Loading Rims of Radio Telescopes with Reconfigurable Reflectarrays for Adaptive Null-Steering

In an attempt to realize a concept presented in a precursor paper by the same authors, the design of a reconfigurable reflectarray providing a radio telescope with adaptive null steering capabilities is presented. The reflectarray occupies a paraboloidal annulus-shaped portion of the original reflector's surface. The remaining reflector surface and the reflectarray is modeled using reflection coefficients. The reflection coefficients for the reflector are set equal to -1. The reflection coefficients for the reconfigurable reflectarray are obtained from full-wave unit cell simulations of pin-diode-loaded patch antennas. The states of the switches required to drive a null in a particular direction are determined using a simple serial search algorithm. The reflection coefficients are related to a physical-optics-based current density. The current density can be integrated to obtain the far fields. An example of an 18m axisymmetric paraboloidal reflector antenna designed to drive a null to an angle of 1.75° from the axis of symmetry is provided.