Cryogenic Integration of the 2-14 GHz Eleven Feed in a Wideband Receiver for VLBI2010

The next generation VLBI systems require the design of a wideband receiver covering the 2-14 GHz range, necessitating a wideband feed. Presented here are the 2009 development of a cryogenic 2-14 GHz Eleven feed for reflector radio telescope antennas, including its integration into a cryogenic receiver. The Eleven feed is designed for dual linear polarization and consists of four log-periodic folded dipole arrays. Each pair of arrays is fed by a differential two-wire transmission line connected either to balun or a differential LNA. The present configuration has been measured in many configurations, at various independent labs - corresponding simulations have been done. The results show (across the band) a high polarization efficiency for the feed, with a nearly constant beam width, a reflection coefficient below -10dB, and a constant phase center. Electrical parameters under cryogenic conditions and measured receiver noise temperatures are presented.