Pattern ripple in near-to-far-field reconstruction

Far-field reconstruction from near-field data acquired over apertures of finite, practically realizable size is examined with point electric dipoles serving as primitive sources that retain some vestige of physical credibility. A fairly rigorous analytic apparatus and its numerical implementation reveal that the far-field patterns so attained are inevitably marred by gain ripples, and thus compromised as to their utility. These ripples, however, are an artifact of the fiction that wave propagation is entirely unburdened by dissipation. Indeed, in the special case of a horizontally aligned dipole, we are able to show quite unequivocally that gain ripples along its broadside and, by extension, along all other pattern directions, duly subside when wave dissipation is admitted into play.