Design of Reconfigurable Rim Scattering Reflectarrays for Null Steering in Reflector Antennas

Abstract

Reflector antennas are susceptible to interference arriving through its sidelobes. The design of a reconfigurable rim scattering reflectarray which can be retrofitted to existing high gain reflector antennas giving the reflector adaptive null steering capabilities is presented thereby giving the reflector interference mitigation capabilities. The conformal reflectarray, placed along the outer rim of the reflector antenna, contains reconfigurable unit cells (RUC). The states of the RUCs allow the reflectarray to place a null in any direction within the first few sidelobes of the reflector pattern. A 1-bit RUC containing two pin diodes with less than 0.44dB loss at the operating frequency is presented. It is found that the dielectric and switch losses do not significantly affect the overall efficiency of the reflector as they are placed only along the outer rim of the reflector which is weakly illuminated. Two reflectarrays are designed. First, a L-band non-reconfigurable reflectarray based on variable patch size for an 18m prime focus fed parabola is presented. A full-wave simulation of this design serves to validate the design approach. Subsequently, a reflectarray design using RUCs is presented. All necessary formulations for complete reproducibility of results are provided in appendices allowing for follow-on work