An Improved Thin Wire Representation for FDTD Transient Simulations

The equivalent radius of a thin wire, which is represented by forcing the tangential electric field along the wire axis to zero in a three-dimensional finite-difference time-domain simulation, has been evaluated on the basis of a surge or characteristic impedance of a perfectly conducting horizontal wire above a perfectly conducting ground. It is 0.199Δs, where Δs is the lateral side length of cubic cells employed, and is smaller than the equivalent radii, 0.230Δs and 0.208Δs, estimated by Noda and Yokoyama (2002) and by Railton et al. (2006), respectively. Further, the thin wire representation of Railton et al. with this equivalent radius, which embeds a wire having the equivalent radius in an artificial parallelepiped medium having modified relative permittivity and permeability, has been proposed, and its validity has been tested for a horizontal wire and a vertical wire.