EMI reducing technique for low‐voltage differential signaling on a flexible printed circuit board

This paper proposes an EMI (unnecessary electromagnetic radiation) reducing technique for FPCs (flexible printed circuits) with LVDS (low-voltage differential signaling) transmission. The equivalent circuit for the common mode component of an LVDS line is presented. By varying the line length on the FPC board, a high-frequency simulation is performed. It is evident that EMI is strongly correlated with the reflection in the line. Considering the FPC board layout, the EMI is measured for the case in which the signal lines, the power supply lines, and the ground line are concentrated on one side, and the case in which they are distributed in a balanced manner while maintaining the same total number of connector pins. Actual measurements demonstrate that an EMI reduction of more than 3dBµV/m is realized in a well-balanced layout. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 88(7): 27–38, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ ecjb.20155