Synthesis and analysis of omnidirectional dual-reflector antennas: Case of the main reflector with circular generatrix

The work considers the synthesis and analysis of dual reflector antennas designed to radiate omnidirectional radiation patterns. The reflectors are circularly symmetric concentric surfaces. Here, the case of the main reflector obtained from a circular generating curve is considered. By applying Geometrical Optics approximations, the subreflector is shaped to produce a uniform phase distribution on a cylindrical aperture placed in front of the main reflector. Depending on the type of ray mapping between the reflectors, two kinds of configurations are identified. By employing the aperture method, an exploratory study is performed to identify efficient and compact design antennas. To validate the results, a full wave analysis based on Method of Moments analysis is employed. Two design examples of omnidirectional antennas radiating vertical polarization are presented.