Design Of Wide-band Metamaterial Absorbers

The absorber is an important functional device and it has some wide applications in stealth technology,microwave communication,microwave darkroom and electromagnetic compatibility.With the rapid development of electronic and information technology,a variety of electronic equipments generate more and more radiation.The traditional absorbing material has not been able to satisfy the requirements of modern electronic information condition,so higher requirements are put forward for the absorber in quality,size,environmental anti-interference and stability.The metamaterial absorber has been widely used as its thin thickness,simple structure,low dependence on materials and high absorbing efficiency.Based on the equivalent circuit theory,some combination and multilayer metamaterial absorbers have been designed.The main contribution and innovation of this dissertation are below.1.The unit cell of the metamaterial absorbers based on the electric resonance and the magnetic resonance is designed.The wideband absorption performance can be achieved by the combination of multiple resonators at different frequency.Firstly,the different structures and dimensions of the metamaterial absorbers are simulated and optimized using high frequency electromagnetic simulation software CST,and the structure dimension,incident angle and polarization mode of absorber for the absorbing performance are analyzed.Then the equivalent circuit model of metamaterial absorbers based on electromagnetic resonances is established according to the equivalent circuit theory and transmission line theory,and it is analyzed theoretically.Finally,the equivalent resistance,inductance and capacitance of the equivalent circuit are calculated based on the resonant frequency and reflection coefficient,and the equivalent circuit is determined and simulated with advanced design system.The full-wave simulation result agrees well with the result obtained from the equivalent circuit model and verifies the accuracy of the equivalent circuit model.2.A fast design procedure of multilayer cascade metamaterial absorbers is presented.By analyzing the equivalent circuit model and applying the circuit parameter extraction method,a rapid design procedure can be realized.Combined with the particle swarm optimization,an optimized performance and structure parameters of the multilayer cascade metamaterial absorber can be obtained.Compared with the conventional design methods,the proposed design procedure has the advantages of fast calculation speed and small memory consumption.By applying the proposed design procedure,a three-layer metamaterial absorber with outstanding performances is realized.The absorption coefficient of the absorber reaches 90% in a broadband from 2.0GHz to 17.5GHz.The full-wave simulation result agrees well with the result obtained from the equivalent circuit model which verifies the feasibility and efficiency of the proposed design procedure.3.Two kinds of the multilayer metamaterial absorbers are designed using the proposed design procedure.At first,the one-layer,two-layer and three-layer metamaterial absorber based on the square are designed,and the permittivity,thickness and loss of dielectric for the absorbing performance are analyzed.After then in order to improve the absorption performance,a finger-cross structure is proposed.Compared with the square sheet structure,the finger-cross structure can increase the equivalent capacitance.At final,the sample of square structure is processed and measured.