ANTENNA FOR MULTIPLE FREQUENCY BANDS

摘要

An exemplary embodiment of an antenna in accordance with the present invention utilizes a sub-reflector and a main reflector with each of them having its own focal-ring type geometry. The antenna cooperates with a signal transmission feed disposed at the center of the antenna axis between the first and main reflectors to emit radio signals towards the sub-reflector. The sub-reflector reflects radio waves towards a main reflector which in turn reflects the radio waves to form the beam pattern emitted by the antenna. The reflecting surface of the sub-reflector is formed by a portion of an axially-displaced ellipse rotated about the antenna axis. The reflecting surface of the main reflector is defined by a section of a parabola rotated about the antenna axis to form a reflecting surface that concavely slopes away from the antenna axis. An embodiment of the antenna provides a wide coverage conical beam with selectable beam peaks that operate over a 2.25:1 frequency band range and provides substantially iso-flux beam density.

主权项

1. An antenna for transmitting and receiving radio frequency signals comprising:
a sub-reflector being an ellipsoid defined by a portion of an ellipse having a major axis not parallel to an axis of the antenna, the portion of the ellipse being in a plane that includes the axis of the antenna, where the portion of the ellipse is rotated perpendicularly about the axis of the antenna to define a first reflecting surface of the sub-reflector, a center of the sub-reflector being on the axis of the antenna with the first reflecting surface facing and cooperating with a signal feed system centered at the axis of the antenna so that radio waves from a distal end of the feed system impinge on the first reflecting surface and signals received by the antenna are reflected from the first reflecting surface to the distal end of the feed system; and a main reflector defined by a portion of a parabola being in a plane that includes the axis of the antenna, where the portion of the parabola is rotated perpendicularly about the axis of the antenna to form a second reflecting surface, the main reflector having a center being on the axis of the antenna with the second reflecting surface facing the first reflecting surface of the sub-reflector so that radio waves reflected from the first reflecting surface strike the second reflecting surface which in turn reflects the radio waves to form radio waves transmitted from the antenna, radio waves received by the antenna strike the second reflecting surface of the main reflector and are reflected to the first reflecting surface which in turn reflects the radio waves to the distal end of the feed system; the antenna producing a signal pattern of a wide coverage conical beam with a selectable beam peak between 45 degrees and 90 degrees relative to the antenna axis.