The PTB R 100 Primary Thermal-Noise Standard

A primary thermal noise standard for the R 100 waveguide band (8.2 to 12.4 GHz), working at 653 K, has been established at PTB. It consists of three different parts: a high-temperature-resistive termination, a transition section, a water-cooled output part. The principles of design and construction technologies meet the standard´s requirements concerning the microwave transmission line properties and the stability and distribution of temperature. Taking advantage of the resonance properties of the different parts, the standard has been optimized at special calibration frequencies.