With the wide application of electronic devices, the problem of electromagnetic interference (EMI) has become increasingly prominent, seriously affecting the normal operation of equipment and the security of information. In order to solve this problem, electromagnetic shielding technology has been widely used in fields such as communication, military industry, medical treatment, and aerospace. Among them, electromagnetic shielding boards, as key shielding materials, the testing of their shielding effectiveness is particularly important. This article will introduce the basic concepts and testing methods of electromagnetic shielding board shielding effectiveness.



1. Definition and Significance of Shielding Effectiveness



Shielding Effectiveness (SE) refers to the attenuation ability of electromagnetic shielding materials to incident electromagnetic waves, usually expressed in decibels (dB). Its calculation formula is:



$$ SE = 20 \log \left( \frac{E_0}{E_1} \right) $$



Among them, $ E_0 $ is the electric field strength measured without shielding, and $ E_1 $ is the electric field strength measured after adding the shielding material. The higher the SE value, the better the electromagnetic protection performance of the shielding material.



2. Main Testing Methods for Shielding Effectiveness



Currently, the testing of electromagnetic shielding panels is mainly divided into two categories: far-field testing and near-field testing.



# 1. Far-field Testing Method



Far-field testing is usually carried out in an electromagnetic wave暗室，where a specific frequency electromagnetic wave is emitted through a transmitting antenna, and the receiving antenna measures the signal strength passing through or around the shielding panel, thereby calculating the shielding effectiveness. This method is suitable for evaluating a wide frequency range (usually between 30 MHz and 40 GHz) and is commonly used for product certification and standard testing.



# 2. Near-field Testing Method



Near-field testing mainly measures the changes in the electromagnetic field near the shielding panel through a probe, which is suitable for rapid evaluation in the research and development stage of the laboratory. This method has relatively low requirements for the testing environment, but the test results are prone to interference from the surrounding environment, so it is mostly used for qualitative analysis and material screening.



3. Testing Standards and Regulations



To ensure the accuracy and comparability of the test results, multiple international standards are used to regulate the testing methods for electromagnetic shielding effectiveness. For example:



- IEC 61000-5-2: Specifies the design and testing methods for electromagnetic shielding rooms;

- MIL-STD-285 and IEEE STD 299: Widely used in military and industrial fields;

- GB/T 33616-2017: China's national standard, which makes detailed provisions on the testing methods for electromagnetic shielding materials.



When enterprises conduct shielding effectiveness tests, they should choose appropriate testing standards according to the product application and industry requirements.



4. Factors Affecting Shielding Effectiveness



The shielding effectiveness of shielding panels is influenced by various factors, including material types (such as metal mesh, conductive rubber, metal foil, etc.), thickness, structural design, frequency range, and defects such as seams and holes. Therefore, these factors should be comprehensively considered during the testing process to ensure that the test results can truly reflect the performance of the product.



Conclusion



Electromagnetic shielding panels, as an important means of suppressing electromagnetic interference, have a direct impact on the operational stability and information security of electronic equipment. Through scientific and reasonable testing methods and combined with relevant standards for evaluation, the quality and application effect of the shielding material can be effectively guaranteed. With the development of technology, the testing methods for shielding effectiveness are also constantly improving, and will be more precise, convenient, and intelligent in the future.