Aspects of EMC at the Equipment Level

The existence of unwanted electro-magnetic (EM) interactions between electric and electronic equipment (or systems, sub-assemblies, devices) and, in particular the prevention of those interactions, forces us to pay attention to electromagnetic compatibility (EMC). In its basic form, such an unwanted interaction or electro-magnetic interference (EMI) problem, can be described by the well-known EMI triptych consisting of a source of EM disturbance, a coupling path and a victim circuit. The triptych can be considered at four levels: (1) system level (2) equipment or subsystem level (3) sub-assembly or printed wiring board level, and (4) device or component level. This tutorial paper addresses Level (2): the equipment or subsystem level, as it is also the level where most of the statutory (as forced by the legislator) operational requirements (as forced by the equipment user) apply. Since the four levels are not independent, the adjacent Level (1) and Level (3) will be considered when necessary. In this paper the emphasis will be on understanding of the various phenomena.