Abstract :
A very simple, but almost exact, image method is proposed for the analysis of vertical thin-wire antennas above ground. The method is based on the approximation of the actual field of a current element above and below the ground surface by the field of a few (typically three) images. The relative image current intensities are obtained by stipulating that the tangential components of the electric and magnetic field for the two cases, at a number of points at the interface, satisfy the boundary conditions. The field of these images is next incorporated into the Hallen equation, current distribution is approximated by polynomials, and unknown coefficients are determined by point-matching. The results obtained for the impedance, current distribution and the radiation field of such dipoles are found to practically coincide with the exact results (i.e. those obtained from the Sommerfeld theory), in spite of the proposed method being conceptually much simpler and requiring about ten times less computing time than the exact method.
