The power supply of electronic devices, such as 220V/50Hz AC power grids or 115V/400Hz AC generators, contains various types of EMI noise. Among them, artificial EMI interference sources, such as radio transmission signals from various radar, navigation, communication and other equipment, will induce electromagnetic interference signals on the power lines and connecting cables of electronic devices. Electric rotating machinery and ignition systems will generate transient processes and radiated noise interference in inductive load circuits; There are also natural sources of interference, such as lightning discharge phenomena and electromagnetic interference noise in the universe. The former has a short duration but high energy, while the latter has a wide frequency range. In addition, electronic circuit components themselves also generate thermal noise during operation.

For electronic devices, when EMI noise affects analog circuits, it can deteriorate the signal-to-noise ratio of signal transmission, and in severe cases, the signal to be transmitted can be overwhelmed by EMI noise and unable to be processed. When EMI noise affects digital circuits, it can cause logical relationship errors, leading to incorrect results.