More on TLM

Expanded node TLM solves for interleaved, or staggered (in space and time) field components.

Other ``condensed'' formulations, such as the Hybrid Symmetric, Super Symmetric etc., solve for the field quantities at the same grid location.

Still just centered differences (but not interleaved). Some comments:

• TLM: a hunt for unitary scattering junctions Observation: In waveguide (or WDF) formulation, do not require scattering matrices to be unitary for power conservation. But if needs be, then we have a Quick fix: Power-normalized waves (unknown in TLM).

• Condensed formulations. Observation: Scattering junctions derived using field-theoretic manipulations (vaguely like MD-circuit approach). Observation: Can also approach the problem by using vector delay lines. Build network, then set impedances (now matrices) accordingly.

• Passive arithmetic properties Observation: unknown in TLM.

Lesson: parochialism is a sad thing.