Measurement Accuracies for Various Techniques for Measuring Amplifier Noise

The National Institute of Standards and Technology (NIST) has a program to develop an amplifier noise calibration service. Extensive measurements of the noise for different types of low-noise, X-band (8 - 12 GHz) amplifiers were made. This paper concentrates on the accuracy of measuring generalized noise figure for various techniques using the NIST 8 - 12 GHz noise calibration radiometer and a commercial automatic network analyzer.Under favorable conditions, the uncertainty of the effective input noise temperature Te of low-noise amplifiers approaches the uncertainty of an ideal Y-factor measurement for all the measurement techniques explored. For Te greater than 100 K, this is about ± 7% or less. The measurement error is dominated by the uncertainty of NIST primary cryogenic noise standard. The different techniques examined have different strengths and weaknesses. Rather than pick one technique, we found it worthwhile to implement all of them and use the redundant information to assure the measurement.