Excitation of a rotating mode in a radial waveguide by a cross slot-coupled rectangular waveguide

A radial line slot antenna (RLSA) is a high gain, high efficiency and low cost planar antenna proposed for DBS subscribers in the 12 GHz band. In the conventional RLSA, a radial waveguide has been fed by a coaxial feeder. In the millimeter wave band, fabrication of the feeder is considerably difficult, since the physical size is small. In this paper, an analysis for excitation of a rotating mode in a radial waveguide by a cross slot-coupled rectangular waveguide is proposed and an excellent transformer is designed. Instead of a ring slot, a cross slot was proposed for the excitation of the rotating mode in a radial waveguide. The lengths of slots are different from each other and the slots are crossed on 90°.