A slot-array antenna on a coaxial cylinder

In mobile communication, omnidirectional directivity and circular polarization are convenient properties because when they are used, acquisition and track operations for direction and polarization are not needed. As an antenna which has such properties, we developed a slot-array antenna on an oversize coaxial cylinder. This array antenna has less loss than microstrip arrays because energy is transported to each slot in the oversize coaxial waveguide. Also we can shape the beam in the vertical plane by controlling the size and position of slots. We developed cosecant and conical beam antennas. They are scale model antennas for respectively indoor communication by millimeter waves and mobile satellite communications. We show the performance of these antennas.