Transmission line
[[Transmission line matrix method|Transmission line matrix]] (TLM) can be formulated in several means as a direct set of lumped elements solvable directly by a circuit solver (ala SPICE, [[HSPICE]], et al.), as a custom network of elements or via a [[scattering matrix]] approach. TLM is a very flexible analysis strategy akin to FDTD in capabilities, though more codes tend to be available with FDTD engines.