3. Shielded cables

3.1 Transfer impedance and admittance

Transfer impedance and admittance have their origin in electromagnetic coupling coefficients derived from the theory of coupled lines.

In an installation or on electronic equipment, shielded cables are generally located close to a ground plane or conductors; a disturbing electromagnetic field can therefore generate, on the shield, a current and a voltage originating on the propagation line composed of the shield parallel to the ground reference.

If the shielding is the local potential reference for equipment connected to the ends of the cable, its imperfection generates voltages and currents at the ends that are much lower in amplitude than those encountered on the propagation line outside the shielded...