Stability tests of electronic calibration units

Electronic calibration units (ECUs) are becoming increasingly important for the calibration of vector network analyzers (VNAs). Undoubtedly, ECUs simplify the calibration of VNAs significantly by reducing the number of required connections. It is however not well understood yet how well ECUs compete with a mechanical calibration in terms of measurement accuracy and stability. This paper summarizes preliminary experimental results that have been carried out to test ECUs with respect to temperature sensitivity, connector repeatability, and stability over time.