Design And Optimization Of Wideband Absorbing Honeycomb Composite Structure

With the rapid development of Fifth Generation（5G）Mobile Communication Technology and radar technology,the electromagnetic environment is increasingly becoming complicated,and absorbing materials have been widely used in military and civil fields.Especially,absorbing honeycomb has become a kind of important functional structural materials due to its excellent absorbing and mechanical properties.In this thesis,based on the theory of equivalent electromagnetic parameters,the structure model of multilayer absorbing media and genetic algorithm,the gradient of absorbing honeycomb is optimized.Aiming at the problem of equivalent half wavelength reflection peak of structural absorbing materials,the broadband performance of absorbing honeycomb was improved by introducing resonance and modifying equivalent propagation path,combining metamaterial,plate waveguide and metasurface.The main research work and conclusions are as follows:（1）The Genetic Algorithm is used to optimize the gradient absorbing honey with four layers,and the 8-18 GHz key frequency band is set.For the absorbing honeycomb with a total thickness of 20 mm,the reflectivity of the whole frequency band of8-12 GHz is lower than-15 d B,with an average of-25 d B,and that of the whole frequency band of 12-18 GHz is lower than-15 d B,with an average of-20 d B.The accuracy and feasibility of the algorithm are verified by comparing the optimization algorithm with simulation and experimental tests.（2）For the problem of constructive interference in the structural absorbing material,a resonant metamaterial loaded on the inner wall is designed.When electromagnetic waves are incident,the metamaterial is equivalent to LC resonant circuit model,and the electromagnetic resonance absorbing performance at constructive interference wavelength is obtained by adjusting the resonant frequency points.The composite structure of uniform absorbing honeycomb loaded metamaterial is further designed.The composite structure has an absorption peak of-20 d B at the target wavelength,and the reflectivity is more than 20 d B lower than that of uniform absorbing honeycomb.The composite structure optimizes the performance of this band and effectively expands the absorption bandwidth of-10 d B.（3）To solve the problem of constructive interference by designing and loading resonant metamaterials into honeycomb holes.Using the parallel plate waveguide structure,the polarization insensitive symmetrical absorbing structure is designed.By forming multiple height gradients,to form multiple narrowband absorption peaks in4-8GHz,and the absorbing performance in this frequency band is optimized.（4）In view of the aforementioned problems of complex structure and difficulty in loading of resonant design,anisotropic scattering metasurface design is adopted to solve the problem of constructive interference of electromagnetic wave.The metasurface is designed to deflect the reflection Angle of the perpendicular incident electromagnetic wave by 30° at the operating frequency point.When the electromagnetic wave incident to the metasurface,the reflection direction of the electromagnetic wave is changed,its propagation path is increased,while the constructive interference cannot be formed on the surface of the absorbing honeycomb.Through simulation and experimental verification,the composite structure of uniform absorbing honeycomb combined with metasurface and the composite structure of gradient absorbing honeycomb combined with metasurface both form absorption peak at the working frequency point,so as to solve the problem of high reflection at the frequency point.The overall absorbing performance of composite structure is obviously better than that of single absorbing honeycomb.