EMI

What is EMI?

Electromagnetic interference (EMI) is a signal or radiation that is spread over the air or transmitted through power or signal lines in such a way as to endanger the proper functioning of radionavigation or other safety services, or to seriously affect, hinder or repeatedly interrupt licensed radiocommunication services. Radiocommunication services include, but are not limited to, AM/FM commercial radio, television, cellular radio communications, radar, air traffic control, pagers, and personal communication services (PCS). These licensed or unlicensed radio services, such as wireless local area networks (WLANs) or Bluetooth, as well as unintentional emitters such as digital equipment, including computer systems, can cause electromagnetic interference.

Dissemination Mechanisms of EMI

The propagation mechanism of EMI is mainly divided into two forms: conducted interference and radiated interference. Conducted interference refers to the propagation of electromagnetic interference signals through conductors (such as wires, cables, printed circuit boards, etc.). This kind of interference usually occurs within the circuit or between different devices, through the direct connection between the conductor or common impedance and other ways of propagation. Conducted interference is characterised by a higher intensity of the interference signal, a wide range of frequencies, and a more significant impact on the performance of the equipment.

Radiation interference refers to electromagnetic interference signals in the form of electromagnetic waves spread in space. This kind of interference usually occurs in the equipment casing or near the antenna, through the electromagnetic wave radiation and reception for transmission. Radiated interference is characterised by a long propagation distance, susceptibility to environmental influences, and may adversely affect the surrounding environment and other electronic equipment.

Factors affecting EMI electromagnetic interference include the source of the interference, the propagation path and sensitive equipment. The source of interference can be the internal circuitry of electronic equipment, components, or external electric field, magnetic field, etc., and its intensity, frequency and waveform characteristics directly affect the severity of the interference. The propagation path refers to the path of the interference signal from the source to the sensitive equipment, its length, impedance and shielding effect and other factors affect the propagation effect and strength of the interference signal. Sensitive equipment refers to equipment or circuits that are susceptible to the effects of electromagnetic interference, and factors such as its immunity to interference, reception sensitivity and working environment determine the degree of its response to EMI.

How to Deal with EMI？

The first is to suppress the source of interference, which is the fundamental way to reduce EMI. The intensity of the interference source can be reduced by optimising circuit design, selecting low-noise components and reducing circuit power consumption. At the same time, the use of filters, isolators and other technical means can also effectively eliminate the interference signal.

The second is to block the propagation path, which is an effective measure to reduce the effect of EMI propagation. Reasonable wiring, increase the shielding layer, the use of electromagnetic shielding materials or conductive coatings and other technical means can effectively enhance the shielding effect of the equipment, blocking the propagation path of the interference signal.

In addition, improving the anti-interference capability of sensitive equipment is also a key step. By optimising the circuit design, improving the reception sensitivity and enhancing the signal processing capability, the resistance of the equipment to EMI can be significantly improved. Selecting components with good anti-interference performance and increasing redundancy design can also effectively improve the reliability of the equipment.

Finally, strengthen the test and evaluation is to ensure that electronic equipment in line with the key aspects of EMI requirements. In the process of equipment design, production and application, rigorous EMI testing and evaluation is required to ensure that the equipment meets the relevant standards and specifications. Through in-depth analysis and evaluation of test results, timely detection and resolution of potential EMI problems, can effectively reduce its adverse effects on equipment and the environment.