Radiation characteristics of a paraboloid with a square aperture are described in this paper. A systematic analysis of the principal plane radiation patterns of the dish employing the uniform geometrical theory of diffraction (UGTD) [3], [4] reveals that for the square paraboloid the backlobes are weak because there is no caustic at the rear boresight as in the case of circular apertures. Based on the method enunciated in [7] the front-to-back (F/B) ratio for different square paraboloids are also tabulated. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.