguide with inductive objects is presented. Although invariance along the waveguide height with the fundamental mode excitation, the problem is treated by 3-D FDTLM nodes for validation. It is found that some computer cost reduction can be achieved as compared with the full meshing approach.

Toward the Coupling of a Discontinuous Galerkin Method With a MoM for Analysis of Susceptibility of Planar Circuits

We aim at coupling a method of moments, the Wave Concept Iterative Procedure, and the Hybridizable Discontinuous Galerkin (HDG) method to study electromagnetic susceptibility of innovative planar circuits in 3-D. Hybridizing the Wave Concept Iterative Procedure with volumic methods such as the Frequency-Domain Transmission Line Matrix method, the finite-element method, and the HDG method in 2-D is a first step for the validation of the proposed coupling technique. The considered problem is Maxwell's equations in the frequency domain. Three test cases in 2-D and a preliminary result in 3-D are provided.

A FAST HYBRID WCIP AND FDTLM APPROACH TO STUDY INHOMOGENEOUS CIRCUITS

The hybrid approach based on the coupling of the Wave Concept Iterative Procedure method and the Frequency Domain Transmission Line Matrix method is improved. The proposed method reduces the computation time by solving waves at the planar circuit interface: the volumic method is replaced by an equivalent surface condition. Thanks to this new approach, planar circuits presenting inhomogeneous dielectric substrates are studied. The proposed approach is compared to other methods on several examples.

The segmentation concept for frequency-domain TLM method combined to the variable mesh technique

In this paper, the segmentation method is implemented in the frequency-domain transmission line matrix (FD-TLM). The method is combined with the variable mesh technique. Although the procedure is general, the examples shown concern the design of waveguide discontinuities. Thus, the structure is decomposed into several sub-domains and a finer mesh is used in the computational domain around discontinuities. An important reduction in computing time and memory resources is achieved with a good accuracy.

Absorbing boundary conditions for the FD-TLM method : the perfectly matched layer and the one-way equation technique

This paper investigates the absorbing boundary conditions for the frequency domain transmission line matrix method. Two approaches are presented, namely the perfectly matched layer (PML) technique and the one-way wave equation. Concerning the PML technique, two-dimensional and three-dimensional transmission line matrix (TLM) nodes, already used in time domain, are exploited in frequency domain where a rigorous formulation of these PML-TLM nodes is presented. In addition, two types of one-way wave operators are also transposed from time to frequency domain TLM approach: Taylor expansion and Higdon's boundary conditions. The simulation of a wideband matched load WR-28 rectangular waveguide is presented for validation. Excellent results are obtained with a very thin PML layer. Results concerning one-way operator techniques also show very good return loss performances. For instance, Higdon's boundary condition was extended beyond third-order approximation, and a return loss better than 160 dB was obtained. Copyright © 2013 John Wiley & Sons, Ltd.

2D FDTLM HYBRIDIZATION WITH MODAL METHOD

This article focuses on the 2D hybrid technique between the Frequency Domain Transmission Line Matrix Method (FDTLM) and the Wave Concept Iterative Procedure (WCIP). 3D hybridization has already been studied, but results may be improved through a better knowledge of method order. Consequently, developing 2D hybridization aims at understanding the hybridization in simplest problems, especially because Transverse Electric (TE) and Transverse Magnetic (TM) are uncoupled. Our study dwells on accuracy and convergence order of the 2D hybrid method, which will help for 3D mesh use. In this perspective, the scattering nodes and electromagnetic flelds expressions are established in the 2D general case with anisotropic materials. As a result, validation examples are presented to check the approach.

A new computationally efficient hybrid fdtLM–WCIP method

This article presents a new hybrid technique which combines two different numerical methods in the frequency domain, namely the Frequency Domain Transmission Line Matrix ( fdtLM) and the Wave Concept Iterative Process, to analyse three-dimensional (3D) microwave structures. As a result, a considerable reduction of the computation time and required computer memory is achieved compared with the classic fdtLM. The good agreement between simulation results and experimental published data validates the present analysis approach.

On the Relationship Between the Time-Domain and Frequency-Domain TLM Methods

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The time- and frequency-domain transmission line matrix (TLM) methods have been developed and shown to be effective and powerful in solving electromagnetic problems. However, their direct relationship has not been clearly described so far. In this letter, we show that if a time-domain TLM method is developed, its corresponding frequency-domain counterpart can also be obtained through the discrete time Fourier transform; in a similar manner, if a frequency-domain TLM method is developed, its time-domain counterpart can also be obtained through the inverse discrete time Fourier transform. The choice of using the frequency- or time-domain depends very much on the types of the problems to be solved and the familiarity of a user with the methods. </para>

Gauge techniques in time and frequency domain TLM

Typical features of the Transmission Line Matrix (TLM) algorithm in connection with stub loading techniques and prone to be hidden by common frequency domain formulations are elucidated within a propagator approach. In particular, the latter reflects properly the perturbative character of the TLM scheme and its relation to gauge field models. Internal ‘gauge’ degrees of freedom are made explicit in the frequency domain by introducing the complex nodal S-matrix as a function of operators that act on external or internal fields or virtually couple the two. As a main benefit, many techniques and results gained in the time domain thus generalize straight away. The recently developed deflection method for algorithm synthesis, which is extended in this paper, or the non-orthogonal node approximating Maxwell's equations, for instance, become so at once available in the frequency domain. In view of applications in computational plasma physics, the TLM model of a relativistic charged particle current coupled to the Maxwell field is traced out as a prototype.

TFDTLM-a new computationally efficient frequency-domain transmission-line-matrix method

In this paper, a new computationally efficient frequency-domain transmission-line matrix (FDTLM) approach is introduced. The new approach combines the superior features of both the time- and the frequency-domain transmission-line matrix (TLM). It is based on a steady-state analysis in the frequency domain using transient analysis techniques and, hence, is referred to as the transient frequency-domain transmission-line matrix (TFDTLM). On the contrary, of all other frequency-domain techniques, the TFDTLM has the advantage of being able to extract all the frequency-domain information in the frequency range of interest from only one simulation. This special feature of the TFDTLM makes it computationally more efficient as compared to any other FDTLM method. The TFDTLM employs digital filter approximations for modeling wave propagation in inhomogeneous frequency dispersive media. The filters can be thought of as some type of compensation equivalent to the stubs in a time-domain transmission-line matrix (TD TLM), yet more accurate and more capable of modeling a wide variety of frequency-dependent material parameters. In addition, the TFDTLM has proven to have superior dispersion behavior in modeling lossy inhomogeneous media as compared to the TD TLM.

The frequency-domain transmission line matrix method-a new concept

A frequency-domain transmission line matrix (TLM) method for the frequency-selective S-matrix computation of 3D waveguide discontinuities is presented. It combines the flexibility of the conventional TLM method with the computational efficiency of frequency-domain methods. The basis for this technique is the excitation of an impulse train of sinusoidally modulated magnitude, which retains the form of an impulse while its envelope contains the information of the structure at the modulation frequency. Utilizing the diakoptics technique in conjunction with the concept of the intrinsic scattering matrix, the original electromagnetic field problem is simplified to a matrix algebra problem. A variety of structures have been analyzed in order to check the accuracy of the approach, and excellent agreement has been observed in all cases. S-parameters for CPW air-bridges including finite thickness and conductivity of the metallizations are computed. The effect of superconducting air-bridges is analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>