Comparison Between NPL and NMIJ of Diameter and Scattering Parameter Measurements of Precision 1.85 mm Coaxial Air Lines

This paper summaries a bilateral comparison of dimensional measurements of the diameters of two precision 1.85-mm coaxial air lines and associated electrical scattering parameter measurements. The measurements were independently made by two national metrology institutes: the National Metrology Institute of Japan and the National Physical Laboratory. The laboratories also calculated the characteristic impedances and their uncertainties based on the measured diameter values and uncertainties. The difference between the characteristic impedances calculated by the two laboratories for the two lines was less than 0.2 Ω. The uncertainty of this difference at a 95% level of confidence was 0.3 Ω. The scattering parameter measurement results agreed well at almost all comparison frequencies from 5 to 65 GHz.