Development of a Compact Eleven Feed Cryostat for the Patriot 12-m Antenna System

The Eleven antenna has constant beam width, constant phase center location, and low spillover over a decade bandwidth. Therefore, it can feed a reflector for high aperture efficiency (also called feed efficiency). It is equally important that the feed efficiency and its subefficiencies not be degraded significantly by installing the feed in a cryostat. The MIT Haystack Observatory, with guidance from Onsala Space Observatory and Chalmers University, has been working to integrate the Eleven antenna into a compact cryostat suitable for the Patriot 12-m antenna. Since the analysis of the feed efficiencies in this presentation is purely computational, we first demonstrate the validity of the computed results by comparing them to measurements. Subsequently, we analyze the dependence of the cryostat size on the feed efficiencies, and, lastly, the Patriot 12-m subreflector is incorporated into the computational model to assess the overall broadband efficiency of the antenna system. Figure 1. a) 2-14 GHz cryogenic Eleven antenna; b) geometric representation of the Eleven antenna used for computations. 1. Validation of Computational Results Computational electromagnetic analysis of the Eleven antenna was performed using the commercial software suite FEKO. To give credence to the computations, a freespace model of the Eleven antenna was first constructed to compare the computational results against their measured counterparts. These results refer to the feed efficiencies, which are calculated from the antenna 420 IVS 2010 General Meeting Proceedings https://ntrs.nasa.gov/search.jsp?R=20110011858 2018-03-12T00:24:25+00:00Z