The Design Of Three-dimensional Electromagnetic Wave Absorber

Since Hertz proved the existence of the electromagnetic wave and Morse invented the first telegraph in nineteenth century,the electromagnetic wave has played a more and more important role in people's daily life and military field.Especially in the information age of the twenty-first century,as the basic carrier of information transmission,the electromagnetic wave has an irreplaceable role.However,the electromagnetic wave also brings some negative effects,such as the electromagnetic radiation to human body,the interference to other electronic devices by the electromagnetic signal,electromagnetic leakage and be detected by the electromagnetic signal in the military field.These adverse effects lead to the generation and application of the absorption material or structure,Especially in the military field,it has an irreplaceable role.Just as its name implies,the absorption material or structure is the material or structure that can absorb the electromagnetic wave.For a excellent absorber,it's structure should be lightweight,low profile,high strength and can adapt to all kinds of application environment,more important,it should perform a very wideband absorption with a high absorption rate,and it may also insensitivity to the polarization.The absorbing principle of the electromagnetic absorber that are derived from Salisbury screen or Dellenbache layer is base on the interference effects of the electromagnetic wave when the medium thickness is integral multiple of the wavelength in the medium.It's working principle and structure is simple,but some disadvantages such as working band is narrow and working frequency is high are also very obvious.Since the last century,due to its plasticity and high absorbility and other characteristics,the coating absorbing material has been widely studied and applied,particularly in military field.But it also works in a high frequency band and the discovery and preparation of the material are difficult.To solve the above problems,circuit analogue(CA)absorbing structure gradually become one of research hotspots.The traditional circuit absorbing structure is consist of printed conductive material on a dielectric substrate,through change the physical characteristics and the geometry of the conductive material to adjust the resonant frequency of the absorber and realize the absorption of electromagnetic wave in a particular frequency band.single-layer CA absorber also has a narrow working band,even though the band can be broadened by a multi-layer structure,but the structure also becomes complicated.In recent years,the CA absorber which employed frequency selective surface(FSS)?carbon-based high-impedance surface(HIS)or lumped elements has been realized,it perform a large relative bandwidth and a high absorbility,It can absorb low-frequency electromagnetic waves while the process is simple and the cost is low.As the requirements to the structure and performance of the absorber,this paper focus on two novel kinds CA absorber which are based on lumped element and carbon-based materials,respectively.The novel absorber can overcome the traditional CA absorber's shortcomings,such as the working band is narrow and high,to realize wideband and low-frequency absorption.Optimization algorithm is used to optimize the absorber's performance and the absorbing principle also be analyzed.The main research work and conclusions are as follows:1.A novel kind of CA absorber which based on a two-dimensional periodic array of parallel-plate waveguide loaded with lumped circuit elements is researched.The electromagnetic theory and equivalent circuit is used and proposed to analysis the Propagation Characteristic and performance of the absorber,we also measured the frequency response of the lumped elements based on the microwave network theory.2.Researched one kind CA absorber which based on the carbon-based material and employed the metallic FSS.Compared with the CA absorber based on the parallel-plate waveguide,this absorber cad realize a bigger angle absorption while the excellent performance is maintained,the physical principles of big-angle absorption is also be analyzed.3.Researched one kind of ultra-wideband CA absorber which is based on carbon-based material,the absorber can broaden the absorption band significantly,realize ultra-wideband absorption.4.Designed a novel kind radome material,through open a window just as the pass band in the absorbing band to realize transmission and absorption function.