Comparisons of different descrambler/power combining boards layout for multi-port, decade bandwidth Eleven feed

Eleven feed based on parallel folded dipole log-periodic arrays has four differential ports above ground plane. This paper presents different possibilities of combining these ports below ground plane so as to have two unbalanced ports for orthogonal linear polarizations. Also the various ways of combining LNA in these boards is discussed. For radio astronomy applications, where lowest noise is desired, the use of differential LNA and further passive power combining is justified as best possible choice.