Design Of Low-Reflection/Reconfigurable Electromagnetic Shielding

With the rapid development of modern high-tech,the harm of electromagnetic radiation in electromagnetic interference,electromagnetic information leakage and electromagnetic environmental pollution is increasing.The effective methods to reduce the harm of electromagnetic radiation include limiting the dose of electromagnetic radiation,using electromagnetic shielding technology and so on.Electromagnetic shield is a kind of key method of blocking or weakening the transmission of electromagnetic energy.Nowadays,the research on electromagnetic shield mainly focuses on the exploration of electromagnetic shielding materials,such as polymers and nanomaterials.However,the electromagnetic constitutive relation of the above materials is very complex,which lacks theoretical guidance for the design of electromagnetic shielding body.In this paper,two kinds of electromagnetic shielding bodies based on the electromagnetic characteristic parameters of dispersive medium are designed by using the transmission matrix method and impedance matching principle:(1)Design of low-reflection and high-absorption seawater electromagnetic shielding.Firstly,a simple three-layer electromagnetic shield is studied,and the feasibility of using electrolyte solution as electromagnetic shielding material is verified.Then,aiming at the reflection effect of electromagnetic shielding designed by using consumable materials,the corresponding multi-layer impedance matching layer is designed by using the impedance matching technology of transmission line principle,so as to achieve the electromagnetic shielding effect of low reflection and high absorption in the narrow band.Finally,the genetic algorithm and impedance matching principle are combined to optimize the electromagnetic shielding characteristics of low reflection and high absorption in the ultra-wide band.(2)Design of reconfigurable electromagnetic shield.In order to realize a transparent propagation of the communication signal in normal electromagnetic environment and electromagnetic interference shielding in the strong electromagnetic interference environment,a reconfigurable electromagnetic shield using electrolyte solution or plasma is proposed.The impedance matching method is used to design the matching layer of low concentration electrolyte solution or cavity layer structure to realize the transmission of electromagnetic signal in normal electromagnetic environment;By increasing the salt concentration of electrolyte solution or exciting the plasma in the cavity,the matching layer will fail,and the electrolyte solution or plasma layer will reflect and absorb the interference electromagnetic radiation,thus forming an effective electromagnetic shielding.Calculation results show that the electromagnetic shield can make a transparent transmission of communication electromagnetic signal in narrow band without reflection and absorption in normal electromagnetic environment.Electromagnetic shielding was constructed by by changing the electromagnetic parameters of the electrolyte solution and plasma,and electromagnetic shield effectiveness varies with the changes of the electromagnetic parameters.The shielding efficiency can reach more than 80 d B in wide band,meeting the high standard of electromagnetic shielding requirements.