The term electromagnetic compatibility can be applied to all levels of electronic systems

The terminology begins with the fact that the electronic devices they develop must undergo electromagnetic compatibility experiments. In China, electromagnetic compatibility requirements have long been a mandatory certification project, so mastering professional knowledge of electromagnetic compatibility has become an inevitable requirement for hardware engineers.

Electronic equipment has good electromagnetic compatibility, which has two meanings.

First, such electronic devices, or systems composed of such electronic devices, can operate in a predetermined electromagnetic environment.

Secondly, there will be no adverse effects between electronic devices or systems.

First, let's take a look at an example where the system and environment have not reached the state of electromagnetic compatibility.

The figure on the right shows a high-speed railway rear-end collision accident in 2011. Two high-speed trains collided with each other due to incorrect signal lights, causing serious casualties. One explanation for the accident is that lightning interfered with the signal control system, causing the system to receive incorrect signals.

If it is really caused by lightning, it is a typical electromagnetic compatibility fault. As lightning is a common natural phenomenon, any electronic system must consider reliable operation in this environment.

The essence of lightning is instantaneous air penetration and discharge. Because air penetrates the conductive system, it emits a dazzling light, which is what we see as lightning. What we hear is thunder, because the current during this discharge process is very large, which can reach 200000 amperes. Huge currents generate enormous amounts of heat. This phenomenon can occur between two clouds, or between clouds and the Earth. When two clouds with different polar charges occur between them, and when the electric field strength between them is sufficient to penetrate the air insulation between them, people sometimes call it a sky thunder. When this phenomenon occurs between clouds and the earth, as shown in the left image, people call it a landmine.

Traditionally, we have paid special attention to touching landmines. Because this kind of lightning can cause direct damage to buildings and personnel. "People discovered that the protruding guide bodies of the earth were more susceptible to lightning strikes, so they invented lightning rods.". As lightning rods, they are actually lightning conductors. People install higher metal objects next to important buildings to prevent lightning strikes on important buildings and attract lightning.

In fact, the lightning process is accompanied by very strong electromagnetic wave radiation, which can endanger all normal operations of electronic circuits. The traditional lightning protection design of electronic systems is all aimed at maintaining the system without causing hardware damage in the event of lightning. Contemporary lightning protection design not only ensures that hardware will not be destroyed, but also stipulates that data signals will not be incorrect. A key new project in electromagnetic compatibility experiments, called surge voltage experiments, is to simulate electromagnetic disturbances caused by lightning. CS116 in GJ151 mainly simulates the effects of lightning on cable lines.