| Electromagnetic metamaterials have become a research hotspot in recent years because of their special physical properties.Through the artificial adjustment of the physical size and structure shape of the metamaterial structural unit,we can obtain the electromagnetic parameters of the electromagnetic metamaterial we need.Therefore,the electromagnetic metamaterial has produced many novel phenomena and unique applications,such as electromagnetic stealth,abnormal light deflection,wave front control and so on.The metamaterial absorber has the advantages of strong absorptivity,light weight,thin thickness,and adjustable frequency,which are not available in conventional wave absorbing materials.However,the absorption bandwidth is generally narrow.Therefore,based on the electromagnetic absorption principle and research methods of electromagnetic metamaterials,two different types of broadband absorbers have been designed.The absorption rate and reflectance are obtained after numerical simulations.The band of high absorption rate is effectively broadened.We mainly do some research in the following aspects.In this dissertation,firstly,based on the slow-wave effect absorbing materials,a terahertz band broad-band microwave absorbing structure based on a multi-layer circular-table structure is designed.The absorber has an absorption rate of over 90% in the frequency range of 1.29 THz to 2.34 THz and a relative absorption bandwidth of 57.85%.Due to its axisymmetric structure,the absorber has polarization-insensitive characteristics.Based on this,the wave-absorbing structure was optimized,metal chromium was used instead of gold as the metal layer,the thickness of the dielectric layer was equal,and a wave-absorbing material with outstanding performance and easy processing was obtained.The structure was 0.85-1.42 THz.The absorption rate in the frequency band exceeds 80%,and the absorption effect remains basically unchanged when the incident angle of the terahertz wave is incident.Then,a broad band metamaterial absorber based on loaded lumped microwaves is designed.The absorber has good absorptivity over 90% in the frequency range of 7.68 GHz to 16.94 GHz and a relative absorption bandwidth of 75.22%,and has characteristics such as polarization insensitivity and wide incident angle.By observing the surface current distribution and energy loss of the absorber,the absorption principle of the absorber is analyzed and it is found that the ohmic loss of the lumped resistor is the main reason why the absorber has strong absorption.By observing the lumped resistance value of the absorber structure,the cell structure period,the metal line width and the thickness of the dielectric layer and other parameters,the absorptivity of the absorber was changed,and the influence of the structural parameters on the absorptivity was analyzed.The device has an optimal structural parameter,which makes it have the highest absorption rate and the widest absorption bandwidth.Finally,a metamaterial absorber is designed,which consists of alternately stacked annular resistive diaphragms and organic dielectric layers.Electromagnetic simulation analysis shows that the absorber absorbs more than 90% of the normally incident electromagnetic waves.From 7.42 to 59.36 GHz,and the TE and TM waves with an oblique incident angle of 45° still have a good absorption effect.In addition,through the analysis of multiple wave absorbers with different number of resistive diaphragm layers,the more resistive film layers,the better the wave absorbing effect,the wider wave-absorbing band,and the more stable in-band wave absorbing effect.Through the effect of the absorbing effect caused by the periodic change of the cell structure,it can be seen that when the cycle of the cell structure changes within a relatively small range,it has little effect on the wave absorbing effect. |
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