Analysis of Differential-Mode Signal Emission From STP Cable by Using Chain Parameter Matrix

Radiated emission from a differential-mode (DM) signal was calculated by using a chain parameter matrix for a shielded twisted pair (STP) cable. The series connection of the matrix represented the multiconductor transmission line inside the shield, and the common-mode current generated from the DM signal was obtained by solving the matrix equation. The matrix elements of the STP cable and the shield's transfer impedance were determined through both measurement and calculation, and these values were used to calculate the current outside the shield and the radiated electric field strength. The maximum current outside the shield and the maximum radiated electric field strength were then measured in the frequency range from 30 to 300 MHz, and these results were compared with the calculated values. The calculation results for the maximum current intensity agreed well with the measured values, and those for the maximum radiated electric field strength agreed fairly well with the measured values.