A numerical method for the analysis of coupling to thin wire structures

A numerical method for determining the response of thin-wire structures to an arbitrary time-varying electromagnetic field is presented. Explicit central-difference techniques are utilized to calculate the vector potential and charge at discrete locations on the wire structure. The scalar potential is obtained by integrating the time-retarded charge distribution over the structure. The unknown current is obtained by solving the discrete equations relating the current and vector potential for each time step. The technique is used to determine the current distribution due to a plane wave incident on a large antenna composed of thin wires. Coupling calculations are in good agreement with well-established numerical methods. This approach is substantially different from existing time-domain integral-equation techniques and allows for easy implementation of wire connections, changes in wire diameter and computer-code optimization by eliminating unnecessary calculations. The technique can be coupled with 3-D finite-difference codes to cover structures that are attached to the wires. The methods described have been used successfully to calculate coupling to a log-periodic antenna