Analysis and design of the Schelkunoff-Friis antenna

Quasi-static (QS) analysis of the Schelkunoff-Friis antenna or asymptotic conical dipole (ACD), previously confined to computation of the effective height and the capacitance, is extended to yield the inductance. This results in a complete equivalent circuit that is useful below first resonance and exact for vanishingly small frequencies. Equipotential contours, obtained using Mathsoft´s Mathcad, permit low-frequency designs to be based on the maximum height and the capacitance, both specified arbitrarily. For use as a wideband wave launcher at frequencies above first resonance, this paper shows how the characteristic impedance of the conical region near the feed is related to the equivalent charge and surface potential governing the shape. Using Ansoft´s HFSS program, low-frequency behavior is shown to agree with QS results asymptotically and wideband impedance behavior is demonstrated