Analysis of Cassegrain cloud profiling radar antenna with arbitrary projected apertures

A millimeter wave Cassegrain dual-reflector radar antenna (~94 GHz) with super-quadric projected aperture boundaries concept, that includes sub-reflector blockage effect, is evaluated for the spaceborne radar measurement of the vertical cloud profile structure. In this paper, we show how the super-quadric aperture representation may be used for optimizing the antenna radiation performance. This facilitates to reduce the noise/clutter level received by the radar through the antenna. Its application is when the design specifications stipulate desired radiation characteristics (gain, sidelobe levels and beamwidths) and maximum allowable antenna dimensions for a nadir-looking beam. Model results based on physical optics (PO) and uniform theory of diffraction, (UTD), for different projected apertures super-quadric boundaries show that the trends of the antenna patterns in the principal planes differ significantly from those in the ±45 degrees planes. These unique characteristics along with the pronounced impact of the edge tapers on the first sidelobe level relative to the adjacent ones provide a basis to obtain an optimum antenna design for the instrument