Research On Theory And Design Of Absorbing And Transmitting Integrated Metamaterial

Frequency-selective surfaces(FSS)are also known as spatial filters and generally consist of a dielectric substrate and a two-dimensional periodic metal array arranged on the dielectric substrate.Compared with the traditional filter,the frequency selective surface has a simple structure and is easy to be processed.It has a wide range of applications in military,especially in radar stealth technology.One of the most common applications of frequency selective surfaces is in making radome.Because the reflected electromagnetic wave can still be detected by detection radars in other directions,only the radar scattering cross section(RCS)of a single station can be effectively reduced,which makes the traditional frequency selective radome easily exposed to the two-station or multi-station radar detection network,which also poses a great threat to the military combat platform.In order to solve this problem,a frequency selective radar absorber(FSR)is proposed,which greatly improves the stealth performance of the radar system.With the deepening of the research,the research of frequency selective radar absorber has become mature.On this basis,the researchers further proposed to combine the frequency selective radar absorber with the active device,and designed a variety of reconfigurable frequency selective radar absorber to realize the dynamic switching and dynamic tuning of functions.At present,the design of frequency selective radar absorber mainly starts from changing its own structure,which also puts forward higher requirements for our work.It not only needs to meet the novelty of frequency selective radar absorber design,but also needs to achieve the richness of functions.Based on the design theory of frequency selective radar absorber and combined with the theory of equivalent circuit,this paper proposes a variety of FSR functional devices.The main research contents are as follows:1.A new A/T-FSR structure is proposed.The lossy layer element metal resonator is composed of miniaturized crossed dipoles with zigzag lines,and the lossless layer is an improved cross ring gap element.The absorbing mechanism is analyzed by equivalent circuit theory,and the structural parameters are optimized by simulation.Finally,the absorption rate of the absorption band is 90% in the range of 3.46-7.68 GHz,the relative bandwidth is 75.8%,and the insertion loss at 10.6 GHz is 0.22 d B.2.On the basis of the traditional frequency selective absorber,further proposed to load active device PIN diode and varactor diode to realize the expansion of FSR function.In this paper,a unit structure is proposed to load PIN diode,and its own structure is used as a part of the feed network.The lumped resistance is loaded at the lossy layer,and the PIN diode is loaded at the bottom layer.In terms of functions,the dynamic switch between wide-band absorption and absorption-transmittance is realized.When the PIN diode is closed,the absorption rate is realized in the range of 2.1-6.41 GHz with a relative bandwidth of 5.58-6.41 GHz.When the PIN diode is switched on,there is a 90% absorption rate between 2.2-5.77 GHz.Furthermore,the FSR design of loaded varactor diode is proposed.When the capacitance value of varactor diode changes with the applied bias voltage,the resonant point of FSR also changes.The dynamic tuning range is 9.7-10.28 GHz,and the insertion loss is 1.10-1.25 d B.3.A three-dimensional metamaterial wave absorber(3D-MA)with extremely asymmetric absorption is proposed.It can observe perfect absorption at forward incidence and near-total reflection at backward incidence.Compared with the traditional MA,the3D-MA designed in this paper is a hollow array of cross-mesh,without a metal back,while using resistive ink,manufactured by screen printing technology.In the forward incidence,broadband absorption is achieved in the range of 2.28-3.97 GHz,and the absorption rate reaches more than 90%.When the electromagnetic wave is reversely incident,the reflection band almost remains unchanged.Outside the absorption band,a T-A-T type FSR is designed to provide a transmission window for incoming waves from both sides of the metamaterial.