Common-mode radiated emissions from UTP/STP cables with differential high-speed drivers/receivers

Common-mode current effects on radiated emissions, due to imbalance between rise and fall time of the differential output of line drivers for high-speed digital signals, are investigated by experimental measurements, numerical and SPICE simulations. Three driver families are characterized: LV34 (RS422), LVDS, and LVPECL. Unshielded (UTP) and Shielded Twisted Pair (STP) of Cat. 5 were the cables used in this investigation in order to minimize the contribution due to the imbalance of the wires. The EMC performances of connectors such as 5×2 pins z-pack, RJ45 and Sub D 9 pins with STP cable are also presented.