Parasitic excitation of circular antenna arrays

A method of calculating the radiation pattern of a circular antenna array of parallel monopoles or dipoles using symmetrical components is presented. The results obtained when only one element of the array is excited are not particularly good. However, if an additional element is added at the center of the array a fairly good directional pattern results. The sidelobe level is dependent upon the tuning of this central element, and a graphical analysis is given which optimizes this tuning. Calculated and measured patterns are shown and compared. Sidelobe levels of 15 db, and a beamwidth of are typical. The principal advantage of this antenna lies in the fact that the pointing of the beam can be changed by simply changing the element that is excited.