Telecommunication signal emissions from unshielded twisted pair (UTP) cable should be suppressed to maintain EMC of telecommunication systems. This paper describes the suppression effects of the ferrite cores which are installed on the UTP cable. Twisted pair wire with ferrite core was modeled by 4-port network to evaluate suppression effect. Parameters of the networks which are constructed with UTP cable or ferrite core with wires, were determined from calculation and measurement. Using the networks, the common-mode current distribution on the cable were obtained, and emitted electric field strength was calculated from the distribution. The emission suppression effect were obtained from the result, and the results were almost agree with measured value. The calculation results suggest that 1) the ferrite cores should be arranged side by side, 2) these should be placed near the signal supply end of the cable.
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