Relating coupling attenuation to shield transfer impedance and pair balance in data communications cables

摘要

This paper explores the relation of coupling attenuation to surface transfer impedance, a measurement of shielding effectiveness and demonstrates that pair balance is independent of shielding effectiveness. It also shows that both shieldingeffectiveness and pair balance contribute to coupling attenuation of a paired cable. Examples are presented of cables having independently varying degrees of pair balance and similar surface transfer impedance. The coupling attenuation of these cableshave been measured and show the effect of pair balance on coupling attenuation as it is independent of changes in shielding effectiveness. Examples are also presented of cables having different levels of shielding effectiveness, measured by transferimpedance, but which have similar pair balance. The coupling attenuation results from these cables are also presented and show the effect of shielding effectiveness on coupling attenuation as it is independent of changes in pair balance.