4. EMC cards

4.1 Phenomena concerned

The sources of the "noise" emitted by the board, whether conducted or radiated, are naturally linked to the activity of the board's electronic components. Symmetrically, the components are the victims of conducted or radiated electromagnetic "disturbances" that reach the board and can cause it to malfunction.

Among the fundamental principles of EMC, there are two that board designers should bear in mind:

• electric current always flows back to its source;

• the electric current takes the path of lowest impedance, which at low frequencies is always the path of lowest resistance, and at high frequencies is usually the path of lowest inductance. This principle naturally...