Importance

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Abstract

A steerable directional antenna assembly steerable about two perpendicular axes is disclosed. It comprises a directional horn antenna rotatably mounted on a horseshoe gimbal to rotate about a first axis. A curved wave guide feed is connected at one end to the feed portion of the directional antenna. The wave guide feed is disposed such that its center of curvature is located on the first axis of rotation. The curved wave guide has a circumferential slot in its outer side, the slot communicating between the ambient atmosphere and the wave guide interior. The gimbal and directional antenna are rotatably connected to a pedestal which is enabled to rotate the gimbal and directional antenna about a second axis which is perpendicular to the first axis. The antenna assembly further comprises a coaxial feed line which passes through an opening in the pedestal and is fixed to the pedestal. The outer conductor of the coaxial feed line is stripped away from one end of the line to expose the center conductor. The center conductor terminates in an enlarged probe portion. The curved wave guide feed is disposed to receive the center conductor through the circumferential slot and the enlarged probe portion is located within the wave guide interior. A reflecting plate is also disposed within the wave guide interior at a predetermined distance from the enlarged probe portion. The reflecting plate is rotatably connected through the slot to the coaxial feed line. The reflecting plate cooperates with the wave guide and enlarged probe portion to couple RF energy between the coaxial feed line and the directional antenna. It forces RF energy to propagate between the probe and the feed portion of the directional antenna regardless of the position of the directional antenna in rotation about the first axis. When the antenna is caused to rotate about the first axis the curved wave guide feed moves relative to the center conductor and enlarged probe portion along the circumferential slot. When the directional antenna is caused to rotate about the second axis the reflecting plate rotates about the second axis to cause all the RF energy to propagate between the enlarged probe and the feed portion of the directional antenna.

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First Claim