Alternative Method for Transfer Impedance Measurements

The objective of this paper is to present a simple alternative method to determine the transfer impedance of coaxial cables of different lengths and referring them to a per-unit-length parameter. The transfer impedance of any cable is of interest since it accounts for coupling between cables (crosstalk), for pick-up of external signals and also for emission of electromagnetic energy. The method proposed here employs a direct injection of a current into the center conductor and into the braid simultaneously from either end of the cable. The alternative method uses a modified line injection. The modified line injection employs a common mode line injection as well as a differential mode line injection. For both ways of current injection equivalent circuits will be shown and the results will be contrasted. The results are based on a forward gain measurement of distinct lengths of the same quality of coax cables and require little post processing.