Study of the field around the focal region of spherical reflector antenna

V.P. Maslov´s (1981) method is applied to derive the expression for the wave reflected by a spherical reflector when the plane wave is incident along the focal axis of the reflector. The expression is reduced to integrals with respect to a single variable. A relatively simple expression is derived which is valid in the caustic region. An asymptotic-ray expression is also derived which can be used in the region far from the caustic. Field distributions around the cusp region are calculated numerically and the results are compared with those obtained by other methods when available. Agreement among them is fairly good. Equi-contours of the field amplitude are obtained in the plane perpendicular to the axis which will serve to determine the optimum feed pattern and location