Superdirective radiation from finite gratings of rectangular grooves

In this paper, the superdirective property of arrays comprising a finite nu mber of rectangular grooves is studied by using the modal approach, which i s a simple but powerful technique for analyzing these gratings. Numerical r esults show that when a specific characteristic mode of the structure refer red to as the pi mode is excited, the intensity of the field scattered in t he specular direction exhibits a maximum, which becomes sharper and narrowe r as the number of grooves is increased. The far field patterns exhibit sup erdirectivity at these resonant frequencies as evidenced by their beamwidth s that are narrower than those expected from apertures of comparable size. The model-based parameter estimation (MBPE) technique has been employed to help locate extremely narrow resonances that are characteristic of superdir ective arrays and its usefulness has been demonstrated.