Frequency and scan angle limitations in UWB phased array

In phased array, mutual coupling from adjacent elements produces scattering and absorption effects during low-angle beam steering. The scattering effect comprises of structure-mode scattering and antenna-mode scattering. The absorption effect occurs when the coupled energy received by an adjacent element is dissipated into the system. Constructive and destructive combinations of structure scattering from periodic array structures such as array elements or feeding structures produce undesired lattice scattering modes which limit the frequency upper bound and maximum scan angles.