Coaxial cable delay measurement with different methods: analyzing influential factors and quantifying numerical effects

Abstract Most of the timing scenarios call for the need of precise delay measurement and compensation for coaxial cables. However, experience to date has shown that the cable delay can only be characterized by other physical quantities such as time interval or group delay, etc. In this paper, the principles of three existing commonly used measurement methods were discussed and the various factors that can affect the measurement results were analyzed. Measurement setups and the corresponding uncertainty budgets for the three techniques were then designed and explained. With the aim to quantify numerical effects of the influential factors, specific experiments on a 50 m antenna cable were conducted on time interval measurement to obtain the optimal range of the instrument’s trigger level based on external pulses with different rise time settings, as well as on group delay measurement to determine the influence of different frequency aperture settings. Then, experiments using the relatively proper parameters, which we believe, to the optimal extent, would mitigate the measurement uncertainties were performed. In order to ensure the measurement consistency across the methods, the measurement results were compared and cross-validated to obtain the recommended selections of parameters to align the measurements for coaxial cable delay utilizing the different methods.