NUMERICAL-ANALYSIS OF HELICAL ANTENNAS BACKED BY FINITE GROUND PLANES

A method of moments for arbitrarily shaped wire antennas with dielectr ic coating is developed. In this paper, we use this numerical method t o investigate monofilar and quadrifilar helical antennas, whose wires are dielectric coated or not, backed by circular ground planes or cavi ties. Low-cost quadrifilar helical antennas that are printed on a thin dielectric substrate are also analyzed using this method. Indeed, the concept of equivalent radius is used to transform the printed wire an tenna into an equivalent dielectric-coated wire structure. (C) 1997 Jo hn Wiley & Sons, Inc.