THE IMPACT OF AUTOMATION ON NBS NOISE TEMPERATURE-MEASUREMENTS

The accuracy of calibrating a thermal noise source using the US National Bureau of Standards' (NBS) automated radiometer and cryogenic primary noise standards is typically plus or minus 2%, compared with plus or minus 3% for corresponding services that used manual radiometers and hot primary standards. Using the automated radiometer, a noise source can typically be calibrated at three frequencies in the time a manual radiometer requires to calibrate one. The automated radiometer contains a six-port reflectometer, and noise sources with reflection coefficients as great as 0. 3 can be tolerated without significantly affecting the calibration accuracy. This makes it practical to use a single broadband, coaxial noise standard from 0. 03 to 14 GHz. The six-port reflectometer also makes it possible to calibrate sources with connectors different from those of the primary standard's with almost no additional accuracy degradation.