Electromagnetic compatibility refers to the ability of electronic devices to work in a coordinated and effective

 manner in various electromagnetic environments. The purpose is to enable electronic devices to suppress 

various external interferences, enabling them to operate normally in specific electromagnetic environments, 

while also reducing the electromagnetic interference of electronic devices themselves to other electronic devices.

Electromagnetic Compatibility (EMC) refers to the ability of a device or system to operate in its electromagnetic 

environment in accordance with requirements without causing unbearable electromagnetic interference to any

 device in its environment. Therefore, EMC includes two requirements: on the one hand, it refers to the 

requirement that the electromagnetic disturbance generated by the equipment to the environment during 

normal operation cannot exceed a certain limit; On the other hand, it refers to the device having a certain degree 

of immunity to electromagnetic disturbances present in the environment, namely electromagnetic susceptibility (EMS).

Since the emergence of electronic system noise reduction technology in the mid-1970s, it has been mainly due to 

the regulations on commercial digital products proposed by the Federal Communications Commission in 1990 and 

the European Union in 1992, which require companies to ensure that their products comply with strict magnetization 

and emission standards. Products that comply with these regulations are called electromagnetic compatibility (EMC).

Introduction to Electromagnetic Interference

Electromagnetic interference, abbreviated as EMI, has two types: conducted interference and radiated interference. 

Conducted interference mainly refers to the interference signals generated by electronic devices that interfere with 

each other through conductive media or common power lines; Radiation interference refers to the interference 

signal generated by electronic devices transmitted to another electrical network or electronic device through spatial 

coupling. In order to prevent the electromagnetic interference generated by some electronic products from affecting 

or disrupting the normal operation of other electronic devices, various governments or international organizations

 have successively proposed or formulated regulations or standards related to electromagnetic interference generated

 by electronic products. Products that comply with these regulations or standards can be called electromagnetic 

compatibility (EMC). The EMC standards for electromagnetic compatibility are not constant, but are constantly changing 

every day, which is also a means often adopted by governments or economic organizations in various countries to

protect their own interests.

Interference source and interference source

In any case, there are always two complementary aspects to the issue of electromagnetic compatibility:

One is the interference emission source and one is the interfered device sensitive to this interference.

If an interference source and the affected device are both in the same device, it is called an EMC situation within the system.

The interference generated between different devices is called the EMC situation between systems.

Most devices have components with characteristics similar to antennas, such as cables, PCB wiring, internal wiring, 

mechanical structures, etc. These components transfer energy through the coupled electric, magnetic, or electromagnetic

 fields of the circuit.

In reality, the coupling between and within equipment is limited by shielding and insulation materials, and the absorption 

of insulation materials has a negligible impact compared to conductors.

The coupling between cables can be either capacitive or inductive and depends on the influence of orientation, length,

 and proximity.