TLM Network Research Articles

A TLM-SPICE interconnection framework for coupled field and circuit analysis in the time domain

A general SPICE-transmission-line matrix (TLM) interconnection framework has been developed. The connection algorithm is based on the representation of the TLM network by equivalent Thevenin and/or Norton sources. Fundamental issues such as source equivalence and SPICE-TLM interconnection options have been examined. The framework opens new and far-reaching possibilities for hybrid global microwave and high-speed digital circuit modeling in the time domain because it combines the extensive circuit and device models of SPICE with general three-dimensional field solutions.

TLM for diffusion: the artefact of the standard initial conditions and its elimination within an abstract TLM suite

AbstractWe demonstrate both analytically and numerically, that for the TLM algorithm for numerically solving the diffusion equation the standard initial conditions for the incident voltage pulses in terms of the initial concentration (or temperature) distribution introduce a significant numerical error. We discover the origin of this error and present an alternative prescription for computing the node voltages at the first time step which removes this artefact and exhibits distinctly improved numerical accuracy. For this, we introduce the term abstract TLM suite (ATS). An ATS is a numerical scheme which formally parallels a TLM scheme, but the scattering coefficients, ρ and τ, may assume values outside the interval [−1, 1] or may not correspond to the values of a real TLM network. Copyright © 2001 John Wiley & Sons, Ltd.

Characteristics of the general rectangular 2D‐TLM network

AbstractIn this paper the traditional square mesh 2D‐TLM algorithm is generalized for rectangular meshes of arbitrary aspect ratio. It is shown that the anisotropic rectangular TLM network can be conceived in such a way that the propagation vector remains independent of the direction of propagation in the infinitesimal approximation. A full dispersion analysis of the rectangular mesh in then performed for the general case, and results are compared to that of the traditional square mesh.

Redundancy and its implications in TLM diffusion models

AbstractRedundancy in the simplest form of a two‐dimensional TLM network is identified and a method of eliminating it is described. Results obtained using the non‐redundant algorithm are compared with those derived from the standard, redundant algorithm. The non‐redundant approach is extended to deal with non‐uniform elemental capacitance; a cylindrical geometry is taken as an example of this. The scope for and benefits of rendering TLM diffusion models non‐redundant are discussed.

A comparative study of two TLM networks for the modelling of diffusion processes

AbstractA comparative study of two alternative networks for TLM modelling of diffusion processes has been undertaken. Some of their inherent advantages and disadvantages are analysed according to the ratio between the impedance of the lossless transmission lines and the lumped resistance. Their relative accuracy and utility in controlling the timestep automatically are examined.