Electromagnetic Interference (EMI)

Abstract

Radiated emissions in high-speed systems are caused by fast switching currents and voltages propagating through printed circuit board traces. As system speed increases, printed circuit board traces are becoming more effective antennas, and these antennas are radiating unwanted energies that interfere with other circuitry and with other systems located nearby. This section outlines different ways to design for low EMI and find the root cause of EMI problems when they occur. It only covers the electrical design aspects of EMI even though shielding, cabling, and other mechanical fixes can also be used to help reduce the emissions below the maximum allowable limits. In general, mechanical solutions are expensive for high-volume designs. Even worse, the mechanical solutions may have to change when the system speed increases.