Knowledge of Noise Meters - Introduction to Wave Traps
Classification of electromagnetic interference
There are many classification methods for electromagnetic interference, and only the main ones will be discussed here.
(1) Electromagnetic interference can be divided into two categories according to its propagation path: conducted interference and radiated interference. The transmission properties of conducted interference include electrical coupling, magnetic coupling, and electromagnetic coupling. The transmission properties of radiation interference include near-field induction coupling and far-field radiation coupling.
(2) Electromagnetic interference can be divided into two categories based on the nature of the interference source: natural interference and human interference. Natural interference includes cosmic interference, celestial interference, and lightning impulse. Human interference includes industrial interference, radiation interference, conducted interference, crosstalk, antenna end conducted interference, broadband interference, narrowband interference, harmful interference, high-power effects, and electromagnetic pulses. (3) Electromagnetic interference can be divided into two categories based on frequency band: narrowband interference and broadband interference.
The Three Elements of Electromagnetic Interference
All electromagnetic interference is generated by a combination of three basic elements. They are: electromagnetic interference sources; Receiver sensitive to interference energy: The medium that transmits electromagnetic interference sources to the receiver, i.e. the transmission channel. Correspondingly, the methods for suppressing all electromagnetic interference should also be addressed by these three elements.
Conducted interference
Conducted interference refers to the propagation along a conductor, so any conductor, such as a wire, transmission line, inductor, capacitor, etc., is a transmission channel for conducted interference. Due to the wired transmission of low-voltage power carrier, the impact of interference on low-voltage power carrier systems is mainly discussed from the perspective of conducted interference.
The signals that cause interference include noise signals without any information and useless signals with information. The spark generated at the moment of the power switch may cause a thousand disturbances to a sensitive circuit. A signal with information is a useful signal in one channel, and if it enters other channels, it is a useless signal with information, which will cause interference to other channels. From this, it can be seen that any electronic device can become a source of interference.
