CN-122016998-A - Comprehensive performance evaluation method of absorption type electromagnetic shielding material

Abstract

The invention relates to the technical field of performance evaluation of electromagnetic shielding materials, in particular to a comprehensive performance evaluation method of an absorption type electromagnetic shielding material. The method comprises the steps of constructing a comprehensive evaluation index system, obtaining total shielding effectiveness, reflection loss and absorption loss of a material through far field testing, determining an absorption coefficient, a reflection coefficient and an absorption dominant factor, comparing the internal field intensity of a cavity with the incident field intensity when a shielding body exists through cavity effect testing, determining a cavity field intensity attenuation factor, determining effective absorption bandwidth according to a frequency change curve of the absorption coefficient, determining a near field absorption coefficient through near field testing, integrating the indexes into a multidimensional evaluation vector, calculating a comprehensive score according to application scene setting weight, and classifying. The invention realizes the multidimensional quantitative evaluation of the comprehensive performance of the absorption type electromagnetic shielding material, and can effectively guide the research and development and the model selection of the material.

Inventors

• LI ZHOU

Assignees

• 重庆沃尔夫化工有限公司

Dates

Publication Date

20260512

Application Date

20260409

Claims (9)

1. 1. The comprehensive performance evaluation method of the absorption type electromagnetic shielding material is characterized by comprising the following steps of: Constructing a comprehensive evaluation index system for an absorption type electromagnetic shielding material, wherein the index system comprises an absorption coefficient, a reflection coefficient, an absorption dominant factor, a cavity field intensity attenuation factor, an effective absorption bandwidth and a near-field absorption coefficient; acquiring total shielding effectiveness, reflection loss and absorption loss of a material through far field testing, determining an absorption coefficient based on the ratio of the absorption loss to the total shielding effectiveness, determining a reflection coefficient based on the ratio of the reflection loss to the total shielding effectiveness, and determining an absorption dominant factor based on the ratio of the absorption loss to the sum of the absorption loss and the reflection loss; measuring the contrast relation between the internal field intensity of the cavity when the shielding body exists and the incident field intensity when the shielding body does not exist through a cavity effect test, and determining a cavity field intensity attenuation factor; setting an absorption coefficient threshold according to a change curve of the absorption coefficient along with frequency, and determining a continuous frequency range of which the absorption coefficient is continuously higher than the threshold as an effective absorption bandwidth; Measuring the total shielding effectiveness and reflection loss of the material under the near field condition through near field test, and determining the difference of the total shielding effectiveness and the reflection loss as a near field absorption coefficient; And integrating the total shielding effectiveness, the absorption dominant factor, the cavity field intensity attenuation factor, the near-field absorption coefficient and the effective absorption bandwidth into a multidimensional evaluation vector, setting weights for all indexes according to a target application scene, calculating a comprehensive score, and classifying material grades according to the comprehensive score.
2. 2. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, In the comprehensive evaluation index system, an absorption coefficient is used for reflecting the proportion of absorption loss to total shielding effectiveness, a reflection coefficient is used for reflecting the proportion of reflection loss to total shielding effectiveness, an absorption dominant factor is used for normalizing the absorption dominant degree of a characterization material, a cavity field intensity attenuation factor is used for quantifying the secondary interference suppression effect of the material in a cavity environment, an effective absorption bandwidth is used for evaluating the absorption stability of the material in a wide frequency range, and a near-field absorption coefficient is used for reflecting the absorption capacity of the material to a near-field magnetic field.
3. 3. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The far field test comprises the steps of measuring the reflected signal intensity and the transmitted signal intensity of a material in a target frequency band by using a vector network analyzer, determining the total shielding effectiveness by comparing the transmitted signal intensities before and after a sample is installed, determining the reflection loss by measuring the reflected wave amplitude on the surface of the material, and determining the difference between the total shielding effectiveness and the reflection loss as the absorption loss.
4. 4. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The cavity effect test comprises the steps of manufacturing a material to be tested into a shielding cavity with standard size, placing an electric field probe in the cavity, externally applying an incident electromagnetic wave, measuring the field intensity of a designated position in the cavity when the shielding body exists, comparing the field intensity with the theoretical incident field intensity of the same point when the shielding body does not exist, and converting the ratio of the field intensity to a cavity field intensity attenuation factor, wherein the field intensity in the cavity is lower than the incident field intensity when the factor is negative.
5. 5. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The effective absorption bandwidth is determined by setting a threshold value on a curve of the absorption coefficient changing along with the frequency, taking the maximum value of the absorption coefficient as a reference, identifying a starting frequency point at which the absorption coefficient reaches and continuously exceeds the threshold value for the first time, and an ending frequency point at which the absorption coefficient falls below the threshold value for the first time, and determining the difference between the ending frequency and the starting frequency as the effective absorption bandwidth.
6. 6. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The near field test comprises the steps of measuring the total shielding effectiveness and the reflection loss of the material under the near field condition by adopting a near field magnetic field test device, and determining the difference between the total shielding effectiveness and the reflection loss as a near field absorption coefficient for representing the absorption loss of the material under the near field magnetic field condition.
7. 7. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The data fusion and comprehensive evaluation comprises the steps of respectively carrying out normalization processing on the total shielding effectiveness, the absorption leading factor, the cavity field intensity attenuation factor, the near-field absorption coefficient and the effective absorption bandwidth, eliminating dimension differences, setting the weight coefficient of each index according to a target application scene, multiplying the normalized index scores by the corresponding weight coefficients, and summing to obtain the comprehensive score of the material.
8. 8. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 7, The setting of the weight coefficient adjusts the emphasis of the material performance according to the target application scene, improves the weight of the absorption dominant factor and the near-field absorption coefficient for the inverter shell application scene, improves the weight of the effective absorption bandwidth for the communication equipment chassis application scene, and improves the weight of the total shielding effectiveness for the scene with higher absolute value requirement on the shielding effectiveness.
9. 9. The method for evaluating the comprehensive properties of an absorptive electromagnetic shielding material according to claim 1, The material grade is classified into an excellent absorption type, a good absorption type, a mixed type, a reflection type and inapplicability according to the comprehensive score.

