Analysis of noise temperature sensitivity for the design of a broadband thermal noise primary standard

摘要

A broadband primary standard for thermal noise measurements is presented and itsthermal and electromagnetic behavior is analyzed by means of a novel hybridanalytical-numerical simulation methodology. The standard consists of a broadbandtermination connected to a 3.5mm coaxial airline partially immersed in liquid Nitrogenand is designed in order to obtain a low reflectivity and a low uncertainty in the noisetemperature. A detailed sensitivity analysis is made in order to highlight the criticalcharacteristics that mostly affect the uncertainty in the noise temperature, and also todetermine the manufacturing and operation tolerances for a proper performance in therange 10MHz–26.5GHz. Aspects such as the thermal bead design, the level of liquidNitrogen or the uncertainties associated to the temperatures, the physical properties ofthe materials in the standard and the simulation techniques are discussed.