A technique of analyzing the principal plane radiation patterns of a subreflector shaped using the method enunciated by Collins [I] has been presented. The analysis is based on the uniform geometrical theory of diffraction (UGTD) [2], and a simplified procedure has been adopted in the determination of the principal plane radii of curvature of the subreflector. The numerical results obtained based on UGTD correlate well with those obtained using the method of physical optics (PO). Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.