Investigation of the Sequential Rotation Technique and its Application in Phased Arrays: R 732

This report documents the investigations of the sequential rotation technique in application to phased array antennas. A spherical wave expansion for the far field of sequentially phased arrays is derived for general antenna elements. This model is approximate in that it assumes that the element patterns are identical and it does not included the effects of mutual coupling between the elements. For this reason it is compared with more accurate numerical models which include the coupling effects. The results show that the sequential rotation technique generally improves the performance of the phased array also when it is scanned off bore sight. For array topologies where the elements are not positioned rotationally symmetric the performance of the sequential rotation is to some extent impaired by the mutual coupling and non-identical element patterns. These effects are not evident from the approximate model but can be seen from the numerical investigations. The report discusses the influence of the element polarisation purity, improvements in axial ratio bandwidth and impedance bandwidth.