A Brief Look Back at Microwave Generator Calibration

Summary form only given, as follows. Since the initial use of noise figure as a measure of receiver noise about 50 years ago, one of the most compelling problems with the measurement has been the uncertainty in the calibration of the noise generator - the device which provides the two ¿known¿ levels of noise power required for the measurement. This presentation is a look at some of the past and present efforts of the National Institute of Standards and Technology (NIST) aimed at solving this problem. The first significant development, in terms of industry application, came about in the early sixties with the development of accurately characterized hot thermal standards and band specific front-end switched-load radiometers. Coupled with transfer and working standards utilizing argon gas discharge tubes as noise generators, such systems were the mainstay of noise calibrations into the eighties. Since then, broadband, highly stable total power radiometers and on-line cryogenic coaxial and waveguide standards have been developed with significant improvements in productivity and ease of use. The presentation will trace the evolution of this technology from early developments to modem systems.