A way to improve the field of view of the radiotelescope with a dense focal plane array

Abstract

We consider a problem of increasing the field of view (FOV) of the radio telescope by means of multi beam performance of the prime focus hybrid reflector systems. It was shown that array feeds of waveguide and horn elements currently used cannot provide closely spaced beams over a wide FOV and a high aperture efficiency in each beam due to the element spacing restrictions imposed by a size of the element aperture. We proposed a feed design in a form of an integrated dense array with a small physical size of the grid element and a volumetric form of the array element. For the feed, the original excitation system of the array elements has been developed to perform the desirable beam illumination pattern with low spillover level. The results have been obtained both for theoretical and experimental radiation patterns of the array feed. Scanning and multi beam capabilities and limitations of the hybrid reflector antenna have been investigated on the basis of the focal field distribution analysis. As an example, 0.35 F/D ratio reflector (Westerbork Telescope) has been considered. It has been shown that the proposed array antenna is a good candidate be used as the feed to improve the properties of source images by the reflector systems and therefore to increase the FOV of the radio telescope.