Output noise temperature of a waveguide cryogenic noise source in W-band

A waveguide cryogenic noise source (CNS) is discussed for noise temperature standards in W-band. The CNS consists of a noise pickup horn, a cavity, an electromagnetic absorber, and a liquid nitrogen container. The output noise temperature (NT) of the waveguide CNS is obtained from electromagnetic radiation of the absorber and the dissipative loss of horn. The waveguide CNS and an ambient temperature noise source serve as reference noise sources. To calibrate an unknown noise source thermal noises emanated from the CNS, the ambient temperature noise source, and the unknown noise source are measured by a dedicated radiometer. Measurement results of a commercial diode noise source are presented.