Anomalous Edge Effects in Finite Arrays

The regular oscillations in scan impedance (normalized by the infinite array values) that occur across a finite array are uniquely altered in two special cases based on computer simulations of finite-by-infinite arrays. First, dipoles with groundplane at broadside in the E-plane, exhibit a slow modulation of the usual oscillations; the period of the modulation varies with dipole radius. For all other cases, the results are insensitive to radius. Second, for a dipole array and lattice spacing and H-plane scan angle that allow a grating lobe to appear at 90 the oscillations disappear, except at the rear edge. These phenomena give some indications of the behavior of the pseudotraveling waves in scan impedance.