Electro Magnetic Interference (EMI)
The term “Electro Magnetic Interference” (EMI) describes the phenomenon where one piece of electronic equipment (the “interference source”) causes interference to other pieces of electronic equipment via electromagnetic waves.
Common examples of electromagnetic interference include blurred TV images caused by nearby hair dryers and electric razors, and background noise on mobile phone calls. If the electromagnetic interference signal interferes with a plane in flight, the results could be catastrophic.
These incidents suggest that electronic devices are subject to an invisible “attack” that can disrupt or even destroy their normal operation.
Conductive interference and radiated interference are the two primary forms of EMI that result from a “attack” scenario. When an interference source uses a conductive medium to send a signal from its own electrical network to another, it is said to be engaging in electromagnetic conduction interference (such as a wire).
For a short period of time, the household’s electric lights may dim when we turn on the air conditioner; this is an example of radiated interference, which occurs when one electronic device causes another to emit radio waves of interference.
Electro Magnetic Susceptibility (EMS)
The antonym of a spear is a shield, and the inverse of electromagnetic interference is anti-interference. This section will introduce our second main character, EMS (Electro Magnetic Susceptibility), which is the propensity for electronic devices to experience a decline in performance as a result of exposure to electromagnetic interference. A hair dryer or electric shaver are just two examples of devices that can cause disruption.
You may notice some distortion in your TV screen while others are unaffected. This demonstrates that the former has higher electromagnetic sensitivity and is more likely to be injured under the “attack” of electromagnetic interference, whereas the latter has lower electromagnetic sensitivity and is not easily injured, demonstrating a higher “defense.”
Electromagnetic compatibility (EMC)
Electromagnetic compatibility, or EMC, is the state wherein electromagnetic energy emitted by electronic devices does not cause or receive interference from other devices emitting or receiving electromagnetic energy.
Consequently, EMC encompasses both EMI and EMS: on the one hand, electronic equipment is required to ensure that the electromagnetic interference (EMI) it generates in the environment during normal operation does not exceed a certain limit, and on the other hand, electronic equipment is required to ensure that it does not interfere with other devices.
The electromagnetic interference that is currently present has some anti-interference capability, which is EMS.
Therefore, the relevant standards specify the maximum value of EMI and the minimum value of EMS, or “low attack” and “high defense,” when we test the EMC of an electronic device. It herds its own sheep gently but can beat and chase away a wolf if necessary.
This necessitates a good shielding of the cable for USB cables in order to prevent electromagnetic waves from radiating into outer space (low attack) while also protecting the cable from other electromagnetic wave radiation. This places stringent demands on the development of cables and plugs. Most of USB cables on the market do not meet the requirements of EMC