Enhancing the radiation efficiency of compact antenna arrays using spatial tilting

In this paper, uniform circular compact antenna arrays, operating at 2.44 GHz, consisting of five to eight radiating elements are investigated. It is shown that the increase of mutual coupling with the increasing number of elements degrades the radiation efficiency of the antenna array, particularly for the super-directive mode. It is found that tilting of the individual elements along elevation results in a reduction of the mutual coupling, consequently restores partially the radiative performance of the antenna array. However, the recovery of radiation efficiency is limited to a certain angular tilting range. In addition, the optimal tilting angle depends on the number of elements of the antenna array.