Indirect evaluation of radiated emissions from a bent signal line on a printed circuit board with two attached cables

Abstract

In this article, the radiated emissions mechanism and the variation of radiated emissions level have been analyzed and investigated, respectively, according to the ratio of the horizontal to vertical traces in a bent signal line when a bent signal line on a printed circuit board (PCB) with two attached cables is used.Though many papers concerning two cables attached to a PCB have appeared, it is seen that the two cables can be modeled as a dipole antenna. In addition, it is conjectured from two- port S-parameters that the ratio between the horizontal and vertical traces in a bent signal line leads to the variation in magnitude of common-mode voltage induced as a noise source of the dipole antenna. As the signal line in parallel with the attached cable becomes longer, the radiated emissions level due to the current-driven mechanism becomes more dominant while the contribution from the voltage-driven mechanism remains unchanged regardless of the ratio between two signal lines. Based on the analysis of measured and simulated S-parameters, we propose an alternate and relatively simple estimation method replacing the 3-m measuring method to measure the radiated emissions level and investigate the accuracy of our analysis using commercially available software CST MWS 2006B. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26114