A set of waveguide primary thermal noise standards and related calibration systems for the frequency range 8.2-40 GHz

The national metrology laboratory, BNM-LCIE, France, has developed a set of four new waveguide primary thermal noise standards for the frequency band from 8.2 GHz to 40 GHz. Each noise standard is made with silicon carbide microwave absorber and inserted into a section of waveguide made in platinum 10% rhodium; the whole is put inside an electrical oven. The output noise temperature range of the standards obtained from temperature and attenuation measurements is within 948-1012 K/spl plusmn/1.21.8 K, in one standard-type uncertainty. The calibration of gas discharge noise sources and/or solid-state noise sources is achieved by comparison to standards using a switching radiometer. The excess noise ratio given is within 15.35-15.65 dB for gas discharge sources and within 14-16 dB for solid-state sources, with typical uncertainty of 0.02 dB.