TLM modeling of thin wires in dispersive media

A new 3-D transmission line matrix-twin wire (TLM-TW) numerical scheme is proposed for modeling thin wires buried in a general inhomogeneous, dispersive, conductive medium. To solve the time convolution product introduced by the dispersive medium, a recursive algorithm obtained by bilinear Z-transform approach is used. This technique is developed for electrically dispersive media (i.e., magnetically non-dispersive) and its generality allows the use of any kind of Debye and Lorentz models or media represented by a ratio of polynomials with full power of (j ω). The TLM-TW numerical scheme is first validated through the simulation of a canonical thin lead cable surrounded by a homogeneous Lorentz dispersive medium. Then, the numerical study of an umbrella antenna, radiating structure typically used in VLF transmissions, is investigated.