An investigation of the effects of PCB module orientation on radiated EMI

Electronic equipment is frequently designed with modular construction to more efficiently use available real-estate, as well as provide for expansion capability and interchangeability. Perpendicular and parallel module configurations are both reasonably common, although perpendicular modules are becoming more prevalent with the standardization of the PCI bus in the computing industry. Modular designs may behave as EMI antennas if excited by a common-mode noise source. Magnetic- and electric-field coupling mechanisms have previously been documented that may excite the EMI antenna at the module bus-connector or on the module. The antenna and transmission-line characteristics of the perpendicular and parallel modules were investigated numerically and experimentally. A case study of a commercially available product using the parallel-module configuration is provided to show the relevance of modules as EMI antennas