VERTICAL WIRE ANTENNA ABOVE GROUND - SIMPLE NEAR-EXACT IMAGE SOLUTION

A very simple, but almost exact, image method is proposed for the anal ysis of vertical thin-wire antennas above ground. The method is based on the approximation of the actual field of a current element above an d below the ground surface by the field of a few (typically three) ima ges. The relative image current intensities are obtained by stipulatin g that the tangential components of the electric and magnetic field fo r the two cases, at a number of points at the interface, satisfy the b oundary conditions. The field of these images is next incorporated int o the Hallen equation, current distribution is approximated by polynom ials, and unknown coefficients are determined by point-matching. The r esults obtained for the impedance, current distribution and the radiat ion field of such dipoles are found to practically coincide with the e xact results (i.e. those obtained from the Sommerfeld theory), in spit e of the proposed method being conceptually much simpler and requiring about ten times less computing time than the exact method.