Shaped-Beam Circularly Polarized Antenna Array of Linear Elements for Satellite and SAR Applications

A circularly polarized planar antenna array consisting of linearly polarized elements is proposed for satellite and synthetic aperture radar applications. The individual linearly polarized elements are arranged in a linear or planar array form with the feed relations of the elements is adjusted to produce circularly polarized radiation. A subarray element of four λ/2 dipoles arranged in a planar cross form is proposed as a sub-element of the high gain arrays. Ten of these subarrays are arranged in a linear form to produce high gain circularly polarized radiation. The particle swarm optimization algorithm has been used in a new manner to reduce the computation time and producing reasonable results at the same time. This has been implemented by applying the PSO algorithm on two perpendicular linear arrays of point sources, without the need to apply the PSO to calculate the amplitudes and phases for the entire elements of the planar array. For 10 × 10 subarray elements arranged in a square planar form, an isoflux beam is generated in the range plane to realize 16° beamwidth radiation pattern with circular polarization. Also, another planar array of a cosecant squared beam is produced using the same array size in the range plane. The beam is flat-topped in the other perpendicular azimuth plane for both the isoflux and cosecant-squared shaped beams.