A 120-degree sector beam from a transverse slot on the corner of a triangular waveguide for a base station antenna in millimeter-wave subscriber radio system

An array of transverse slot antennas cut on the corner of a triangular waveguide is proposed for a base station in a millimeter-wave subscriber radio system. The bent slot with an interior angle of 60 degrees provides a 120-degree beamwidth in the horizontal plane for a three sector system. In principle, the triangular waveguide has a quite small transmission loss in comparison with a coaxial line and a microstrip line especially in millimeter waves. The array of slots gives a synthesized radiation pattern in the vertical plane to illuminate the coverage effectively. A single slot is discussed in this paper to demonstrate the feasibility. The internal field distributions in the triangular waveguides are analyzed at first to enhance the vertically polarized slot radiation. The far-field pattern with 120-degree beamwidth and the sufficient coupling are then confirmed for the 12 GHz band experimentally.