Description

Comprehensive performance evaluation method of absorption type electromagnetic shielding material Technical Field The invention relates to the technical field of performance evaluation of electromagnetic shielding materials, in particular to a comprehensive performance evaluation method of an absorption type electromagnetic shielding material. Background As electronic devices move toward higher density and higher power, electromagnetic interference becomes increasingly more problematic. Traditional electromagnetic shielding materials are mainly made of metal (such as aluminum, copper and steel), the shielding mechanism is mainly made of reflection, and electromagnetic waves are reflected back to the space through wave impedance mismatch on the surface of the material. However, the reflective shielding has inherent defects in practical application that on one hand, reflected electromagnetic waves are reflected repeatedly in a device cavity, standing waves are easy to form, local field intensity is amplified, secondary interference is generated on a sensitive circuit, and on the other hand, shielding efficiency of a metal material on a near-field low-frequency magnetic field is extremely low, density is high, and the light-weight requirement of the device is difficult to meet. In order to solve the above problems, an electromagnetic shielding material mainly comprising absorption has been developed. Such materials fundamentally reduce the risk of secondary interference by converting electromagnetic energy into thermal energy. However, the conventional electromagnetic shielding material evaluation system still uses the conventional reflection type material evaluation standard, and mainly has the defects that firstly, the evaluation index is single, only the total shielding effectiveness is concerned, the absorption contribution and the reflection contribution cannot be distinguished, the core advantage of the absorption type material is covered, secondly, the secondary interference risk of the material cannot be quantified, the reflection wave of the material with high total shielding effectiveness is still strong, the electromagnetic environment in the cavity is deteriorated, thirdly, the evaluation on the absorption dominant degree is lacking, no index can reflect whether the shielding mechanism of the material is mainly absorption or reflection, fourthly, the near field evaluation is confused with the far field evaluation, the existing standard mainly aims at far field plane waves, the near field interference is mainly dominant in practical application, the evaluation result difference of the two is huge, and thirdly, the material optimization and selection cannot be effectively guided, and an engineer cannot easily judge whether the material is suitable for an application scene which is mainly absorbed only by the total shielding effectiveness. Disclosure of Invention The invention aims to provide a comprehensive performance evaluation method for an absorption type electromagnetic shielding material, which realizes multi-dimensional quantitative evaluation of the comprehensive performance of the absorption type electromagnetic shielding material and can effectively guide material research and development and model selection. In order to achieve the above object, the present invention provides a comprehensive performance evaluation method of an absorption type electromagnetic shielding material, comprising the steps of: Constructing a comprehensive evaluation index system for an absorption type electromagnetic shielding material, wherein the index system comprises an absorption coefficient, a reflection coefficient, an absorption dominant factor, a cavity field intensity attenuation factor, an effective absorption bandwidth and a near-field absorption coefficient; acquiring total shielding effectiveness, reflection loss and absorption loss of a material through far field testing, determining an absorption coefficient based on the ratio of the absorption loss to the total shielding effectiveness, determining a reflection coefficient based on the ratio of the reflection loss to the total shielding effectiveness, and determining an absorption dominant factor based on the ratio of the absorption loss to the sum of the absorption loss and the reflection loss; measuring the contrast relation between the internal field intensity of the cavity when the shielding body exists and the incident field intensity when the shielding body does not exist through a cavity effect test, and determining a cavity field intensity attenuation factor; setting an absorption coefficient threshold according to a change curve of the absorption coefficient along with frequency, and determining a continuous frequency range of which the absorption coefficient is continuously higher than the threshold as an effective absorption bandwidth; Measuring the total shielding effectiveness and reflection loss of the material under the near field co