Modeling the Series Impedance of a Quad Cable for Common-Mode DSL Applications

New digital subscriber line (DSL) technologies are being developed to meet the ever-increasing bandwidth demand of the user. One very promising approach injects ??common-mode?? signals that superimpose a signal on two regular differential pairs. This technique requires new reliable multiconductor models for the telephony cables. Therefore, good approximations of the series impedance of the line are indispensable. In this paper, a model for this series impedance is theoretically derived and validated with measurements.