Synthesis and Analysis of Low Profile, Metal-Only Stepped Parabolic Reflector Antenna

This paper describes an intuitive approach for synthesizing metal-only, low-profile, high-gain stepped reflector antennas that can aid emerging technologies in the areas of communications and remote sensing. The required reflector aperture is synthesized using a family of confocal parabolic sections, each of which scatters in phase to provide a focused beam in the far field. The parabolic sections provide a distinct advantage over the conventional Fresnel zone plate (FZP) antenna, since the radiation is inherently unidirectional. Furthermore, the metal-only structure avoids the need for dielectric characterization, which is essential for reflectarrays. Using this technique, it is possible to achieve depths of the order of one wavelength while ensuring high efficiencies. Starting from a symmetric stepped reflector synthesis, two distinct approaches to synthesize offset stepped reflectors are explored in this paper. We highlight several interesting tradeoffs between electromagnetic performance and mechanical complexity that arise for each of these approaches. A thorough analysis of the frequency performance of stepped parabolic reflectors is also presented. Comprehensive simulations using both physical optics and multilevel fast multipole method validate our theoretical predictions. The formulations presented in this paper are especially relevant at mmWave frequencies and beyond, which has attracted significant interest for modern technologies.