Surface waves on a finite planar dipole array in free space

Munk et al. (2002) and Janning et al. (2002) have demonstrated the excitation of surface waves, which can exist under certain conditions, on a planar periodic finite × infinite planar array of dipoles in free space when a plane wave is incident on the array. In this paper, the above work is extended to study the excitation of such surface waves on a completely finite, or finite × finite, planar rectangular array of dipoles which is excited by an external plane wave. It is noted that these surface waves are guided by the perfectly conducting dipole elements of the array, and they should be distinguished from the more conventional surface waves of a printed dipole array on a grounded substrate which essentially correspond to the modes of the grounded substrate. Here, such surface waves are clearly isolated via a numerical moment method (MoM) solution of an exact governing array integral equation for the element currents. It is interesting to note that most array designs keep the array interelement spacing small enough to avoid the excitation of array grating lobes; it is precisely for such spacings that the present surface waves can be excited.