TAMING EMI IN MICROPROCESSOR SYSTEMS

The authors point out that whereas the physics, electronics, and mathematics of EMI - as well as interference caused by electrostatic discharge, a related area - are fairly well documented, problems arise because of the many variables that typically are involved. The difficulty of tracing interfering signals is discussed, and the basic principles of interference are reviewed. The discussion covers the principle sources of radiation from microprocessor-based equipment, the ability of logic gates to function as both sources and receptors of noise, and the radiation emitted from printed circuit boards. Five coupling paths that should be considered in typical systems comprising two or more pieces of equipment are outlined.