Multi-Layered Dual-Band Dual-Polarized Reflectarray Design Toward Rim-Located Reconfigurabable Reflectarrays for Interference Mitigation in Reflector Antennas

Abstract

The rise of satellites in Low Earth Orbit (LEO) is causing more terrestrial electromagnetic interference in the important L- and X-band frequencies which are crucial for astronomical observations. This thesis introduces reflectarray design which can serve as a basis for an interference mitigation solution for radio telescopes. In the envisioned application, When the reflectarray is placed around the circumference of an existing radio telescope, it can drive a null into the radio telescopes radiation pattern sidelobe distribution. Since the reflectarray only occupies a small potion of the rim of the paraboloidal main reflector, its presence does not significantly effect the main lobe peak gain. Since Iridium and Starlink are the target mega-constellations, the reflectarray must be dual band. To cover the operational bandwidths of these constellations, the target bandwidth in the L-band (Iridium) is 0.7%, and that in the X-band (Starlink) is 17.1%. This makes the design of the reflectarray challenging as the frequencies are widely separated and the bandwidth in the X-band is wide The work of this thesis marks a first step in this effort. It includes a reflectarray design containing a multi-layer stack consisting of: (1) a grounded substrate, (2) an X-band slot loaded unit cell geometry, (3) a dielectric superstrate, and (4) an L-band layer containing crossed dipoles. The dual band reflectarray is dual linearly polarized to maintain symmetric response. The reflectarray is designed and simulated using full-wave solvers. The results show that the reflectarray designs are capable of pattern shaping at both bands and operate across the required bandwidths. This architecture could serve as a basis for future reflectarrays capable of nulling satellite interference from mega-constellations in observatory applications in the future.