Design of super-resolving Toraldo Pupils for radio astronomical applications

More than half a century ago, in 1952, Giuliano Toraldo di Francia suggested that the resolving power of an optical instrument could be improved using a filter consisting of finite-width concentric coronae of different amplitude and phase transmittance, now known as Toraldo Pupils (TPs). The concept of 'super-resolution' was born, and in the current literature it is generally associated with various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. In the microwave range, the first successful laboratory test of TPs was performed in 2003. These first results suggested that TPs could represent a viable approach to achieve superresolution in Radio Astronomy. We have therefore started a project devoted to an exhaustive study of TPs and how they could be implemented on a radio telescope. In this work we present a summary of the status of this project, and then we describe a preliminary design to implement a TP system on a 32-m radio telescope.