The concept and design method of electromagnetic compatibility (I) - the importance of electromagnetic compatibility

1 For the reliability of electronic equipment

Electromagnetic compatibility refers to the ability of electronic equipment to work normally in an electromagnetic environment. Electromagnetic interference is an electromagnetic change phenomenon that is harmful to the working performance of electronic equipment. Electromagnetic interference not only affects the normal operation of electronic equipment, but also causes damage to some components in electronic equipment. Therefore, full attention should be paid to the electromagnetic compatibility technology of electronic equipment. It is necessary to pay attention to the normal operation of electronic equipment without being affected by the surrounding electromagnetic interference, and to pay attention to the fact that the electronic equipment itself does not generate electromagnetic interference to other surrounding equipment, which affects the normal operation of other equipment.

2In order to make electronic equipment internationally compatible

Recently, electromagnetic compatibility has evolved from post-processing to pre-analysis, prediction and design. Electromagnetic compatibility has become an important part of modern engineering design. Electromagnetic compatibility certification has developed from a national scope to a global region, making electromagnetic compatibility as important as safety and environmental adaptability.

For example, the European Community has included the electromagnetic compatibility requirements of products into technical regulations and enforced the 89/336/EEC Directive, stipulating that from January 1, 1996, electrical and electronic products must comply with the electromagnetic compatibility requirements and be affixed with the CE mark before they can be sold on the market.

In order to keep pace with international practices, China's Ministry of Foreign Trade and Economic Cooperation and the State Entry-Exit Inspection and Quarantine Bureau implemented mandatory electromagnetic compatibility testing for personal computers, monitors, printers, switching power supplies, televisions and audio equipment from January 1999. The State Technical Supervision Bureau stipulated that from October 2002, compulsory electromagnetic compatibility certification would be implemented for audio and television broadcasting equipment, information technology equipment, household appliances, power tools, power supplies, lighting appliances, electric ignition drive devices, financial settlement electronic equipment, security electronic products and low-voltage electrical appliances.

3 For the safety of people and some special materials

Electromagnetic waves are inductively coupled with the control circuit of the electric explosion device, and the interference current formed may cause the explosion of the electric explosion device. Therefore, GJB786 stipulates that the electromagnetic interference induced current and voltage on the electric detonator wire must be less than 15% of the maximum non-ignition current and voltage. In addition, various fuels are in danger of combustion and explosion under the action of strong electromagnetic fields (direct irradiation, electric sparks, electrostatic discharge); electromagnetic energy will produce harmful physiological effects through physical and chemical effects on human tissues. Therefore, for the safety of people and some special materials, GJB786 also stipulates that the average power density of continuous waves of electromagnetic radiation from electronic equipment is not allowed to exceed 4mW/cm2, and the average power density of pulse waves is not allowed to exceed 2mW/cm2.

4 For the needs of current and future wars

The electromagnetic pulse generated by a nuclear explosion radiates outward at the speed of light, with an electric field strength of up to 105V/m, a magnetic field strength of up to 260A/m, a pulse width of the order of 20ns, and a peak frequency of 105Hz. When this electromagnetic pulse acts on electronic equipment, it can cause the performance of the electronic equipment to deteriorate at the least, and damage circuit components at the worst.

Especially in current and future wars, the electromagnetic pulse bombs that have been used and the high-power microwave weapons that are being developed have electromagnetic pulse radiation similar to that generated by nuclear explosions, which will pose a fatal threat to electronic equipment. Electromagnetic compatibility can provide basic technical guidance for combating this threat.