Multi-Band,Miniaturization And Broadband Technology Researches On Frequency Selective Surface

The Frequency Selective Surface(FSS)is a spatial filter which is a kind of multi-layer composite periodic structure with the effects of absorbing and filtering.In addition to playing a important role in reducing radar or target RCS,with the development of mobile communication technology,the application of FSS become more and more extensive.This paper focuses on high-selectivity frequency surfaces used in radar and multi-band/wideband miniaturized frequency selective surface applications using in mobile communication systems.This paper first summarizes the application method of equivalent circuit in FSS design based on FSS related papers and research status.For the equivalent circuit analysis method of the FSS,the following two methods are generally used.The first one is to construct the FSS equivalent circuit after designing the FSS unit based the certain equivalent principles.This method is generally used to analyze the working principle of the FSSs.The second one is to construct the equivalent circuit firstly,and then construct the physical unit structure model of FSS according to its equivalent circuit.In the second chapter of this paper,the usages of the above equivalent circuit is analyzed by some specific FSS design example.Then the theoretical method of current distribution used in the equivalent circuit is introduced.A highly selective frequency selective surface is proposed.The proposed highly selective frequency selective surface is a hybrid unit structure having a top surface of a Jerusalem structure and a bottom surface of a hexagonal ring patch structure.By using a hybrid structure,the advantages and disadvantages of the top and bottom layers can be complemented well,which is crucial to get a highly selective broadband unit structure.For the dielectric layer structure,the air layer is added,which not only reduces the weight of the FSS prototype,but also reduces the insertion loss,and can well achieve the impedance matching of the upper and lower layers and improve the passband flatness.By using an equivalent circuit,the top and bottom layers are equivalent to the lumped elements,and the thickness and dielectric constant of the dielectric layer can be quickly determined by the equivalent circuit simulation.A low profile miniaturized FSS unit structure with broad passband is studied.The design idea of the structure is different from the above.We get the equivalent circuit firstly,and then replace the lumped component in the equivalent circuit with the physical structure.In this structure,miniaturization of the unit cell can be well achieved by connecting the top and bottom unit structures through the via holes,and the miniaturization of the unit structure makes the FSS structure have good cell stability and angular stability.In the following sections,we conducted researches on the miniaturized dualband FSS.For the dual-band FSS,we firstly design the circuit liking the design method of the above part,and then design the cell structure.The difference between the above part and this section is the equivalent circuit of the dual-band FSS and the equivalent circuit of the wideband FSS are different.The square spiral structure is used to miniaturize the unit structure.We combined the equivalent circuit to analyze the relationship between the physical structure and the frequency response of FSS.Beside the above way to design the miniaturized dual-band FSS,then we design a dual-band FSS structure based on the topology structure.The FSS unit is miniaturized by adopting a meander structure in the FSS unit cell.In this topology structure,the metal ring works in different operating modes and produces different operating frequencies.All of the above FSS designs were machined and tested.