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Background
Electromagnetic Compatibility (EMC) refers to the ability of electrical and electronic components, equipment and systems to function satisfactorily in the environment, without introducing intolerable disturbance to that environment. Thus it implies the limitation of emissions from the device or system, as well as a certain level of immunity to interference, that must be expected from other devices and systems in that environment.
The proliferation of electronic devices in our modern world increases the likelihood that sensitive and disturbing devices are operated in close vicinity. Rather than waiting for interference to happen and fixing the problem then, it is therefore necessary to specify electromagnetic requirements for devices before they are installed, to ensure they are compatible when operated in a common environment.
Emissions, in the radiated or conducted form, are usually an unwanted side effect caused by physical and electrical characteristics of circuits. These characteristics are typically related to parasitic parameters and the non-ideal behavior of components, and are not explicitly shown in schematics and layout diagrams. EMC design is therefore still regarded as black magic by many electronic engineers, resulting in the need to re-engineer products in costly and time-consuming processes to make them conform to specifications.
With some experience and a basic knowledge of electromagnetic theory however, EMC design is no mystery but a skill. The EMC characteristics of an electrical product are an inherent result of its design. And when EMC constraints are incorporated into the design process from the beginning EMC is not the result of a painful trial-and-error procedure, but can be achieved with little or no extra cost and time. The alternative, designing non-compliant products, and bringing them in line with EMC requirements, e.g. by adding shielding and filtering, is intrinsically flawed and wasteful.
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