Geometrical Optics and the Design of Feed-Motion-Scan, Parallel-Plate, Radar Antennas

Design configurations of nonoscillatory feed, line-scan, parallel- plate radar antennas were explored. Some historically important designs are described as a basis for understanding several new, proposed antenna geometries. It is shown that the continuous-motion scanner developed by Lewis can be combined with many parallel-plate lenses and reflectors in various geometric layouts to obtain useful microwave antennas. Designs that would normally produce good radiation by combining the continuous-motion scanner and the cut, rolled, and folded sectoral horn-lens assemblies. The continuous-motion scanner can be combined with dielectric, metal-plate, and geodesic lenses. Multiple linear and nonlinear reflectors may be installed in the sectoral horn and planar reflectors may be used in some geodesic lenses to achieve compactness. Some of these 'oblique' layouts are shown to be analogous to optical telescopes. Methods of reducing antenna size by folding over or rolling up flat portions of the sectoral horn are explained. Optical laws are shown to apply to the geometrical design of parallel-plate antennas and lenses. Coma and spherical aberration are defined and procedures for designing parallel-plate radar antennas are proposed. Choice of optical and radar system parameters and the interrelationship of such parameters as scan angle, focal length, beamwidth, scan rate, and physical dimensions are discussed. Fermat's extremum principle is defined and some fundamental criteria for designing geodesic lenses are outlined.