Shaped wire antennas for circular polarisation

The configurations of several wire antennas for circular polarization are studied. The advantages and disadvantages of conventional wire antennas, such as turnstile or spiral antennas, for circular polarization are discussed. Two CAD optimization techniques for the synthesis of circularly polarized antennas are described; the equation for calculating the figure of merit is presented. Various designs of truncated conical spiral antennas are examined. The relation between the figure of merit and the cone angle and pitch angle is investigated. The advantages the truncated conical spiral antenna design provides to circular polarization are analyzed.