Beam sharpened pencil beam antenna systems

Claim 1

A dual mode antenna system, having a sum mode and a ring mode and providing 360 degree beam sharpening, comprising: an array of radiating elements positioned at zero, 90, 180 and 270 degree relative positions around a central axis, each said radiating element arranged to provide an antenna pattern nominally in the directions of said central axis; intercoupling means, intercoupling said radiating elements, including: (a) means for combining signals from said radiating elements at said zero and 180 degree positions to provide a first sum output and a first difference output; (b) means for combining signals from said radiating elements at said 90 and 270 degree positions to provide a second sum output and a second difference output; (c) means for combining said first and second sum outputs to provide a sum mode signal; and (d) means for combining said first and second difference outputs in a quadrature phase relationship to provide a linearly polarized ring mode signal representing an antenna pattern having a zero to 360 degree progressive phase characteristic around said central axis; sharpening adjustment means, coupled to said means for combining said first and second difference outputs, for adjusting the amplitude of one of said first and second difference outputs prior to said combining of said outputs in said quadrature phase relationship, to cause said ring mode signal to have portions of different amplitude; a sum mode port and a ring mode port, coupled to said intercoupling means, for respectively enabling said sum mode signal and said ring mode signal to be coupled from said intercoupling means; and processing means, coupled to said sum and ring mode ports, for processing said sum mode and ring mode signals to provide a beam sharpened antenna pattern representing portions of said sum mode signal of amplitude greater on a predetermined basis than the amplitudes of selected portions of said ring mode signal.