Accurate modeling of thin wires in the FDTD method

In many electromagnetic problems analyzed numerically with the finite-difference time-domain (FDTD) method, thin wires need to be modeled. A wire is considered thin when its diameter is less than the selected mesh size. It certainly is possible to select a sufficiently small mesh, so that the wire diameter occupies one or more computational cells, but this approach open results in a very fine discretization and excessive computational resources. We have performed a detailed numerical evaluation of the input impedance and the resonant frequency of a dipole antenna, and compared the results with with those obtained with the method of moments (MoM) based code, the Numerical Electromagnetic Code, NEC. But the results are obtained by use of an incorrect (not physics based) normalization factor. These limitations of available subcell wire models provided motivation for our work. In this article we describe a new algorithm and its implementation. Dipole parameters (the input impedance, resonant frequency and resistance at resonance) computed with the new algorithm are compared with those obtained with the standard algorithm, and modified one, as well as with the reference solution.