  The near-field channel gain is analyzed by considering both radiating and
reactive components of the electromagnetic field. Novel expressions are derived
for the channel gains of spatially-discrete (SPD) and continuous-aperture (CAP)
arrays, which are more accurate than conventional results that neglect the
reactive region. To gain further insights, asymptotic analyses are carried out
in the large aperture size, based on which the impact of the reactive region is
discussed. It is proved that for both SPD and CAP arrays, the impact of the
reactive region on near-field channel gain is negligible, even as the array
aperture size approaches infinity.
