Absorptive/Transmissive Frequency-selective Surface Utilizing Metamaterial

Meta-materials have earned widespread attention and research focus due to their properties that appear non-existent in nature,and breakthroughs have been made in a goodly number of aspects,such as amplitude,phase,and polarnzation control,thus making exotic objects that once existed only in science fiction possible,such as perfect lenses and invisible cloaks.The meta-materials absorbers in this paper overcome the thickness limitations of Salisbury screen or Jaumann absorber and promotes the development of stealth materials in modern information warfare.Their lightness,thinness,wideness,and powerfulness imply potential applications in national defense and military industry.Based on meta-material absorbers,a novel absorptive/transmissive frequency selective surface(FSS)that both absorbs and transmits electromagnetic wave is proposed.It consists of two layers:a lossy layer and a transmissive layer.They work together to yield integrated absorption and transmission.The absorber is mainly designed for use on radomes.This structure has good transmission performance at our side's frequency band and does not interfere with signal transmission or reception of our side.Outside the transmission band,however,the radome works as an absorber that absorbs enemy's radar detection signal,thus reducing radar cross section(RCS).This feature greatly improves our side's anti-reconnaissance ability and enhances our side's combat performance.III(1)In this paper,a dual-polarized high-pass absorptive/transmissive FSS is studied and designed.Its transmission peak is located above the absorption range,and it is therefore a structure that transmits high frequency wave and absorbs low frequency wave.For short,it can be called a high-pass absorptive/transmissive FSS.(For the same reason,a low-pass absorptive/transmissive FSS means a structure that has a transmissive peak located below the absorption range,i.e.,a structure that transmits low frequency wave and absorbs high frequency wave.)A metamaterial absorber and traditional frequency selective surfaces(FSSs)are adopted,optimized and recombined,yielding a two-layer structure consisting of an absorption layer and a transmission layer.The transmission layer is mainly made of a slot FSS.The lossy layer is a wideband absorber with through holes covered by copper.The main working mechanism of the absorptive layer is the electrical and magnetic resonance of the structure and the power consumption of incident wave by metallic loss and dielectric loss.The loss is enhanced further by resistors loaded on the surface.A square slot that corresponds to the transmission frequency of the transmission layer is gouged out on those places of low surface current density on the absorption layer.The slot works together with the FSS of transmissive square slot of the transmissive layer,forming a transmission window.Numerical simulation is conducted to verify its performance.The square hole is then substituted for circular hole.Further numerical simulation and experiment results demonstrate wave absorption at X band and transmission at 17 GHz.(2)In this paper,a switchable absorptive/transmissive FSS is studied and designed.First,an equivalent circuit model is used to design the absorptive layer and the transmission layer of low-pass and high-pass absorptive/transmissive structures.The high-pass absorptive/transmissive FSS is verified by the circuit model in ADS.In addition,according to the equivalent circuit model of high-pass absorptive/transmissive FSSs,a square-ring array is used as the absorptive layer,with a square-ring slot array used as a transmission layer.The model is analyzed by CST Microwave Studio and shows an absorption band between 1.5 GHz and 4.5 GHz and wave transmission at 4.3 GHz.Next,PIN diodes of model SMP1345-079LF is introduced into the high-pass absorptive/transmissive FSS.They are loaded around the square ring slot FSS.The transmission frequency peak can be opened or shut by changing the bias voltage:When the PIN transistor is turned OFF,the absorption band is 1.9 GHz-4.7 GHz,and the transmission peak is at 4.6 GHz with an insertion loss of 0.35 dB.When the PIN is turned ON,the transmission window shuts,and the absorption band is 2 GHz-3.4 GHz.