The treatment of thin wire and coaxial structures in lossless and lossy media in FDTD by the modification of assigned material parameters

It has been shown recently that the use of modified assigned material parameters (MAMPs) Within the finite-difference time-domain (FDTD) method provides a systematic, readily extensible, accurate, and efficient approach to the electromagnetic analysis of microstrip structures. In this paper, it is shown that this technique can also be applied with equal effect to lossless and lossy coaxial lines, wires in a lossy medium such as earthing grids, and more complex structures which include coaxial feeds and shorting posts. The modified parameters are calculated directly from the known asymptotic fields near the wire and do not rely on the concept of "equivalent radius." Results are given which show equal or superior performance compared to those obtained using other methods but with the added advantage of flexibility and rigor.