Single-feed four-arm curl antenna for circularly polarized radiation

A circularly polarized single-feed four-arm curl antenna is presented in this paper. We demonstrate that a four-arm curl antenna can be fed by a single 50-H source without a matching network and can produce good circularly polarized (CP) radiation at the desired frequency. A curl antenna normally exhibits as a resonant antenna and its input impedance depends on the number of turns, the spacing between its turns, the width of its arm, and the dielectric substrate. In this paper, the CP radiation was obtained via the proper choice of the number of turns, i.e., the turn numbers for the curl arms were chosen such that the real part of their input admittances were equal and the angle of the input admittances differed by 90°.