The Design And Manufacture Of Broadband Absorbing Structure Of Multilayered Composite

As the urgent need for absorbing material in stealth technology applications, to improve the performance of the absorbing material towards the direction of “thinner thickness, lighter weight, wider band and stronger absorption” has been a continuous research subject. Compared with single-layered absorbing material, multilayered absorbing material could better meet the requirements of stealth technology, so the performance improvement of multilayered absorbing material is an important research point. The design of multilayered magnetic material and composite material contain FSS are researched in this paper, and the design results are validated by experiments.To design a multilayered absorbing material with high performance, one method is by optimization algorithm. As the multilayered absorbing material involve many parameters,it is necessary to adopt valid optimization algorithm. In this paper, the reflectivity of multilayered absorbing material is calculated according to transmission lines theory, the absorption bandwidth and thickness of multilayered absorbing material is optimized by Genetic Algorithm based on a database of electromagnetic parameters. The applications of Genetic Algorithm on this subject is adjusted in this paper, the surface layer is selected by resistance match characteristics and absorption characteristics at the beginning of the optimization. The optimization effectiveness of Genetic Algorithm is analyzed from different aspects to validate the advantage of the Genetic Algorithm adopted in this paper.According to the optimization results, EW-type carbonyl iron ball milled for 8 hours can be used for absorbing material in the surface layer, Y01-type carbonyl iron ball milled for12 hours can be used for absorbing material in the bottom layer. The double-layered sheet is 1.1 mm thick while the reflectivity bandwidth at the level of-10 dB is 6 GHz which indicates practical value.To improve the performance of multilayered absorbing material, the structure of the multilayered absorbing material is adjusted in which a resistive frequency selected surface(FSS) is inserted into the double-layer sheet. The three-layer composite absorbing structure is simulated by finite element method in which the dimension of the basic unit of FSS and the value of the resistance of the resistors loaded on the FSS is choosed. Finally,the experiment is carried out to verify the effect of the adjustment in which the FSS is inserted into the double-layer sheet. The result shows that the FSS inserted can improve the absorption performance of the double-layered magnetic sheet. As the resistors loaded on the FSS causes high ohmic loss, the three-layered sheet exhibits low reflectivity within X band and Ku band. The reflectivity at the level of-13 dB of the three-layered sheet containing resistive FSS ranges from 7.9 GHz to 18 GHz which indicates high practical value.