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 perunit-
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.