Sheath current

Sheath currents may lower the efficiency of transmission and can interfere with nearby electronic devices.

In the simplest case, this is a ferrite bead, it includes the coaxial inner and outer conductor and acts as a common-mode choke.

At the same time, a ferrite bead has a transformer effect, so that a useful signal is confirmed as differential-mode.

To increase the inductance compared to the unwanted common mode signal component, the cable can also be repeatedly passed through or wound around the bead.

In addition, higher frequency signals are often used with a capacitive coupling filter.