Transmission-line matrix method: Difference between revisions

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{{short description|Method of computing electromagnetic fields}}

The '''transmission-line matrix (TLM) method''' is a space and time discretising method for computation of [[electromagnetic fields]]. It is based on the analogy between the electromagnetic field and a mesh of [[transmission line]]s. The TLM method allows the computation of complex three-dimensional electromagnetic structures and has proven to be one of the most powerful time-___domain methods along with the finite difference time ___domain ([[FDTD]]) method.

The '''transmission-line matrix''' ('''TLM''') '''method''' is a space and time discretising method for computation of [[electromagnetic fields]]. It is based on the [[analogy]] between the electromagnetic field and a mesh of [[transmission line]]s. The TLM method allows the computation of complex three-dimensional electromagnetic structures and has proven to be one of the most powerful [[Time ___domain|time-___domain]] methods along with the [[finite difference time ___domain]] (FDTD) method. The TLM was first explored by British electrical engineer [[Raymond Beurle]] while working at [[English Electric Valve Company]] in [[Chelmsford]]. After he had been appointed professor of [[electrical engineering]] at the [[University of Nottingham]] in 1963 he jointly authored an article, "Numerical solution of 2-dimensional scattering problems using a transmission-line matrix", with [[Peter B. Johns]] in 1971.<ref name="de Cogan TLM">{{cite book |last1=de Cogan |first1=Donard |title=Transmission Line Matrix (TLM) Techniques for Diffusion Applications |date=12 December 2018 |publisher=Routledge |isbn=978-1-351-40712-0 |url=https://books.google.com/books?id=1lEPEAAAQBAJ |language=en}}</ref>

== Basic principle ==

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In order to describe the connection between adjacent nodes by a mesh of series nodes, look at the figure on the right. As the incident pulse in timestep ''k+1'' on a node is the scattered pulse from an adjacent node in timestep ''k'', the following connection equations are derived:

: <math>_{k+1}V^i_1(x,y)=_kV_{k+1}V^r_3(x,y-1)</math>

: <math>_{k+1}V^i_2(x,y)=_kV_{k+1}V^r_4(x-1,y)</math>

: <math>_{k+1}V^i_3(x,y)=_kV_{k+1}V^r_1(x,y+1)</math>

: <math>_{k+1}V^i_4(x,y)=_kV_{k+1}V^r_2(x+1,y)</math>

By modifying the scattering matrix <math>\textbf{S}</math> inhomogeneous and lossy materials can be modelled. By adjusting the connection equations it is possible to simulate different boundaries.

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== Open-sourced code implementation of 3D-TLM ==

The [[George Green (mathematician)|George Green]] Institute for Electromagnetics Research (GGIEMR) has open-sourced an efficient implementation of 3D-TLM, capable of [[Parallel computing|parallel computation]] by means of [[Message Passing Interface|MPI]] named GGITLM and available online. <ref>{{cite web|title=George Green Institute for Electromagnetics Research - TLM time ___domain simulation code|url=https://www.nottingham.ac.uk/research/groups/ggiemr/our-research/projectslarge-scale-electromagnetic-modelling/ggitlmlarge-scale-electromagnetic-modelling.aspx|website=University of Nottingham - George Green Institute for Electromagnetics Research|publisher=University of Nottingham|accessdate=23 March 2017}}</ref>

== References ==

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* Mansour Ahmadian, Transmission Line Matrix (TLM) modelling of medical ultrasound [https://www.era.lib.ed.ac.uk/handle/1842/427 PhD thesis], University of Edinburgh 2001

[[Category:NumericalComputational differential equationselectromagnetics]]

[[Category:Computational science]]

[[Category:Computational physics]]

[[Category:Electromagnetism]]

[[Category:Electrodynamics]]