Suppression Effect of Radiated Emission from Twisted Pair Wires with Ferrite Core

Telecommunications 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 was obtained, and emitted electric field strength was calculated from the distribution. The emission suppression effect was obtained from the result, and the results were almost agreed 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.2003 IEEE Symposium on Electromagnetic Compatibility, August 18-22, 2003, Boston, MA, US

Common-Mode and Differential-Mode Analysis of Common Mode Chokes

In this paper three methods for the measuring common-mode and differentia-mode S-parameters of common mode chokes are presented. The three methods involve (1) ABCD chain matrix, 2) using hybrid couplers and 3) modal decomposition. Each measurement method provides a specific level of accuracy. The modal decomposition method can work up to 10 GHz. Given a full characterization of a common mode choke, a passive equivalent circuit model can be synthesized that provides a fundamental understanding of the physical performance. SPICE equivalent circuit model of common mode chokes and the extraction of model parameters are provided