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Noise-Parameter Measurements at Room and Cryogenic Temperatures
Noise-figure measurements are well-known and are often used for characterizing low-noise amplifiers (LNAs). However, noise figures alone do not provide a comprehensive understanding of the circuit’s optimal noise performance and its sensitivity to variations in the signal-source impedance. Noise parameters can be viewed as “vector noise figures.” Although they are not commonly measured, they offer a complete perspective on the noise-performance possibilities with specific devices. This becomes even more crucial for applications where receiver sensitivity is paramount, necessitating cryogenic cooling to minimize LNA noise levels. This presentation will review noise parameter measurement techniques at room temperatures and demonstrate methods for measuring them at cryogenic temperatures.