Spherical wave expansions for reflector antennas with truncated field data

Spherical wave expansions (SWEs) for focus-fed symmetric paraboloids and hyperboloids using truncated field data have been investigated. The input field data for obtaining the SWE coefficients of a symmetric reflector have been determined in terms of numerical single integrals using the formulation given by A.W. Rudge et al. (1986). Patterns obtained for a hyperboloidal reflector are shown. These patterns indicate that the on-axis accuracy of the patterns produced from truncated field data is determined by the pattern intensity at the truncation angle. Truncation at a point of relatively high field intensity results in an appreciable ripple level for the on-axis field amplitude as a function of distance from the reflector.<>