4.2 The Path to Ground

The best way to avoid noise problems is to generate no noise in the first place, but this is usually not applicable. Most kinds of noise are side effects of intended behavior of other parts of the system, and therefore cannot be avoided.

All kinds of currents, AC or DC, high-power or low-power, signals or noise, are always trying to find the easiest path to ground. The basic idea behind many EMC design techniques is to control the path to ground for all signals, and make sure that this path is away from signals and circuits that may be disturbed. For transmitted noise, this means making sure that the noise will find a path to ground before it leaves the system. For received noise, it means making sure that the noise will find a path to ground before it reaches sensitive parts of the system.