Multiple beam synthesis of low sidelobe patterns in lens fed arrays

Low sidelobes in lens fed multibeam arrays present some unique problems. The technique of synthesizing low sidelobe patterns by the superposition of multiple orthogonal beams offers several advantages, particularly in lens fed arrays. It is shown that the Taylor line-source distribution is a superposition of multiple orthogonal beams. It is further shown that use of only three beams provides patterns close to the exact Taylor pattern for theoretical sidelobe levels as low as -43 dB. In an experimental implementation of the technique, sidelobe levels of -29.9 dB have been measured using three central beamports in a lens fed multibeam array. Over a 10-percent band, -28 dB levels were maintained. Trimming array cables to eliminate random phase errors lowered the sidelobe levels to -32.6 dB over a narrow band.