Study of the Input RF noise of a THz superconductor-insulator-superconductor receiver

The receiver noise temperature of THz superconductor-insulator-superconductor (SIS) receivers is composed of several contributions, in which the input RF noise is usually not negligible. In this paper, we investigate the input RF noise (T_rf) of a waveguide superconducting niobium nitride (NbN) SIS receiver operating at 0.5THz. In particular, the input RF noise is measured for two respective cases of a small beam aperture surrounded by an aluminum plate and a blackbody, which is located just in front of the 0.5THz NbN SIS receiver. Detailed measurement results will be presented.