A Method for Acquiring the Terminal Common Mode Impedance of Cables

A method is presented for quickly acquiring the equivalent terminal common-mode impedance of cables. Firstly, the parallel cables are treated as equivalent multi-conductor transmission line. Using vector network analyzer (VNA) and current probe to measure voltage reflection coefficients at two locations of each cable. Then a nonlinear equation about terminal equivalent impedance is constructed. By solving the nonlinear equations, broadband terminal equivalent impedance for each cable can be acquired. Compared with existing methods, the efficiency of this method is improved significantly. Furthermore, the precision is improved in that this method including the coupling effect between cables. This method helpful to the EMC test and fault diagnosis.