Designing Embedded Hardware, 2nd Edition

Electrical Noise and Interference

Digital systems are inherently analog in operation. Digital signals suffer degradation and noise due to analog effects present in the system. Spurious noise or reflections from nearby electrical machinery or radio transmissions can induce signals within your circuit that can cause false events to occur, or even prevent a digital system from functioning at all. The one way to ensure that your system is immune to electromagnetic interference is to avoid the use of electricity! Unfortunately, the steam-powered microprocessor is not a reality, so if your system is to operate reliably in the real world, you must take electromagnetic effects into account. What follows is not a comprehensive overview of noise and associated problems and solutions, which is far too complex a field to cover properly here. What I will do is provide an introduction. It is worth seeking out information that is more detailed to understand these concepts more thoroughly.

Warning

The United States, Australia, the European Union, and many other countries have very strict guidelines and requirements for electromagnetic emission and immunity. The recommendations presented here are good practice only and are not necessarily sufficient to warrant compliance in your country. Therefore, it is important that you check your local regulations and ensure that you meet the appropriate requirements. Compliance cannot be guaranteed just by design. A system must be tested to ensure that it is ...