Developing a common-mode choke coil with high-permeability core used high-speed telecommunications port for UTP cable

The choke coil used in a telecommunications port for unshielded twisted pair (UTP) cable needs a high common mode impedance across a wide range of frequencies because UTP cable has no grounding port. A high permeability ferrite core was used to get a high common-mode impedance across a wide range of frequencies and a low level of insertion loss at high frequencies. As a result, the frequency range is about four times better than that for a conventional core and an insertion loss for telecommunications signals is about half that for the choke coil used with 10Base-T Using the coke coil for a 100Base-T LAN port, the measured improvement in immunity indicates that a wire length of more than 0.5 m is desirable to give sufficient performance.