Surface fields on linear antennas

Surface fields are calculated for a source-excited flat-strip antenna in free space by modifying a variationalimpedance formulation. The exciting fields are related by an integral to the antenna current, and approximate current distributions correspond to nonvanishing tangential-electric-field components on the metallic antenna surface. Current distributions consisting of sine and shifted cosine waves violate the edge conditions and excite strong tangential electric fields near the ends of the conducting antenna surface. These field singularities are avoided by making the antenna current decay in proportion to the square root of the distance from the antenna edge. The more accurate current distributions produce smaller surface fields on the antenna, and it is possible to distinguish the more accurate current distribution even in cases where the variationally determined antenna impedances differ insignificantly. The calculated current distributions and impedances are compared with experimental data and with results of iterative calculations.