On-Wafer LNA Noise Measurements for Cryogenic LNAs

Applications in radio astronomy and quantum computing require microwave cryogenic low-noise amplifiers with as low of noise as possible. Characterization of these devices requires special approaches, which require careful calibration and traditionally have not been compatible with on-wafer measurement. As activity in quantum computing has grown, interest in on-wafer cryogenic noise measurements has followed. In this talk, I will first review methods for coaxial cryogenic noise measurement. I will then present two approaches to on-wafer cryogenic noise measurement and explain how these methods can be applied to characterize cryogenic LNAs while achieving uncertainties of the order of ±1K. The first method employs a cryogenic attenuator in conjunction with a room temperature noise source whereas the second method employs a novel cryogenic noise source. The talk will conclude with a brief discussion of how these approaches may be employed in future built-in-self-test systems.