Direct Optimization of Quasi-Periodic Surfaces in Multi-Reflector Systems

In recent years, there has been an increasing interest in replacing traditional periodic surfaces, e.g., frequency selective surfaces, with quasi-periodic surfaces (non-identical elements) in multi-reflector systems for satellite applications. Quasi-periodic surfaces can be used to improve existing antenna solutions or to provide innovative concepts not possible with periodic surfaces. In many scenarios, the periodic/quasi-periodic surface is used in a multi-reflector configuration, e.g., as a subreflector, where the design specifications are on the radiation pattern from the main reflector. For these applications, the design of the surface is usually carried out using an in-direct optimization approach which may provide sub-optimal designs. In this paper, we demonstrate the direct optimization of quasi-periodic surfaces for the final pattern performance. This means that all array elements in the quasi-periodic surface are optimized simultaneously to directly fulfill the goal specifications on the final pattern from the main aperture.