Design methodology in EMC - Equipment layer

Electromagnetic compatibility (EMC) design is a complex art that combines different disciplines such as electronics, microwave technology, electromagnetism, and mechanics. It is therefore important for designers to use a working methodology that allows them to integrate these diverse constraints. The steps in this methodology will enable them to establish and justify design specifications based on expertise and modeling and simulation tools. At the end of the design phase, the qualification tools and methods must also be precisely defined in the "Test Plan" in order to guarantee the representativeness and repeatability of the tests.

The starting point for routing an electronic board is to analyze the space reserved for it within an existing mechanical structure. As this structure may or may not be metallic, it is important to know how to use these properties to improve the electronic board's performance in terms of high-frequency electromagnetic interference emissions and external damage.

The routing of the electronic board is also guided by electrical safety rules (low voltage directive) that introduce concepts of galvanic isolation.

The number of layers allocated in the board guides the choice of whether to use a full ground plane or a mesh. In addition, current flows in this ground plane have an impact on the rules of segregation between disturbance-generating functions, such as fast digital electronics, and those that will be sensitive, such as low-level analog functions. Great importance must be attached to the design of this plane, which provides the necessary protection in terms of both emission and immunity.

However, the use of generic routing rules does not guarantee the required EMC performance. Furthermore, due to constraints other than EMC, these generic rules are generally not applicable without exception. Modeling, calculation, and simulation are the most appropriate ways to validate routing choices or filter dimensions. Examples of equivalent component models are presented and used to describe this approach.

The EMC Test Plan is the document on which all EMC tests are based. It must enable a qualification campaign to be carried out by eliminating the risks associated with misinterpretation of the specifications or incorrect implementation of a test method. To do this, it contains a large amount of information specific to the equipment to be qualified, such as a description of how the product works or any feared events. In addition, it must contain as much information as possible to ensure the reproducibility of the tests, in particular a description of the environment, such as the load bench or the various beams.

EMC non-compliance has critical consequences,...