Measuring the capacitance coefficients of coaxial open-circuits with traceability to national standards

Coaxial open-circuits are often used as measurement reference standards and can be found in most commercially available vector network analyzer (VNA) calibration kits. The capacitance characteristics of these devices are usually summarized in terms of the coefficients of a polynomial used to describe their frequency dependence. This article describes a method of measuring these capacitance coefficients and presents a detailed analysis of the uncertainty of the measurement, which includes using the Monte Carlo method in conjunction with a least-squares fitting process. The resulting measurement method enables these standards to be 'calibrated' with known uncertainty and with traceability to national measurement standards.