Design And Research Of Multi-frequency And Broadband Metamaterial Absorbers

Metamaterial is a kind of artificial compound materials which has many abnormal physical properties that have never been seen in nature and has great application value in many fields.Metamaterial absorbers,a branch of metamaterial,have a rapid development in recent years.They receive widespread attention from researchers because of their excellent performance in radiation protection,EMC and radar stealth.This thesis focuses on two aspects of the new type metamaterial absorbers.The one is multi-frequency absorber and the anther one is broadband absorber.Two new types of metamaterial absorbers are designed and proposed.The main research contents and results are shown as follows:A multi-frequency metamaterial absorber based on the structure of double slits metal sheet is designed to solve the problems of electromagnetic compatibility for ships and other platforms.The absorber has simple structure and good wave absorption performance.The simulation results show that the absorption rates at 4.64GHz,8.67GHz,13.93GHz and 18.53GHz are 99.99%,99.95%,99.94%and 93.50%respectively.The thickness of the absorber is only 0.72mm which is 3.3%,6.3%,10.0%and 13.3%of the working wavelength respectively.In order to explain the absorption mechanism of the absorber,the surface current of each wave absorption points are analyzed and the resonant modes of each frequency point are given.The equivalent impedance of the absorber is extracted and the cause of the high absorption rate is explained by the impedance matching theory.Then the energy loss mode of the absorber is studied by using the different combinations of lossy dielectric and lossless dielectric and copper and perfect electric conductors.Finally,the influence of the structural parameters on the absorption of the absorber is analyzed and discussed and a design scheme of five-frequency absorber is proposed.A metal annular broadband high absorption metamaterial absorber which is loaded collector resistance is proposed and made for radar stealth of X band.The simulation result shows that the absorption rate at 8.4-13.6GHz band is over than 90%,X band is basically covered and the relative wave absorption bandwidth is 47.3%.The absorption rate at 10.3-13.1GHz band is over than 99%and the relative wave absorption bandwidth is 23.9%.The absorption mechanism of the absorber is expounded from the view of simulation and theory by studying the surface current distribution at the frequency of wave absorption and the extraction of the equivalent impedance of the absorber.In addition,the main ways of the energy loss of the absorber are also taken into consideration.Then the equivalent circuit model of the absorber is given and the causes of the broadband absorption of the absorber is given by using circuit theory.The characteristics of polarization sensitivity and wide incidence angle of the absorber are discussed.Besides,the influence of the changes of the structure parameters on absorption rate of the absorber is also analyzed.Finally,the experimental sample of the absorber is produced and the experiment is carried out.