A High-Accuracy Microwave-Attenuation Standard for Use in Primary Calibration Laboratories

This paper describes the theory and construction of an improved X-band rotary-vane attenuator. A maximum error of the order of 0.02 db per 10 db is obtained as opposed to 0.2 db per 10 db in commercially available models. Error reduction was achieved by careful attention to the mechanical construction of the unit and the reference setting at the maximum attenuation position. Deviations from the calculated cos² law of operation were evaluated and presented in terms of attenuation errors. A cross-check between the experimental model and an audio-substitution type system showed agreement to within 0.04 db over a 40-db range.