A Standard Attenuator and the Precise Measurement of Attenuation

An attenuator calibration system is described consisting of a waveguide-beyond-cutoff attenuator operating at 31.25 Mc and electronic equipment designed for parallel-substitution, series-substitution, and heterodyne measurements. Radio-frequency power is supplied by a crystal-controlled signal generator, stabilized so that variations in the power output do not exceed 0.001 db per hour. Measurements of a 10-db step made by the standard attenuator, and by two other methods, agree to within 0.001 db. A number of possible sources of error are examined including nonlinearity in microwave mixers.