A compact UWB passive balun solution for cryogenic 2-13 GHz Eleven feed for future wideband radio telescopes

The decade bandwidth Eleven antenna can be considered to have either 4 differential ports or eight single-ended ports, and different ways of combining the eight ports are needed for different purposes and applications. This paper presents a new passive balun for the Eleven antenna and a way to integrate four of these baluns together with the antenna in such a way that the 4 differential ports reduce to 4 single-ended ports. The baluns are realized on printed-circuit-boards (PCB) that are located vertically to the ground plane on the rear side of it.