Generalized classical axially-symmetric dual-reflector antennas

Classical axially-symmetric Cassegrain and Gregorian reflectors are widely used in high-gain antenna applications. The main disadvantage of these configurations is the subreflector blockage, which causes a number of deleterious effects. However, this problem can be reduced by decreasing the main-reflector radiation toward the subreflector. This may be accomplished either by shaping both reflectors or by using alternative classical configurations. This work considers the second option by presenting, in an unified way, generalized classical axially-symmetric configurations that prevent, from a geometrical optics (GO) stand point, the main-reflector scattered energy from striking the subreflector surface. Starting from initial design variables, closed-form expressions are derived for the relevant surface parameters, as well as for the corresponding aperture field distributions. These expressions can be used as effective design tools to determine the final antenna geometry or even to establish an initial configuration for a shaping procedure.