Pattern synthesis of spherical circular array antenna by conjugate gradient method

In this paper, the spherical circular array antenna pattern is synthesized and the results are compared with the planar circular array. Since the pattern function is complicated, analysis of pattern syntheses of solid surface arrays such as the spherical array becomes difficult. Herein, pattern synthesis is done numerically by minimizing the mean‐square‐error between the desired and synthesized power patterns using the conjugate gradient method. This method is found to be effective in the pattern synthesis of the spherical array. Calculations show that when elements with sharp patterns are used in the array, phase control is more advantageous in practice than amplitude control. Also shown here is the excitation method by which a circularly polarized pattern along the apex direction can be obtained when turnstile antennas are arrayed conformally on the sphere. With this excitation method, the pattern is synthesized and the axial ratio of polarization for main‐beam scan degrades less for spherical than planar array. Furthermore, for spherical array the axial ratio can be improved by placing the elements on a conducting sphere.