Beam tilt-angle compensation for a rotatable flush-mounted surface-wave antenna on an asymmetrical ground plane

The beam tilt angle of a rotatable flush-mounted surface-wave antenna mounted on the underside skin of an aircraft varies as the antenna is mechanically scanned in azimuth. This beam tilt-angle variation results because the antenna is presented with a finite asymmetrical ground plane, which introduces a wide range of ground-plane conditions to the antenna as a function of azimuth angle. A method that can compensate partially for these beam tilt variations for low beam tilt angles is described.