A Brief Discussion on Electromagnetic Compatibility Design for Electronic Devices

I. Electromagnetic Compatibility Analysis
Electromagnetic compatibility refers to the ability of a device, equipment, or system to operate properly in its electromagnetic environment without generating any intolerable electromagnetic interference that would disturb the surrounding environment. Electromagnetic compatibility encompasses both electromagnetic interference and electromagnetic susceptibility. To ensure that devices within a system can operate without interfering with each other and remain compatible, it is necessary both to control the electromagnetic emissions from disturbance sources and to enhance the immunity of devices that are susceptible to such disturbances.
II. Analysis of Electromagnetic Interference Modes
Natural factors and human-induced factors are the two primary sources of electromagnetic interference. Based on their origin, we can also classify them into internal interference and external interference. Internal interference refers to the interference among various electronic components within an electronic device itself. For example, interference caused by leakage current, interference due to mutual inductance between wires, interference caused by component heating affecting other components, and interference generated by magnetic fields produced by components—all fall under this category. External interference, on the other hand, encompasses interference factors that originate from sources outside the electronic product itself. These include interference from external electromagnetic fields, external electromagnetic waves, external high-voltage disturbances, as well as interference caused by external humidity, temperature, acidity or alkalinity levels, and voltage instability.
3. Electromagnetic Compatibility Design
Electromagnetic interference has three major factors, specifically referring to the receiver, the interference source (such as a signal generator like an electrostatic gun), and... Surge tester (Equipment and coupling paths). Electromagnetic interference will not occur as long as these three factors are all met.
Based on this, when designing electronic products, it is necessary to take into account two key aspects: first, the electronic product itself must be immune to interference from both internal and external factors; second, the electronic product itself must not cause interference to other products. To address these two considerations, design efforts primarily focus on three major factors. The content of electromagnetic compatibility design includes: limiting electromagnetic emissions from interference sources, controlling the propagation of electromagnetic interference, and enhancing the anti-interference capability of sensitive equipment.
1. PCB Design
The primary task in electromagnetic compatibility (EMC) design is PCB design. The quality of PCB design directly determines the EMC performance of electronic products. A well-designed PCB can reduce electromagnetic interference and mitigate its adverse effects. In the EMC design of electronic device PCBs, the key lies in addressing the inherent electromagnetic sensitivity characteristics of analog and logic active components. Since square-wave signals contain high-order harmonic components, when designing digital circuits, one should, while meeting product design requirements, strive to select devices with slower edge-transition speeds whenever possible. In addition to component selection, it is also essential to comprehensively employ effective techniques such as decoupling capacitors, ferrite terminations, circuit layout, and proper grounding and power supply design to enhance decoupling effectiveness and optimize anti-interference performance.
2. Shielding Design
Shielding design refers to a technique that uses a medium to reduce or block electromagnetic fields. Typically, this medium is a metal with absorption properties, capable of effectively blocking electromagnetic radiation. Classified by the type of medium used, shielding materials can be divided into electric shields and magnetic shields. In the design process, it is also essential to consider the issue of gaps. Research has shown that when the maximum linear dimension of a gap is an integer multiple of half the wavelength of the interfering source, the electromagnetic leakage through the gap reaches its maximum.
3. Grounding Technology
Grounding design is an important and conventional method for reducing electromagnetic interference through grounding. In the design process, it’s essential to consider factors such as grounding points and grounding methods. In electromagnetic compatibility design, the following approaches can be taken into account: minimizing potential differences between grounding points, using tubular grounding conductors, ensuring the reliable electrical connection of grounding wires, and selecting appropriate grounding methods.
4. Filtering Technology
Filtering technology primarily suppresses interference by means of electromagnetic interference filters, which are a key approach for enhancing electromagnetic compatibility. The application of filters can reduce the intensity and level of electromagnetic interference signals. However, in the design process, it is crucial to have a thorough understanding of the filter’s installation location and installation method.
5. Reasonable layout

Proper layout is a fundamental skill that designers should possess—ensuring that all electronic components and wiring within an electronic product are arranged in a scientific and rational manner, avoiding mutual interference and minimizing mutual inductance between wires, thereby reducing electromagnetic interference to the lowest possible level.