Design And Study Of Radar Absorbing Structure Embedded In Frequency Selective Surface

Electromagnetic stealth plays an important role in military warfare and weapon equipment.Radar absorbing material technology is one of the important ways to reduce radar cross section and achieve stealth.Because of FSS has the selective permeability to electromagnetic wave,it is widely used in radar absorbing material design to improve its comprehensive absorbing effect.In this paper,two kinds of absorbing structures are designed in this respect.However,once the traditional FSS is designed,its electromagnetic transmission characteristics are fixed,which can not meet the ever-changing application requirements.Therefore,this paper studies active/active absorbers,which are based on circuit analog absorbers,using active impedance layer to adjust the reflectance.Active impedance layer is a kind of FSS controlled by microwave diode.The simulation results of active/active FSS radar absorber optimization are obtained by using the commercial software Ansoft HFSS based on finite element method.The main results are as follows:(1).According to the criterion of radar absorbing structure: absorbing bandwidth and angle stability,two kinds of absorbing structures are designed in this paper.The first one is designed for bandwidth.The simulation results show that the design broadens the bandwidth of 3GHz in high frequency band compared with the existing technology.The second one is improved for angle stability.The simulation results show that the design structure is improved.It is only insensitive to the angle and enlarges the absorbing bandwidth by 81% compared with the previous one.In addition,the thickness of these two absorbing structures meets the requirement of thinness.Finally,the physical and test results are given for both boards,and the test results meet the design requirements.(2).Because of the complexity of the combat environment and the concealment of military aspects,it is generally impossible to accurately predict the electromagnetic band of the enemy.The first two designs in this paper are passive,that is,once the design is completed,the absorbing band is fixed.Obviously,this is defective in practice.Demand-driven technology.In this paper,two design structures of active radar absorbing structure are given.The first structure is designed to achieve discontinuous wave absorption in the range of 7-9 GHz by changing the voltage loaded on both sides of the varactor.The second structure is developed on the basis of the first one,which is an array composed of four elements.The simulation results show that the design can achieve uninterrupted wave absorption in the range of 7-9.2 GHz.The improved design improves the absorbing performance.