Design Of Low Frequency Absorber Based On Metamaterials

Electromagnetic metamaterial is a new concept in the field of material design.It can manually design the structure and shape of the unit,which provides a new way for the design of the new electromagnetic absorption materials and the stealth materials.In addition,due to the high absorption,ultra-thin,miniaturization,frequency selectivity and other advantages,metamaterial absorbers get much attention.With the deepening of the study of the metamaterial absorbers,the frequency range of the absorbers is more and more widely,and gradually develops from the initial THz band to the low frequency band.And the low frequency of the absorbers has been the urgent need to the field of the military and the electromagnetic protection,especially through the thin and light materials to achieve high absorption of electromagnetic wave in the low frequency is a major problem in the development of absorbing materials.In this thesis,the background and the significance of the research are expounded,and then the concept,the research status and the application of electromagnetic metamaterial and metamaterial absorbers is introduced.Then we study the basic theory of metamaterial absorbers,including impedance matching principle,equivalent dielectric theory and metamaterial interference theory.Finally,the following two types of low-frequency metamaterial absorbers are designed:The first type is the polarization-insensitive wind-shaped absorbers,including a single-frequency absorber and a dual-frequency absorber.The simulation result of the single frequency absorber shows that there is a strong absorption peak at 2.65GHz.The absorption rate reaches 99.99%,and it has the polarization insensitivity and the wide angle incident characteristic.Then we discuss the effect of substrate thickness and ring radius on the absorber.The dual-frequency absorber is a hollow,wind-driven structure which is designed on the basis of the single-frequency absorber.lt can absorb strongly at frequencies of 2.23 GHz and 5.40 GHz,and it still has a good polarization-insensitive and wide angle incident characteristic.The second type is the absorbers with the flexible substrate and the adjustable frequency.lt also includes a single-frequency absorber and a dual-frequency absorher.Both absorbers use the flexible polytetrafluoroethylene substrate,which enhances the plasticity of the structure.In addition,they can adjust a structural parameter to significantly change the absorption frequency,which achieves the frequency adjustable...