Geodetic VLBI ultra low noise broad-band receiver for 13 meter VGOS radiotelescopes

This paper shows the design, construction and characterization of an ultra-low noise and broad-band receiver system, to be used for geodetic very long baseline interferometry (VLBI) observations with the Spanish new 13.2 meter radiotelescopes, in the frame of the VLBI Global Observing System (VGOS). The cryogenic receiver front-end covers the frequency range 2 - 14 GHz in two simultaneous linear polarizations. It has an average receiver noise temperature lower than 20 Kelvin, except for those frequencies affected by radio frequency intereferences (RH). The detected signals are sent to the hack-end room using broad-band RF over fiber optic links. Then, the signals are distributed to four dual-channel frequency up/down converters, which provide the base-band signals for the digital VLBI back-ends.