Using time-domain measurements to improve assessments of precision coaxial air lines as standards of impedance at microwave frequencies

This paper presents an in-depth assessment of precision coaxial air lines for use as impedance standards at RF and microwave frequencies. The assessment is based primarily on using several different types of time-domain reflection measurement options that are available on commercial Vector Network Analyzers (VNAs). The paper includes a comparison of these time-domain measurement options, made independently at the national measurement institutes of Japan and the United Kingdom. Mechanical measurements and frequency-domain measurements are also included to complete the assessment of the lines.