Cryogenic IF Balanced LNAs Based on Superconducting Hybrids for Wideband 2SB THz receivers

Future heterodyne 2SB THz receivers for Radio astronomy shall require better sensitivity and higher IF bandwidth. This paper investigate, in a modular approach, the use of balanced amplifiers based on superconducting quadrature hybrids, as an option to realize wide band low noise amplifiers with improved input matching without compromising the noise performance. Measurements of the proposed wideband balanced amplifier shows very good agreement with the standalone amplifier in terms of gain and noise temperature. The input matching of the balanced amplifiers are limited by the input matching of the hybrids, still showing return loss better than 15 dB.