Study On Measurement Methods For Electromagnetic Parameters Of Absorbing Materials

With the development of 5G technology,the progress of artificial intelligence technology and the popularity of wearable equipment made the electromagnetic environment of human being living became more and more complex and changeable.It brings serious challenges to the electromagnetic compatibility(EMC)problem between equipment and system.People also pay more attention to the EMC problem between equipment.Many EMC laboratories are springing up in cities in the South and north of China.Among many EMC laboratories,anechoic chamber is one of the most common and important EMC laboratories.The key and the biggest cost of the establishment of the chamber is the design of electromagnetic absorbing materials.The important aspect of electromagnetic absorbing material designs is that we need to have a full understanding of the electromagnetic parameters of the absorbing materials.At present,the general data of electromagnetic parameters of absorbing materials still stay in the statistics data given by foreign scholars at the end of 1990 s.These data are aimed at the statistical research of foreign absorbing materials,which is not suitable for the electromagnetic characteristics of absorbing materials in China.Therefore,it is urgent to give the electromagnetic parameters data of the simulation model for the common absorbing materials in China,so as to facilitate further research on the absorbing materials.This paper mainly studies the measurement methods of electromagnetic parameters of electromagnetic absorbing materials.Firstly,the related measuring equipment and calculation process of electromagnetic parameter measurement are introduced.The problems in the algorithm are studied,and the realization process of de embedding of measuring fixture is given.After the calibration of the measurement system and the embedding of the fixture,the measurement system is verified with the samples of known electromagnetic parameters and the electromagnetic parameters of the electromagnetic absorbing materials are measured.On the basis of obtaining the measurement results of electromagnetic parameters of the absorbing material,the parameters of Debye model are extracted to pave the way for the modeling and Simulation of the absorbing materials.The specific research contents are as follows:(1)New measurement system is built.Based on the determination of the measurement method,the existing shielding efficiency tester in the laboratory is designed and modified.A new metal container is added to the coaxial part of the flange of the shielding effectiveness tester.The new metal container has the same cross-section dimension as the original flange coax.The new design of metal container is more flexible and convenient in loading and operation of samples than traditional fixture of coaxial method,and can reduce the measurement error caused by human operation.(2)The simulation of fixture is embedded.The general research on the processing of measuring fixture are to treat the fixture as a transmission line with certain electrical size without electromagnetic wave transmission loss,and only the phase compensation of the scattering parameters is carried out.In this paper,the method of embedding is used to simulate the fixture directly by numerical simulation software,and the more accurate scattering parameters of the fixture are obtained.And from the point of view of experimental verification,the whole de embedding process is verified to ensure the correctness of the de embedding process.(3)The electromagnetic parameters of electromagnetic absorbing materials are measured.The electromagnetic absorbing material is a kind of high performance angular cone absorbing material produced by a domestic manufacturer.The sampling and measurement were carried out in different parts of the angle cone absorbing material,and the influence of blue emulsion paint on the electromagnetic parameters measurement was analyzed.The results show that the electromagnetic parameters of the gradient part of the conical absorbing material are consistent and almost equal.But there are great differences between the electromagnetic parameters at the bottom of the absorbing material and the electromagnetic parameters of the gradual part.Meanwhile,the electromagnetic parameters of the measured absorbing materials will be changed by spraying blue emulsion paint.Based on the measurement of electromagnetic parameters of absorbing materials,the first-order medium model parameters of absorbing materials are extracted by least square method.The simulation model of absorbing materials is convenient by numerical simulation software.The process of building this dispersion material in the simulation software is introduced.The reflectivity of the absorbing material is obtained by the simulation model,and compared with the actual measurement.The rationality of the whole measurement system design is verified,which lays a foundation for the further study of the absorbing materials.