An Improved Ground Beacon Antenna

An electromechanical scanning antenna technique is proposed to provide improved TACAN ground-beacon performance over the full 960-to 1215-Mc band.A radially symmetric, shaped-beam reflector is illuminated by an off-set, radial-pillbox horn. The horn is driven by a radial transmission line which contains a central radiator. Parasitic elements are arranged in dielectric rings positioned concentrically with the central radiator. The rings are rotated uniformly about the center line to generate an amplitude-modulated, omnidirectional azimuth pattern. The complex response of the elements controls the percentage modulation, while the geometry of the reflector and its feed independently control the shape of the elevation pattern. The antenna generates uniform azimuth modulation over the elevation angles of interest.