Multiple beam lens antenna for LEO communication satellite

The design of a multiple beam antenna system for a low earth orbiting (LEO) cellular communication satellite is a topic of current interest. A typical uplink requirement is to provide a number of closely overlapping beams to illuminate Earth-fixed super cells at Ka band. These cells span a field of view of approximately /spl plusmn/40/spl deg/ degrees in elevation and azimuth. Their beamwidths vary with position, going from a 6.3 degrees circular beam at the centre of earth coverage to an elliptical beam of 4.5/spl times/3.2 degrees at the edge of coverage. Further, the sidelobes should be less than -30 dB two beamwidths away and below -35 dB four beamwidths away to minimise interference between beams. A design procedure is outlined that will lead to an antenna with these specifications.