Modeling And Evaluation Of Absorbing Materials For Anechoic Chamber

Because there is a large demand for electromagnetic testing in the communications and other industries,and there is a lack of free space to shield electromagnetic interference in nature,the researchers designed and built anechoic chamber as a test place.It takes a lot of time and material cost to build anechoic chamber.The rapid development of computer technology and network promotes the research on the simulation design and virtual anechoic chamber.The key to the performance of anechoic chamber is the absorption efficiency and layout of the absorbing materials.In practical application,manufacturers usually only provide the reflectivity of the absorbing materials,and it is difficult to obtain the electromagnetic parameters of the absorbing materials,and the design of the ultra-large anechoic chamber with high precision using ray tracing technology requires the wide-angle and wide-band reflection coefficient of the absorbing materials.Based on the above background,this paper mainly studies the method of electromagnetic parameter inversion by means of software,and establishes a model to characterize the wide-angle and wide-band reflection characteristics of absorbent materials,which is used for the design and evaluation of microwave anechoic chamber.Firstly,a new method of electromagnetic parameter inversion based on genetic algorithm is proposed to establish a model to characterize the wide-angle single-frequency point reflection characteristics of absorbent materials.Based on the error of reflectivity,the flow chart and genetic operator of the inversion method are preliminarilydetermined by taking the cone absorbing material of single frequency point as the object.Then,by comparing the inversion reflectance curve with the actual reflectance curve,the reasons for the larger reflectance error were analyzed,and the maximum value of reflectance error was introduced to construct the fitness function optimization algorithm.Finally,the optimized algorithm is applied to a wide band honeycomb absorbing material,and the consistency of wide-angle reflectivity is significantly improved,which proves the effectiveness and correctness of the proposed method.Secondly,the space size and layout of the anechoic chamber are introduced,and the principle and advantages of replacing the far field test with the compaction field are expounded.The process of the paraboloid transforming the electromagnetic wave from the feed into the plane wave in the microwave anechoic chamber is analyzed,and the selection method of the paraboloid is calculated,and the method of adding the source in the anechoic chamber simulation is determined.The ideal medium(PML)was applied to the full size ideal compaction field to simulate the anechoic chamber and evaluate the indicators.By analyzing and observing the amplitude and phase distribution of the scattering electric field in the plane and encrypting the sampling points for many times,the position of the static zone in accordance with the cross-polarization degree and phase amplitude characteristics was finally determined.Finally,on the basis of confirming the correctness of the characterization of wide-angle and wideband reflection characteristics of the absorbing material,the cone model absorbing material was covered in anechoic chamber and applied to the simulation of the full-size simple contraction field.The position and range of the static zone,the unevenness of the electric field distribution in the amplitude and phase in the space range,and the components of the electric field in the cross-polarization direction and the horizontal polarization direction respectively were analyzed.The simulation results are compared with the simulation results of anechoic chamber using PML to further prove the correctness of the method.