A Correction Technique for Reflection Measurement of Data Cables

摘要

The measurement of return loss or characteristic impedance of data cables is made more difficult by a parasitic inductance due to an unavoidable untwisting of the wires for connecting them to the terminals of the balun. As the impedance of cables at high frequencies mainly has a real part only, this parasitic inductance can be calculated from measurement data. The calculation is described and measurements are shown demonstrating the benefit of this technique. Restrictions are given for the values of the calculated parasitic inductance as well as for the standard deviation of this inductance for all used frequency points. Also the frequency range is limited as for higher frequencies the assumed model does not cover stray capacitances that gain influence.