A verification method for noise-temperature measurements on cryogenic low-noise amplifiers

We report a verification method for noise-temperature (NT) measurements on cryogenic low-noise amplifiers (LNAs) at liquid helium temperature. The method uses a comparison between the individual measurements of the LNA and an attenuator and the joint measurements of the tandem of the two. As a first step, we were able to determine the loss and the added NT of the cables that connected the cryogenic devices (the LNA, the attenuator, or their combination) to the test ports outside of a cryostat. The attenuator was also characterized successfully with 3% measurement uncertainty.